
LIBRARY OF CONGRESS 


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CHEMICAL TECHN 


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By RUDOLF WAGNER, PH. D., 

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Professor of Chemical Technology at the University of Wurtzburg. 


Translated and Edited from the Eighth German Edition , 
with Extensive Additions , 


By WILLIAM CROOKES, F. R. S. 


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WITH 330 ILLUSTRATIONS. 


NEW YORK: 

D. APPLETON AND COMPANY, 

549 & 551 Broadway. 

1877 . 



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T ransrer 

Engineers School Uby. 

June 29 >i 93 i 



TRANSLATORS PREFACE, 


Tue several Editions of Professor Rudolf Wagner’s “ Handbuch der Cliemischen 
Technologie” have succeeded each other so rapidly that no apology is needed in 
offering a translation to the public. 

There is little to be said as to the arrangement. Improvements in Technological 
processes that have appeared since the publication of the Eighth German Edition 
have been added during translation. Only when necessary have Foreign weights 
and measures been stated in English equivalents ; where the point has been one of 
comparison, the weights have been left unaltered. The Metrical System has in 
some cases been of great service in avoiding the repetition of tiresome distinctions 
between English and Prussian grain weights, English and Bavarian foot measure, 
&c. The formulae have been subjected to careful revision, and are molecular 
throughout. Indeed, every care has been taken to merit the confidence of the 
manufacturer and of the student. 

Under the head of Metallurgical Chemistry, the latest methods of preparing Iron, 
Cobalt, Nickel, Copper, Copper Salts, Lead and Tin and their Salts, Bismuth, Zinc, 
Zinc Salts, Cadmium, Antimony, Arsenic, Mercury, Platinum, Silver, Gold, Man- 
ganates, Aluminum, and Magnesium, are described. The various applications of 
the Voltaic Current to Electro-Metallurgy follow under this division. The Prepara¬ 
tion of Potash and Soda Salts, the Manufacture of Sulphuric Acid, and the Recovery 
of Sulphur from Soda-waste, of course occupy prominent places in the consideration 
of chemical manufactures. It is difficult to over-estimate the mercantile value of 
Mond’s process, as well as the many new and important applications of 
Bisulphide of Carbon. The Manufacture of Soap will be found to include much 
detail. The Technology of Glass, Stoneware, Limes, and Mortars, will present 
much of interest to the builder and engineer. The Technology of Vegetable Fibres 
has been considered to include the preparation of Flax, Hemp, Cotton, as well 
as Paper Making; while the applications of Vegetable Products will be found 
to include Sugar-b’oi^ng, Wine and Beer Brewing, the Distillation of Spirits, 
the Baking of Bread, the Preparation of Vinegar, the Preservation of Wood, &c. 



TRANSLATORS PREFACE. 


Dr. Wagner gives much information in reference to the production of Potash 
from Sugar residues. The use of Baryta Salts is also fully described, as well as the 
Preparation of Sugar from Beet-roots. Tanning, the Preservation of Meat, Milk, 
&c., the Preparation of Phosphorus and Animal Charcoal, are considered as 
belonging to the Technology of Animal Products. The Preparation of the Materials 
for Dyeing has necessarily required much space; while the final sections of the 
book have been devoted to the Technology of Heating and Illumination. 

We cannot let this work pass out of our hands without expressing the hope 
that, at no distant date, Chairs of Technology will be founded in all our Univer¬ 
sities, and that the subject will be included in the curriculum of every large schooL 


London, May , 1872. 


AUTHOR’S PREFACE TO THE EIGHTH EDITION 


The Eighth Edition of my “ Chemischen Technologie” liaving followed the Seventh 
within two years, but few words of introduction are necessary. 

The arrangement of the subject-matter in former Editions has essentially been 
left unaltered, with the exceptions that I have brought the consideration of the 
materials and products of Chemical Industry, and the Technology of Glass and of 
Stoneware, in former Editions arranged as one section, under distinct headings 
The various processes of Chemical Manufacture have had much detail added. The 
descriptions of the Technological Preparation of Alkali and Ammoniacal Salts, 
as well as of the Tar-colours, have in consequence of the extended application 
of these products, been much enlarged. The Chemical formulse are molecular, 
throughout. 

Of the present Edition translations will be made into English by Mr. William 
Crookes, of London, and into French by Professor L. Gautier, of Melle, Deux- 
Sevres. A translation into Dutch of part of the Seventh Edition that has recently 
appeared has been made without my permission or that of my publishers. 

The First Edition of this work, written whilst I held the position of Private Tutor 
in Chemistry to the Philosophical Faculty to the High-School of Leipsic, appeared 
in September, 1850. The Second in May, 1853, and the Third Edition in July, 
1856, were presented to the public during my Professorship of Technological 
Chemistry in the Imperial Industrial Schools of Nuremburg. The later Editions 
appeared— 

The Fourth in May, 1859. 

„ Fifth in May, 1862, 

„ Sixth in October, 1865, 

„ Seventh in March, 1868, 

during intervals in my official duties in Wurtzburg; and in these I have been much 
assisted by the contributions and suggestions of many friends, to whom I now tender 
my sincere thanks. 

Dr. RUDOLF WAGNER. 

University of Wurtzburg, 

December 10 th, 1870. 





























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CONTENTS 


DIVISION I. 

CHEMICAL METALLURGY, ALLOYS, AND PREPARATIONS MADE AND OBTAINED PROAi 

METALS. 


General Observations. — Meaning of the term Metallurgy, 4. Ores, 4. Dressing of 
Ores, 5. Preparation of Ores, 5. Smelting of the Ores, 6. The Mixing of the 
Smelt, 7. Products of the Smelting Operation, 7. Slags, 7. 

Iron.—I ts Occurrence, 8. 

Pig or Crude Iron.— Extraction of Iron from its Ores, g. Theory of the Iron Extraction 
Process, 10. Blast-furnace Process, 10. ^Description of the Blast-furnace, n. The 
Blowing Engine and Blast, 12. Course of the Smelting Process, 13. Chemical Pro¬ 
cess going on in the Interior of the Blast-furnace, 13. Temperature in the Blast¬ 
furnace at Different Points, 15. Blast-furnace Gases, 15. Application of these 
Gases to the Manufacture of Sal-ammoniac, 16. Crude Iron, Cast-iron, 16. White 
Cast-iron, 16. Grey Cast-iron, 16. Statistics concerning the Production of Crude 
Iron, 18. Iron Foundry Work—Re-smelting Crude Cast-iron, 18. Shaft or Cupola 
Furnace, 18. Reverberatory Furnace, 18. Making the Moulds, 19. Annealing, 
Tempering, 20. Enamelling of Cast-iron, 20. 

Malleable, Bar, or Wrought-Iron. —Bar Iron, Refined Iron, 20. German Iron-refining 
Process, 21. Swedish Refining Process, 22. The Puddling Process, 22. Puddling 
Furnace, 22. Heating with .Gases, 24. Refining of Iron by Mechanical Means, 24. 
Boiler-plate Rolling, 24. Iron Wire Manufacture, 25. Properties of Bar Iron, 26. 

Steel.— Steel, 26. Rough Steel, 27. Steel Making by Imparting Carbon to Wrought- 
iron, 28. Refined Steel, Shear Steel, 29. Cast-steel, 2g. Steel made from Malleable 
and Crude . Cast-iron, 29. Surface Steel Hardening, 29. Properties of Steel, 2g. 
Tempering, 30. Steel and other Metals, 30. Damascene or Wootz Steel, 30. Sidero¬ 
graphy or Steel Engraving, 31. Statistics of Steel Production, 31. 

Iron Preparations. —Copperas—Green Vitriol, 31. Preparation of Green Vitriol as a By¬ 
product in Alum Works, 32. Preparation of Green Vitriol in Beds, 32. Green 
Vitriol from the Residues of Pyrites Distillation, 32. Green Vitriol from Metallic 
Iron and Sulphuric Acid, 32. From Spathic Iron Ore, 32. Uses of Green Vitriol,32. 
Iron Minium, 32. Yellow Prussiate of Potassa, 33. Applications of the Yellow 
Prussiate, 35. Red Prussiate, 35. Cyanide of Potassium, 35. Berlin Blue, 36. Old 
Method of Preparing Prussian Blue, 36. Recent Methods of Preparing Berlin Blue, 
36. Turnbull’s Blue, 37. Berlin Blue as a By-product of the Manufactures of Coal- 
gas and Animal Charcoal, 37. Soluble Berlin-Blue, 37. 

Cobalt. —Metallic Cobalt, 37. Cobalt Colours, 37. Smalt, 38. Cobalt Speiss, 38. Appli¬ 
cations of Smalt, 38. Cobalt Ultramarine, 38. Canuleum, 39. Rinmann’s or Cobalt 
Green, 39. Chemically pure Protoxide of Cobalt, 39. Nitrate of Protoxide of 
Cobalt and Potassa, 39. Cobalt Bronze, 39. 

Nickel.— Nickel and its Ores, 39. Preparation of Nickel from its Ores, 40. The Concen¬ 
tration-Smelting of the Nickel Ores, 40. Preparation of Metallic Nickel, or of Alloys 
of Nickel and Copper, 41. Projierties of Nickel, 43. • 

Copper.— Where it Occurs, and How, 43. Ores of Copper, 43. Mode of Treating the 
Copper Ores for the Purpose of Extracting the Metal, 44. The Working-up of the 
Copper Ores in the Shaft Furnace, 44. Refining the Copper, 46. Refining on the 
Hearth, 46. Refining Copper in Large Quantities, 46. Liquation Process, 47. 
English Mode of Copper Smelting, 47. Calcining or Roasting the Ores, 48. Smelting 
the Ores, 48. Roasting or Calcining the Coarse Metal, 49. Smelting for White 
Metal, 49. Blistered or Crude Copper, 49. Refining the Blistered Metal, 49. Mode 
’of Obtaining Copper from Oxidised Ores, 49. Hydro-Metallurgical Method of Prepa¬ 
ring Copper, 49. Copper obtained by Voltaic Electricity, 50. Properties of Copper, 
50. Alloys of Copper, 51. Bronze, 51. Brass, 52. German or Nickel Silver, 53, 
Amalgam of Copper, 54. 



viii 


CONTENTS. 


Preparations of Copper. —Blue Vitriol, Sulphate of Copper, 54. Preparation of Blue 
Vitriol, 54. Double Vitriol, 55. Applications of Blue Vitriol, 56. Copper Pigments, 56. 
Brunswick Green, 56. Bremen Blue or Bremen Green, 56. Casselmann’s Green, 57. 
Mineral Green and Blue, 57. Oil Blue, 57. Schweinfurt Green or Emerald Green, 
58. Stannate of Oxide of Copper, 58. Verdigris, 58. Applications of Verdigris, 59. 

Lead. —Occurrence of Lead, 59. Method of Obtaining Lead by Precipitation, 59. 
Obtaining Lead by Calcination, 60. Baw Lead, 61. Revivification of Litharge, 61. 
Properties of Lead, 62. Applications of Metallic Lead, 62. Manufacture of Shot, 62. 
Alloys of Lead, 62. 

Preparations of Lead. — Oxide of Lead, 63. Massicot, 63. Minium, Bed-lead, 63. 
Superoxide of Lead, 64. Combinations of Oxide of Lead, 64. Acetate of Lead, 64. 
Chromate of Lead, 64. Neutral or Yellow Chromate of Potassa, 64. Applications of 
the Chromates of Potassa, 65. Chrome Yellow or Chromate of Lead, 66. Chrome 
Bed, 66. Chrome Oxide or Chrome Green, 67. Chrome Alum, 67. White-lead, 67. 
English Method of Manufacturing White-lead, 68. French Method of Preparing White- 
lead, 69. Apparatus used in White-lead Manufacture at Clichy, 69. White-lead from 
Sulphate of Lead, 70. Theory of Preparing White-lead, 70. White-lead from Chloride 
of Lead, 70. Basic Chloride of Lead as a Substitute for White-lead, 71. Properties of 
White-lead, 71. Adulteration of White-lead, 72. Applications of White-lead, 72. 

Tin. —Occurrence and Mode of Obtaining the Metal, 73. Properties of Tin, 74, 
Tinning, 75. Tinning of Copper, Brass, and Malleable Iron, 75. Tinned Sheet-iron’ 
75. Moire Metallique, 75. 

Preparations of Tin. —Aurum Musivum, Mosaic Gold, 75. Tinsalt, 75. Nitrate of 
Tin or Physic, 76. Stannate of Soda, 76. 

Bismuth. —Occurrence and Mode of Obtaining, 76. Bismuth Liquation-Furnace, 76. 
Properties of Bismuth, 77. Applications of Bismuth, 77. 

Zinc. —Occurrence of Zinc, 77. Method of Extracting Zinc, 77. Distillation of Zinc in 
Muffles, 78. Distillation in Tubes, 79. Distillation of Zinc in Crucibles, 79. Mode 
of Obtaining Zinc from Sulphuret of Zinc, the Black-Jack of the English Miners, 79. 
Properties of Zinc, 79. Application of Zinc, 80. 

Preparations of Zinc. —Zinc-white, 80. White Vitriol, Sulphate of Zinc, 81. Chromate 
of Zinc, 81. Chloride of Zinc, 81. 

Cadmium, 82. 

Antimony. —Antimony, 82. Properties of Antimony, 84. 

Antimonial Preparations] in Technical Use. —Oxide of Antimony, 84. Black Sulphuret 
of Antimony, 85. Neapolitan Yellow, 85. Antimony Cinnabar, 85. 

Arsenic. —Arsenic, 85. Arsenious Acid, 85. Arsenic Acid, 86. Sulphurets of Arsenic, 
86. Bealgar, 87. Orpiment, 87. Rusma, 87. 

Quicksilver or Mercury. —Occurrence and Mode of Obtaining Mercury, 87. Method of 
Extracting Mercury pursued in Idria, 87. Spanish Method of Extracting Mercury, 
89. Method of Decomposing the Ore by the Aid of other Substances, go. Proper¬ 
ties of Mercury, 91. Applications of Mercury, gi. 

Preparations of Mercury. —Mercurial Compounds, 91. Chloride of Mercury, 91. Cin¬ 
nabar, 91. Fulminating Mercury, 92. Percussion-Caps, 93. 

Platinum. —Occurrence of Platinum, 93. Platinum Ores, 93. Wollaston’s Method of 
Extracting Platinum from its Ores, 94. Method of Deville and Debray, 95. Proper¬ 
ties of Platinum, 95. Black Platinum, Spongy Platinum, 95. Hammered or Cast 
Platinum, and its Applications, 95. Platinum Alloys, 96. Elayl-platino-chloride, 96. 

Silver. —Silver and its Occurrence, 96. Extraction of Silver from its Ores, 96. Smelting 
for Silver directly, 97. Extraction of Silver by Amalgamation, 97. European 
Amalgamation Process, 97. American Amalgamation Process, 98. Augustin’s 
Method of Silver Extraction, gg. Ziervogel’s Method, gg. Sundry Hydro-Metallur¬ 
gical Methods of Extracting Silver, 99. Extraction of Silver by the Dry Process 100. 
Mode of Preparing the Lead-containing Silver, 100. Refining Process, 100. Pattin- 
son’s Method, 101. Reduction by Means of Zinc, 102. The Ultimate Refining of 
Silver, 102. Chemically Pure Silver, 102. Properties of Silver, 102. Alloys of 
Silver, 103. Silver Alloy for Plate, &c., 103. Silver Assay, 103. Dry Assay, 103. 
Wet Assay, 104. Hydrostatical Assay, 104. Silvering, 104. Igneous or Fire 
Silvering, 104. Silvering in the Cold, 104. Silvering by the Wet Way, 10s. 
Nitrate of Silver, 105. Marking Ink, 105. ’ 

Gold.— Occurrence and Mode of Extracting Gold, 105. Mode of Extracting Gold, 103 
Extraction by Means of Mercury, 106. Smelting for Gold, 106. Treating’with 
Alkali, 106. Extraction of Gold from other Metallic Ores, 106. Extraction of Gold 
from Poor Minerals, 106. Refining Gold, 106. By Means of Sulphuret of Antimony, 
106. By the Aid of Sulphur, 107. Cementation Process, 107. Quartation, 107! 


CONTENTS. 


IX 


Refining Gold by the Aid of Sulphuric Acid, 107. Chemically Pure Gold, 108. Pro¬ 
perties of Gold, 108. Alloys of Gold, 109. Colour of Gold, iog. Testing the Fine¬ 
ness of Gold, iog. Applications of Gold, no. Gilding, no. Gilding with Gold- 
leaf, no. Gilding by the Cold Process, no. Gilding by the Wet Way, no. Fire¬ 
gilding, no. Cassius’s Purple, in. Salts of Gold, in. 

Manganese and its Preparations.— Manganese, in. Testing the Quality of Manganese, 
in. 

Permanganate of Potassa.— Permanganate of Potassa, 112. 

Aluminium.— Preparation of Aluminium, 113. Properties of Aluminium, 113. Applica¬ 
tions, 114. 

Magnesium.— Magnesium, 114. 

Electro-Metallurgy.— Application of G-alvanism, 114. Electrolytic Law, 114. Electro- 
typing, 115. Reproduction of Copper-plate Engravings, 115. Deposition of Metals, 
115. Electro-plating with Gold and Silver, 115. Gold Solution, 116. Silver Solu¬ 
tion, 116. Copper Solution, 116. Zinc and Tin Solution, 116. Etching by Gal¬ 
vanism, 117. Metallochromy, 117. Electro-stereotyping, 117. Glyphography, 117. 
Galvanography, 117. 


DIVISION II. 

crude materials and products of chemical industry. 

Carbonate of Potassa. —Sources whence Potassa is Derived, 118. Potassa Salts from the 
Stassfurt Salt Minerals, 118. Mode of Obtaining Potassa from Felspar, 122. 
Potassa Salts from Sea-water, 122. Potash from the Ashes of Plants, 122. Potash 
from Molasses, 125. Potassa Salts from Sea-weeds, i2g. Potassa Salts from Suint, 
132. Caustic Potassa, 133. 

Saltpetre, Nitrate of Potassa. —Saltpetre, 134. Occurrence of Native Saltpetre, 134. 
Mode of Obtaining Saltpetre, 135. Treatment of the Ripe Saltpetre Earth, 135. 
Preparation of Raw Lye, 136. Breaking up the Raw Lye, 136. Boiling down the 
Raw Lye, 136. Refining the Crude Saltpetre, 137. Preparation of Nitrate of 
Potassa from Chili Saltpetre, 138. Testing the Saltpetre, 140. Quantitative Estima¬ 
tion of the Nitric Acid in Saltpetre, 140. Uses of Saltpetre, 141. Nitrate of Soda, 141. 

Nitric Acid.— Methods of Manufacturing Nitric Acid, 142. Bleaching Nitric Acid, 143. 
Condensation of the Nitric Acid, 144. Other Methods of Nitric Acid Manufacture, 145. 
Density of Nitric Acid, 146. Fuming Nitric Acid, 147. Uses of Nitric Acid, 147. 

Technology of the Explosive Compounds—Gunpowder, and the Chemistry of Fireworks, 
or Pyrotechny. —On Gunpowder in General, 148. Manufacture of Gunpowder, 148. 
Mechanical Operations of Powder Manufacture, I4g. Pulverising the Ingredients, 
i4g. Mixing the Ingredients, i4g. Caking or Pressing the Powder, 150. Granula¬ 
tion of the Cake and Sorting the Powder, 150. Polishing the Granulated Powder, 
150. Drying the Pow r der, 151. Sifting the Dust from the Powder, 151. Properties 
of Gunpowder, 151. Composition of Gunpowder, 152. Products of the Combustion 
of Powder, 153. New Kinds of Blasting Powder, 154. Testing the Strength of Gun¬ 
powder, 154. White Gunpowder, 154. Chemical Principles of Pyrotechny, 155. 
The more commonly used Firework Mixtures, 156. Gunpowder, 156. Saltpetre and 
Sulphur Mixture, 156. Grey-coloured Mixture, 156. Chlorate of Potassa Mixtures, 
156. Friction Mixtures, Percussion Powders, 156. Mixture for Igniting the Cart¬ 
ridges of Needle-guns, 157. Heat-producing Mixtures, 157. Coloured Fires, 157. 

Nitroglycerine. —Nitroglycerine, 158. Nobel’s Dynamite, 160. 

Gun-cotton. — Gun-cotton, 160. Properties of Gun-cotton, 161. Gun-cotton as a Substi¬ 
tute for Gunpowder, 162. Other Uses of Gun-cotton, 162. Collodion, 162. 

Common Salt. — Occurrence, 163. Method of Preparing Common Salt from Sea-water, 163. 
Method of Obtaining Common Salt in Salines, 164. By Freezing, 165. By Artificial 
Evaporation, 165. Rock-salt, 165. Mode of Working Rock-salt, 167. Mode of 
Working Salt Springs, 167. Preparation of Common Salt from Brine, 168. 
Concentrating the Brine, 168. Enriching by Gradation, 1G8. Faggot Gradation, 168. 
Boiling down the Brine, 168. Properties of Common Salt, i6g. Uses of Common 
Salt, 170. 

Manufacture of Soda—Native Soda. —Occurrence of Native Soda, 170. 

Soda from Plants or Soda-Ash. —Soda from Soda Plants and from Beet-root, 171. 

Soda Prepared by Chemical Processes.— Soda from Chemical Processes,"172. Leblanc’s 
Process, 172. Sulphate or Decomposing Furnace, 172. New Decomposition Fur¬ 
nace, 173. Conversion of the Sulphate into Crude Soda, 174. Soda Furnace with 


CONTEXTS. 


& 


Rotatory Hearth, 175. Lixiviation of the Crude Soda, 176. Evaporation of the 
Ley, 1S0. Theory of Leblanc’s Process, 183. Utilisation of Soda Waste, 184. 
Schaffner’s Sulphur Regeneration Process, 185. Sundry Methods of Preparing Soda 
from Sulphate of Soda, 187. Direct Conversion of Common Salt into Soda, 188. 
Soda from Cryolite, 188. Soda from Nitrate of Soda, 189. Caustic Soda, 189. New 
Methods of Caustic Soda Manufacture, 189. Bicarbonate of Soda, 190. 

Preparation of Iodine and Bromine. — Preparation of Iodine, 191. Preparation from 
Kelp, igi. Stanford and Moride’s Method of Preparing Iodine from Carbonised Sea¬ 
weed, 192. Preparation of Iodine from Chili Saltpetre, 192. Properties and Uses of 
Iodine, 193. Preparation of Bromine, 193. 

Sulphur.— Sulphur, 194. Smelting and Refining Sulphur, 194.- Lamy’s Refining Appa¬ 
ratus, 196. Roll Sulphur, 197. Flowers of Sulphur, 197. Preparation of Sulphur 
from Pyrites, 197. Preparation of Sulphur by Roasting Copper Pyrites, 198. Sul¬ 
phur obtained as a By-product of Gras Manufacture, 198. Sulphur from Soda- 
Waste, 198. Production of Sulphur by the Reaction of Sulphuretted Hydrogen upon 
Sulphurous Acid, 198. Sulphur obtained by the Reaction of Sulphurous Acid on 
Charcoal, 198. By Heating of Sulphuretted Hydrogen, 198. Properties and Uses of 
Sulphur, 199. 

Sulphurous and Hyposulphurous Acid.— Sulphurous Acid, igg. Sulphite of Lime, 201. 
Hyposulphite of Soda, 201. 

Manufacture of Sulphuric Acid.— Sulphuric Acid, 201. Fuming Sulphuric Acid, 202. 
Ordinary or English Sulphuric Acid, 203. Present Manufacture of Sulphuric Acid, 
203. Use of Pyrites for the Preparation of Sulphurous Acid, 206. Chamber Acid, 
206. Concentration of Sulphuric Acid, 206. Concentration in Leaden Pans, 207. 
Concentration in Glass Retorts, 208. Other Methods of Sulphuric Acid Manufac¬ 
ture, 208. Properties of Sulphuric Acid, 209. 

Sulphide of Carbon.' —Sulphide of Carbon, 210. Carbon, 211. Chloride of Sulphur, 211. 
Hydrochloric Acid and Glauber’s Salt, or Sulphate of Soda. —Hydrochloric Acid, 211. 
Properties of Hydrochloric Acid, 213. Uses of Hydrochloric Acid, 213. Glauber’s 
Salt, 213. Uses of Sulphate of Soda, 214. Bisulphate of Soda, 214. 
Bleaching-powder and Hypochlorites. —Chlorine, 214. Preparation of Bleaching- 
powder, 214. Preparation of Chlorine without Manganese, 214. Apparatus for Pre¬ 
paring Chlorine, 216. Condensing Apparatus, 217. Utilisation of the Chlorine 
Production Residues, 218. Dunlop’s Process, 218. Gatty’s Process, 219. Hofmann’s 
Process, 219. Weldon’s Process, 219. Other Methods of Utilising the Residues, 219. 
Theory of the Formation of Bleaching-powder, 220. Properties of Bleaching- 
powder, 220. Chlorimetry, 221. Gay-Lussac’s Chlorimetric Method, 221. Perrot’s 
Test, 221. Dr. Wagner’s Method, 222. Chlorimetrical Degrees, 222. Alkaline 
Hypochlorites, 223. Chlorate of Potassa, 223. 

Alkalimetry. —Alkalimetry, 224. Volumetric Method, 224. Mohr’s Method, 225. 

Gruneberg’s Method of Estimating the Value of Potash, 226. 

Ammonia and Ammoniacal Salts. —Ammonia, 226. Preparation of Liquid Ammonia, 227. 
Inorganic Sources of Ammonia, 228. Organic Sources of Ammonia, 229. Ammonia 
from Gas-water, 230. Mallet’s Apparatus, 230. Rose’s Apparatus, 232. Lunge’s 
Apparatus, 232. Ammonia from Lant, 234. Ammonia from Bones, 235. Ammonia 
as a By-product of Beet-root Sugar Manufacture, 236. Technically Important 
Ammoniacal Salts, 236. Sulphate of Ammonia, 238. Carbonate of Ammonia, 238. 
Nitrate of Ammonia, 238. 

Soap Making. —Soap, 239. Raw Materials of Soap Boiling, 239. Ley, 242. Theory of Saponi¬ 
fication, 242. Chief Varieties of Soap, 243. Olive Oil Soap, 244. Oleic Acid Soap, 245. 
Resin Tallow Soaps, 245. Fulling Soaps, 245. Soft Soap, 246. Various other 
Soaps, 247. Toilet Soaps, 247. Transparent Soap, 248. Uses of Soap, 248. Soap 
Tests, 248. Insoluble Soap, 249. 

Boric or Boracic Acid, and Borax.— Theory of the Formation of the Native Boracic Acid, 

250. The Production of Boracic Acid, 250, Properties and Uses of Boracic Acid, 

251. Borax, 252. Borax from Boracic Acid, 252. Purifying the Borax, 254. Octa¬ 
hedral Borax, 255. Uses of Borax, 255. Diamond Boron or Adamantine, 256. 

Production of Alum, Sulphates of Alumina, and Aluminates. —Alum, 256. Material of 
Alum Manufacture, 256. Preparation of Alum from Alum-stone, 257. Preparation 
of Alum from Alum-shale and Alum-earths, 257. Alum-shale, 237. Alum-earths, 

257. Preparation of Alum, 257. Roasting the Alum-earths, 257. Lixiviation, 257. 
Evaporation of the Ley, 257. Alum Flour, 258. Washing and Re-crystallisation, 

258. Preparation of Alum from Clay, 258. Preparation of Alum from Cryolite, 258. 
Preparation of Alum from Bauxite, 259. Preparation of Alum from Blast-furnace 
Slag, 260. Alum from Felspar, 260. Properties of Alum, 260. Ammonia-alum, 260. 


CONTENTS. 


si 


Soda-alum, 261. Sulphate of Alumina, 261. Aluminate of Soda, 262. Uses of 
Alum and of Sulphate of Alumina, 263. Acetate of Alumina, 263. 

Ultramarine. —Ultramarine, 264. Native Ultramarine, 264. Artificial Ultramarine, 264. 
Raw Materials, 264. Manufacture of Ultramarine, 265. Preparation of Soda Ultra- 
marine, 266. Preparation of Silica Ultramarine, 267. Constitution of Ultramarine, 
267. Properties of Ultramarine, 267. 


DIVISION III. 

TECHNOLOGY OF GLASS, CERAMIC WARE, GYPSUM, LIME, AND MOllTAR 

Glass Manufacture. — Definition and General Properties of Glass, 268. Classification 
of the Various Kinds of Glass, 268. Raw Materials used in Glass Making, 269. 
Utilisation of Refuse Glass, 270. Bleaching, 270. The Melting Vessel, 270. The 
Glass Oven, 271. Preparation of the Material, and Melting, 274. Drying the 
Materials, 274. Melting the Glass Material, 275. Clear-melting, 275. Cold-stoking, 

275. Defects in Glass, 276. Various Kinds of Glass, 276. Plate or Window Glass, 

276. Tools, 277. Crown Glass, 277. Sheet Glass or Cylinder Glass, 278. Plate 
Glass, 279. The Melting and Clearing, 280. Casting and Cooling, 281. Polishing, 
281. Slivering, 281. Silvering by Precipitation, 281. Platinising, 282. Bottle 
Glass, 282. Pressed and Cast-glass, 283. Water-glass, 283. Stereochromy, 285. 
Crystal Glass, 285. Polishing, 286. Optical Glass, 286. Strass, 288. Coloured 
Glass and Glass Staining, 28g. Glass Painting, 289. Enamel, Bone Glass, Alabaster 
Glass, 2go. Cryolite Glass, 291. Ice Glass, 291. Hsematinon Astralite, 291. Aven- 
turin Glass, 291. Glass Relief, 291. Filigree, or Reticulated Glass, 292. Millifiore 
Work, 292. Glass Pearls, 292. Blown Pearls, 292. Hyalography, 292. 

Ceramic or Earthenware Manufacture.— Clays aud their Application—Felspar, 293. 
Kaolin or Porcelain Clay, 293. The Technically Important Qualities of the Clays, 293. 
Colour, 294. Plasticity, 294. Kinds of Clay, 294. Potter’s Clay, 295. Walkerite, 
295. Marl, 295. Loam, 296. Composition of Kaolin, 296. Kinds of Clay Ware, 296. 

I. Hard Porcelain.— Grinding and Mixing the Material, 297. Drying the Mass, 298. 

Kneading the Dried Mass, 298. The Moulding, 298. The Potter’s Wheel, 298. 
Moulding in Plaster-of-Paris Forms, 299. Casting, 299. Preparation of Porcelain 
Articles without Moulds, 299. Glazing, 299. Drying the Porcelain, 299. Porcelain 
Glaze, 300. Applying the Glaze, 300. Immersion, 300. Dusting, 300. Watering, 
300. By Volatilisation or Smearing, 300. Lustres and Flowering Colours, 301. The 
Capsule or Sagger, 301. The Porcelain Oven, 301. Emptying the Oven and Sorting 
the Ware, 302, Faulty Ware, 302. Porcelain Painting, 302. Ornamenting the Por¬ 
celain, 303. Bright Gilding, 303. Silvering and Platinising, 303. Lithophanie, 303. 

II. Tender Porcelain. —French Fritte Porcelain, 304. English Fritte Porcelain, 304. 
Parian and Carrara, 304. 

III. Stoneware. —Stoneware, 305. Stoneware Ovens, 306. Lacquered Ware, 307. 

IV. Fayence Ware. —Fayence Ware, 307. Ornamenting Fayence, 308. Flowing Colours, 
309. Lustres, 309. Etruscan Vases, 3og. Clay Pipes, 309. Water Coolers, 309. 

V. Common Pottery. —Common Pottery, 310. Burning, 310. 

VI. Brick and Tile Making, &c. —Bricks, 310. Terra Cotta, 311. Brick Material, 311. 
Preparation of the Clays, 311. Moulding the Brick, 312. Brick Moulding by 
Machinery, 312. Bricks from Dried Clay, 314. The Burning of the Bricks, 315. 
Annular Kilns, 317. Field Burning, 318. Dutch Clinkers, 318. Roofing and Dutch 
Tiles, 318. Drain and Gutter Tiles, 318. Floating Bricks, 318. Fire-bricks, 319. 
Sanitary Ware, 321. Crucibles, 321. 

Lime and Lime-Burning.— Lime, 322. Properties, 322. Lime-Burning, 322. Occasional 
or Periodic Kilns, 323. The Continuous Kilns, 324. Kilns for Burning Lime and 
Bricks, 325. Properties of Lime, 325. Slaking Lime, 326. Uses of Lime, 326 
Mortar.— Mortar, 326. 

A. Common or Air-Setting Mortar. —Setting of the Mortar, 327. 

B. Hydraulic Mortar. —Hydraulic Mortar, 327. Cement, 327. Artificial Cements, 328. 

Manufacture of Artificial Cement in Germany, 330. The Setting of Hydraulic 
Mortars, 331. 

Gypsum and its Preparation.— Occurrence, 333. Nature of Gypsum, 333. The Burning 
of Gypsum, 333. Kilns or Burning Ovens, 334. Grinding the Gypsum, 335. Uses 
of Gypsum, 335. Gypsum Casts, 336. Hardening of Gypsum, 336. 


xii 


CONTENTS. 


DIVISION IV. 

VEGETABLE FIBRES AND THEIR TECHNICAL APPLICATION. 

The Technology op Vegetable Fibre—Flax. —Flax, 338. Hot Water Cleansing, 339. 
Beating or Batting the Flax, 339. Combing the Flax, 340. Tow or Tangled Fibre, 
340. Flax Spinning, 340. Weaving the Linen Threads, 340. Linen, 340. 

Hemp. —Hemp, 340. Its Substitutes, 340. 

Cotton. —Cotton, 342. Species of Cotton, 342. Cotton Spinning, 342. Fine Spinning, 
343. Yarn, 343. Cotton Fabrics, 343. Substitutes for Cotton, 343. Detecting 
Cotton in Linen Fabrics, 343. 

Paper Making. —History of Paper, 345. Materials of Paper Manufacture, 346. Sub¬ 
stitute for Bags, 346. Mineral Additions to the Bags, 346. Manufacture of Paper by 
Hand, 346. Cutting and Cleaning the Bags, 347. The Separation of the Bags for 
Half-stuff and Whole-stuff, 347. Stamp Machine, 347. The Hollander, 347. 
Bleaching the Pulp, 349. Anticlilore, 349. Blueing, 350. Sizing, 350. 

A. Hand Paper. —Straining the Paper Sheets, 350. Pressing the Paper, 351. Drying the 

Paper, 351. Sizing the Paper, 351. Preparing the Paper, 351. The Different 
Kinds of Paper, 351. 

B. Machine Paper. —Manufacture of Machine Paper, 352. Paper Cutting Machine, 353. 

C. Pasteboard and Other Paper. — Making Pasteboard, 353. Coloured Paper, 355. 

Parchment Paper, 355. 

Starch.— Nature of Starch, 356. Sources of Starch, 357. Starch from Potatoes, 357. 
Drying the Potato Starch, 358. Preparation of Wheat Starch, 358. Constituents 
and Uses of Commercial Starch, 360. Bice Starch, Chesnut Starch, Cassava Starch, 
Arrow-root, 360. Sago, 361. Dextrine, 361. 

Sugar Manufacture. —History of Sugar, 362. Nature of Sugar, 362. 

Cane Sugar. —Sugar from the Sugar-cane, 364. Components of the Sugar-cane, 364. 
Preparing the Baw Sugar from the Sugar-cane, 365. Varieties of Sugar, 366. 
Molasses, 366. Befining the Sugar, 366. Production of Baw Sugar, 367. 

Beet-root Sugar. —Its Nature, 367. Species of Beet, 367. Chemical Constituents of 
the Beet, 368. Saccharimetry, 369. Mechanical Method, 369. Chemical Method, 
369. Ferment Test, 370. Physical Method, 370. Preparation of Sugar from the 
Beet, 370. The Besidue, 372. Components of the Juice, 373. Other Methods of 
De-Liming the Juice, 374. Purifying with Baryta, 374. The Filter, 375. Dumont’s 
Filter, 375. Evaporation Pans, 375. Vacuum Pans, 377. Evaporating the Juice, 
380. Draining the Crystals, 381. The Centrifugal Drier, 381. Bemoving the Sugar 
from the Form, 381. Beet Molasses, 382. Sugar-candy, 382. 

Crape Sugar. —Grape Sugar, 383. Preparation of Grape Sugar, 384. Composition of 
Starch Sugar, 386. Uses of Grape Sugar, 386. 

Fermentation. —Fermentation, 386. Vinous Fermentation, 387. Yeast, 387. Condi¬ 
tions of Alcoholic or Vinous Fermentation, 389. 

Wine-Making. —Wine, 390. The Vine and its Cultivation, 390. Vintage, 390. The Pres¬ 
sing of the Grapes, 391. The Centrifugal Machine, 391. Chemical Constituents of 
the Must, 391. The Sugar of the Grape, 392. The Fermentation of the Grape 
Juice, 393. Drawing Off and Cashing the Wine, 393. Constituents of Wine, 393. 
Maladies of Wines, 396. Ageing and Conservation of Wines, 397. Clearing or 
Fining the Wine, 399. The Besidue or Waste of Wine Making, 399. Effervescing 
Wines, 399. The Improving of the Wine Must, 401. 

Beer-Brewing. —Beer, 403. Materials of Beer-Brewing, 403. Hops, 404. Quality of the 
Hops, 404. Substitutes for Hops, 405. Water, 405. The Ferment, 405. The Pro¬ 
cess of Beer Brewing, 405. The Malting, 405. The Bruising of the Malt, 408. 
Mashing, 408. Decoction Method, 409. Thick Mash Boiling, 409. Augsburg 
Method, 410. Infusion Method, 410. Extractives of the Wort, 411. Boiling the 
Wort, 411. Adding the Hops, 412. Cooling the Wort, 413. The Fermentation, 414. 
Sedimentary Fermentation, 415. After-Fermentation in the Casks, 416. Surface- 
Fermentation, 417. Steam-Brewing, 418. Constituents of Beer, 418. Beer-Testing 
420. Balling’s Saccharometrical Beer Test, 420. Fuchs’s Beer Test, 422. By-pro 
ducts of the Brewing Process, 423. 

Preparation or Distillation of Spirits. —Alcohol, 424. Alcohol and its Technicallv 
Important Properties, 424. Baw Materials of Spirit Manufacture, 425. 

A. Preparation of a Vinous Mash. —Vinous Mash from Cereals, 426. The Bruising, 426. 
The Mixing with Water, 426. The Cooling of the Mash, 426. The Fermentation of 


CONTENTS. 


xiii 

the Mash, 427. Mash from Potatoes, 427. Mash with Sulphuric Acid, 428. The 
Fermentation of the Potato Mash, 429. Mash from Roots, 429. Spirits from the 
By-products of Sugar Manufacture, 430. Spirits from Wine and Marc, 430. 

B. Distillation of the Vinous Mash.— Distillation of the Mash, 431. The Distilling 
Apparatus, 432. Improved Distilling Apparatus, 432. Dorn’s Apparatus, 433. Pis- 
torius’s Apparatus, 435. Gall’s Apparatus, 435. Schwarz’s Apparatus, 436. 
Siemens’s Apparatus, 440. Continuous Distilling Apparatus, 440. Tangier’s Appa¬ 
ratus, 443. Removing the Fusel Oils—Defuseling, 445. Yield of Alcohol, 446. 
Alcoholometry, 447. Areometer, 447. Relation of Brandy Distilling to Agriculture, 
448. The Residue or Wash, 448. Dry Yeast, 449. So-called Artificial Yeast, 450. 
Vienna Yeast, 450. Duty on Spirits, 451. 

Bread Baking. —Modes of Bread Making, 451. The Details of Bread Baking, 451. The 
Mixing of the Dough and the Kneading, 452. Kneading, 452. Kneading Machines, 
453. The Oven, 454. Substitutes for the Ferments, 456. Yield of Bread, 459. 
Composition of Bread, 459. Impurities and Adulteration of Bread, 460. 

The Manufacture of Vinegar.— Vinegar and its Origin, 460. 

A. Preparation of Vinegar from Alcoholic Fluids. —Vinegar from Alcohol, 461. Pheno¬ 

mena of Vinegar Formation, 462. The Older Method of Vinegar Making, 462. 
Quick Vinegar Making, 463. Vinegar from Sugar-beet, 466. Vinegar with the help 
of Mycoderma Aceti, 466. Vinegar with the help of Platinum Black, 467. Testing 
Vinegar, 467. Acetometry, 468. 

B. Preparation of Vinegar from Wood Vinegar.— Wood Vinegar, 469. Purifying Wood 

Vinegar, 471. Wood Spirit, 472. 

The Preservation of Wood.— On the Durability of Wood in General, 472. Preservation 
of Wood in Particular, 474. Drying Wood, 474. Elimination of the Constituents of 
the Sap, 474. Air Drains, 475. Chemical Alteration of the Constituents of the Sap, 
475. Mineralising Wood, 476. Boucherie’s Method of Impregnation, 477. 

Tobacco. —Tobacco, 477. Chemical Composition of the Tobacco Leaf, 478. Manufacture 
of Tobacco, 478. Smoking Tobacco, 479. Snuff, 480. 

Technology of Essential Oils and Resins. —Essential Oils and Resins, 480. Prepara¬ 
tion of Essential Oils, 481. Preparation of Essential Oils by Pressure, 481. Extrac¬ 
tion of Essential Oils by Means of Fatty Oils, 481. Properties and Uses of 
Essential Oils, 481. Perfumery, 481. Chemical Perfumes, 482. Preparation of 
Cordials, 482. Resins, 483. Use of Resins as Sealing-wax, 483. Asphalte, 484. 
Caoutchouc, 484. Solvents of Caoutchouc, 485. Properties and Use of India-rubber, 
486. Vulcanised Caoutchouc, 486. Production and Consumption of Caoutchouc, 486. 
Gutta-percha, 486. Solvents of Gutta-percha, 487. Uses of Gutta-percha, 487. 
Mixture of Gutta-percha and Caoutchouc, 488. Varnishes, 488. Oil Varnishes, 
488. Gold Size, 489. Printing Ink, 489. Oil Varnishes, 489. Spirit Varnish, 489. 
Coloured Spirit Varnishes, 4go. Turpentine Oil Varnishes, 490. Polishing the 
Dried Varnish, 490. Pettenkofer’s Process for Restoring Pictures, 490. 

Cements, Lutes, and Putty. —Cements, 491. Lime Cements, 4gi. Oil Cements, 491. 
Resin Cements. 492. Iron Cement, 493. Paste, 493. 


DIVISION V. 

ANIMAL SUBSTANCES AND THEIR, INDUSTRIAL APPLICATION. 

Woollen Industry.— Origin and Properties of Wool, 494. Chemical Composition of Wool, 
495. Properties of Wool, 497. Colour and Gloss, 497. Preparation of Wool, 497. 
Wcol Spinning, 498. I. Washing, 498. II. Dyeing, 498. III. Willowing or Devilling, 
498. Oiling or Greasing, 498. V. The Carding, 498. VI. Roving, 499. Artificial 
Wool, 499. Weaving the Cloth, 499. Washing and Milling the Bough Cloth, 499. 
Teasling and Shearing the Cloth, 499. Dressing the Cloth, 499. Other Clotl 
Fabrics, 500. Worsted Wool, 500. 

Silk.— Silk, 501. Sericiculture—Varieties of Silkworms, 501. Manipulation of the Silk, 
503. The Throwing of Silk, 504. Conditioning or Testing of Silk, 504. Scouring or 
Boiling the Gum out of Silk, 504. Weaving of Silk, 505. Means of Distinguishing 
Silk from Wool and from Vegetable Fibre, 506. 

Tanning. —Tanning, 508. Anatomy of Animal Skin, 508. 

I. Red- or Bark-Tanning. —Tanning Materials, 509. Oak Bark, 509. Sumac, 510. 
Dividivi, 511. Nut Galls, 511. Valonia Nuts, 511. Chinese Galls, 511. Cutch, 512. 
Kino, 512. Estimation of the Value of the Tanning Materials, 512. The Skins, 513. 
The Several Operations, 513. Cleansing the Hides, 514. Cleansing the Flesh 



xiv CONTENTS. 

Side, 514. Cleansing the Hair Side, 514. Stripping off the Hair, 515. Swelling the 
Hides, 515. The Tanning, 516. Tanning in the Barli, 516. Tanning in Liquor, 517. 
Quick Tanning, 517. Dressing or Currying the Leather, 518. Sole Leather, 518. 
Upper Leather, 518. The Paring, 518. The Scraping or Smoothing, 518. Graining 
the Leather, 5ig. Polishing with Pumice-stone, 5ig. Eaising the Grain slightly 
with Pommels of Cork, 5ig. Smoothing with Tawer’s Softening Iron, 5ig. Rolling, 
5ig. Finishing Off, 5ig. Greasing, 5ig. Yufts, Russia Leather, 520. Morocco 
Leather, 520. Dressing Morocco Leather, 521. Cordwain, Cordovan Leather, 521. 
Lacquered Leather, 521. 

II. Tawing. —Tawing, Preparation of White Leather, 522. Common Tawing, 522. Hun¬ 
garian Tawing Process, 524. Glove Leather, 524. Knapp’s Leather, 525. 

HI. Samian ok Oil-Tawing Process. —Samian Tawing Process, 525. Parchment, 527. 
Shagreen, 527. 

Glue Boiling. —General Observations, 528. Leather Glue, 52g. Treating with Lime, 
52g. Boiling the Materials, 530. Practioned Boiling, 530. Moulding, 531. Drying 
the Glue, 531. Glue from Bones, 532. Liquid Glue, 533. Test for the Quality 
of Glue 533. Isinglass, 535. Substitutes for Glue, and New Preparations obtained 
from Glue, 536. 

Manufacture of Phosphorus. —General Properties, 537. Preparation of Phosphorus, 
537. Burning of the Bones to Ash, 538. Decomposition of the Bone-ash by 
Sulphuric Acid, 538. Distillation of Phosphorus, 53g. Refining and Purifying the 
Phosphorus, 540. Moulding the Refined Phosphorus, 541. Other Proposed Methods 
of Preparing Phosphorus, 543. Fleck’s Process, 543. Gentele, Gerland, Minary, 
and Soudry’s Methods of Preparing Phosphorus, 544. Properties of Phosphorus, 544. 
Amorphous or Red Phosphorus, 545. Properties of Amorphous Phosphorus, 546. 

Requisites for Producing Fire. —Generalities and History, 546. Manufacture of Lucifer 
Matches, 548. The Preparation of the Wood Splints, 548. The Preparation of the 
Combustible Composition, 54g. Dipping and Drying the Splints, 550. Anti- 
Phosphor Matches, 552. Wax or Yesta Matches, 553. 

Animal Charcoal. —Animal Charcoal, 553. Preparation of Bone-black, 553. Properties 
of Bone-black, 554. Testing Bone-black, 554. Revivification (re-burning) of Char¬ 
coal, 555. Substitutes for Bone-black, 555. 

Milk. —Milk, 556. Whey, 557. Lactose, Sugar of Milk, 557. Means to Prevent Milk 
becoming Sour, 557. Testing Milk, 557. Uses of Milk, 558. Butter, 558. Chemical 
Nature of Butter, 55g. Cheese, 55g. 

Meat. —Generalities, 562. Constituents of Meat, 562. The Cooking of Meat, 563. The 
Boiling of Meat, 564. Preservation of Meat, 564. Preservation of Meat by with¬ 
drawal of Water, 565. Salting Meat, 565. Smoking or Curing Meat, 566. 


DIVISION VI. 

DYEING AND CALICO PRINTING. 

On Dyeing and Printing in General. —Dyeing and Printing in General, 56S. Dyes, 568. 
Lake Pigments, 56g. Colouring Materials, 56g* The Coal-Tar Colours : Coal-Tar, 
4 56g. Benzol, 570. Nitro-benzol, 572. Aniline, 573. 

I. ANiLiNiE Colours. —Aniline Colours, 575. Aniline Red, 575. Aniline Violet, 577. 

Anilne Blue, 578. Aniline Green, 578. Aniline Yellow, Aniline Orange, 57g. 
Aniline Black, 57g. Aniline Brown, ^yg. 

II. Carbolic Acid Colours. —Carbolic Acid Dyes, 580. Picric Acid, 580. Phenicienne, 
581. Grenate Brown, 581. Coralline, 581. Azuline, 581. Pigment Directly from 
Nitro-benzol, 581. 

III. Naphthaline Pigments. —Naphthaline, 581. Martius Yellow, 582. Magdala Red, 
583. Naphthaline Blue and Naphthaline Violet, 583. 

IV. Anthracen Pigments. —Anthracen Pigments, 584. 

V. Pigments from Cinchonine. —Cinchoine Pigments, 585. 

Red Pigments Occurring in Plants and Animals. —Red Dye Materials—Madder, 58G. 
Madder Lake, 587. Flowers of Madder, 587. Azale, 587. Garancine, 587. Garan- 
ceux, 587. Colorine, 588. Brazil or Camwood, 588. Sandal Wood, 588. Safflower, 
58g. Cochenille or Cochineal, 58g. Lac Dye, 5go. Orchil and Persio, 5go. Less’ 
Important Red Dyes, 5gi. 

Blue Dye Materials. —Indigo, 5gi. Properties of Indigo, 5g2. Testing Indigo, 5g2. 
Berzelius’s Indigo Test by Reduction, 5g3. Penny’s Test, 5g3. Indigo Blue, 5gl.* 
Logwood or Campcachy, 5gq. Litmus, 5gq. 


CONTENTS. 


xx 


Bellow Dyes.— lellow-wood, Fustic, 595. Young Fustic, French Fustet, 595. Annatto 
or Arnotto, 595. Yellow Berries or Simply Berries, 596. Turmeric, 596. Weld 
596. Quercitron Bark, 596. Brown, Green, and Black Dyes, 596. 

Bleaching. —Bleaching, 597. Bleaching of Silk, 599. 

Dyeing op Spun Yarn and Woven Textile Fabrics. —Dyeing, 599. Mordants, 601. 
Dyeing Woollen Fabrics, 601. Dyeing Wool Blue, 601. Indigo Blue, 602. ’Blue 
Yats, 602. Saxony Blue, 603. Recovering Indigo from Rags, 604. Berlin or Prussian 
Blue on Wool, 604. Dyeing Blue with Logwood and a Copper Salt, 604. Dyeing 
Yellow, 604. Dyeing Wool Red, 605. Green Dyes, 605, Mixed Shades, 605. Black 
Dyes, 605. White Cloth, 606. Silk Dyeing, 606. Calico Dyeing, 608. Turkey Red 
608. Dyeing Linen, 6og. 

The Printing of Woven Fabrics.— Printing of Woven Fabrics, 609. Mordants, 609. 
Thickenings, 610. Resists, or Reserves, 610. Discharges, 611. Acid Discharges, 
611. Oxidising Agents as Discharges, 611. Reducing Agents as Discharges, 611.’ 
Calico Printing, 612. Topical or Surface Colours, 613. Discharge Style, 614. 
Aniline Printing, 614. Hotpressing, Finishing, and Dressing, 616. Printing Linen 
Goods, 616. Printing Woollen Goods, 616. Printing Silk Goods, 616. Mandarin 
Printing, 616. Bandanas. 616. 


DIVISION VII. 

THE MATERIALS AND APPARATUS FOR PRODUCING ARTIFICIAL LIGHT. 

Artificial Illumination in General, 617. Flame, 618. 

I. Artificial Light from Candles.— Light from Candles, 620. Manufacture of Stearine 

Candles, 621. Preparation of Fatty Acids by Means of Lime, 621. Saponification 
with* Less Lime, 623. Saponification by Means of Sulphuric Acid, 624. Sapo¬ 
nification with Water and High Pressure, 626. Manufacture of Fatty Acids by 
Means of Superheated Steam and Subsequent Distillation, 627. Candle Making, 
627. Moulding the Candles, 628. Tallow Candles, 629. Paraffin Candles, 630. 
Candles from Fatty Acids, 631. Wax Candles, 631. Other Kinds of Wax, 632. 
The Making of Wax Candles, 633. Sperm or Spermaceti Candles, 634. Glyce¬ 
rine, 634. 

II. Illumination by Means of Lamps.— Illumination with Fluid Substances, 636. Puri¬ 

fying or Refining the Oils, 636. Lamps, 636. Various Kinds of Lamps, 639. 
Suction Lamps, 639. The Lamp with Constant Oil Level, 640. Pressure Lamps, 
641. Mechanical Lamps, 642. Clockwork Lamp, 642. Moderateur or Moderator 
Lamp, 642. Petroleum Oil and Paraffin Oil Lamps, 644. 

III. Gas. —General Introduction and Historical Notes, 645. Raw Materials of Gas 
Lighting, 646. Coal-Gas, 646. Products of the Distillation, 647. Manufacture of 
Coal-Gas, 648. Retorts, 648. Mouth-piece and Lid of Retorts, 649. Retort Fur¬ 
naces, 650. Charging the Retorts and Distillation, 650. The Hydraulic Main, 650. 
Cooling or Condensing Apparatus, 652. The Scrubber, 653. Exhauster, 654. 
Purifying Gas, 654. Gas Holders, 656. Distribution of Gas, 660. Hydraulic Valve, 
66r. Pressure Regulator, 661. Testing Illuminating Gas, 661. Methods of 
Testing Illuminating Gas, 662. Gas Meters, 664. Burners, 665. Gas Lamps, 665. 
By-Products of Coal-Gas Manufacture, 665. Composition of Coal-Gas, 668. Wood 
Gas, 668. Method of Wood Gas Manufacture, 669. Wood Gas Burners, 670. Peat 
Gas, 670. Water Gas, 671. Gillard’s Gas, Platinum Gas, 672. Carburetted Water 
Gas, 672. White’s Hydrocarbon Process, 673. Leprince’s Water Gas, Isoard’s 
Gas, 674. Baldamus and Grune’s Gas, 674. Carburetted Gas, 674. Air Gas, 674. 
Oil Gas, Resin-Gas, 674. Gas from Suint, 675. Gas from Petroleum Oil, or Oil 
from Bituminous Shales, 675. Petroleum Gas, 676. Resin Gas, 678. Lime-Light, 
678. Tessie du Motay’s Method of Illumination, 679. Magnesium Light, 679. 
Chatham Light, 680. Electric Light, 680. 

Paraffin and Solar or Petroleum Oils. —Paraffin Oils,' 683. Manufacture of Paraffin, 
683. Preparation of Paraffin from Petroleum, 684. Paraffin from Ozokerite and 
Neftgil, 684. Paraffin from Bitumen, 685. Preparation of Paraffin by Dry Distilla¬ 
tion, 685. Preparation of the Tar, 685. Condensation of the Vapours of the Tar, 
686. Properties of Tar, 687. Mode of Operating with the Tar, 688. Distillation 
of the Tar, 688. Treatment of the Products of Distillation, 68g. Rectification of 
the Crude Oils, 68g. Refining of the Crude Paraffin, 690. Hubner’s Method of 
Preparing Paraffin, 690. Yield of Paraffin, 691. Brown-coal, 691. Properties of 
Paraffin, 692. Paraffin Oil, 693. Preparation of Mineral Oil, 694. 


XVI 


CONTENTS. 


Petroleum.— Petroleum Oil and its Occurrences, 695. Origin and Formation of Petro- 
leum, 695. Refining of Crude Petroleum, 696. Constitution of Petroleum, 696. 
Technology of Petroleum, 697 


DIVISION VIII. 

FUEL AND HEATING APPARATUS. 

A. Fuel. —Fuel, 698. Combustibility, 698. Inflammability, 698. Calorific Effect, 698. 
Determination of Combustive Power, 699. Karmarsch’s Evaporation Method, 699. 
Berthier’s Reduction Method, 700. Elementary Analysis, 700. Stromeyer’s Test, 
701. Pyrometrical Calorific Test, 701. Mechanical Equivalent of Heat, 702. 

Wood. —Wood, 702. Constituents of Wood, 703. Heating Value of Wood, 704. Wood 
Charcoal, 704. Carbonisation of Wood, 705. Carbonisation in Heaps, 705. Con¬ 
struction of the Heap, 705. Charcoal Burning, 706. Carbonisation in Beds, 706. 
Carbonisation in Ovens or Kilns, 706. Carbonisation of Wood in Ovens, 708. Pro¬ 
perties of Charcoal, 710. Composition of Wood Charcoal, 711. Combustibility and 
Heating Effect, 711. Charbon-Roux; Torrified Charcoal, 711. Roasted Wood; 
Bois-Roux, 712. 

Peat —Peat, 712. Drying Peat, 713. Heating Effect of Peat, 715. New Method of 
Utilising Peat, 715. 

Carbonised Peat. —Carbonised Peat, 715. 

Brown-coal. —Brown-coal, 716. Brown-coal as Fuel, 717. 

Pit Coal, or Coal. —Coal, 717. Accessory Constituents of Coal, 718. Classification of 
Coals, 718. Anthracite, 719. Caking Coal, 719. Calorific Effect, 721. Evaporative 
Effect of Coals, 721. Boghead Coal, 722. 

Petroleum as Fuel. —Petroleum as Fuel, 722. 

Coke. —Coke, 723. Coking in Heaps, 724. Coking in Ovens, 724. Properties' of Coke, 
729. Composition of Coke and its Value as Fuel, 729. 

Artificial Fuel. —Artificial Fuel, 729. Peras, J2g. Briquettes, 730. 

Gaseous Fuel. —Gaseous Fuel, 730. Gas for Heating Purposes, 731. 

Heating Apparatus. —Warming, 731. 

Heating Dwelling Houses. —Heating Dwelling Houses, 732. Direct Heating, 732. 
Chimney Heating, 733. Stove Heating, 733. Iron Stoves, 734. Fire-clay Stoves, 
734. Compound Stoves, 735. Air Heating, 737. Calorifiers, 738. Flue Heating, 
739. Hot Water Heating, 739. Heating with Steam, 740. Combination of Steam 
and Hot Water Heating, 740. Gas Heating, 740. Heating without Ordinary Fuel, 
740 - 

Boiler Heating and Consumption of Smoke.— Boiler Heating, 740. Smoke Consuming 
Apparatus, 741. Step Grate, 742. Etage, or Stage Grate, 743. Movable Grate, 
743 * Chain Grates, 743. Rotating Grate, 744. Improved Fuel Supply, 744. Pult 
Fires, 744. Vogl’s Grate, 744. Boquillon’s Grate, 744. Apparatus of Cutler and 
George, 744. Apparatus with Unequal Distribution, 744. Consumption of Smoke 
by the Aid of Collateral Air Currents, 745. Gall’s Fireplace, 745. Resume, 745. 


INTRODUCTION. 


Man’s labour, considered from an economical point of view, is of a threefold kind, 
being either productive, improving, or converting. We distinguish likewise between 
the productions obtained from the soil taken in its widest sense, and between com¬ 
merce and manufacturing industry. 

The department of labour, the object of which is to prepare and render fit for use 
the raw materials yielded by nature, is that which, in a more restricted sense, is 
called manufacturing industry, and the description and elucidation of the methods 
by which this object is attained is called technology, from rex^rj and Xoyor. Taken 
in a general sense, this word would apply to all trades, arts, and manufactures, 
whatsoever; exclusive, however, of actual artist’s work—notwithstanding the 
latter exceeds the industries in respect of the money-value of its productions—and 
exclusive, also, of such trades as tailoring, dress- and shoe-making, in which only 
certain commodities from materials that have been produced by manufacturing 
industry are worked up. 

Mining and quarrying operations, as well as commerce, do not belong to tech¬ 
nology, because the former deal with the getting to hand of naturally existing 
materials, and the object of the latter is either the carrying and distributing of the 
products from various parts of the world to the wholesale consumers, or the pro¬ 
ducts of different kinds of one and the same country to the population thereof. The 
position of some industries is somewhat difficult to define in this sense, for while 
metallurgy and the knowledge of tools and machinery are undoubtedly an integral 
portion of technology, taken in its widest sense, the construction of railways, roads, 
and bridges, as well as shipbuilding, architecture, artillery science, &c., do not come 
within the province of technology, but belong either to engineering science or are 
specialities to be separately taught and described. 

Technology is not a self- contained science which possesses its own peculiar doctrine 
and foundation ; it simply borrows the principles and experience obtained by 
mechanical and natural sciences, always taking into consideration the best mode of 
applying these principles to the preparation of raw materials to become objects suit¬ 
able for use. Technology is accordingly practical natural science, having for its 
object the reduction of manufacturing industry to the natural principles upon which 
it is based, and teaching the most advantageous methods and processes by which the 
raw materials are prepared for use. Raw products, which are either in the con¬ 
dition nature yields them, or which have already been in the hands of the manu- 



? CHEMICAL TECHNOLOGY. 

facturer, are changed by the labour of men, either in their outw ard form only, or in 
their inner composition, and upon this distinction is based the division of technology 
into mechanical and chemical; the former division embraces such industries as have 
only for their object the changing, altering, and modifying the form and shape of the 
raw material, its inner composition remaining unaltered; as instances we quote the 
joiner and carpenter working in wood, the making of iron rails, sheath metal, and 
wire, the casting of iron, zinc, and alloys of copper into various objects, the spinning 
and weaving of various fibres, flax, cotton, jute, to become materials of greater 
value ; also the manufacturing of paper from rags, of horn into combs, and bristles 
into brushes, belong to this section. 

Chemical technology, however, deals with the operations by which a raw material 
is not only changed in its form, but especially as regards its nature: such, for instance, 
is the case with the extraction of metals from their ores; the conversion of lead into 
white-lead and sugar of lead (acetate of lead); the conversion of sulphate of baryta 
into chloride of barium and baryta white (permanent or Chinese white); the conver¬ 
sion of cryolite into sulphate of alumina, alum, and soda; the conversion of rock salt 
into sulphate and carbonate of soda ; the conversion of carnallite and kainite into 
chloride and bromide of potassium, sulphate and carbonate of potassa; the conver¬ 
sion of copper into verdigris and sulphate of copper; the manufacture of paraffin and 
paraffin or crystal oils from peat, Boghead coal, and lignite ; the preparation of kelp 
and iodine from seaweeds ; the manufacture of stearine candles (stearic acid properly) 
and soap from oils and fats; the preparation of sugar and alcohol from starch ; the 
conversion of alcohol into vinegar; the brewing of beer from barley and hops ; the 
manufacture of pig-iron into malleable iron (puddling process), and the conversion of 
malleable iron into steel; the production of gas, coke, and tar from coals; the extrac¬ 
tion from the tar of such substances as benzol, carbolic acid, aniline, anthracen, 
asphalte, naphthaline ; the preparation of tar colours, as rosaniline, aniline blue, 
Manchester yellow, Magdala red, alizarine, iodine green, picric acid, &c. In very 
many cases, however, the preparation which the raw materials have to undergo 
before fit for use is simultaneously, or at least consecutively, a mechanical 
as well as a chemical process; for instance, in the manufacture of glass, sand, 
potash, Glauber salt (sulphate of soda), carbonate of soda, and limestone, are first 
fused together to form glass (a true salt, a silicate), and the soft mass is next wrought 
in various ways to form window-glass, tumblers, bottles, &c. Another instance is the 
manufacture of beet-root sugar, in the extraction of which the sugar itself is, it is 
true, not altered or changed in any way (this being as much as possible avoided), but 
the process of extraction is a combination of mechanical and chemical operations, the 
latter bearing chiefly upon the purification of the sugar, so as to free it from adhering 
foreign substances. The same observation applies to the manufacture of starch, to 
tanning operations, also to the various processes of dyeing and calico printing. 

The ceramic arts (that is to say, the manufacture of earthenware, pottery, china, 
&c.), are generally included in chemical technology, although, in the production of 
the objects alluded to, the mechanical operations and fine art processes predomi¬ 
nate. Pyrotechny (that is to say, the consideration of fuel and of its most useful 
and advantageous application to the production of heat, and the best mode of 
constructing furnaces, ovens, chimneys, &c.), is one of the most important parts 
of chemical technology. 

From the foregoing the reader will readily perceive that it is scarcely possible 


INTRODUCTION. 


3 


to draw a sharp line of demarcation between the two divisions of technology 
(mechanical and chemical) alluded to. We therefore define chemical technology 
best by designating it as that branch of industrial science which treats of the pro¬ 
cesses and methods by which the nature of raw materials is usually altered. 

In mechanical technology, machinery of various description, acting as the motive 
agent or for the exertion of great power, for the transference of movement or for the 
regulation thereof, and, lastly, as an actual implement, always plays a very prominent 
part, whilst in chemical technology its position is altogether subordinate ; the great 
aim of improvement being chiefly directed towards:—i. Economisation of raw 
material, and, if by any possible means, its regeneration. 2. Economy of fuel. 
3. Economy of time by improved and shortened methods of the various operations. 

The ideal of a chemical manufactory is that there should be no real waste products 
at all, but only chief or main, and by-products. The better, therefore, the waste 
products are applied to good and advantageous use, the more nearly the manu¬ 
factory will approach the ideal, and the larger will be the profit. 


DIVISION I 


CHEMICAL METALLURGY, ALLOYS, AND PREPARATIONS MADE AND OBTAINED FROM METALS. 


General Observations. 

MeZ Metai°iurgy. term Metallurgy, in a more restricted sense, embraces tbe doctrine of 
the various processes and operations, some of which are purely mechanical, others 
again purely chemical, by means of which metals and some preparations thereof are 
obtained on a large scale. We treat in the following pages almost exclusively of 
the chemical operations and processes by the aid of which ores are converted into 
metal or into some other product, and we shall therefore investigate the changes 
which the ore undergoes when submitted to different processes and operations re¬ 
sulting in the extraction of the metal. The number of the metals which belong to 
this category is not very large; the chief are iron, cobalt, nickel, copper, lead, 
chromium, tin, bismuth, zinc, antimony, arsenic, mercury, platinum, silver, gold. 
Excepting chromium and cobalt,* other metals are brought into the metallic state by 
means of smelting furnaces; but preparations of nickel, antimony, and arsenic are 
also obtained metallurgically. Magnesium and aluminium are as yet only prepared 
in chemical manufactories. Metallurgy, as a part of technology, treats chiefly of 
the physical and chemical principles upon which the extraction of metals from their 
ores is based; and includes, therefore, the description of the operations as based upon 
these principles. Only very few metals are found in the native, that is, metallic 
state : most of them occur as chemical compounds in the mineral kingdom, and these 
ores, are termed ores; they are partly chemical combinations of the metal with 
metalloids, and partly consist of rock or gangue. Moreover, the term ore applies 
only in an industrial sense to those minerals which are worth the miner’s working. 
Metals are found chiefly in combination with oxygen and sulphur. Metals occur in 
the ores in the following conditions i. In the native state, embedded in quartz, 
granite, gneiss, and other minerals,—gold, silver, platinum, mercury, copper, and 
bismuth. 2. Combined with sulphur, as, for instance, antimony, arsenic, and lead; 
these combinations being—(a) single ores, as, for instance, cinnabar (sulphuret of 
mercury), HgS; galena (sulphuret of lead), PbS; speisscobalt (a compound of cobalt 
metal and afsenic), CoAs; ( b ) double ores, as, for instance, sulphuret of iron and 
copper (peacock ore), Ee 2 S 3 ,3Cu 2 S ; iron and copper pyrites, Pe 2 S 3 ,Cu 2 S; red-silver 

* * Since 1862 M. Fleitmann has prepared chromium and cobalt on the large scale by a 
metallurgical process. 



PREPARATION OF ORES. 


5 

ore, Sb 2 S 3 ,3AgS. 3. Combined with oxygen, ores occur as—(a) basic oxides, as, for 
instance, hematite iron ore, Fe 2 0 3 ; tinstone, Sn0 2 ; red copper ore, Cu 2 0; (b) as 
hydrated oxides, as, for instance, bog iron ore, Fe 2 0 3 ,3H 2 0 ; (c) as oxysalts, as for 
instance, malachite, CuC0 3 -j-CuII 2 0. 4. Combined with sulphur and oxygen, 
as for instance, red antimony ore, 2Sb 2 S 3 -j-Sb 2 0 3 . 5. Combined with haloids, as for 

instance, the so-called horn silver ore, AgCl. 6. I11 combination with haloids and 
oxygen, as, for instance, horn lead ore, PbC0 3 -|-PbCl 3 . 

Dre ores S of Since the ores are not found in a state anything approaching to purity, 
but are mixed in the first place with what is technically termed gangue—rock, stone, 
or earth of any kind; and moreover, since very frequently the ores of different 
metals occur mixed together, they require, on being brought out of the mine, to be 
broken up and to be separated by mechanical means from the gangue and from 
other impurities. These operations as a rule are carried out on, or near, the spot 
where the ores are raised, and are designated by the name of dressing; the 
mechanical preparation of the ore is partly executed by hand, women and children 
being frequently engaged in picking out worthless stuff from among the minerals 
brought to bank; this sorting, accompanied commonly by the breaking up of the 
ore into small lumps, an operation executed by men with suitable hammers, is 
usually so carried on as to separate the ore into three kinds. The ore thus selected 
is placed in separate heaps, which may be classed as follows :—a heap containing 
rich ore of sufficiently good quality to be fit to be directly smelted ; another heap 
contains ore which, previous to its being fit for the smelter, has to be further 
prepared, that is, purified from mechanically adhering impurities; while the third 
heap is devoted to such poor ore as would not pay the expense of the extraction of 
the comparatively small quantity of metal it contains. The mechanical operations 
alluded to are frequently effected by the aid of machinery, stamp and dressing mills, 
while very often water is used in completing the operations, its use being chiefly 
to remove the clay and earthy matter, sand, and pulverised rock from the specifi- 

prepatatkm of ca ]jy heavier mineral. The dressing-of the ores having been finished, 
they are fit for the smelting operations, but in many instances these cannot be pro¬ 
ceeded with until the ores have undergone a preparation, consisting in some cases 
of an exposure to air—weathering; in others, again, in a heating of the ores, without 
access of air, designated calcination, or a heating with access of air, termed roasting. 

The object of the exposure to air is in some instances to effect the weathering and 
subsequent loosening and separation (mechanically) of such minerals as slate, clay, 
and marly materials, which frequently adhere to certain kinds of iron and zinc ores ; 
in other instances, again, the object of the exposure of metallic ores to air is the 
oxidation of iron pyrites, which is washed out by rain as sulphate of protoxide of 
iron. The object of the calcination of ores is partly to drive off water, carbonic 
acid, and bituminous materials ; partly, also, to render the ores softer, and thus 
better fitted for the metallurgical processes by which the reduction to the metallic 
state is effected. The roasting of ores is carried on with the same object, but since 
the temperature is far higher, although not carried to the fusion of the ores, a more 
energetic chemical action takes place, and is in some cases promoted by the addition 
of common salt; moreover, the great object of the roasting of ores is to effect an 
oxidation of the same, accompanied in some, if not in all, cases by the volatilisa¬ 
tion of various substances. As instances of the action of this process, we quote 
what occurs when magnetic iron ore, (Fe 2 0 3 ,Fe0), is roasted; the protoxide in this 


6 


CHEMICAL TECHNOLOGY. 


case is gradually converted into peroxide. When oxidation is accompanied by 
volatilisation three different things may happen. 

1. A volatilisation of certain substances attended by oxidation. The ores which are 
chiefly submitted to this process are such as are combinations of sulphur, arsenic, and 
antimony, either jointly or singly, in which cases sulphurous and arsenious acids and oxide 
of antimony are volatilised, with the result that either pure metal is obtained, as is the 
case with cinnabar, which yields mercury, or the formation of metallic oxides and sulphates. 
The volatilised substances may be collected and utilised, as, for instance, the arsenious 
acid, and the sulphurous acid for the production of sulphuric acid, &c. 

2. Volatilisation of certain substances by reduction is a less frequently occurring opera¬ 
tion, chiefly carried on with some sulphates and arseniates of metallic oxides by heating 
the same with coal or charcoal, the result being the volatilisation of sulphur in the form of 
sulphurous acid and of arsenic per se. 

3. Volatilisation by conversion into chlorides of metal. When an ore is roasted with the 
addition of common salt and free access of air, some partly volatile chlorides may be 
formed, as, for instance, in the extraction of silver from its ores by the European amalga¬ 
mation process and M. Augustin’s method. 

smelting of the ores. As soon as the ores are sufficiently prepared by the methods just 
described, they are submitted to an operation having for its object the conversion of 
the ore into metal, or into some other combination thereof; the process, which is a 
true chemical operation, is called the smelting process. It rarely happens that only 
one kind of ore is operated upon; the more usual plan is to mingle richer and poorer 
ores together in certain quantities, so as to obtain a suitable mixture, attention also 
being paid to the various kinds of rock which accompany the ores, so as to obtain by 
the smelting process a proper slag; but if, as is more often the case, this end cannot 
be attained by the mixing of ores of different quality, it becomes almost always 
necessary to add other materials which either chiefly or solely act as fluxes, and 
also as reducing or converting agents, by promoting in various ways, to be presently 
more fully described, the separation of the metals from their ores. We distinguish 
accordingly between such materials as charcoal, coal and coke, lime, and common 
salt, which we term roasting materials (Rostzuschlage), and smelting or.fluxing 
materials, such as quartz and various silicates, among which are hornblende, feld¬ 
spar, augite, greenstone, chlorite-schist, slag; lime-containing minerals, as lime¬ 
stone, fluor-spar, gypsum, heavy-spar; minerals containing alumina,'as, for instance, 
clay-slate and marl. Saline materials (admixtures) are also used, as potassa, borax, 
G-lauber salt, and saltpetre; likewise metallic admixtures, as, for instance, iron used 
in the decomposition of cinnabar and sulphuret of lead ; zinc, for the extraction of 
silver from lead; arsenic, in the preparation of certain nickel and cobalt ores; pro¬ 
toxide of iron (anvil dross), hematite iron ore, and manganese, used in the puddling 
process; certain saline admixtures, by which we understand, in this instance more 
especially, such blast furnace slags as contain a large proportion of protoxide of iron, 
and are applied in the process of puddling on account of the oxygen they contain ; 
or, on the other hand, are used as so-called precipitating agents, on account of the 
iron they contain, e.g., for the throwing down of lead from galena. The sub¬ 
stances which act only as fluxes promote the separation of the metal, because the 
ore is more readily rendered fluid, thereby causing the particles of metal to unite 
more easily. According to their mode of action, fluxes can be brought under three 
heads, viz. : 1. Such as exercise no chemical action, but are only substances pro¬ 

moting fluidity, as, for instance, fluor-spar, borax, common salt, and various slags; 
2. Such as at the same time exert a reducing action, as, for instance, a mixture of argol 
and saltpetre, so-called black flux ; 3. Such as act as absorbents, either of acids or of 
bases • but this class belongs more properly to admixtures already alluded to above. 


SLAGS . 


7 


Ths Mixing of the smelt. That operation, by which the ore and the materials required for 
the smelting process are intimately mixed together, often in previously weighed out 
quantities, is called the mixing, and the quantity which is to be used within a given 
lapse of time (generally 12 or 24 hours) is called the charge. 

8memng C operation. The following are the products which, generally speaking, arc 
obtained by the smelting process :—1. Metals—Educts. The relative degree of the 
purity of these substances is indicated when gold or silver is alluded to by the title 
of their fineness (purity), fine gold or fine silver being understood as the perfectly 
pure metal; but as regards the metals not designated by the term noble, they are 
called raw or crude metal, while a higher degree of purity is indicated by refined. 
2. Such products as are not present ready formed in the ore, but are the result of 
peculiar reactions which take place during the smelting process between the various 
ingredients submitted to the operation; these materials are, in most instances, 
ready for the market, and comprise the so-called hard lead which contains antimony, 
arsenic, and other impurities; arsenical preparations, as, for instance, arsenious 
acid, orpiment, realgar; and black sulphuret of antimony. 3. The preparation of 
educts is often accompanied by the formation of intermediate or by-products; if 
these happen still to contain a sufficient quantity of the metal operated upon to 
make it worth while to extract it, they are termed intermediate products ; but if 
the reverse is the case they are called—4. Dross. Such intermediate products are 
often alloys; as, for instance, one consisting of silver, copper, and lead—the so- 
called Tellersilber —silver containing lead, consisting chiefly of lead, with a smaller 
or larger quantity of copper and some silver; so-called black copper, a mixture of 
copper, iron, and lead; sulphurets ; arsenic alloys, so-called Speiss, as, for instance, 
the cobalt and nickel compounds obtained in smalt works, chiefly consisting of 
arsenical nickel; carburetted metals, as, for instance, pig-iron and steel; oxides, 
as for instance, litharge (oxide of lead). 

siags. The material which usually passes by this name exhibits, when cold, an 
enamel or glass-like appearance, and is generally made up of various combinations 
of silica with earths, such as lime, magnesia, alumina, and metallic oxides, as the 
protoxides of iron and manganese. The slags are formed during the smelting process 
because the raw materials, and the various substances employed, contain the elements 
for their formation. The functions of the slag during the smelting process are rather 
important, serving to protect the particles of metal, or of sulphuret of metal, from the 
oxidising action of the blast, and promoting the adhesion and union of the particles. 
Slags are applied in some smelting processes as a flux; and if they should still contain 
a sufficient quantity of metal, they are added to another batch of ore to be operated 
upon. As regards their composition and nature, they are classified according to the 
quantity of silica they contain as sub-, mono-, bi-, and tri-silicates. The proportion 
which the oxygen of the silica bears to that contained in the bases is as follows :— 

Subsilicate .3:6 

Monosilicate.3*3 

Bisilicate.6:3 

Trisilicate.3 : 1 

Slags are either vitreous or crystalline. It very frequently happens that from the 
latter kind portions of silicates separate, which, as regards their chemical and mineral - 
ogical characters, agree with minerals met with in nature, such as augite, olivine, 
Wollastonite, mica, idocrase, chrysolite, feldspar, &c. Generally speaking, the 






8 


CHEMICAL TECHNOLOGY. 


mixtures of monosilicates produce slags which, are very fluid, and apt to consolidate 
rapidly while cooling, while the mixtures of bi- and tri-silicates produce slags which 
have the opposite properties, being pasty and tough. 

The following properties and constitution denote that the slags are suited to the smelting 
process :—i. The specific gravity of the slag while molten should be less than that of the 
product (metal) it is desired to obtain, in order that the slag may cover the surface of the 
molten metal. 2. The slag should be homogeneous throughout the duration of the process 
of smelting; since the contrary would denote an abnormal working of the operation. 
3. The slag should melt readily, and thus admit of the particles of metal readily sinking 
downwards as a consequence of their higher specific gravity. 4. The chemical composition 
of the slag should be so regulated as to prevent them exerting any decomposing action 
ut>on the metal. 

Ikon. 

(Fe = 56; Sp. gr. = 77.) 

iron; its occurrence. Iron is the most important and most useful of all metals. Its 
application is most intimately connected with all branches of industry, and almost all 
the wants and requirements of common daily life. The reason of this very extended 
employment of iron is due, partly to its being plentifully and even superabundantly 
met with in nature, but partly, if not chiefly, in consequence of the great ease where¬ 
with this metal, during its reduction from the ore, assumes various modifications and 
exhibits different characters, each possessing some special feature of usefulness. 
Although the number of minerals which contain iron is very great, comparatively few 
are used in practice for the extraction of the metal. Those that are used are all 
oxygen compounds of iron, and chiefly what are technically known to ironmasters 
and the trade as ironstones. 

The following is a list of the minerals termed “ironstones ” :— 

1. Magnetic iron ore, (Fe 2 0 3 ,Fe 0 =Fe 3 0 4 ), the richest of all iron ores (it contains 
upwards of 72 per cent, of iron), is pretty largely found, especially in Russia, Norway, and 
Sweden, in the crystalline schistose rock. The celebrated Dannemora (Sweden) iron is 
obtained from this ore. It not unfrequently happens that this mineral is more or less 
mixed with iron pyrites, galena, copper pyrites, apatite (chiefly phosphate of lime), and 
other minerals, which, by their presence, impair the good qualities of the magnetic iron ore 
as a mineral. 

2. Haematite iron ore, red ironstone, (Fe 2 0 3 ), contains about 69 per cent, of iron. This 
mineral occurs in seams and veins in the older geological formations, often embedded in 
gneiss and granite. It is also met with in the metamorphic rocks, and is frequently called 
glassy head, owing to its external lustre; also bloodstone, on account of exhibiting, when 
scratched with a file or a knife, a deep red-coloured streak. When this ore is found mixed 
with silica, it is called siliceous ironstone ; when occurring along and mixed with alumina, 
it is called red aluminous iron ore ; mixed with lime, the ore is known as minette. The 
quantity of iron present in these ores varies, of course, considerably. This ore occurs 
in crystalline state, in especially large quantities in the Island of Elba, and ores of the 
same kind, but different in quality, are found in England and Ireland, Saxony, and many 
parts of Germany. They are, in all cases, especially as regards the first-named country, 
largely applied, c.g., Lancashire (Ulverston and Barrow-in-Furness). 

3. Spathose iron ore, (FeC 0 3 ), with 48-3 per cent, of iron. This ore, which occurs in great 
variety, is, indeed, the chief iron-stone, often containing carbonate of protoxide of manganese 
in larger or smaller quantity. This ore is often met with in a globular or kidney-likelhape, 
and hence called kidney iron; in mineralogy, spherosiderite. The ore bears a great many 
other names, derived from some peculiarities in its composition; for instance, it is known 
and very largely worked in Scotland as black-band, owing to its being mixed with carbon¬ 
aceous and bituminous matters, and alternating with seams of coal. It is known, also as 
clay-ironstone, being then mixed with more or less argillaceous matter, and occurring in 
enormous quantities in that condition in Cleveland and Rosedale (Yorkshire), in Wales, 
and also on the Continent in various countries. 

4’ When the last-named ore is acted upon by air and water containing carbonic acid, a 
secondary ore is formed, known as brown ironstone (partly Fe„ 0 3 ,H„ 0 , partly Fe CP,HI 6) 
In mineralogy this ore is named according to its varying physical properties, asMows:- 
Lepido-crocite, needle-iron ore, pyrosiderite, and stilpnosiderite. As may be expected. 


IRON. 


9 


this mineral is often mixed with carbonate of lime, silica, alumina; the yellow ironstone 
being a variety of the aluminous kind. Bauxite may in some instances range along with 
this kind of ore, when that substance consists of an intimate mixture of alumina and 
peroxide of iron. 

5. Pea-iron ore, in smaller or larger globular-shaped particles, formed of concentric 
layers, containing either an intimate mixture of silica, protoxide of iron, and water, or 
brown iron ore and siliceous clay. The origin and mode of formation of this ore are un¬ 
known. It occurs in France and in the South-West of Germany. 

6. Marsh iron ore, limonite, met with in parts of Europe, generally those which are 
only little elevated above the sea level, and more especially in or near moors and marshes, 
peat bogs, &c.; in some parts of the Netherlands, Denmark, Sweden, and North Germany, 
and also in the United Kingdom to some extent. This ore owes its origin to the action of 
decaying vegetable matter upon water containing carbonate of protoxide of iron in solution. 
The ore is met with in irregularly shaped lumps, as hard sometimes as pebbles, but also 
in a soft and spongy condition; its colour is brownish, or black, and it consists of prot¬ 
oxide of iron, oxide of manganese, phosphoric acid, organic matter, and sand. According 
to M. Hermann, however, the ore contains hydrated peroxide of iron, hydrated oxide of 
manganese, phosphate of peroxide of iron, tribasic crenate of peroxide of iron. This 
ore is in some instances largely used for the manufacture of cast-iron objects (especially 
for domestic and ornamental uses), on account of its yielding an iron of great fluidity, 
which fills the moulds very completely, giving sharp-figured castings. This condition is 
due to the presence of the phosphorus in such iron; but the presence of this element also 
causes the pig-iron made from this ore, if puddled, to yield a wrought-iron which is both 
cold- and red-short. 

7. Franklinite, (Fe 2 0 3 [Zn 0 ,Mn 0 ]), containing 45 per cent, of iron, 21 per cent, of zinc, 
and 9 per cent, of manganese. This ore occurs in New Jersey, U.S., and is there employed 
both for the extraction of iron and zinc. 

Iron is also obtained from rich slags, which often contain, in the shape of protoxide of 
iron, an amount varying’ from 40 to 75 per cent, of that metal; they are employed in the 
puddling process. The scraps of iron resulting from various operations, old iron, and 
waste pieces of the metal, are usefully applied, either alone or with the ores, to be re-con¬ 
verted into metal. 

Taken from a metallurgical point of view, iron ores are distinguished as reducible easily 
or with difficulty (convertible into metal readily, or fusible with difficulty). To the former 
class belong all those ores which, while being submitted to a preliminary roasting, become 
porous, and hence more readily penetrable by the reducing gases present in the blast¬ 
furnace ; and, as a consequence, more rapidly reduced and molten. The spathose iron 
ore and brown iron ore belong to this class; the former because on roasting it loses 
carbonic acid, while the latter loses water. Magnetic iron ore, and hematite iron ore in all 
its varieties, are reducible with difficulty. 

a. Pig or Crude Iron. 


Extraction of Iron 
from its Ores. 


The extraction of iron from its ores is chiefly based upon the two 
following properties :—1. While particles of pure or nearly pure iron are infusible 
even by the heat produced in the blast furnace, they are possessed of the property 
of agglutination to larger masses ; in other words, the property (possessed by iron 
and only a few other metals) of welding together at a bright red heat. 

2. Iron is capable of uniting, while exposed to a high temperature, and in the 
presence of an excess of carbonaceous matter or gases containing carbon, with 
that metalloid, forming with it an easily fusible compound, viz., a carburet of iron, 
the so-called pig- or cast-iron. 

The direct manufacture of malleable iron from iron ores was in former times a 
very usual proceeding, and is yet carried on to a small extent in some parts of 
Europe (Styria, Andorra, Sardinia, and Sicily), and far more so inHindostan ; but 
this method, known as the Catalan process, is wasteful, and although it yields iron 
of excellent quality, it also requires ores of great richness. The process is not 
suited to meet the large demands now made for iron; with these trifling exceptions 
all iron at the present day is obtained by the production first of pig-iron, which is 
afterwards converted into malleable iron by the puddling process. 


IO 


CHEMICAL TECHNOLOGY. 


The operations by which iron is extracted from its ores are:—calcination or roast¬ 
ing, and smelting. The object of the first-named operation is the removal from the 
ore of such substances as water, carbonic acid, carbonaceous matter (as present in the 
black-band ironstone); also the conversion of any protoxide into peroxide, because 
the latter is less apt to become absorbed by the slag, and to promote the porosity of 
the ore. The calcined ores are next broken up to lumps of suitable size by means 
either of stamping mills or cylinders, or by machinery specially made for the purpose 
on the principle of quartz and stone crushers; after this has been done the ores are 
mixed, rich and poor together, in such proportions as have been found in the ex¬ 
perience of the workmen to yield the best quality and largest quantity of iron. 

Theory of the^iron^Extraction q^e ores having thus been mingled, constitute a mixture made 
up chiefly of an oxide of iron and of gangue (silica) or lime; carbonaceous matter 
is added thereto, and the mass is submitted to a strong heat, the result being the 
reduction of the iron to the metallic state, according to the following equation : — 

Fe 2 0-f 3 3C= 3 C0+2Fe; 

the action, therefore, of coal is to serve as fuel and at the same time as reducing 
agent along with carbonic oxide and carburetted hydrogen ; if, however, the opera¬ 
tion were performed by simply mixing the broken up ores and coal or coke, and 
submitting this mixture to the smelting process, the iron would be obtained in a 
finely divided and spongy condition; and in order to procure the union of the particles 
of metal so as to form a molten mass previous to the smelting operation being pro¬ 
ceeded with, certain substances which have the property of forming with the gangue 
a readily fusible glassy mass are added. The substance added is technically known 
as slag, and it serves not only the purpose just mentioned, but also that of with¬ 
drawing and absorbing from the ore such materials as might injure the quality of 
the iron; and, lastly, the slag being by far specifically lighter than molten iron, floats 
on the surface and protects the metal from the oxidising action of the air blown into 
the furnace. Slag is a mixture of various silicates; in some instances the ore itself 
contains, along with the oxide of iron, the constituents necessary to form a good 
slag, but in most instances ores require the addition of such materials as will form, 
with the constituents (excepting the iron oxides), a proper slag; thus, for instance, 
if silica were wanting, quartz or sand would be added; and if bases were wanting, 
lime-stone or fluor spar (fluoride of calcium) would be added. The slag should 
become fluid at or about the same temperature as the metal. The mixture of iron¬ 
stone and slag-forming material is called a batch, and is so arranged as not to contain 
above 50 per cent, of iron. When iron in the molten condition and carbonaceous 
matter (coal, coke, or charcoal, although the latter is very rarely used) come in 
contact, as is the case during the smelting process just alluded to, the molten 
metal dissolves a large proportion of carbon ; but when the metal cools a portion of 
the carbon separates in the crystalline form; this is termed blast-furnace graphite: 
another portion of the carbon remains, however, in chemical combination, and it is 
therefore evident that the smelting of iron ores produces an iron—pig or crude iron 
—which contains carbon, and is, therefore, not a pure metal. 

Biast-furnace Process. At the present day the extraction of iron from its ores (smelting) 
is chiefly carried on either in what are termed blast-furnaces or blowing-furnaces. 
These contrivances are not essentially different from each other as regards their 
action, but their arrangement and construction is so far different that the slag from 
blast-furnaces, working as they do with what is termed an open breast-plate, runs 


IEOK 


11 



off continuously, while the slag from the blowing-furnace has to be cleared from 
time to time when tapping the metal. 

D iiiast p -fl2rnace t ! ie A blast-furnace is an oven showing on the exterior a heavily made 
wall (Fig. i, A, the outer wall), haying a height of from 14 to 35 metres ; the inner 
lining is made in the shape of two truncated cones placed together at their bases; 
the brickwork (fire bricks) which constitute this double cone-like structure, b, is 

Fig. 1. 


surrounded by a casing made up of broken scoriae or refractory sand, which is en¬ 
veloped by the external coating of heavy masonry; the sand is a bad conductor of 
heat and admits also of space being allowed for the expansion by heat of the interior 
structure. The portion of the internal cone extending from b to c is called the shaft, 
or chamber, while the portion which extends from D to E is named the boshes; the 
part of b where the diameter is greatest is called the belly or upper part of the 
boshes. Below the boshes at E, the space is gradually made narrower, and called 
the throat, or tunnel hole, the lower part of which is intended for collecting the 
molten metal, and named the crucible or hearth; this portion of the blast-furnace 
is the most important, because the smelting process goes on in it; the crucible is 
provided with two opening placed opposite to each other, and containing conically- 
shaped tubes (see Fig. 2) called the tuyeres, ending in what are termed the nozzles 
or nose pipes, or the blast pipes; these tubes serve to convey the air necessary for 
the furnace. As shown in the engraving, the admission of air to the nozzles is re- 















12 


CHEMICAL TECHNOLOGY. 


gulated by a valve. The upper open end of the furnace at A is called the mouth or 
furnace top ; through this opening the fuel and mixture of ore and flux are put into 
the furnace, which is (as also shown in Fig. i) situated on or near the slope of a hill, 
so as to have ready access to the mouth by means of the bridge for conveying the 
materials to the furnace-top. The lower part of the hearth is prolonged towards the 
front, thus forming the breast-pan, which is enclosed by the dam-stone, M; this 
stone is somewhat removed at one side from the wall, thereby forming a slit, which 
is technically called the tap-hole ; this is the discharge aperture ; while the smelting 
is going on this aperture is closed up with fire-clay, which is removed when it is 
required to withdraw the slags or tap the crucible, that is to say, discharge the molten 

Fig. 3. 



metal. The dam-stone is protected by an iron plate. Three only of the sides of the 
hearth are continued to the stone constituting the bottom of the arrangement; the 
fourth is merely brought to within a certain distance of the base, where it is supported 
by strong girders of cast-iron firmly fixed into the masonry of the walls, and on 
which rests a heavy block of sandstone called the tymp (see Fig. 1), which is 
. supported by a very heavy and stout piece of iron called the tymp iron. 

The B and ngine I 11 order to provide the necessary quantity of air for the blast¬ 
furnace, a blowing engine is attached; this is now almost exclusively constructed 
upon what is termed the cylinder principle, which in one of its most convenient 
forms is delineated in Fig. 3. The cast-iron cylinder, A, contains a piston, c, which 
by means of the piston rod, a, passing air-tight through the stuffing box, e, can 
be moved upwards and downwards; at b and d the cylinder is in communication with 
the outer air, and by means of / and g it communicates with the chest, E. The 
openings alluded to are provided with self-acting valves for regulating the flow of air, 
which is conveyed through i into the pipes communicating with the blast-furnace. In 
order to regulate the blast, a large sheet-iron vessel, in construction very similar to 
the gas-holders of gas-works, and acting on the same principle, is applied. The 
application of hot air for the blast is one of the most important improvements in the 


































IEOX. 


*3 


manufacture of iron, since, in tliis way, a decreased consumption of fuel, to the 
extent on an average of 0*366 (from J to §), lias been obtained; while, moreover, 
the absolute gain in the production of iron amounts to about 50 per cent. It is also 
stated by many iron-masters that the furnace is more readily and regularly worked; 
but this statement is discredited by others, who aver against the hot blast that dis¬ 
turbances arise more frequently in the regular course of working ; also, that the very 
high temperature in the crucible causes the rapid destruction of the fire-bricks, and 
consequently impairs the time of what is technically termed the campaign, that is to 
say, the duration of the fabric of the blast-furnace. The air intended for the hot 
blast is heated either by the gases given off by the blast-furnace, or by means of 
separate fire-places which heat a pipe apparatus, or lastly by means of Siemens’s 
regenerative furnace system. This system consists in first conducting the gases of 
the blast-furnace through a fire-brick built space filled with fire-bricks loosely 
piled together, which becoming thoroughly red-hot are in that condition capable of 
heating the cold air previous to admitting it, care being taken to shut off the blast¬ 
furnace gases; by this means the air can be heated to a temperature very far ex¬ 
ceeding that which is attainable by passing the air through iron tubes, these not 
admitting without serious injury of being heated to so high a temperature in con¬ 
tact with air. The hot blast air is heated to from 200° to 4oo°0.; blast furnaces fed 
with coke as fuel require per minute of time from 2000 to 4000 cubic feet of air. 
smelting Process. The blast furnace is worked in the following manner:—The furnace 
' is first heated by igniting in it a quantity of wood. When this has rendered the 
oven thoroughly dry, the fuel intended for use in the course of the continued process 
is put in (this fuel used to be in Germany wood charcoal, but at the present time 
there, as in England, coke is employed, or sometimes anthracite ; common coals are 
rarely used); the furnace is at first entirely filled with fuel, and when quite full the 
blast is turned on and a beginning made with the charging of the mixture of ore 
and flux, alternating with fresh fuel. By the burning of the fuel, and the fusing of 
the ore and flux, the layers sink downwards, the silica fuses, forming, while com¬ 
bining with the earths and some of the oxides present in the ore, a slag which is 
commonly coloured by the presence therein of oxide of iron, while the iron reduced 
to the metallic state, and semi-fluid at first, combines with carbon to form readily 
fusible pig-iron ; the molten metal collects in the hearth or crucible; the fused slag 
floats on the top of the metal, but is run off over the dam-stone. The molten metal is 
tapped off about twice every 24 hours, or as soon as it appears to reach the height of 
the dam-stone. The aperture here alluded to, and closed provisionally by means of 
fire-clay, is opened by the piercing of the latter, while the molten metal is conveyed 
through channels made in the sand to the moulds, also formed in the same material; 
during the operation of tapping, the blast is shut off. Crude iron cast in the shape of 
cakes is called lump-iron, and when run into bars, pig-iron. The campaign, that 
is, the operation of smelting with the same furnace, often lasts many years ; it is, 
in fact, continued until the oven or blast furnace becomes worn out. 
chemical Process going The chemical process which is going on in the interior of 

piast Furnace. the blast furnace when at work (technically, while in blast) differs 

considerably in different portions of the vertical section. The annexed Eigs 4 and 5 
represent the interior of a blast furnace exhibited in perpendicular section, and filled 
with alternate layers of fuel and mixed ore and flux, the latter being indicated by the 
narrower, the former by the wider layers. Counting from the surface of the fluid slag, 


CHEMICAL TECHNOLOGY. 


*4 


//, up to the mouth of the furnace the interior may be divided into five zones or 
regions, viz.:— 

1. The first heating zone, a b. 

2. The reduction zone, b c. 

3. The carburation zone, c d. 

4. The melting zone, d e. 

5. The combustion zone, ef. 

In the upper part of the furnace, the first heating zone, the materials become 
warmed and are rendered thoroughly dry, but they hardly become hotter than a low 
red heat. The reduction zone is the largest in extent. In the lower part of the shaft of 
the furnace, and especially towards the belly, the oxide of iron is, by the action of the 
reducing gases, first converted into protoxide of iron and next into metal. The reduc¬ 
ing agents present in this zone are—carbonic oxide, carburetted hydrogen gas, and 
hydrocyanic acid gas (cyanide of hydrogen), or vapours of cyanide of potassium; at 
a certain part in this zone the iron is present as malleable iron. Deeper down in the 
furnace the carburation zone is met with; here the combination between the iron and 


Fig. 4. 



Fig. 5. 



a 


b 


0 


d 


e 

f 


carbon takes place, producing a more or less steel-like and somewhat caked iron, 
which, when sinking, enters the melting zone and is saturated with carbon and en¬ 
tirely brought to the state of pig-iron. At the portion forming the combustion or oxi¬ 
dation zone, which is, as compared with the other zones, only of very small extent, 
the air from the blast enters the furnace through the nozzles, and meeting with incan¬ 
descent coke at the highest possible white heat, causes the formation of carbonic acid, 
but this gas in passing upwards through other layers of incandescent fuel becomes 
reduced to carbonic oxide (C 0 2 -f C=2CO); by the combustion of the hydrogen con¬ 
tained in the fuel, water is also formed, which, along with the aqueous vapour con- 



















IRON. 


15 


fcained in the air of the blast (recently it has been tried to eliminate this aqueous vapour 
by passing the air previous to reaching the nozzles through concentrated sulphuric 
acid) is decomposed by the enormous heat of the middle portion of the furnace as well 
as by the presence of carbon, forming hydrogen and oxygen, the former of which 
enters into combination with the carbon, forming carburetted hydrogen, while the 
latter combining with the same element produces carbonic oxide. The nitrogen 
present in the coke, as well as a portion of the nitrogen present in the air of the blast, 
combines with the carbon, forming cyanogen (either as cyanide of some metal or as 
cyanide of hydrogen).* The reducing gases meeting with the ores cause the oxides 
present to be converted into metal, while the gases remaining (the blast furnace 
gases) escape from the mouth of the furnace. The reduced iron combines, while 
sinking downwards, with carbon, forming the crude metal, and fuses in so doing; 
the union of the particles being promoted by the slag. As soon as the iron reaches 
that portion of the furnace where the heat is strongest, the carbon contained in the 
metal begins to exercise its reducing action upon such substances as alumina, 
lime, silica, &c., which in the reduced, or metallic, state combine with the iron. 

Recent researches have proved that the copious production of hydrocyanic acid generated 
by the process going on in the blast furnace greatly and very essentially assists the reduc¬ 
tion of the ores; that compound of course combines with the alkalies and alkaline earths 
contained in the fuel and other materials. It has been surmised that the crude iron is not 
solely a carburet of that metal, as might be produced by the decomposition of cyanide of 
iron, but, in addition to a small quantity of that body, contains also nitride (a nitrogen 
compound) of that metal. In support of this view the fact is brought forward, that Dr. 
Wohler, of Gottingen, found many years ago that the cubical crystals of what was con¬ 
sidered to be metallic titanium, and found in the blast furnace slag, turned out to be a 
compound of nitride of titanium and cyanide of that metal. In order to give some idea 
if the large quantity of metallic cyanides generated by the blast furnace process, we 
briefly quote from the researches made on this subject by Drs. Bunsen and L. Playfair, 
that an English blast furnace, fed with coal as fuel, produced daily a quantity of 225 
pounds. M. Eck, who made some researches on this subject at Konigshiitte, in Upper 
Silesia (Prussia), discovered the formation of both cyanide and sulphocyanide of potassium, 
and he found by calculating from the quantity of potassa contained in the ores, flux, and 
fuel, a daily production of 35 1 pounds of cyanide of potassium. The reduction of alumina 
and silica to aluminium and silicium also takes place in the melting zone. 

jurna P reat^Afferent plants Fig- 5 exhibits the temperature prevailing at the limits of 
each zone. The temperature of the combustion zone would be far higher than 
happens to be the case were it not that, by the conversion of carbonic acid into 
carbonic oxide—that is, the absorption, or more correctly vaporisation of carbon— 
a considerable lowering of temperature (in other words, absorption of heat which 
becomes latent) is produced. It should be remembered that here the volume of the 
carbonic acid is also doubled, while this reaction is taking place, and that process 
of course also absorbs heat. 

Taking into due consideration the fact that, under the most favourable conditions 
only i 6'55 per cent, of the fuel supplied to a blast furnace is usefully consumed, 
while no less than 83*45 per cent, escapes from the mouth in the shape of com- 

B a Gas , e™ ace fustible gases, it cannot excite any wonder that the idea arose o) 
utilising the 3e gases ; this idea has actually resulted in various useful ways, as, 
for instance, for the fusion and puddling of the iron, for the refining and cleansing 
by welding of the iron, for the heating of the blast, the roasting of the ore, and 
the drying and carbonisation of the wood. 

* Accoiding to the view of M. Berthelot [1869] there is in this instance first formed 
acetylide of potassium, C 2 K 2 , which then combines directly with nitrogen to form cyanide 
oi potassium, 2(CNK). 


i6 


CHEMICAL TECHNOLOGY. 


Application of these Gases The application of the gases to the useful purposes just mentioned 

t0 t sai-arnmoni t ac r . e of does not exhaust the list of such applications. Drs. Bunsen and 
Playfair found that the gases emitted by blast-furnaces fed with coal as fuel contain such 
a large amount of ammonia that the presence of that gas in the lower parts of the blast¬ 
furnace is even perceptible to the smell. These eminent savants proposed to convey the 
gases previous to being used as fuel through a chamber containing hydrochloric acid gas; 
the solution of sal-ammoniac thus obtained should be run into the pan of a suitably con¬ 
structed reverberatory furnace ; and a small portion of the current of gas, after having 
been ignited, being carried over the surface of the liquid, the evaporating process can be 
regulated so as to obtain a continuous stream of a concentrated solution of sal-ammoniac 
as a metallurgical by-product. Experiments instituted at the Alfreton Iron Works (blast 
furnace) proved that in this way about 2^44 cwts. of sal-ammoniac could be produced daily 
without any great expense and without any interference with the process of iron manu¬ 
facture. The formation of sal-ammoniac is intimately connected with the formation of 
cyanogen just spoken of. When cyanide x>f potassium comes into contact with aqueous 
vapour, it is decomposed into ammonia and formiate of potassa— 

(KCN+ 2 H 2 0 =NH 3 + CHKOJ; 

the reverse reaction, that is to say, the withdrawal of all oxygen in the form of water, 
from formiate of ammonia would result in the formation of cyanide of hydrogen— 

[CH(NH 4 ) 0 2 - 2 H 2 0 =CHN]. 

c cast-iron! The iron obtained by the blast-furnace process is impure, and therefore 
called crude cast-iron; it contains carbon (in the shape of graphite as well as 
in a state of intimate chemical combination with iron as a carburet of that metal), 
silicium again as so-called silicium graphite and as a silicinret of iron, sulphur, 
phosphorus, arsenic, and aluminium. The colour and physical properties of the iron 
are determined by the quantity of carbon it contains. Formerly the more or less 
deep colour of the crude iron was believed to be dependent upon the larger or 
smaller quantity of carbon the iron contained, and accordingly, the deepest 
coloured metal was supposed to contain the largest, and the least coloured iron, the 
smallest quantity of carbon; investigations have, however, satisfactorily proved 
that it is not so much the quantity as the manner in which the carbon (likewise 
the silicium) is present that determines the quality. The fact is, that with carbon 
and silicium a portion only is chemically combined with the iron, while the largest 
proportion of these metalloids is only mechanically mixed with the metal, being, 
as already stated, present in the form of graphite (graphitic carbon and silicium). 
According to the researches of M. Fremy and others, it is probable thst crude iron 
frequently contains nitrogen, and that the presence of this element influences the 
quality of the metal; but this view is not endorsed by MM. Caron, Gruner, and 
Dr. Bammelsberg. There are two chief qualities of crude iron in the trade, viz., 
white and grey coloured. 

white Cast-iron. White cast-iron is distinguished by its silvery white colour, hard¬ 
ness, brittleness, strong lustre, and higher specific gravity, which ranges from 7*58 
to 7*68. Sometimes this kind of iron happens to contain prismatic crystals visible 
to the naked eye, and such iron is then called spiegeleisen, or crystalline pig (crude 
steel iron.) This variety of iron may be viewed as a combination of CFe6, or, more 
accurately stated as FeeC+FesC, with 5*93 per cent, of C. If the structure of the 
white cast-iron is radiated and fibrous, while the colour is bluish-grey, the metal 
is known as white pig-iron with a granular fracture. When the white colour dis¬ 
appears still more, and the fracture becomes jagged, such a metal holds a medium 
between white and grey pig, and is therefore called porous white pig. 

Grey cast-iron. Grey cast-iron exhibits a bright grey to deep blackish grey colour. 
Its texture is granular or scaly ; its specific gravity averages about 7, consequently 
less than the white variety, and the grey iron is also less hard. When pigs happen 


IRON. 


57 


to contain both grey and white iron in portions only, or dispersed through their entire 
mass, such metal is called half-and-half iron, and is specially applicable to foundry 
purposes. The chemical difference between white and grey cast-iron is due to the 
fact that the former only contains chemically-Combined carbon (from 4 to 5 per cent), 
while the latter contains from 0-5 to 2 per cent, of this element in the combined 
state, with rather more than that amount mechanically mixed, viz., from 1*3 to 37 
per cent. As regards the melting-point of cast-iron, the white variety fuses at a 
lower temperature and more easily; but the grey cast-iron possesses far greater 
fluidity. Crude cast-iron is not malleable, and cannot be welded or forged ; when 
made red-hot, it becomes very soft—so soft that it can be cut with a saw such as is 
used for sawing wood; but when placed on an anvil and hammered, this iron 
breaks into fragments even when red-hot. Grey cast-iron is the best, and, in fact, 
only suitable kind of crude iron to be used for making iron castings. The perfect 
fluidity of this metal when molten causes it to fill the moulds well, and to yield excel¬ 
lently sharp and well-defined forms. White cast-iron, on the contrary, is not used 
for iron-foundry purposes, because, while solidifying, it warps, and the surface 
becomes concave. Grey cast-iron can be filed, cut with the cold chisel, turned upon 
the lathe, and planed. White cast-iron is too hard to admit of any such operations 
being performed upon it. Grey cast-iron, molten and then suddenly cooled, is 
converted into white cast-iron; on the other hand, white cast-iron, molten at a 


very high temperature (heated far above its melting-point), and cooled very slowly, 
becomes converted into grey cast-iron. 

The quality of the iron produced by the blast-furnace process does not so much depend 
upon the ores and other materials used, in this respect the temperature is of far greater 
importance. It would appear that after every fresh charge there is at first produced white 
cast-iron, which is only convened into nrey cast-iron by a very much increased tempera¬ 
ture. If the reduction of the ore to metal—care being of course taken to have a proper 
proportion of ore and the other materials—proceeds regularly, the furnace is said to be in 
a healthy state of working. Under such conditions, the slag, which contains only very 
little protoxide of iron, is never deeply coloured. If fuel were not supplied in proper 
proportion and the ore to prevail, the reduction would probably be imperfect and the slag 
a deep colour, in consequence of the presence of a large quantity of protoxide of iron 
(colour of dark green bottle glass). Such a condition of working is termed irregular. 
When, in consequence of an excess of fuel, the heat in the furnace becomes very great, 
that condition of working is termed hot, and only grey cast-iron is formed. 

The results of the chemical analysis of some varieties of crude metal may elucidate the 
general composition of cast-iron: the under-mentioned samples are :—1. Spiegel iron, made 
from 14 parts of spathose ironstone and 9 parts brown iron ore (Hammerhiitte). 2. White 

pig-iron, with a granular fracture, from Styria. 3. 'White pig. 4. Half-and-half pig. 
5. Grey cast-iron (from brown iron ore and charcoal). 6. Grey cast-iron, from brown iron 
and spathose iron ore mixed. 7. Grey cast-iron, from ochreous brown iron ore and coke. 
The sign — indicates that no search or testing was made for the substance ; the sign o in¬ 
dicates that the substance was not found. 



1. 

2. 


4 - 

5 - 

6. 

/• 

Combined carbon 

•• 5' r 4 

4-920 

2-91 

2-78 

0-89 

1-03 

0-58 

Graphite 

.. 0 

0 

0 

1-99 

37 i 

3-62 

2’57 

Sulphur 

. . 0’02 

0-017 

O'OI 

0 

— 

— 

— 

Phosphorus.. 

.. 0-08 

0 

o-o8 

123 

— 

— 

— 

Silicium 

• • 0-55 

0 

0 

8-71 

— 

- u 

— 

Manganese .. 

. . A-AO 

0 

1-79 

0 

-—■ 

— 

.... 

tie results below are 

those obtained by M. Buchner, 

while examining the 

quantities 


carbon and silicium contained in crude iron: 1, 2, 3, 4, are Spiegel iron, almost or quite 
crystalline; 5, 6, porous white pig. 

1. 2. 3. 4. 5. 6- 

C 7 .4-i4 3 'So 4'°9 375 3'3 J 3‘°3 

03 . - - - - - 


Si 


o-oi 


o-c: 


0-26 


0*27 Spur 015 


3 







i8 


CHEMICAL TECHNOLOGY. 


io. 


White pig. II. Half-and-half pig. 


8 . 

270 

0*12 


9- 

2-13 

0-10 


10. 

3-60 

o‘66 


11. 


12. 


3'34 272 


o-io 


0'20 

17. Coarse¬ 


grained 


7, 8, 9. White, very bright, crude iron. 

12. Strongly mixed half-and-half. 

7- 

C 7 .3‘4° 

CjB . - 

Si .0-14 

13. Less strongly mixed half-and-half. 14, 15? 16. Grey cast-iron, 
cast-iron. f8. Over-coaled black-greyish cast-iron. 

13 - 

. 2-17 

.. 2-n 

.0-09 

The present (1870) production of crude iron (pig-iron) amounts to 
rather more than 200 millions of hundred weights. Of this quantity 
the under-mentioned countries produced :— 

United Kingdom of Great Britain and Ireland.. 

France . 

North America, U.S. 


Cy 

C /3 

Si 


14. 

15 - 

16. 

i 7 - 

18. 

1*35 

1 ■ 18 

071 

078 

0-26 

2*47 

2-42 

279 

3-28 

3* 8 3 

070 

o’66 

i *53 

1-62 

079 


Statistics concerning 
the Production of 
Crude-Iron. 


Prussia 
Belgium 
Austria 
Russia 
Sweden 
Luxemburg 
Bavaria 
Saxony 
Wurtemburg 
Baden.. 
Hesse .. 
Brunswick 
Thuringia 
Australia 
Italy .. 
Spain .. 
Norway 
Denmark 


115,000,000 cwts. 
24,500,000 „ 
20,200,000 „ 

16,300,000 ,, 
8,900,000 „ 

6,750,000 „ 
6,000,000 ,, 
4,500,000 „ 
1,100,000 „ 
732,000 „ 
280,000 „ 

138,000 „ 
16,000 „ 

2 50,000 „ 
90,000 ,, 
18,000 „ 
2,000,000 „ 
750,000 „ 
1,200,000 „ 
500,000 „ 
300,000 „ 


209,524,000 cwts. 

Having a value of about 97-5 million pounds sterling. 

iron-"foundry work. For the manufacture of iron castings a somewhat mixed grey iron 

Re-meiting Crude Cast-iron. j s employed, because its qualities best suit the purpose. These 
qualities are closeness of grain, strength, a capability to well fill the moulds, coupled with 
sufficient softness to admit of boring, filing, &c. Although iron castings can be made 
directly from the tapping of the blast-furnace, it is found advantageous and preferable in 
practice to re-melt the pigs. This operation is carried on in crucibles in a cupola furnace, 
or in a reverberatory furnace. Crucibles (made of plumbago or fire-clay) are only used 
for making castings of small size. The quantity of iron melted in crucibles does not usually 
exceed five or eight pounds. 

Shaft or Cupola Furnace. For the purposes of the iron-foundry, the shaft or cupola furnace, 
represented in Figs. 6 and 7, is more generally used. The cupola furnace is in form cylin¬ 
drical, and from 27 to 3-5 met. high. The pig-iron, previously broken up to lumps of 
suitable size, and the fuel, which may be either coke or wood charcoal, are placed in 
alternate layers in the shaft a ; the openings c and d are intended for the insertion of the 
tuyeres connected with the blast. The opening leading to the spout, b, is closed during 
the progress of the melting; as soon as the molten iron reaches the orifice at a, this opening 
is closed by means of fire-clay, and the tuyere first placed in a is transferred to the 
opening d. The molten metal is either conducted by the aid of channels direct to the 
moulds, or tapped into suitable vessels and carried to the moulds. In many instances 
cranes are used to transport the molten metal. Here also the application of hot- air has 
been attended with a great saving of fuel. 

Reverberatory Furnace. In some cases pig-iron is melted in a reverberatory furnace, the iron 
being placed on the smelting-hearth, which is covered with sand; the hearth is slightly 
inclined and narrowed towards the tapping-hole. A strong coal fire is made up, and the 
name playing across the fire-bridge is directed over the entire length of the furnace, and 





























IRON. 


19 


thence into a high chimney. The molten metal on being tapped is conducted to the 
moulds in the same manner as with the cupola furnace. Rather more than 50 cwts. of 
pig-iron can be melted at once in a reverberatory furnace ; but since the air has free access, 
the iron becomes gradually decarbonised, and is thus rendered unfit for castings. 

Making the Moulds. The most essential, and also most difficult, part of the iron-founder’s 
work is the proper construction of the moulds. According to the materials from which the 
moulds are constructed, we distinguish—1. Sand moulding or green-sand moulding, the 
material being a peculiar kind of sand (foundry-sand).—It is necessary for this sand to-be 
exceedingly fine, and yet sufficiently coherent that the sharpest angles and corners will 
remain standing. This latter property is imparted to the sand by adding as much clay as 
will render the mass capable of being squeezed with the hand into balls when moistened 
with water. A certain amount of porosity is also requisite to enable the steam which is 
formed when the molten iron comes into contact with the mould to readily escape. This 
property is communicated by the addition of powdered charcoal. Sand-moulds are not 
dried before the molten iron is poured in. Such objects as plates, grates, railings, and 


Fig. 6 . 


Fig. 7. 



wheels, which are level on one side, are cast in open sand-moulds ; that is to say, on the 
floor of the foundry, previously covered with sand of the requisite quality, the moulds 
being obtained by pressing the patterns into the sand. For other branches of the work, 
as, for instance, iron-pots, the box mould is used. 2. Dry sand moulding.—The forms are 
made in sand and clay, or loam, care being taken to dry the moulds thoroughly before 
casting. 3. Loam-casting.—The material used for this purpose is loam, which, previous 
to being used, is sifted, moistened, and mixed with horse-dung to prevent the moulds from 
cracking during drying. 4. Case-hardening, or casting in iron moulds.—This mode of 
casting iron only applies to some peculiar descriptions of work, as, for instance, the 
cylinders of rolling-mills, some kinds of shot and shells, and railway waggon - wheels. * 
By the use of iron moulds, the casting cools and solidifies very rapidly, and, as a con¬ 
sequence, the outer layer becomes converted into white cast-iron, which is very hard. 
Thus the cylinders for rolling-mills can be so made, that while the surface is very hard, they 
are not brittle, and, therefore, fragile, because the interior consists of grey cast-iron. 

Green-sand casting is by far the most general mode of casting: furnace bars, cast-iron 
railings, grates, plates, wheels, and a variety of objects, are thus made. Dry-sand 
moulding is used for the casting of iron gas- and water-pipes, and also of cast-iron 
ordnance. This latter is preferably made from such pig-iron as contains grey and white 
iron mixed; a higher degree of toughness and elasticity can thus be obtained. Dry-sand 
moulding is also used for the making of small ornamental objects, so-called for de Berlin , 
such as cast-iron ink-stands, candlesticks, and a peculiar kind of cast-iron pins, as well as 
brooches, ear-rings, and similar things. Loam-moulding is used for the casting of large¬ 
sized cauldrons, bells, and other large objects for which no wooden pattern is made ; also 
for the casting of steam-engine cylinders. We distinguish in this kind of moulding three 
chief parts, viz. :— 


* This may be the case in Germany; but in this country the wheels are made of best 
wrought-iron, and forged by means of steam-hammers.— Ed. 






























































20 


CHEMICAL TECHNOLOGY 


a. The core, or kernel, the size and shape of which corresponds to the interior of the 
object to be cast. 

b. The foundry-pattern. 

c. The exterior mould, also termed the case. 

The loam mouldings are very rapidly dried; the casting of statues and other monumental 
work is done by loam moulding, but zinc is beginning to supersede iron for this purpose. 
Whenever objects have to be cast, the surface of which is very unequal, i.e., so shaped 
that a partial dismounting of the case is impossible, as may happen for instance with 
statues and monumental work, the shape is made on the core by means of wax : the 
pattern maker constructs a pattern, often consisting of a number of loose pieces; into this 
the molten wax is poured, and the mould thus obtained is carefully placed on the core and 
properly joined. The wax mould is brushed over with a mixture of pulverised graphite and 
very finely divided clay, which operation is several times repeated; after this the mould is 
covered with a layer of loam mixed with cow hair, and as soon as this layer is dry the wax is 
removed by applying a gentle heat, a channel having been left by which the wax can escape. 
Annealing. The castings, when sufficiently cool, are cleaned from adhering sand, the seams cut 
Tempering. 0 ff w ith a cold chisel, and in many cases submitted to a series of mechanical opera¬ 
tions, as, for instance, cast-iron ordnance, which has to be bored, while other objects have to 
be worked in the lathe and planed. Frequently cast-iron objects have become as hard and 
brittle as if they had been cast from white pig-iron, and consequently are unfit for filing, 
&c.; such iron is restored to the requisite softness by annealing or tempering. In this 
operation the castings are submitted to a strong red heat and cooled slowly, being at the 
same time protected from the oxidising influence of the air; the annealing is effected 
either by a physical or chemical process. If the former is used, the castings are simply 
covered w T ith a thick layer of clay and made red-hot, the effect being a simple rearrangement 
of the molecules of the iron, which is thus rendered soft again ; the heating to redness is also 
sometimes effected by placing the castings under a layer of dry sand or in suitably con¬ 
structed vessels filled with charcoal or coke powder. If it is desired to impart to the 
castings somewhat of the strength and toughness possessed by steel and malleable iron, 
the tempering is so arranged, and heat applied for a longer time, wdiile the metal is 
surrounded by a mixture of pulverised charcoal, bone-ash, and forge scales, red oxide of 
iron, oxide of manganese, or oxide of zinc ; cast-iron which has been uniformly and 
thoroughly decarbonised, is called malleable cast-iron. A great many objects formerly 
exclusively made of wrought-iron are now cast and treated in this way, while a number of 
othei’s, inclusive even of razors, are made of cast-iron superficially converted into steel by 
a method which will be described under the heading’ of Steel. In order to prevent the 
rusting of articles made of cast-iron, they are frequently covered with a varnish made from 
coal tar and powdered graphite, or boiled linseed-oil and lamp-black, and when intended 
for ornamental or domestic use they are bronzed or burnished. 

Enamelling of Among the first cast-iron objects ever enamelled were the pans used in 
Cast-iron, ldtchens for culinary purposes, but at the present time, especially in England, 
the enamelling of cast-iron is carried on to a large extent, and includes a variety of things 
made of cast- and even wrought-iron. The process in use is briefly as follows : — -The. 
surface of the cast-iron to be enamelled is first carefully cleaned by scouring with sand 
and dilute sulphuric acid, next a somewhat thickish magma, made of pulverised quartz, 
borax, feldspar, kaolin, and water, is brushed over the clean metallic sui-face as evenly as 
possible, and immediately after a finely powdei’ed mixture of feldspar, soda, borax, and 
oxide of tin is dusted over, after which the enamel is burnt in by the heat of a muffle. 
In France an enamel is applied which consists of a mixture of 130 parts of flint glass, 
20 2 parts of carbonate of soda, and 12 parts of boracic acid fused together and afterwards 
ground to a fine powder. Enamelled iron has in some manufactured articles taken the 
place of tinned iron or zinc. 

13 . Malleable, JBak, or Wrought-Irox. 

Refined Iron. In comparatively olden times the custom was to produce malleable 
iron direct from its ores by a process still in use to some extent in Styria, Illyria, Italy, 
Sweden, some parts of Asia, Andorra, and other localities. The process (a modifica¬ 
tion of which is known as the Catalan process) consists in the reduction of the iron 
ores, which must be very rich and pure, by means of charcoal, which serves also as fuel 
on a hearth, the combustion being aided by a blast, often simply bellows; the lump of 
iron thus obtained is immediately submitted to the blows of a heavy forge hammer. 
Excepting in the few instances just mentioned, this process of direct extraction of iron 


IRON. 


21 


from its ores has been altogether abandoned, and has given place to the production of 
malleable iron from pig-iron; the process by which this is effected is termed refining, 
and consists in the removal of the greater portion of the carbon and other impurities 
contained in the crude metal by oxidation. The crude metal chiefly employed for 
refining is white pig-iron, preferably that containing the least possible quantity of 
carbon, because this kind of iron becomes soft before melting and remains for a long 
time very fluid, and therefore presents a larger surface to oxidising agents; the chemi¬ 
cally combined carbon of white pig-iron burns far more readily than the graphite con¬ 
tained in the crude grey cast-iron. The refining process is executed either:—(i) On 
hearths (the German process); or (2) In reverberatory furnaces (puddling or English 
process); In the preparation of bar-iron (3) by the forcing of air into the molten metal 
(Bessemer and other similar processes). This latter process is described under Steel. 

German^iron-Rcflning on w hich this process is carried out is represented in 

Fig. 8. The crude iron is placed in the cavity a of the hearth, b, and the metal is 
brought to fusion in such quantity that the molten mass has a length of from 1 to 
1 *3 metre, a width of about 27 centims., and a thickness of from 4 to 9 centims. The 
cavity, a, is lined with thick plates of iron, and the tuyere, c, supplies the necessary 
air from a blast which is directed against the molten metal. The hearth is first filled 
with ignited charcoal; next the blast is turned on, and then the crude metal is placed 
on the hearth, b, and becoming gradually melted, flows into the cavity, a. The action 
of the blast causes the combustion of the carbonaceous matter of the metal, while the 


Fig. 8. Fig. 9. 



fi/ 


sand adhering to the pigs, the silica due to the oxidation of the silicium contained in 
the crude iron, and the silica contained in the ash of the fuel also play an important 
part in the process, because these substances combine with the protoxide of iron which 
is present, forming a slag,* composed of basic silicate of protoxide of iron (in 100 parts, 
68*84 protoxide and 31 *16 silica). This slag protects the iron during the refining pro¬ 
cess, but is gradually run off, care being taken, however, to leave a sufficient quantity 
to cover the metal. Mixed with forge scales (a mixture of proto- and peroxide of iron,) 
the slag of the first refining is employed in the further refining process to decarbonise 
the iron. When crude cast-iron is heated to redness along with these materials, the 
oxygen contained in them is given off, and combining with the carbon contained in 
the cast-iron, forms carbonic oxide and leaves malleable iron. The refining process 
also causes the more or less complete elimination of such substances as aluminium, 
phosphorus, and manganese from the crude metal, by converting them into alumina, 
phosphoric acid, and protoxide of manganese, all of which are taken up in the slag. 
As soon as all the iron has become fluid the slag is run off and the metal exposed to the 

* According to MM. Mitscherlich, Hausmann, Rothe, and others, the slag sometimes 
assumes the crystalline form and composition of olivine. 







22 


CHEMICAL TECHNO LOG Y. 


action of the blast, care being taken to work the metal about so as to render the action 
uniform; the somewhat thickish fluid mass becomes during decarbonisation more and 
more fluid ; and the stirring up, or raising up, as the operation is termed, is continued 
until the iron is refined, which is shown by the fact of the slag becoming very rich in 
protoxide of iron. Towards the end of the operation, the rich slag, Si 0 4 ,Fe 2 , is 
formed, which along with forge scales, is employed for decarbonising the metal. 
This rich slag is never crystalline in structure, but exhibits a dense tough mass of 
higher specific gravity than the raw slag. The operation, called the last breaking 
up of the lump, consists, first, in the rendering of the entire mass (the contents of 
the hearth) semi-fluid by increased heat; and, secondly, in the separation of the 
slag from the metal. This end having been attained, the lump, or ball, or bloom, 
is removed from the fire, in the red-hot state, and brought under the lift-hammer, 
a (Fig. 9) which is set in motion by means of a lifter and beam. By the blows of 
the hammer all the particles of slag are squeezed out from the metal; afterwards 
the lump is cut into smaller pieces, which are forged into bars ; 100 parts of crude 
cast-iron yield on an average 70 to 75 parts of malleable iron. 

Swedish Refining Process. The Swedish process of iron-refining (also called Walloon-forging) 
differs from the German process, inasmuch as only small quantities of crude metal are 
operated upon at a time, while no slag is added, the decarbonisation being effected by the 
action of the oxygen of the air. This process requires a great deal of fuel (in Sweden 
almost exclusively charcoal), while at the same time a not inconsiderable quantity of the 
iron is oxidised. The malleable iron obtained is, however, of far better quality, being 
denser and tougher, owing to greater purity and freedom from slag. 

The Puddling Process. The process designated by this name is carried on in a reverbera¬ 
tory furnace. In countries where charcoal is scarce, and hence too expensive to be 
applied to the refining of iron, coal is used, and, indeed, of later years, has be¬ 
come more generally employed on the Continent for this purpose. For, although 
the iron thus obtained is of inferior quality to that refined with charcoal, to the use of 
coal alone must the increase in the production of iron to the present enormous 
extent be attributed. Since coal contains sulphur, direct contact with iron has to 
be avoided, and the operation is carried on in a reverberatory furnace, which, in 

Puddling rumace. this instance, is termed a puddling furnace, represented in vertical 
section in Fig. 10, and in horizontal section in Fig. 11. E is the fire-place, A the 
puddling hearth, and c the flue along which the gases are carried to the chimney. 
The puddling-hearth, A, consists of a square iron box, to which air has free access 
from the fire-place. A layer of refining (puddling) slag, to which some forge-scales 
have been added, is first placed on the hearth, and heated’until it begins to soften at 
the surface. This point reached, the crude metal (by preference white cast-iron) is 
placed on the hearth in quantities of from 300 to 350 lbs. at a time and heated. 
When softened, the iron is spread evenly over the surface of the hearth by means 
of a rake or stirrer, and continually stirred about (puddled), the heat being greatly 
increased. D and E represent openings giving access to the hearth for the tools, 
capable of being readily closed. 

The soft pasty mass of metal exhibits on its surface blue flames of burning carbonic 
oxide, the metal becoming at the same time thicker and thicker: the slag which is 
formed runs off at B, and is tapped at intervals at 0. When the iron has been 
sufficiently puddled, it is scraped together and formed into lumps or balls, which are 
submitted to the action either of heavy hammers or squeezers, to free the metal from 
slag. Grey cast-iron, when used for puddling, is first converted into white cast 
iron by smelting in a reverberatory furnace, known as the refining process. 


IRON. 


23 


The theory of the puddling process is the following:—The current of air which comes 
into contact with the molten iron causes the formation of a not inconsiderable quantity of 
protoperoxide of iron, the oxygen of which eliminates the carbon contained in the pig-iron 
in the shape of carbonic oxide, which bums off with a bluish flame. The progress of the 
decarbonisation renders the mass more and more pasty; while, in the interior, pieces of 
malleable iron are gradually formed, which, being gathered together by means of the rake, 
become loosely welded, and the iron not fully decarbonised runs together, and being well 
stirred up soon undergoes the same change. Although this resume of the puddling process 

Fig. 10 



is theoretically correct, in practice the process is not so simple, because—1. It is scarce! 
possible to mix all the carbon-containing iron intimately with the protoperoxide, and, as 1 
consequence, some of that oxide remains mixed with the iron, which is thereby rendere ! 
incapable of being welded (the iron loses cohesion and becomes of a gritty nature) ; thi 
substance has to be, therefoi’e, removed by the addition of coarse slag, which is thus con 
verted into refined slag. The oxidation of the iron causes a loss of some 4 to 5 per cent, 
while the loss from the combustion of the carbon amounts to a further 5 per cent. 2. Th 

Fig. 11. 



crude iron always contains more or less blast-furnace slag* and adhering sand and dirt con¬ 
taining silica. During the puddling process any free silica present combines with the 
blast-furnace slag, and when this slag, rich in silica, comes at the end of the process into 
contact with protoxide of iron, while carbon is deficient, a portion of the silica (or silicic 
acid) combines with the oxide, forming’ a slag which adheres to the sides and bottom of the 
hearth, while a basic, not easily fusible slag remains mixed up with the metal. In the 
puddling process the great drawback is that the complete removal of the slag from the 
iron is practically impossible ; at least, such has been the case hitherto. That iron pre¬ 
pared in this way, which may even contain two or more per cent, of such slag, is some 
times brittle and cold-short is not to bo wondered at. 
















































































































24 


CHEMICAL TECHNOLOGY. 


Heating with Gases. Instead of employing coal or coke as fuel, the reverberatory furnaces 
are often heated with combustible gases escaping from the blast-furnaces or with gas made 
for the purpose in a generator—an arrangement not unlike a coke-oven, in which such 
refuse fuel as cannot be otherwise utilized, viz., waste of timber-yards, refuse charcoal, 
peat, and small coal, is submitted to dry distillation. The generator is coimected to the 
reverberatory furnace in such a manner that the gases evolved in the former reach the 
latter very highly heated. For some years Siemens’s regenerator-furnace has been applied 
to this purpose, and found to surpass all other arrangements of the kind. 'When crude 

pig-iron contains much phosphorus, that element 
may be eliminated during the puddling process by 
adding to the metal a mixture of manganese, 
common salt, and clay, reduced to powder. Sulphur, 
when present, may be burnt off by adding litharge; 
steam has also been used successfully for this latter 



purpose. 

Refining of Iron by 
Mechanical Means. 


4 

M 

Q 


The metal obtained by the 
jiuddling process is submitted to heavy hammer¬ 
ing or to squeezers in order to remove as much 
mechanically adhering slag as possible; after 
this it is ready for the operations carried out 
Roiling Mills, in the rolling mill (Fig. 12) which 
consists in the main of the following parts :—B b' 
and A a' are grooved rollers made of chilled cast- 
iron ; A a' are destined for shaping flat bars, and 
B b', for the shaping of square bars; by means of 
the nuts, 0 0, the position of the rollers towards 
each other can bo regulated: tho tubes, i i, carry 
water for keeping cool portions of the machinery. 
The contrivance M n serves to connect or dis.- 
connect the rollers from the steam engine or 
water- wheel from which is obtained the motive 
power ; the cog-wheels F and c impart motion to 
the cog-wheels f' and c connected with the upper 
rollers a' and b', which are thus made to move in 
tbe opposite direction to the under rollers. The 
metal to be rolled is first roughly shaped by 
means of heavy hammers (steam hammers are 
now often used), and then passed gradually 
through the variously sized grooves of the rollers. 
Fig. 13 exhibits rollers of a peculiar construction, 
viz., steel rings or discs wedged to iron shafting 
so as to form alternately large and small grooves 
for the manufacture of thin bars of iron, such as 
nail-rods, &c. 

A variety of rolled iron objects are made; 
among these, square and flat bars, round bars, 
T-pieces, angle-iron, hoop-iron, and nail-rods ; 
railroad rails constitute an important item. 

Boiler Plate Rolling. The rolling of boiler- and armour plate is an isolated branch, since it 
requires a metal of good quality, combining softness with toughness, and capable of being 
worked far below red heat without becoming too brittle or requiring annealing too often; 
for boiler- and armour-plates the metal is formed into slabs of proper size, which, while 
nearly white hot, are forced through the rollers. After each succeeding passage of the 
slab, the rollers are set tighter, the oxide (forge scale) which is formed on the surface cf 


















































































































IRON. 


25 


the metal is removed by brushing with wet coarsely-made heather brushes. Thin sheet- 
iron is rolled out from plate-iron cut into small slabs, which are at first hot, but at a later 
stage of the operation the rolling is performed cold, the metal 
having been previously annealed in properly constructed Fig. 13. 

furnaces. Under the headings of Zinc and Tin the galvanising 
and the tinning of iron are treated of; corrugated iron is 
made by peculiarly shaped and grooved rollers. 

irm Wire The drawing of iron into wire requires particu- 

Manufacture. larly tough and fibrous metal. In former days iron 
wire was made by drawing thin circular bars,by theaid of tongs, 
through holes made in steel plates; in the present day iron 
wire, if stout, is made with rollers, while the thinner wire is 
made with machinery to be presently described. The rolling- 
mill for the drawing of iron wire up to a diameter of about | of 
an inch consists of three rollers provided with grooves which correspond to and catch a bar 
of iron when placed between, the bar being thus squeezed in the grooves; these rollers 
make 240 revolutions a minute, and since the diameter is 8 inches their circumferential 
velocity is — 8*37 feet, or in other words 8 feet 44 inches of wire pass through the rollers- 
in a second of time; thinner wire is obtained by drawing, with the aid of machinery, the 
stouter kinds of wire through holes made in hard and unchangeable materials, the size 
of these holes gradually decreasing. For this purpose the previously annealed ware, from 
k to i^th of an inch diameter, is wound on the reel, A (Fig. 14) ; the end of the wire shaped 
somewhat to a point is put through the hole made in the draw-plate, B; this hole being of a 
slightly less diameter than that of the wire, which is next fastened to the hook, c (Fig. 15), 
of the conically-shaped drum, c, which acquires a rotatory motion from the main shaft, n, 
(Fig. 14), by means of conically-shaped cog-wheels, an arrangement being provided to con¬ 




nect or disconnect the apparatus from the steam-engine, so as to stop or set in motion the 
wire-drawing machinery without stopping the steam-engine. The shape of the holes in 
the draw-plate is of the highest importance for the success of the operation, and to obtain 
perfectly round wire the holes ought to be quite true; if, however, the holes were made 
perfect cylinders through the entire thickness of the draw-plates the result would be that 
the wire, instead of suddenly diminishing in size, would break ; on that account the holes 
are bored funnel-shaped. The draw-plate is made of steel, but for very thin ware hard gems 
properly fastened and pierced are employed. Iron wire has to be repeatedly annealed during 
the process, and since by this annealing operation, unless carried on with complete exclu¬ 
sion of air, a layer of oxide of iron is formed, the wire requires treatment in what is 
technically termed a scour bath, composed of dilute sulphuric acid and a certain amount 
of sulphate of copper; the thin layer of copper deposited on the wire during the immersion 
in this bath lessens the friction on the wire in passing through the holes. The thinnest 
iron wire met with in the trade has a diameter of only y^th of an inch, and is known as 
piano wire. Iron wire is rendered soft by being heated to redness, and is protected from 
rusting by immersion in a bath of molten zinc, so-called galvanising. The uses to which 
iron wire is applied are so varied that it is scarcely possible to enumerate them; this is 










































































































26 


CHEMICAL TECHNOLOGY. 


the less necessary, as in no country in the world is iron wire so largely used as in the 
United Kingdom, especially instead of hemp for rope-making. 

Pr rX S n 0f Malleable- or bar iron is made up of an aggregation of fibres which, 
according to the researches of Dr. Euchs, are composed of a series of very small 
crystals. Heavy blows, continuous vibration, and sudden cooling of the metal while 
red-hot, all cause the particles to lose cohesion and alter the texture from fibrous to 
granular: a well-known consequence of this change of structure, wdiich is also 
suddenly induced by great cold, is the loss of tenacity in the iron, often attended with 
breakage, as happens frequently enough to railway wheel-tyres, axles, &c. The 
colour of malleable iron is bright grey, the fracture granular or jagged : its specific 
gravity varies from 7*6 to 7‘9 (that of chemically pure iron being 7*844); from 0*24 
to 0-84 per cent, of carbon is present in the iron, the greater part in a state of 
chemical combination, in fact there is only a trace of graphite. 

The chemical constitution of malleable iron is shown in the following analytical 
results:—Sample I. being English iron from South Wales; II., soft iron from Magde- 
sprung on the Harz (Prussia); III., Dannemora iron from Sweden. 


I. II. III. 

Iron.98-904 98-963 9 8 775 

Carbon .0-411 0400 0-843 

Silicium.0-084 0-014 O’liS 

Manganese .. .. 0-043 °' 3°3 0-054 

Copper . nil 0-320 0-068 

Phosphorus .. .. 0-041 nil nil 


Malleable iron of g-ood quality does not become brittle when placed red-hot into cold water ; 
it ought not to lose its malleability when thus treated: it is far softer than white and 
bright grey cast-iron, and is therefore easily filed, cut with the cold chisel, planed, and 
shaped in various ways even cold; it melts with far more difficulty—requiring a much 
higher temperature—than cast-iron; but malleable iron is possessed of the valuable property 
of becoming, at a bright red heat (orange heat), so soft as to admit of two pieces being firmly 
welded together. The malleable-iron of commerce is often more or less mixed with foreign 
substances which in some cases impair its quality; if sulphur, arsenic, or copper is present, 
the iron is thereby rendered red-short (breaks when hammered in the red-hot state); 
silicium renders iron hard and brittle ; phosphorus makes it cold-short, i.e. rather readily 
breakable when cold, although not so when red-hot; calcium has the effect of greatly 
impairing, if not altogether destroying, the welding capability of the metal. As regards 
the choice of the different qualities of malleable iron for various uses, it is not in the scope 
of this work to enter into detail, the question being one of applied mechanics and 
engineering rather than of chemistry. Swedish bar-iron is for certain purposes in high 
repute, owing to the purity and strength of this kind of iron. 

y. Steel. 

steel. This substance differs from crude pig-iron and from bar-iron in the amount 
of carbon it contains; from crude iron, moreover, by being capable of welding ; 
and again from bar-iron by being comparatively readily fusible : in reference to the 
amount of carbon present, steel holds a position between crude pig-iron and bar-iron. 
Kecent researches have revealed the fact that steel contains nitrogen ; but whether 
this element really contributes to the peculiar properties of steel obtained from 
different sources is not a definitely settled point. Steel is obtained of various quali¬ 
ties by a number of processes, as will be seen in the following brief reference :— 
a. Directly from iron ores 

1. By the reduction of iron ore3 directly with the aid of fuel (chiefly charcoal), and a 
blast on the hearth, the steel being obtained in the form of lumps (so-called 
natural steel). 

• 2- By the heating of certain iron ores along with coal, but without fusion (cementa¬ 

tion steel from ores). 

3. By the fusion of the iron ores along with charcoal in crucibles (cast-steel from ores). 






IRON. 


27 


b. By the partial decarbonisation of pig-iron (rough steel, furnace-steel, or German steel):— 

4. By the refining (partial decarbonisation) of pig-iron by means of charcoal fuel on 
the hearth (shear-steel). 

5. By treating pig-iron in reverberatory furnaces fed by coal or blast-furnace gases 
as fuel (puddled-steel). 

6. By forcing air through molten cast-iron (Bessemer-steel). 

7. By heating cast-iron to redness along with substances which will effect decarboni¬ 
sation below the fusion point of the metal; if the substances employed for partial 
decarbonisation are iron ores, the steel is called iron ore steel. 

8. By melting crude cast-iron with such substances as those just mentioned. 

9. By treating crude cast-iron with sodium nitrate (Heaton-steel, Hargreave-steel). 

c. By imparting carbon to bar or malleable iron:— 

10. By ignition with carbonaceous matter, but without fusion (cementation-steel). 

11. By fusion with charcoal (cast-steel). 

d. By combination of methods b and c, as in fluxed steel:— 

12. By melting crude pig-iron and malleable iron together. 

In India a kind of steel is still made directly from iron cres, and known as wootz (as to 
the composition of this substance, see the “ Chemical News,” vol. xxii., p. 46); it is possessed 
of excellent qualities. The Japanese also understand the art of making steel of most 
excellent quality by rather rough and primitive means. According to the modes of 
manufacture, we distinguish the following kinds of steel:— 

Rough steel. This material, obtained by the partial decarbonisation of crude pig- 
iron, may be either: 

1. Bough steel made on a hearth (natural steel), chiefly obtained from the pure 
spathic iron ore, from which in Styria, Carinthia, Tyrol, and various other parts, 
porous white pig-iron, or white pig-iron, with granular structure, is first obtained by 
means of charcoal and coke as fuel; the ordinary grey cast-iron can also be used, but 
the resulting steel is not of such good quality. The general arrangement of the 
hearths on which rough steel is made is the same as for the 0 peration of iron refining; 
the only difference is in the mode of placing the metal in reference to the blast, the 
operation being so conducted as to cause only the gra dual combustion of the carbon ; 
the workmen take care to control the blast and place the metal in a manner which 
enables them to stop the further action of the air the moment the proper amount of 
decarbonisation has been effected. 

2. Steel obtainedin a reverberatoryfurnace, orpuddled steel, obtained from various 
ki ids of cast-iron by a process akin to the puddling of crude cast-iron, the burning off 
of the carbon not being carried so far. This mode of manufacturing steel is exten¬ 
sively employed, and yields a material well suited for the making of various kinds 
cf machinery, railway carriage-wheel tyres, and is also largely used in the manu¬ 
facture of cast-steel. 

Styrian and Carinthian cast-steel (charcoal iron-steel) is far more expensive than 
puddled steel, but the former is indispensable—at least on the Continent—for the manu¬ 
facture of all kinds of cutting-tools. 

3. Bessemer-steel. Mr. Henry Bessemer, in 1855, first applied a process of making 
steel directly from cast-iron ; the process consists in forcing large quantities of air 
through molten crude iron; the consequence is that the conversion of the iron into steel 
is effected in a comparatively brief space of time; moreover, the resulting steel remains 
fluid ; the difference of the action of the air as an oxidising or decarbonising agent in 
this instance, as compared with the process of steel-making, mentioned under No. 1 
and 2, is that in the case of the Bessemer method, the air thoroughly penetrates and 
comes into contact with every particle of iron ; whereas, in the other instances, the 
action of the air is only at the surface; and since the steel obtained by methods 


28 


CHEMICAL TECHNOLOGY. 


i and 2 is less fusible than the crude iron used, a second refining or smelting becomes 
necessary to render tbe steel uniform and homogeneous. 

The Bessemer process is executed either in diminutive shaft-ovens or in egg-shaped 
vessels made of boiler-plate converters, and lined with fire-clay; projecting for some inches 
through the inside of the bottom, five fth inch wide fire-clay tubes are carried, through 
which powerfully compressed air can be forced. The apparatus is placed in close 
proximity to a blast furnace, so as to admit of running the molten iron, purposely kept at 
a very high degree of heat, readily into the oven or other vessel, while at the bottom of the 
converter there is an aperture closed with a fire-clay plug, through which the molten steel 
can be discharged. As soon as the blast is turned on and the vessels half filled with 
molten iron, a very violent action ensues, the metal apparently begins to boil, flames and 
myriads of sparks burst forth from the converter (this phenomenon appears to be due to 
the fact that particles of partly decarbonised iron and a mixture of iron and oxide are 
driven against each other). According to the duration of the action of the blast (io to 25 
minutes) steel or bar-iron may be made, and of late, even in making steel, the action is 
carried to the highest possible pitch, and to the resulting metal a portion of molten white 
pig-iron is added. Bessemer steel is largely used for a variety of purposes; but it is not 
suitable for the manufacture of such cutting tools and instruments as require a keen and 
durable edge; on the other hand, Bessemer metal is an excellent material for the manu¬ 
facture of boiler and armour-plates, ordnance, railroad-rails, and a great variety of heavy 
machinery. As might be expected, this method of steel-making has rapidly spread from 
England to all parts of Europe and to America; and as a proof of the handsome profit 
earned by the inventor, whose royalty amounts to is. per cwt., we may state that the total 
quantity of Bessemer steel produced in Europe in the year 1869 amounted to 5*5 millions 
of cwts., 70 per cent, thereof being produced in Great Britain. 

4. Uchatius and Martin Steel are also directly prepared from crude cast-iron, by 
mining granulated crude pig-iron, made from native magnetic iron ore, along with 
pulverised spathic iron ore, and fusing this mixture in plumbago crucibles. M. 
Martin replaced the use of the crucibles in this process by that of the somewhat 
hollow floor of a reverberatory furnace heated by means of a Siemens’s regenerative 
gas-furnace. A quantity of crude pig-iron is melted under a layer of slag, and 
from time to time bar-iron is added until a sample taken out is found to possess the 
texture and good qualities of malleable-iron. When this stage has been reached, 
a certain amount of crude cast-iron is added, whereby the entire quantity of metal 
is converted into a kind of cast-steel, chiefly suited to the making of railroad-rails, 
wheel-tyres, and especially gun-barrels and ordnance. Tunner’s steel, which dates 
from 1855, also known as malleable cast-iron, is obtained by igniting white pig- 
iron to bright redness with substances which give off oxygen (oxides of iron and 
zinc and peroxides of manganese) when thus treated. 

5. Heaton steel. Prepared by a process devised by Mr. Heaton, in which* crude 
iron is heated with nitrate of soda (Chili-saltpetre). By this method not only the 
carbon is eliminated, but the sulphur and phosphorus being oxidised and converted 
into phosphates and sulphates, find their way into the slag. The principle of this 
method is the same as in Mr. Hargreaves’s plan, and again identical with a proposed 
new method of Bessemer steel-making. 

Carbon to Wrought-Iron.° II. The second kind of steel is that known as cementation- 
steel—a metal prepared by the ignition of bar-iron in contact with carbonaceous 
matter, preferably containing nitrogen. The bar-iron to be employed for this 
purpose should be of the very best quality, and since in Great Britain and France, 
the best iron produced is not good enough, both these countries draw largely upon 
Sweden for a supply of Dannemora iron, made from magnetic and red haematite-iron 
ores mixed. The Russian iron from the IJral is of the same good quality, but the 
transport is at present far too costly. It is almost superfluous to mention that the 
chief seat of the steel manufacture in England is Sheffield* 


IRON. 


29 


The process of making- cementation-steel is simple enough. The bars of iron are placed 
in fire-clay boxes, in layers alternating with the carbonaceous matter (cementation- 
powder). Two of such boxes are placed in a furnace which is heated with coal, and the 
boxes are kept at a red heat for some six or seven days, and after cooling, the bars, con¬ 
verted into steel, are taken out. Each furnace contains from 300 to 350 cwts. of iron. In 
the cementation-powder such substances as will form cyanide of potassium, or ready- 
formed cyanides, ought to be present. It appears from recent researches that cyanogen 
(CN) is to be viewed as the carrier of the carbon to the metal. The crude steel (blistered- 
steel) obtained by this operation is not, as such, fit for use, but has to undergo a process 
of purifying. 

Refined-Steel. Not only cementation-steel, but also that obtained by the other methods, is 
sheur-steei. too coarse and not sufficiently homogeneous for immediate use, and therefore 
a process of refining has to be resorted to. This process consists, firstly, in the hammering 
out of the steel bars, previously made red-hot, into thin rods, which are, while red-hot, 
quenched with cold water. Next a number of these are placed together in the form of a 
bundle, which is again made red-hot, well hammered, and afterwards rolled into bars. 
The method of refining here alluded to is more suited to the quality of steel obtained from 
crude pig-iron than to cementation-steel. Steel thus refined, on account of being used for 
making large pairs of scissors or shears, bears the name of shear-steel. 

cast-steei. Cast-steel, in modern industry, has assumed a most enormous importance, 
as evidenced by such gigantic works as those of M. Krupp, at Essen (Prussia). The 
existence of these works notwithstanding, Sheffield takes the foremost rank in the 
manufacture of cast-steel. The following is the plan pursued:—The bars of blistered- 
steel, cut to a convenient size, are introduced into crucibles made of Stourbridge clay, 
which are heated in furnaces similar to glass-melting ovens, fed with coke or coal as 
fuel ; the molten metal is cast into bar-shaped moulds, and the bars are, after cooling, 
again heated to redness and hammered or rolled out in a mill. As to the uses to 
which cast-steel is applied, suffice it to say that heavy ordnance, as well as large 
bells, excellent cutting-tools and files, best cutlery, and many surgical instruments, 
number among them. Cast-steel is homogeneous, and therefore strong and durable. 

Ste aid crude°casmrou ble IH. A third kind of steel (varying according to the mode and 
materials of production) is that called Glicenti-steel, obtained by melting together a 
peculiar white pig-iron (spiegel-iron), and bar or malleable-iron. The toughness, 
hardness, and malleability of this metal depend upon the quantity of bar-iron which 
has been added to the mixture. 

surface steei-Hardening. It frequently happens that for certain purposes soft iron only 
requires to be converted into steel superficially, an operation termed surface-harden¬ 
ing or surface-steel hardening, which is done by placing the metal, previously 
polished with emery, in a suitable vessel covered in cementation-powder (see 
above); the vessel and contents being next heated to redness, malleable iron tools, 
spanners, for instance, keys, and small objects, may be readily surface-hardened 
by being, while red-hot, dusted over with powdered ferrocyanide of potassium, 
yellow prussiate, or with pulverised borax and pipe-clay. 

Properties of steii. The colour of steel is bright greyish-white, its texture is uniformly 
granular, the better the quality the smaller the grain. Sound soft (that is not 
hardened) steel, never exhibits the coarse texture characteristic of crude cast-iron, nor 
the fibrous texture of bar-iron. Hardened-steel exhibits a fracture very similar to 
that of the finest silver, so close that the granular texture can hardly be detected with 
the naked eye. When red-hot, steel is nearly as readily malleable as bar-iron, and 
may be welded, but very careful management is required to prevent its becoming 
decarbonised. By immersing a piece- of steel in dilute hydrochloric or nitric acid, the 
texture of the metal becomes apparent, and this test may be applied to determine the 
quality The specific gravity of steel varies from 7*62 to 7*81, and decreases in 


CHEMICAL TECHNOLOGY. 


3 ° 

hardening (for instance, from 7-92 to 7*55); the quantity of carbon contained in steel 
varies from o‘6 to 1*9 per cent; the toughness, tenacity, and hardness of steel, 
increase with the quantity of carbon it contains, but good steel never contains 
graphite ; the high degree of elasticity exhibited by good steel decreases with the 
hardness. When red-hot steel is suddenly quenched with cold water, the metal 
becomes far harder, but also brittle, and will even scratch glass and withstand the 
file; when brightly polished, if steel is gradually heated, it assumes peculiar shades 
of colour (annealing or tempering colour). This colouration is due to the formation 
on the surface of the steel of thin layers of oxide, which exhibit colours like other 
very thin surfaces—soap bubbles, for instance, or a drop of oily or tarry matter 
extended over water. The operation which causes the formation upon steel of these 
colours is called tempering. 

Tempering. In judging the proper temperature and the corresponding hardness these 
tints serve admirably. Since it is often rather difficult to heat a piece of steel 
uniformly, molten metallic mixtures are employed, being chiefly made up of tin and 
lead ; the bright hardened steel is kept in these molten mixtures until it has assumed 
the temperature of the bath. The following tabulated form exhibits the composition 
of the metallic baths, which experience has proved.to be the best for the tempering of 
cutlery:— 

Composition of Melting Temperature, 
metallic mixture. point. 


Lancets. 

Razors . 

Pen-knives . 

Pairs of scissors 
Clasp-knives, joiners’ and j 
carpenters’ tools 
Swords, cutlasses, watch- 
springs .. 

Stilettos, boring -tools, and j 


Pb. 

7 

8 

8* 

14 

19 


Sn. 

4 

4 

4 

4 


;| 4 8 


fine saws .} 

) in boiling ) 


220° Hardly pale yellow. 

228° Pale-yellow to straw-yellow. 

23 2 0 Straw-yellow. 

254 0 Brown. 

265° Purplish-coloured. 

288° Bright-blue. 

292 0 Deep blue. 


Ordinary saws .. • • j linseed-oS j 3l6 ° Blackish blue. 

Such tools as are required to work iron and other metals and hard stones are 
heated to bright-yellow; razors, surgical-instruments, coining dies, engravers’-tools, 
and wire-drawing plates follow next to straw-yellow; carpenters’-tools to purplish- 
red ; while such tools and objects as are required to be elastic are heated to the violet 
or deep-blue tint; the less steel is heated the harder it remains, but also the more 
brittle. Other substances than carbon (for instance, silicon and boron) maybe capable 
of imparting to iron properties similar to those we are acquainted with in steel. Some 
other Mewls. otlier metals mixed with steel in greater or lesser quantity improve the 
quality in some respects; for instance, for the last few years steel has been made in 
Styria, which, owing to its containing tungsten, is exceedingly tough and hard. 

D wootz ce steeL This steel > specially celebrated for making swords, was first made 
at Damascus. Its name, Damascene, is applied to the property it possesses of 
exhibiting a peculiar appearance when acted upon by an acid; but this appears to be 
due rather to some imperfection of the welding of the metal, since, after melting, the 
same peculiar shades of colour do not appear. We have already alluded to the recent 
researches concerning the true composition of this metal. One of the largest collec- 







IRON. 


3« 


tions of tools, swords, gun-barrels, and bars of tbis kind of steel to be found in Europe 
is in the India Museum, Whitehall. In order to elucidate the composition of some 
kinds of steel, the following analyses are appended :—The samples are—1. Refined 
steel, from Siegen (Prussia); 2. Cast-steel, from Schmalkalden (Prussia); 
3. Puddled-steel; 4. Steel from Russian cast-ordnance; 5. Cementation-steel, 
Elberfeld (Prussia); 6. English cementation-steel; 7. Krupp’s steel (Essen). 



1. 

2. 

3 - 

4 - 

5 - 

6. 

7 * 

Iron 

.. 97*91 

98*154 

98*602 

9875 

99*01 

99*12 

99 .‘ 35 i 

Carbon {g,} 

.. 1*69 

1*730 

0*010 

1*380 

trace 

1*02 

0*15 

0*41 ] 

0*08 J 

H 

do 

0*532 

Silicium 

0*03 

0*202 

0*006 

0*04 

— 

0*10 

0*032 

Sulphur 

trace 

0*003 

— 

— 

— 

— 

0*001 

Phosphorus.. 

— 

— 

trace 

— 

— 

— 

0*001 

Manganese .. 

— 

— 

0*012 

— 

— 

— 

— 

Copper.. 

0*37 

— 

— 

— 

— 

— 

— 


100*00 

100*000 

100*000 

100*00 

99*50 

101*09 

99*917 


siderography or steel The engraving of steel requires plates made of cast-steel, which, in 
Engraving. order to be sufficiently soft for the engraver’s tools, are first superficially 
decarbonised, and after the engraving is made, again hardened. The engraved plate is 
not employed direct for printing, but is used as a matrix for the preparation of plates to 
be printed from; this process is carried out in the following manner:—A solid cast-steel 
cylinder, turned in a lathe, is superficially softened, and the engraved plate is placed 
under this cylinder, so that with great pressure and a slow revolution of the cylinder, the 
plate moving also very slowly, a relief of the engraving is produced on the cylinder, and 
this being again hardened, is employed to reproduce the engraving on other metallic 
plates, which may be either copper or soft steel. Instead of engraving the design on 
soft steel plates, etching is often resorted to, for which purpose corroding fluids, such as 
nitric acid (aquafortis), nitrate of silver, sulphate of copper in solution, or, lastly, a solu¬ 
tion of 2 parts of iodine, 5 of iodide of potassium, and 40 of water, are used, 
statistics of steel The annual production of steel in Europe may be roughly estimated for 
production. 1870 at 6,285,000 cwts. at 50 kilos, to the cwt. 

The imperial English cwt. is equal to 508*023 kilos.; of this total the undermentioned 
countries produce:— 


United Kingdom of Great Britain and Ireland 2,300,000 


France.! 1,350,000 

Belgium. 125,000 

North German Confederation. 1,120,000 

Austria. 900,000 

Sweden. 250,000 

Russia. 150,000 

Italy . 75,000 

Spain . 15,000 


Total 


6,285,000 


Iron Preparations. 

Green^vurioi. The substance called copperas and green vitriol, sulphate of protoxide 
of iron (FeSC^-f^HgO), is met with in the trade in the form of greenish-coloured 
crystals possessed of an inky astringe.it taste; on exposure to dry air the crystals 
effloresce, and are gradually converted into a yellowish powder—basic sulphate of 
peroxide of iron. 100 parts of the chemically pure crystallised salt consist of:— 
26*10 parts of protoxide of iron. 

29*90 ,, sulphuric acid. 

44*00 ,, water. 




















3 2 


CHEMICAL TECHNOLOGY. 


V 


Preparation of Green Since the minerals ordinarily used in the manufacture of alum— 
Vlt in 1 Aium b wwk?. uct the alum schists—generally contain iron pyrites (FeS a ), either as 
such or already partly converted into a basic sulphate of the peroxide (which, on 
being treated along with the alum shale, becomes by weathering and roasting 
converted into protosulphate and peroxide of iron), green vitriol is frequently a by¬ 
product of alum manufacture, and is obtained by evaporating the mother-liquor 
containing iron, and leaving it to crystallise. In some localities, as, for instance, 
at Goslar (Prussia), on the Hartz mountains, the liquor obtained by the lixiviation 
of the iron-containing minerals alluded to is first evaporated for the separation of 
the green vitriol, then a potassa or ammonia salt added to the remaining acid liquid 
to obtain alum. 

The material sometimes rather largely found in coal pits, and 
called brass (iron pyrites), is collected and placed in layers over a somewhat 
excavated surface, which has been rendered impervious to water by puddling with 
clay, and made to incline slightly in one direction where water-tanks stand, 
into which scraps of old iron are placed with the view of saturating any free acid ; 
the pyrites, placed on these beds to a thickness varying from to 3^ or 4 feet, is 
slowly oxidised by atmospheric agency, and the falling rain carries into the tanks a 
more or less strong solution of copperas, which, when sufficiently concentrated, 
is slowly evaporated, some scrap iron being placed in the evaporating-pans. In 
Grefn vitriol from countries where iron pyrites abounds, and fuel and labour are 
pyrite^Distfiia/ion. sufficiently cheap to make the distillation of sulphur from pyrites a 
profitable business, the residues are utilised in green vitriol making, a salt which 
thus made must, of necessity, contain a good deal of impurity. The brown sulphuric 
Green vitriol from acid or chamber acid, also such waste sulphuric acid liquids as are 
an^sinphuric^cid. obtained in the oil and petroleum refining, are sometimes used as 
solvents for scrap-iron for the preparation of green vitriol, which may also be made 
by boiling the finely pulverised puddling and iron refining slags with sulphuric acid. 

From spathic In localities where spathic iron (carbonate of protoxide of iron, FeC 0 3 ) 
iron ore. occurs in a pure state, that mineral may be usefully applied to the prepara¬ 
tion of green vitriol by treatment with sulphuric acid, and evaporating the solution thus 
obtained. The sulphate of iron (protoxide), prepared on the large scale, is often met with 
crystallised round a small thin stick of wood, which is hung up in the solution to promote 
crystallisation; sometimes, at least abroad, a so-called black vitriol is met with, which is 
simply green copperas superficially coloured black by means of some astringent decoction, 
such as nut galls. 

uses of Green vitriol. This substance is employed as a disinfectant, as a mordant in dyeing 
and calico printing for various black and brown shades, for the preparation of ink, the 
deoxidation of indigo—so-called cold vat—in gas purifying, in the precipitation of gold 
from its solutions, in the preparation of Prussian blue, in the manufacture of fuming 
(Nordhausen) sulphuric acid, and for a host of other purposes. 

iron Minium. During the lust 10 or 15 years a large number of substances under this 
name have been introduced as paints, especially for iron sea-going vessels and other 
ironwork. The late Dr. Bleekrode analysed two samples of this paint, one of which, 
made and sold by M. Cartier in Belgium, was found to consist in 100 parts of:— 


Moisture. 275 

Red peroxide of iron 68-27 

Clay.27-60 

Lime. 0-40 

A sample of Holland’s iron minium was found to contain in 100 parts :— 

Water . 6-oo 

Peroxide of iron .. 85-57 

Clay (burnt) .. .. 8-43 





IRON. 


33 


In Dr. G. J. Mulder’s work on the “ Chemistry of Drying Oils”*—second or applied 
part—attention is called to the fact, and supported by results of analyses of different iron 
miniums obtained by the author, that some of these paints contain free sulphuric acid, 
which is always present in colcothar; this acid may exercise an injurious effect on iron 
pa inted with such materials. 

It is hardly necessary to point out that the use of iron minium as paint is less expen¬ 
sive than the use of red-lead, in the proportion of 20 to 30 for coating the same extent 
of surface. 

Ye ofPotossa! ate The yellow-coloured salt, generally known as yellow prussiate of 
potassa (ferrocyanide of potassium, Iv 4 FeCy6 -f 3H2O), is, in a technical point of 
view, a very important substance. It crystallises in large lemon-coloured prismatic 
crystals, which are not affected by exposure to air, are not poisonous, and possess 
a sweetish bitter taste. This salt is soluble in 4 parts of cold and 2 of boiling 
water, but is insoluble in alcohol; in 100 parts there are:— 

37*03 Potassium, 

17*04 Carbon, ) 

19*89 Nitrogen, j 3 anogen, 

13*25 Iron, 

12*79 Water. 

At ioo° the water is driven off. The salt is prepared on a large scale by igniting 
such carbon as contains nitrogen to a red heat with potassa-carbonate in closed 
vessels. The quantities of the materials may be varied, the relative proportions 
being given by some makers as 100 parts of potassa-carbonate to 75 of the nitro¬ 
genous carbon, or, according to Runge, 100 parts of carbonate of potassa, 400 of 
calcined horn, and 10 parts of iron-filings. 

The fusion of these ingredients is carried on either in closed iron vessels of a 
peculiar shape, or in a reverberatory furnace. The iron-vessel, a, termed a muffle 



(Fig. 16) is egg or pear-shaped, having a diameter of 1 *2 metres, a width of o*8 metre, 
and varying from 12 to 15 centims. in thickness. As shown in the woodcut, the iron 
vessel is placed in the furnace in such a manner as to be exposed to the action of the 
flame and hot gases on all sides, being supported at the back by a projection about 27 
centims. long, and resting at g on the brickwork, leaving space sufficient for the gases 
generated in the interior to pass off by c into the chimney-flues ; m is an iron cover 
which is closed during the operation of melting, g being an opening in the front wall 
of the furnace, through which the ingredients are put into the iron vessel, and the 

* The original is in Dutch, and the work has not been translated into any other language. 


















34 


CHEMICAL TECHNOLOGY. 


molten mass taken out. The shallow pan, i, on the top of the furnace, is intended 
for the evaporation of the liquor obtained by treating the molten mass with water. 
The use of the iron vessel, however, is attended with the serious drawback that the 
iron is eaten into holes in a comparatively short space of time; and, though this 
action is greatest on the lower part of the vessel, and it may therefore be turned 
bottom upwards, and the holes stopped with fire-clay, the vessel has soon to be 
replaced by another. It is on this account, and also owing to the fact that a larger 
quantity of raw material can be operated upon at once, that instead of the apparatus 
described above, there has come into general use a reverberatory furnace, Pig. 17, 
arranged with a shallow cast-iron pan, a, from 1 to 1 ‘8 metre in diameter, with a rim 
about 1 decim. high ; b is the fire-place ; g the bridge; c a flue leading to the 
chimney, e. Sometimes the hot air is applied to the heating of evaporating-pans, 
being carried under them before entering the chimney. The result of the ignition 
is the formation of a black mass, technically called the metal , yielding the liquor 
from which the crude salt crystallises. The salt is purified by re-crystallisation, 
while the black residue is employed as a manure. 

The theory of the formation of the ferrocyanide of potassium is as follows:—The 
carbonate and sulphate of potassa, the nitrogenous coal and the iron reacting upon each 
other, give rise to the formation first of sulphuret of potassium, which in its turn 
converts the iron into sulphuret, while the nitrogen contained in the charcoal unites, 
under the influence of potassium, with the cyanogen of the carbon, which again in its turn 
combines with the potassium, giving rise to the formation of cyanide of potassium. When 
the fused mass is treated with water, cyanide of potassium and sulphuret of iron decom¬ 
pose each other, the result being the formation of ferrocyanide and sulphide of potassium, 
the last-named salt remaining in the mother-liquor. M. E. Meyer states (1868) that it is 
more advantageous to employ, instead of the sulphuret of iron, the carbonate of that 
metal, for the purpose of converting cyanogen into ferrocyanogen, because the ferro¬ 
cyanide of potassium crystallises far more completely and freely from solutions not con¬ 
taining any sulphuret of potassium. Professor Dr. von Liebig has since proved that the 
fused mass only contains cyanide of potassium and metallic iron, and not any ferrocyanide 
of potassium, which is only formed by treating the molten mass with water, or more 
slowly by its exposure to moist air. Among the materials frequently added to the fusing- 
mass are—seraps of metal, the refuse of leather, dried blood and other dry animal offal, 
because the ammonia evolved by their decomposition in the presence of an alkali aids the 
formation of cyanide of potassium. According to M. P. Havrez, the crude suint obtained 
from wool is an excellent material for the preparation of ferrocyanide of potassium, since 
100 kilos, of the suint contain about 40 kilos, of carbonate of potassa, from 1 to 2 kilos, 
of cyanide of potassium, and about 50 kilos, of combustible hydrocarbons, the heating 
value of which is at least equal to that of 40 kilos, of coal. 

It has been tried to obtain the cyanide of potassium on a large scale, by causing a 
current of ammoniacal gas to pass through and over carbonate of potassa heated to 
redness; and also to obtain cyanide of potassium from, or by aid of, the nitrogen of the 
atmosphere. This process was tried nearly 40 years ago at Mr. Bramwefl’s works near 
Newcastle-on-Tyne, but was found to be a failure commercially. The reader interested in 
a detailed account of this process may find it in the excellently-written chapter on the 
manufacture of the prussiates, in Richardson and Watts’s “ Chemical Technology.” As it 
has been proved by experiment that baryta, far more readily than potassa, converts carbon 
and nitrogen into cyanogen, forming cyanide of barium at a lower temperature, baryta 
might perhaps be substituted for potassa, but as yet this plan is not carried out commer¬ 
cially. • According to G-elis (1861), the yellow prussiate maybe prepared by the mutual 
reaction of sulphide of carbon and sulphide of ammonium, the resulting sulphocarbonate 
being converted into sulphocyanide of potassium by means of sulphuret of potassium, by 
which reaction sulphuret of ammonium and sulphuretted hydrogen are volatilised. The 
sulphocyanide of potassium is next converted into ferrocyanide of potassium by beino- 
heated with metallic iron to redness, sulphuret of iron being at the same time formecf. 
It is evident that this process could not be carried out commercially. Mr. H. Eleck 
described, in 1863, a plan for preparing the ferrocyanide by the action of a mixture of 
sulphate of ammonia, sulphur, and carbon, upon fusing sulphide of potassium, which 
thus becomes sulphocyanide of potassium, one-half of the nitrogen of the sulphate ol 


IRON. 


35 

ammonia remaining in the fused metal as cyanogen, while the other half escapes as sul¬ 
phide of ammonium, which is again converted into sulphate of ammonia. The suipho- 
cyanide of potassium produced is treated with metallic iron at a red-heat, and thus 
cyanide of potassium and sulphide of iron are produced. This process is also too cumbrous 
and expensive on a large scale. 

Applications of the This salt is employed in the manufacture of the red-cyanide or prussiate, 
Yellow Prussiate. the preparation of Berlin blue, and of cyanide of potassium (the impure 

salt as met with in commerce), in dyeing and calico-printing for the production of blue and 
brown-red colours, for the purpose of surface-hardening small iron articles, and lastly as 
an ingredient of white gunpowder, and for use in chemical laboratories. 

Ked Prussiate. The so-called red prussiate of potassa, properly ferricyanide of 
potassium, or Gmelin’s salt, K 3 FeCy, is prepared on a large scale and extensively 
used in dyeing and calico-printing. This salt crystallises in prismatically-shaped 
ruby-red-coloured, anhydrous crystals, which consist in ioo parts of:— 

35*58 Potassium, 

21*63 Carbon, 1 

25 -54 Nitrogen, j Cyanogen, 

17*29 Iron. . 

It is prepared by submitting either the solution of the yellow prussiate or that 
salt in powder to the action of chlorine gas until a sample, when heated, yields 
no precipitate with a solution of a per-salt of iron. When the dry and pulverised 
yellow prussiate is acted upon by chlorine gas, the salt is frequently placed in casks, 
closed so as only to leave a small outlet, while the vessel can be made, by means 
of machinery, to turn slowly on its axis, so as to bring all the particles of the 
salt into contact with the chlorine. Sometimes, again, the pulverised yellow prus 
siate is placed on trays in a chamber, into the top of which chlorine gas is admitted; 
when no more chlorine is absorbed the newly-formed salt is, if a solution of the 
yellow prussiate has been operated upon, evaporated to dryness, or in the case where 
the dry powder of the salt has been taken, the newly-formed salt is dissolved in the 
smallest possible quantity of water, and the solution left to crystallise, the mother- 
liquor containing chloride of potassium. This reaction is represented by— 
E^FeCye + Cl = KOI + KgFeCy. 

Yellow prussiate. Bed prussiate. 

The powdered red prussiate is of an orange-yellow colour. According to 
M. E. Reichardt (1869) bromine may be successfully employed instead of chlorine 
for the preparation of this salt, which is chiefly used for dyeing wollen fabrics blue, 
and, with solutions of caustic soda or potassa, for the Mercerising process of cotton. 

Cyanide of Potassium. This salt is obtained in an impure state — Liebig’s or crude cyanide of 
potassium—by the fusion of the yellow prussiate of potassa in a porcelain crucible, con¬ 
tinued as long as nitrogen escapes. Carburet of iron sinks to the bottom of the crucible, 
while the crude cyanide is poured off in a state of fusion; 10 parts of the yellow prussiate 
of potassium yield 7 parts of crude cyanide, (K 4 FeCy 6 “ 4KCy FeC 2 -f- 2N). According 
to Liebig’s plan, the cyanide of potassium is prepared by fusing 1 molecule of ferrocyanide 
of potassium with 1 molecule of carbonate of potassa; by this method 10 parts of the 
ferrocyanide, yielding 8*8 cyanide of potassium, mixed with 2 - 2 parts cyanite of potassa. 
For all technical and industrial purposes it is far cheaper to use cyansalt, a mixture of 
the cyanides of potassium and sodium, prepared by fusing together 8 parts of previously 
dried (anhydrous) ferrocyanide of potassium and 2 parts of caibonate of soda. As 
tliis mixture fuses readily, the carburet of iron easily separates; moreover, the salt thus 
obtained is less liable to decomposition on exposure to air, and its preparation requires 
less heat. The industrial applications of the crude cyanide of potassium, or of the cyan- 
salt, are the following :—In the process of electro-gilding, for the preparation of Grenat 
soluble , isopurpurate of potassa, from picric acid, and in the reduction of metals. It 


36 


CHEMICAL TECHNOLOGY. 


has been mentioned, while treating 1 of the blast-furnace process, that cyanide of potassium 
is formed during 1 the reduction of iron. 

iseriin-B;ue. This substance, so named when it was accidentally discovered at Beilin, 
in 1710, by Diesbach, is chemically a ferrocyanide of iron, more correctly ferrous- 
ferric cyanide. A distinct variety of this substance is known as Paris-blue. Three 
different kinds of Berlin-blue are known, viz., neutral, basic, and a mixture of the 
two, differing in composition and prepared by different processes. 

(a). Neutral Berlin-blue, also known as Paris-blue, is obtained by pouring a solution of 
vellow prussiate into a solution of chloride of iron, or into a solution of a peroxide salt of 
iron ; the result is the formation of a large quantity of a magnificently blue-coloured pre¬ 
cipitate, very difficult to wash out and always retaining a certain quantity of the yellow 
prussiate, which cannot be removed by washing. 

(/,). Basic Berlin-blue is obtained by precipitating a solution of yellow prussiate with a 
solution of a salt of protoxide of iron (green copperas), the result being at first the forma¬ 
tion of a white precipitate of protocyanide of iron, which, either by exposure to air, or by 
the action of oxidising substances, becomes blue ; because a portion of the iron is oxidised 
and another portion takes up the cyanogen thus liberated, converting some of the proto¬ 
cyanide into percyanide, which in its turn combines with the unattacked protocyanide to 
form Berlin-blue, with which, however, some peroxide of iron remains mixed. It is stated 
that basic Berlin-blue is distinguished from neutral Berlin-blue by being soluble in water; 
but this solubility is due to the presence of some of the yellow prussiate, and is not a 
property inherent in the basic Berlin-blue in a pure state. 

(r). As the materials employed on a large scale are neither pure protoxide nor pure 
peroxide salts of iron, but a peroxide containing protosalt of iron, the precipitate obtained 
consists at first of a mixture of neutral Berlin-blue with more or less of the white proto¬ 
cyanide of iron, which afterwards becomes basic Berlin-blue ; accordingly the Berlin-blue 
of commerce is a variable mixture of neutral and basic Berlin-blues. The iron salt 
employed is green copperas (sulphate of protoxide of iron), which of course should not 
contain any appreciable amount of copper, the salts of this metal, as is well known, 
yielding with yellow prussiate of potassa a chocolate-brown coloured precipitate, 
oid Method of Preparing The sulphate of iron and alum are dissolved together in boiling 
Prussian-Blue. rain or river-water; the fluid, while yet hot, is decanted from any 
sediment and forthwith poured into a hot aqueous solution of yellow prussiate, care being 
taken to stir the mixture, and to add the copperas and alum-solution as long as any preci¬ 
pitate is formed. The liquor is run off, and the precipitate washed with fresh water, until 
all the sulphate of potassa is removed; after which the precipitate is drained on filters 
made of coarse canvas. This having been accomplished the substance is suspended in 
water in a boiler, and, while being heated to the boiling-point, nitric acid is added ; after 
a few minutes’ boiling, the contents of the boiler are poured into a large wooden tub or 
cask, and strong sulphuric acid is added. The solution is now allowed to stand for some 
time, during which the blue colour fully developes. The Berlin-blue is then thoroughly 
washed with water, drained on coarse canvas filters, next dried, pressed, and cut into 
cakes; finally it is dried in rooms heated to 80 °. As Berlin-blue, when once quite dry, is 
reduced to powder with great difficulty, and cannot be brought to the state-of fine division 
as when first precipitated, it is also sent into the market in the 'state of paste. The 
alumina derived from the alum is so intimately mixed with the blue that the bulk of the 
mass is thereby increased without any very perceptible- decrease in the intensity of the 
colour. If the quantity of alumina is very much increased, the colour, of course, becomes 
much lighter, and this variety of Berlin-blue is then known as mineral-blue ; a name also 
given to a preparation of copper obtained either from the native hydrated carbonate of 
copper, or artificially prepared by precipitating nitrate or chloride of copper by means of 
lime and chalk. 

Recent Methods of Among the improvements made more recently, we may briefly notice 
Preparing Berlin-Blue, the following:— i. The mixing of the solutions of copperas and alum 
with that of yellow prussiate is effected as above described, but great care is taken to 
prevent any oxidation of the white precipitate, which is converted into an intense blue by 
being treated with nitro-liydrocliloric acid, the chlorine evolved serving as an oxidising 
agent. The remaining operations, viz., washing, drying, &c., are performed as in the 
former methods. 2. Pereliloride of iron solution is employed for the purpose of converting 
the white precipitate into blue, while the protochloride of iron thus formed serves at a 
subsequent operation instead of protosulphate of iron. 3. In some cases pereliloride of 
manganese (Mn 2 Cl 6 ), is applied; likewise a solution of chromic acid, a mixture of 
bichromate of potassa and sulphuric acid; but it is self-evident that the application of 


COBALT. 


37 


any of these improvements is dependent as regards success in a commercial point of view, 
upon local conditions, and upon the possibility of advantageously obtaining the various 
ingredients. 

Turnbull’s-Blue. By mixing together a solution of red pmssiate and of protosulphate of 
iron in such proportions as to prevent the entire saturation of the former salt, there is 
obtained a blue-colaured precipitate known in commerce as Turnbull’s-blue, consisting of 
Fe 2 Cy 3 ,3FeCy, but also containing some chemically-combined yellow prussiate. MM. 
Berlin-Blue as a By- Mallctt and Gauticr-Bouchard have proved experimentally that Berlin- 
Manufactures of ^ ue ma y be obtained as a by-product of coal-gas manufacture from the 
' Coal-Gas and ammoniacal liquor from the spent lime of the purifiers, and from Laming’s 
Animal Charcoal, purifying mixture. The spent lime contains, in addition to the cyanides 
of calcium and ammonium, a good deal of free ammonia, mechanically absorbed in the 
moist lime. Free ammonia is first removed by forcing steam through the lime, and col¬ 
lecting the ammoniacal gas in dilute sulphuric acid. The lime is next washed with water, 
and the liquor obtained, containing the cyanogen compounds, is employed for the manu¬ 
facture of Berlin-blue. According to M. Krafft’s experiments, 1000 kilos, of spent gas- 
lime yield, when treated as described, from 12 to 15 kilos, of Berlin-blue, and from 15 to 
20 kilos, of sulphate of ammonia. Mr. Phipson states that 1 ton of Newcastle gas-coal 
yields a quantity of cyanogen which corresponds to from 5 to 8 lbs. of Berlin-blue. The 
manufacture of animal-charcoal also yields, if desired, Berlin-blue as a by-product. 

soluble Berlin-Blue. As ordinary Berlin-blue is quite insoluble in water, and the basic 
variety only soluble in the presence of ferrocyanide of potassium, these pigments are only 
fit for use as paints, and the discovery of the solubility of pure Berlin-blue in oxalic acid 
is of some importance, for thereby its application as a water-colour becomes possible. 
This soluble blue is obtained by digesting the Berlin-blue of commerce for 1 to 2 days, 
with either strong hydrochloric acid or with strong sulphuric acid, which latter, after 
having been mixed with the Berlin-blue previously pulverised, is diluted with its own bulk 
of water. The acid is next decanted from the sediment of blue, and the latter thoroughly 
washed and dried, and then dissolved in oxalic acid, the best proportions being 8 parts of 
Berlin-blue, treated as just mentioned, 1 part of oxalic acid, and 256 of water. According 
to other directions, Berlin-blue readily soluble in water can be obtained: — 1. By the 
precipitation of protoiodide of iron with yellow prussiate of potassa, care being taken to 
keep the latter in excess. 2. By mixing a solution of perchloride of iron in alcoholic 
ether (tinctura ferriclilorati cetherea, Ph. Buss.) with an aqueous solution of yellow 
prussiate. 

Pure Berlin-blue is of a very deep blue colour, with a cupreous gloss; it is insoluble in 
water and alcohol, is decomposed by alkalies, concentrated acids, and by heat. The 
lighter and more spongy it is, the better is its quality; it is employed as a pigment and in 
dyeing and calico-printing, but in the two latter instances, pigment-printing excepted, it 
is obtained on the tissues by a circuitous process. The Berlin-blue of commerce is fre¬ 
quently adulterated with alumina, pipe-clay, kaolin, magnesia, heavy-spar, and, according 
to Pohl, even with starch-paste coloured blue by means of tincture of iodine. 


Cobalt. 

(Co = 59; Sp.gr. = 87). 

Metallic Cooait. This metal is found native as cobalt-speiss (CoAs 2 ), containing from 
3 to 24 per cent, of cobalt, and from o to 35 per cent, of nickel; also as cobalt-glance, 
bright white cobalt (CoAsS), containing from 30 to 34 per cent, of cobalt. Cobalt is 
prepared on a large scale as a metal at Iserlohn, and at Pfannenstiel, near Aue,'in 
Germany. Metallic cobalt exhibits a steel-grey colour, somewhat verging upon red, 
a strong metallic lustre, assumes a brilliant polish, is malleable and ductile, and far 
tougher than iron. It requires a very high temperature for fusion, is only slowly 
acted upon by dilute acids, but readily dissolved by nitric acid and aqua regia, 
cobait colours. The ores intended for the manufacture of the cobalt colours are roasted 
for the double purpose of volatilising the sulphur and arsenic they contain, and for 
effecting the oxidation of the cobalt. After roasting, the ores are known as Zaffer 01 
Saphera. According to the degree of purity, the trade distinguishes the ores as 
“common,” “medium,” and “very fine;” they contain essentially a mixture of 


CHE MIC A L TECIINO10 G Y 


38 

proto-peroxide of cobalt, arsenic, nickel, and traces of the oxides of manganese and 
bismuth, and are used in the preparation of cobalt-colours. In Sweden “ zaffers” 
are prepared by precipitating a solution of sulphate of protoxide of cobalt with a 
solution of carbonate of potassa. Zaffer is used for the manufacture of smalt, 
cobalt, ultramarine,—a misnomer, for evidently ultramarine is contracted from 
ultra-mare, because the lapis lazuli was brought across the seas from India—Cseru- 
leum, Kinnman’s-green (cobalt-green or Saxony-green), and also cobalt-yellow, 
cobalt-violet, and cobalt-bronze. 

Smalt. Compounds of cobalt have the property of imparting a blue colour to glassy 
substances at a red heat; when, therefore, impure protoxide of cobalt is fused with silica 
and carbonate of potassa, the result is the formation of an intensely blue-coloured glass, 
which when pulverised is known as smalt. This substance was discovered and first pre¬ 
pared by the Bohemian glass-blower, C. SchUrer, who lived in the sixteenth century. 
•Smalt is now prepared by melting the roasted cobalt ores •with quartzose sand and potash, 
in crucibles placed in a glass-furnace. The red-hot glass produced is quenched in cold 
water to render it brittle. It is next pulverised and scoured with water, by which opera¬ 
tion smalts are obtained of different degrees of fineness, not simply as regards minute state 
of division, but also depth of colour, all of which varieties abroad—where to a limited 
extent the smalt is still used though it is almost entirely superseded by artificially-made 
ultramarine—bear distinctive names. It has been proved experimentally that the colouring- 
matter of smalt is potassio-silicate of protoxide of cobalt, in which the proportion of the 
oxygen of the acid to that of the base is as 6:1. According to M. Ludwig, 100 parts of 
the undermentioned cobalt colours contain:— 

Norwegian Smalt. German Smalt. 


Termed Coarse and 
High colour. high Eschel. pale coloured. 

Silica . 70-86 66’20 72-11 

Protoxide of cobalt .. 6-49 675 1-95 

Potassa and soda .. .. 21-41 1631 r8o 

Alum i na. 0-43 8-64 20-04 


These substances, moreover, contain small quantities of protoxide of iron, lime, prot¬ 
oxide of nickel, arsenic acid, carbonic acid, water, and oxides of lead and iron. Dr. Oude- 
mans lately analysed a beautifully ultramarine-coloured sample of smalt, which was 
found to contain 57 per cent, of protoxide of cobalt. As cobalt-glass obtained with soda 
is never of a pure colour, that alkali cannot replace potassa in the manufacture of smalt. 
Since the roasting of the cobalt ores is not continued long enough to oxidise the nickel 
contained in them, that and some other metals present fuse during the preparation of the 
smalt, and, settling to the bottom of the crucible, form an alloy termed Cobalt-speiss. 

Cobalt Speiss. This substance is of a reddish-white hue, has a strong metallic lustre, is fine¬ 
grained in structure, and contains on an average from 40 to 56 per cent, nickel, 26 to 44 
per cent, arsenic, as well as copper, iron, bismuth, sulphur, See. Dr. Wagner found that 
(1870) a sample of this alloy from a Saxon mine contained in 100 parts :— 

Nickel 
Cobalt 
Bismuth 
Iron .. 

Copper 
Arsenic 
Sulphur 


T 00-00 

The material is chiefly used for the preparation of nickel. 

Applications of Smalt is still employed in washing and dressing blue, and for impartm" 

Smalt. a blue tint to paper. It is not, however, very suitable for this purpose as 
on account of its hardness, it soon destroys the points of writing pens. Smalt is more 
extensively used for blue-enamelling glass, porcelain, and earthenware. 

Cobalt Ultramarine. This substance, also known as Thenard’s blue, is a pigment eonsistino 
of alumina and protoxide of cobalt. Curiously enough this pigment has" been discovered 
and prepared at three several periods and localities by different people ; first, by Wenzel 


1- 63 

2- 44 
0*63 
i ‘93 

42-08 

ro 7 






















NICKEL. 


39 


at Freiberg", Saxony; next by Gahn, at Fabian, Sweden; and lastly, simultaneously at 
Paris and Vienna, by Thenard and Von Leithener. The pigment is prepared either by 
mixing solutions of alum and a salt of protoxide of cobalt, precipitating the mixture by a 
solution of carbonate of soda; or by the decomposition of aluminate of soda by means of 
chloride of cobalt. The ensuing precipitate, consisting of an intimate mixture of hydrate 
of alumina and hydrate of protoxide of cobalt, is first well washed, then dried and heated 
for some time. The pigment thus produced is, when seen in daylight, of course after pul¬ 
verisation, very similar to ultramarine, but by artificial light its colour is a dirty violet. It 
is, however, not acted upon by acids, as distinguished from artificial ultramarine; neither 
is it affected by alkalies nor heat, as is copper or mineral blue. Cobalt-ultramarine, 
chiefly under the denomination of Thenard’s blue, is employed as a paint in oil- and water¬ 
colours, and also for staining glass and porcelain. 

Casruieum. Is a pigment prepared in England, exhibiting a bright blue colour, not 
changing in artificial light, and consisting of stannate of protoxide of cobalt (Sn 0 2 ,CoO), 
mixed with stannic acid and gypsum in the proportions, in 100 parts, of 49-6 of oxide of 
tin, iS’6 protoxide of cobalt, 31-8 gypsum. This pigment is not affected by heat, or the 
action of dilute acids and alkalies; nitric acid dissolves the proxtoxide of cobalt, leaving 
the other ingredients, from which the gypsum may be cleared by water. 

Rinmann’s or This substance, also known as cobalt-green, zinc-green, and Saxony-green, 
Cobait-Green. j s a compound similar to the cobalt-ultramarine, for the alumina of which 
oxide of zinc is substituted. This green is prepared by mixing a solution of white vitriol 
with a solution of a salt of protoxide of cobalt, precipitating by carbonate of soda, and 
washing, drying, and heating the precipitate. This pigment when pure contains 88 per 
cent, of oxide of zinc and 12 per cent, of protoxide of cobalt. It is not affected by strong 
heat, tinges the borax-bead blue, dissolves in warm hydrochloric acid, forming a blue 
colour, which, upon water being added, becomes a pale red. Treated with caustic potassa, 
the oxide of zinc is dissolved, and may be detected, after previous dilution with water, by 
the addition of a solution of sulphuret of potassium. 

ohpmicaiiy Pure This substance is occasionally employed for the preparation of fine 
Protoxide of Oobait colours. It maybe obtained by heating one part of previously roasted 
and finely-pulverised cobalt ore with two parts of sulphate of potassa until no more 
sulphuric acid is given off. The fused mass, consisting of sulphate of potassa, sulphate of 
protoxide of cobalt, and insoluble arsenical salts, is, when cooied, first treated with water, 
and next digested with hydrated protoxide of cobalt to precipitate any iron which may 
happen to be present, and in order to eliminate the oxide of that metal the solution is 
filtered. It is next precipitated with carbonate of soda, and finally the precipitate is 
washed and heated. 

Nitrate of Protoxide of This double salt, known by its trade name of cobalt-yellow, is 
Cobalt and Potassa. obtained by mixing a solution of protoxide of cobalt with nitrite of 
potassa; it is a yellow crystalline precipitate, perfectly insoluble in water. M. Saint-Evre 
first investigated this body, and struck with its beautifully yellow colour, quite like that of 
purrhee (euxanthinate of magnesia), and with the fact that cobalt-yellow resists oxidising 
and sulphuretting influences, suggested its applicability to artistic purposes. He prepares 
this pigment by precipitating with a slight excess of potassa the double salt of protoxide 
of cobalt and potassa, obtaining a rose-red-coloured protoxide of cobalt and potassa. Inco 
this thickish magma dcutoxide of nitrogen gas is passed. According to Hayes, this pig¬ 
ment is readily obtained by causing the vapours of hyponitric acid to pass into a solution 
of protonitrate of cobalt, to which some potassa has been added ; the whole of the cobalt 
is then converted into cobalt-yellow. As the nitrite of protoxide of cobalt and potassa 
can be obtained even from impure solutions of protoxide of cobalt, so as to be quite free 
from any nickel, iron, &c., the use of this preparation of cobalt is preferable for glass and 
porcelain staining, when a pure blue is required. 

Cobalt-Bronze. This substance, a double salt of phosphate of protoxide of cobalt and 
ammonia, prepared at Efannenstiel, near Aue, in Saxony, has been but lately brought into 
commerce. It is a violet-coloured powder, very much like the violet-coloured chloride of 
chromium, and exhibits a strong metallic lustre. 

Nickel. 

(Ni = 59; Sp. gr. = 8-97 to 9-20). 

Nickel and its ores. This metal occurs in the following ores :—Copper nickel or 
arsenical nickel, NiAs, containing about 44 per cent. Ni.; antimonial nickel, NiSb, 
with about 31*4 per cent. Ni. ; white arsenical nickel, NiAs 2 , with about 28*2 pei 


CHEMICAL TECHNOLOGY . 


4° 


cent. Ni; in some varieties of cobalt speiss, as, for instance, tbe capillary pyrites 
(snlphurct of nickel) with 64*8 per cent. Ni); and the antimonial nickel-ore, 

NiS 2 +Ni(Sb,As 2 ), 

with about 26*8 per cent. Ni. There is found at Rewdansk, Oural, Russia, a mineral 
known as Rewdanskite, a silicate of hydrated protoxide of nickel (12*6 j)er cent. Ni), 
from which the metal is obtained. Nickel is also extracted from ores which contain 
it accidentally, as, for instance, some species of iron and copper pyrites, cobalt- 
speiss, and certain copper ores known as Mansfield ores, which yield sulphate of 
nickel as a by-product. Several varieties of manganese contain nickel and also 
cobalt; and in England the residues arising from the manufacture of chlorine are 
in some instances applied in the production of these metals, the process jdelding, 
according to Geiiand, 2'5 kilos, of nickel and 5 kilos, of cobalt for 1 ton of manga¬ 
nese. Some magnetic iron ores yield nickel, a specimen of such ore from Pragaten, 
Tyrol, Austria, containing, according to M. T. Petersen, 1*76 per cent, of NiO. 

rrcp rrom 1 its ores! ckcl It very rarely happens that the natural ores of nickel are so pure, 
that is to say, contain the metal in such a state of combination, as to admit of the 
direct extraction of the metal, and therefore, as is the case with copper, a preliminary 
operation is required, which aims at the concentration of the metal in combination 
either with sulphur, in which case the combined substance is termed regulus, and 
sulphuret of iron is applied as a means of concentrating the nickel contained in the 
ore as sulphuret: or, if the nickel happens to be combined chiefly with arsenic, the 
concentrated mass is termed speiss; while in a few instances an alloy of nickel and 
coarse or black copper is obtained. Prom all these products the metallic nickel, or 
sometimes an alloy of nickel and copper, is prepared by the dry or moist process. 


The method of obtaining* nickel embraces two distinct features, viz. :—- 
I. A smelting process, which aims at rendering the nickel of the ores richer, and con¬ 
centrating the metal— 
a. In a regulus. 

/3. In a speiss, or 

7 . In alloy with coarse or black copper. 

LI. In the separation of the nickel, or a definite alloy from the products obtained by 
the concentration-smelting; this can be done— 


a. By the dry, or 

b. By the hydro-metallurgical method. 

As it is found that the preparation of an alloy of copper and nickel for the manufac¬ 
ture of so-called German-silver, impairs the most valuable properties of nickel—its 
white colour and resistance to chemical action—the obtaining of pure metallic nickel is 
preferred. 

Th smeittae of*the n * I* This operation is carried on (a) for regulus, when the nickel-ores are 
Nic kef ores. mixed Avith iron pyrites and magnetic pyrites, and consists in smelting the 

previously partly roasted ore with quartz or substances rich in silica. During the process 
the greater portion of the oxide of iron generated is absorbed by the slag, while the nickel, 
also first oxidised, and more readily reduced than the oxide of iron, is converted to the 
metallic state and taken up by and concentrated in, the regulus, a mixture of undecom¬ 
posed sulphurets of metals and reduced sulphates. If at the time the ore contains 
copper, that metal is even more readily and completely incorporated with the regulus than 
the nickel itself. If the roasted mass contains too much protoxide of iron, a portion of 
that metal is reduced, and either taken up by the regulus, or separated as containing nickel. 
The separation of the iron from the regulus frequently requires the application of a refining 
furnace provided with a blast so as to oxidise the iron. A better result is obtained by 
treating the previously roasted ore in a reverberatory furnace with quartz, heavy spar, 
and charcoal or coal; sulphuret of barium results, which, becoming converted into baryta, 
transfers its sulphur to the oxides of nickel and copper, while the baryta forms with the 
quartz and protoxide of iron a readily fusible slag. At Dillenburg 'an ore which con¬ 
tains the sulphurets of nickel to about 7*5 per cent., and copper, is treated in the fol¬ 
lowing manner:—It is roasted in stacks, built not unlike coke-ovens; next broken up an:l 


NICKEL. 


4i 

smelted in a low-blast furnace heated by means of coke, no other ingredients being added, 
as the ore contains silica, alumina, and lime in sufficient quantities, so as to obtain crude 
regulus (I.) This crude regulus is next melted with slags, so as to obtain concentrated 
regulus (II.) It is lastly submitted to the action of a refining blast-furnace in order 
to lessen the quantity of iron, care being taken to leave enough sulphur to keep the 
refined regulus (III.) brittle; finally, the regulus is employed in the manufacture of nickel 
and alloys of nickel. Composition— 


I. II. III. 

Nickel. 19 24 35 

Copper. 13 39 43 

Iron .35 12 2 

Sulphur .33 25 20 


100 100 100 

This mode of operation is employed at Ivlefver (Sweden), and in some other localities. 

(iS). The smelting of nickel ores for the purpose of concentrating the metal in speiss is 
applied when the nickel occurs in combination with either arsenic only or with that 
metal and antimony, such compounds being occasionally obtained in the operations of 
smelting copper, lead, and silver ores, and as by-products of the smelting of metals not 
containing arsenic, as, for instance, in slags from copper-smelting, in which case there 
is added arseniuret of iron (arsenical iron pyrites, FeAs -f- FeS , which when heated by 
itself splits up into As and 2FeS). When a mixture consisting of nickel, iron, and arsenic 
is first submitted to a partial calcination, and next to a simultaneously reducing and 
fusing smelting, the iron is taken up by the slag, the nickel-oxide is reduced, and the 
arseniates are converted into arseniurets, and as the nickel has a greater affinity for 
arsenic than for sulphur, the speiss will also take up that metal. If the compound 
originally operated upon happens to contain copper, that metal is present in the speiss, 
from which it may be separated as a sulphuret by the addition of ordinary pyrites to tl e 
arsenical pyrites during the smelting. By frequently roasting and smelting the speiss, 
aided occasionally by an oxidising blast and the use of heavy spar and quartz as slag, the 
iron is gradually eliminated. At Birmingham, Hungarian and Spanish nickel ores aio 
smelted for speiss, these minerals containing on an average from 40 to 55 per cent, 
of nickel, and from 30 to 40 per cent, of arsenic, as well as sulphur, bismuth, and 
copper. 

(7). Smelting for the concentration of coarse copper or nickeliferous pig-iron. Wlien 
the quantity of nickel contained in the copper ores is very small, the nickel accumulates 
in the first portions of the refined copper in such quantities as to repay the trouble of 
extraction. M. Wille analysed some refined copper, obtained from the cupriferous slate 
of Biechelsdorf, and found it to contain from 7-8 to i3 - 6 per cent, of nickel; occasionally 
the surface-discs of rosette-copper contain crystals of protoxide of nickel. 

Metamc a Nickei°or of II- This is effected by submitting the product oftheconcentra- 
Aiioj s of xickei anu copper, tion-smelting to either («) a dry method of treatment, or (b) a 
hydro-metallurgical process. 

(a). Preparation of nickel by the dry method. It appears that the methods hitherto 
employed have not led to very satisfactory results; it is true that when nickel-speiss is, as 
suggested by M. von Gersdorf, repeatedly roasted with charcoal-powder and wood- 
shavings, oxide of nickel is obtained, and may be reduced by means of coal, coke, or char¬ 
coal ; but as this oxide is always mixed with arseniate of oxide of nickel, the metal also 
contains arsenic, and any German-silver made with it is brittle and turns brown on 
exposure to air; moreover, a small quantity of iron is always present in the nickel thus 
prepared. A better result is obtained by the process proposed by the late H. Bose, in 
1863, for the preparation of the metal free from arsenic, and which consists in mixing 
the pulverised speiss with sulphur, and heating this mixture, thereby forming sulphuret of 
nickel and sulphuret of arsenic, the latter being volatilised. This operation is repeated 
as often as may be necessary; the sulphuret of nickel is roasted, and sulphate of protoxide 
of the metal is formed, which, at a high temperature, as is the case with protosulphate of 
iron, loses its sulphuric acid, leaving the oxide of nickel to be reduced to the metallic 
state by means of charcoal. At Dillenburg experiments have been made in order to 
obtain from what is termed a refined stone—a compound of nickel, copper, iron, and 
sulphur—an alloy of nickel and copper, by first completely calcining the sulphurets, and 
so driving off the free sulphur ; next mixing the remainder of the substance in quantities 
of 100 lbs. with 45 lbs. of soda, and submitting this mixture to the heat of a reverberatory 
furnace in order to render the sulphur soluble in water as sulphuret of sodium and 








42 


CHEMICAL TECHNOLOGY. 


sulphate of soda, leaving an alloy which, of course, has to be refined in order to eliminate 
the last traces of iron. 

(b). Obtaining nickel by the wet, or hydro-metallurgical method. A preliminary 
roasting of the ores or products of metallurgical operations containing nickel is required 
in order to convert the iron into an oxide soluble in acid, and to convert the nickel, 
copper, and cobalt, either into sulphates soluble in water or into oxides or basic salts, 
both of which are soluble in sulphuric and hydrochloric acids. From any such solution 
the nickel is precipitated by a suitable reagent, either as oxide or as sulphuret, and from 
these materials metallic nickel or an alloy of that metal -with copper is prepared. The 
preparation of nickel by the moist method consists of three different operations:— 
i. The preparation of the nickel solution. When nickeliferous and metallurgical products 
are roasted, either with or without the addition of copperas, the result is the formation of 
the sulphates of iron, copper, nickel, and cobalt, and this mixture when roasted becomes 
decomposed, the sulphuric acid being driven off first and most readily from the sulphates 
of the oxides of iron, and with greater difficulty from the sulphate of protoxide of cobalt. 
Accordingly, after roasting, the mass on being treated with water, yields the larger portion 
of the nickel and cobalt with some of the copper, while the greater part of the latter, 
with very small quantities of cobalt and nickel, and the whole of the iron, remain undis¬ 
solved as oxides; by the use of acids the protoxides of copper and nickel are extracted 
from this residue. If the roasted material is immediately treated with hydrochloric acid, 
the result is that more of the oxide of copper than of the protoxide of nickel is dissolved ; 
but by again treating the residue with boiling acid the oxides of iron and nickel are 
extracted. Speiss may be used for obtaining a nickel solution by first heating the pre¬ 
viously roasted speiss with a mixture of soda and nitrate of soda, next extracting the 
arseniate of soda by means of water, and afterwards treating the residue with sulphuric 
acid, roasting the sulphates obtained so as to decompose only that of iron, and finally 
treating the mass again with water to obtain the sulphates of nickel and cobalt in solution. 
According to Professor Wohler’s plan, the arsenic of the speiss can be removed by fusion 
with sulphuret of sodium, and a subsequent treatment with water, in which it, as a sulplio- 
salt, is soluble. 2. The nickel may be precipitated from the solution in various 
ways. According to M. Stapff’s plan (1858), a fractioned precipitation may be obtained 
by means of chalk employed at various temperatures, the result being that first iron 
and arsenic, and next copper, are separated, so that only the nickel remains in solution, 
and can be thrown down by milk of lime. According to M. Louyet (1849), Aon and 
arsenic are first precipitated by milk of lime mixed with bleaching-powder, and the 
liquid containing this precipitate filtered off. Prom the acid filtrate the bismuth, lead, 
and copper that may be present are removed by sulphuretted hydrogen; the filtrate from 
these joint sulphides is next boiled with bleaching-powder, the cobalt being separated as 
a peroxide, and the nickel remaining in solution. If it is desired to obtain the cobaltic 
peroxide in a pure state, the precipitation should be so conducted as to leave a little 
cobalt with the nickel, no injury therefrom accruing to that metal. At Joachimsthal, 
Bohemia, the nickel is precipitated from the acid solution after the removal of the 
copper by sulphuretted hydrogen, by means of bisulphate of potassa as bisulphates of 
protoxide of nickel and potassa, leaving the cobalt in solution free from nickel, which in 
its turn is thrown down by carbonate of soda. 3. The conversion of the nickelif erous 
precipitate into metal, or into an alloy with copper, may be carried out in the following 
manner :—The protoxide of nickel is first separated from the liquid by filtration, thou 
pressed so as to admit of its being dried by intense heat, and next ground up with water 
and washed with very dilute hydrochloric acid, in order to remove the gypsum, of which 
some 8 to 12 per cent, is mixed with the oxide. The oxide is then made with beet-root 
sugar, molasses, and coarse rye-meal, into a stiff paste, which is shaped into cubes from 
1-5 to 3 centimetres in size; these cubes are next rapidly dried, and after drying are 
placed with charcoal powder in crucibles, or in perpendicular fire-clay cylinders, where, 
being submitted to a very strong white heat, the metal is reduced, an operation which, iii 
the case of the alloy of copper and nickel, or of cupriferous nickel, is finished in 1hour, 
the reduction of the pure metal taking fully three hours. The copper soon becomes 
molten, but the nickel only sinters together, on account of the very great infusibility of 
this metal. The small cubical pieces of nickel as met with in commerce exhibit externally 
a strong metallic lustre, produced by putting the cubes with water into casks, which are 
made to rotate. In order to ensure uniformity of composition, and hence a good sale for 
the alloy of copper and nickel, rosette-nickel, care is taken to procure the mixture of 
the two metals in the proportion of 66-67 P er cent, copper, and 33-33 percent, nickel while 
the cubical nickel contains from 94 to 99 per cent, of pure metal. At a nickel-oven at 
Dillenburg, the metal is not made into cubes, but treated in the same way as rosette- 
copper. 


COPPER. 


43 


properties of Nickel. Pure nickel has a nearly silver-white colour, with a slight 
: yellowish hue, is very difficult to melt, rather hard, very ductile, and easily polished; 
sp. gr. = 8*97 to 9*26. When quite pure this metal may be drawn into wire, rolled 
into sheets, hammered, and forged; its tensile strength stands to that of iron as 9 : 7. 
Nickel is analogous to iron, but distinguished from it by possessing a greater power 
of resisting chemical agents; on this account, and for its not becoming rusty in air 
or when in contact with water, nickel is used for obtaining silver-like alloys (see 
Copper). In Belgium, Switzerland, the United States, and Jamaica, small coins 
have been made of an alloy of nickel with zinc and copper, pure nickel being too 
hard to admit of readily coining. An alloy known as tiers-argent , one-third silver, 
consists in 100 parts of:— 


Silver. 

.. .. 27*56 

Copper 

.. 59-06 

Zinc .. 

•• •• 9*57 

Nickel 

.. .. 3-42 


99-61 


The total annual production of nickel on the Continent of Europe amounts (1870) 
to 11,200 cwts., exclusive of what is made in England. Very pure nickel is obtained 
at Val Benoit, near Link, Belgium, from an Italian nickel ore, the metal containing 
less than 1 per cent, impurities. 

Copper. 

(Cu = 63-4; Sp. gr. = 8-9). 

Copper and how . 1 occurs ’ Copper is one of the metals met with most abundantly. It has 
been known from a very remote antiquity—even before iron—and bears the Latin 
name Cuprum , because it was obtained by the Romans and Greeks from the Island 
of Cyprus; from the Latin name of this metal the English, German, Dutch, and 
French names are derived. Copper is found to some extent in a metallic state 
naturally, but it is chiefly obtained from ores, among which the oxides and sulphides 
are the chief. 

ores of Copper. Native copper is found in large quantities near Lake Superior, in North 
America; and in Chili there is known a peculiar kind of sand called copper-sand, or 
copper-barilla, consisting of from 60 to 80 per cent, of metallic copper, and 20 to 40 per 
cent, of quartz. This sand is imported into England and smelted, with other copper ores, 
at Swansea. 

Red copper or (suboxide, or red oxide of copper), Cu 2 0 , containing 88-8 per cent, of 
copper, is met with in octahedrical-shaped crystals, disseminated or instratified through 
rock in Cornwall. An intimate mixture of suboxide of copper and iron-ochre is known as 
tile-ore, or earthy-red oxide of copper. Azurite, or blue copper ore, containing 55 per 
cent, of copper, is a compound of carbonate of protoxide of copper and hydrated protoxide 
(2CuC0 3 -f- CuH„0 2 ). It occurs in beautifully blue-coloured crystals disseminated through 
rock and gangue in'Comwall, and was formerly found at Chessy, near Lyons. 

Malachite, containing 57 per cent, of copper, consists of basic carbonate of hydrated 
oxide of copper (CuC 0 3 -j- CuH 2 0 2 ), and occurs in rhombic crystals, also as stalactite and 
stalagmite, and in Atlas ore, a veined and earthy ore called copper-green or earthy 
malachite, and very frequently with azurite in Australia and Canada. 

Copper-glance, copper-glass, sesquisulphuret of copper (Cu 2 S), contains 80 per cent, of 
the metal. Purple copper ore, variegated copper ore, a compound of copper-glance and 
sesquisulphuret of iron (3Cu 2 S Fe 2 S 3 ), with 55:54 per cent, of copper and copper pyrites 
(Cu 2 S Pe 2 S 3 or CuEeS„), with 34'6'per cent, of copper are the chief sulphur ores used in 
the extraction of copper" Copper pyrites is often mixed with iron pyrites, and also often 
contains silver and nickel. The mineral known as Boumonite, although a lead ore, often 
contains as much as 1276 per cent, of copper. 






44 


CHEMICAL TECHNOLOGY. 


Slaty copper ore is a bituminous marly schist belonging to the Permian formation, 
through which sulphuretted copper ores are disseminated; this ore is chiefly found in 
Germany. 

Grey or black copper ores, so called Fahl ores, are compounds consisting of electro¬ 
positive sulphurets, viz., sulphuret of copper and of silver, with electro-negative 
sulphurets, viz., those of arsenic or antimony. As these ores contain silver they are usually 
considered as silver ores, the quantity of copper contained in them amounting to about 
14 to 14*5 per cent. Atacamite is also a copper ore (3CuH 2 0 2 -{- CuCl 2 ), containing 56 per 
cent, of copper. This substance is chiefly met with in Chili and other parts of the Western 
Coast of South America, in Southern Australia, and in Peru, and in that country it is 
ground to powder and used instead of sand or sawdust to strew on the floors of rooms. 
It is imported in that state under the name of Arsenillo, and is smelted with the atacamite 
in lumps at Swansea. 

Modp of treating the Copper It is quite evident that the treatment of the ores must vary 
Extracting the Metai. according to the constitution of the metals. The ores in 
which copper is contained as oxide, or ochrey ores, are reduced readily enough by 
simple treatment with carbonaceous matter and a flux ; but these ores are by no 
means abundantly found, and are, therefore, usually mixed with pyritical sulphu¬ 
retted ores. The smelting of copper from its ores therefore embraces:— 

1. The smelting from ores containing oxides. 

2. From pyritical ores, and 

3. The hydro-metallurgical method. 

Pyritical copper ores are smelted either in a shaft, or pit-fumace, or in a reverbera¬ 
tory furnace. In the latter instance the reduction of the metallic regulus of copper 
obtained from a previous roasting of the ore, is effected by the aid of sulphur, not by 
that of coal. The regulus is gradually rendered richer and richer in metal, until at 
last the decomposition of the sulphur is completed by the action of the oxygen of the 
air; by this operation suboxide is plentifully formed, and as a consequence the metallic 
copper obtained is in the state technically termed “over-refined.” When the shaft- 
furnace is employed, the first portion of the operation is similar to that alluded to, 
but the metal is reduced with coal or charcoal, and hence the copper obtained— 
leaving out of the question the presence of the foreign metals—is never over-refined, 
but contains carbonaceous matter, so that in order to render the copper, as it is 
technically termed, tough—that is to say, malleable when cold as well as when hot, 
another operation is required, which it is evident from the foregoing must differ for 
the two qualities of crude metal. 

The working-up of the The ores are first roasted or calcined, and a portion of the 

Copper Ores jn the . * 

Shaft Furnace. sulphur, arsenic, and the antimony they contain volatilised; sul¬ 
phates of the metals as well as arseniates and antimoniates are* at the same time 
formed, while a portion of the ore is not acted upon at all. When the smelting 
operation is commenced, fluxes are added, and any oxide of copper present is reduced 
to the metallic state, while simultaneously the sulphates are again converted into 
sulphurets, which jointly with the metallic copper form the rather richer crude 
regulus of copper; while if arsenic and antimony prevail speiss is formed. The 
more readily oxidised metals present, chiefly iron, form, as protoxides, compounds 

with the fluxes. By a repetition of this process with the coarse metal regulus_the 

operation being known as a concentration-smelting—there are obtained thin matt, 
and what is termed black copper, containing foreign metals, which are got rid of by 
a first or coarse refining, a portion of the impurities under the influence of a high 
temperature, the oxygen of the air and fluxes, being partly volatilised, partly taken 
up in the slag. The copper obtained by this operation, rose- or disc-copper, contains. 


COPPER. 


45 

because the calcination is carried rather too far, suboxide of copper, which impairs 
the ductility of the metal. . This defect is remedied by a rapid smelting under a 
layer of charcoal, the suboxide being reduced and tough copper obtained. When a 
reverberatory furnace is employed, the coarse and last refinings are usually included 
in one process. 

According to the Continental methods, the calcined ore is smelted and converted 
into coarse regulus in a shaft-furnace, the fuel employed being charcoal or coke, or 
a mixture of the two. Fig. 18 exhibits the vertical section of the furnace ; Fig. 19 
is a front view, the front wall being removed to show the interior construction. 
Fig. 20 exhibits the lower part of this furnace; 11 are the tuyere-holes for the blast ; 
the apertures, 0 0, placed just above the lowest part of the breast of the hearth, com¬ 
municate by means of channels with the smelting-pots, c' c', the object being to 
gradually collect the molten contents of the furnace. Since copper ores always contain 
more or less iron, it might happen that by simply employing a reducing smelting, 
some of that metal would become mixed with the copper; in order to avoid this, 
fluxing materials rich in silica are added, with which the protoxide of iron forms a 


Fig. 18. Fig. 19. 



readily fusible slag. The oxides of copper present in the calcined materials are 
reduced to the metallic state by the sulphuret of iron— • 


3 OuO + FeS = SO2 + FeO -f 3 Cu. 

The metal regulus, a mixture of sulphurets of copper and iron and other metals, 
containing on an average 3 2 per cent, of copper, collects in the lower part of the 
furnace, and the slag formed is called crude or coarse slag. The roasting of the 
regulus aims at its most complete oxidation, while the sulphur is eliminated. The 
calcined regulus is next smelted in a shaft furnace with the addition of a flux, a pro¬ 
cess technically known as concentration-smelting. * The refined regulus obtained by 
this smelting contains some 50 per cent, of copper, and is next treated to obtain black- 
copper, coarse metal. But if the regulus contain a sufficient quantity of silver, that 
metal is extracted by methods which will be fully elucidated when silver is treated 
of; in some cases this operation is combined with the extraction of lead from the 
copper, and effected by what is termed liquidation, of which more presently. 

* There are no equivalent terms in English to express the real meaning of the German 
words, a fact which is readily accounted for, if we consider that these operations are 
essentially German and of very ancient standing. 
















46 


CHEMICAL TECHNOLOGY. 


The operation of smelting for a refined regnlns is omitted if tolerably pure copper 
ores are operated upon, and such ores after calcination are immediately treated in a 
low blast-furnace to obtain the black-copper. In addition to black-copper, a thin 
matt containing from 93 to 95 per cent, of that metal is obtained. As an instance 
of the composition of black-copper, we quote Dr. Fach’s analysis of a sample of 
that material produced at Mansfeld, in 1866 ; in 100 parts there are :— 


Copper . 93-49 

Lead.. . 1 *49 

Zinc. 1 *47 

Iron. 1 *03 

Nickel and cobalt together. 1*25 

Silver . .. 0*03 

Sulphur. 0*99 


9975 

nefinir.g the copper. The black-copper is next submitted to an energetic oxidising 
smelting process in order to get rid of the impurities in the slag. This process is 
carried on either— 

1. In a small refining furnace; 

2. In a large refining furnace; or 

3. In a reverberatory furnace. 

Refining on the Hearth, i. This operation is effected in a furnace or hearth, represented 
in vertical section in Fig. 21, and in perspective in Fig. 22 ; a is a semi-globular 


Fig. 21 


Fig. 22 



excavation, termed the crucible; b is a cast-iron bed-plate ; h represents one of the 
two tuyeres by means of which a blast is conveyed to the fuel and the surface of the 
copper. The black or coarse copper is melted by the heat of charcoal aided by the 
blast, the sulphur, arsenic, and antimony being volatilised, while the oxides of iron 
and of the other non-volatile metals are taken up with the suboxide of copper by the 
slag, which gathers at the surface of the molten metal, and is from time to time 
removed. As soon as the refining is complete, the blast is turned off and the sur¬ 
face of the copper, the metal being heated far above its melting-point, covered with 
charcoal-dust. When cooled sufficiently, water is poured on, and a portion of the 
metal thus suddenly solidified admits of being lifted off from the rest of the molten 
mass in cakes or discs, technically known as rose or rosette-copper ; this operation 
is repeated until the crucible contains no more metal. 

R iarge* quantities! 1 As tlie refining of copper on the hearth has been found to yield but 
poor results, another contrivance, shown in vertical section in Fig. 23, is now more 
generally employed. A is the smelting-hearth; b the refining crucible, of which there 

















COPPER . 


47 


are two ; n, the opening for the tuyere of the blast; l, the furnace. The mode of 
operation is similar to that just given. When the refining is complete the molten 
metal is run into the crucibles, and after having cooled sufficiently, water is sprinkled 
on and the discs of rose-copper lifted off. For the reason that in this kind of rever - 
beratory furnace the copper is not, as is the case on the hearth, in contact with the 
fuel, the result is a purer metal. 

Liquation Process. When the copper ores contain silver,the black copper is submitted, 
before being refined, to a process known as liquation, unless it should be preferred 
to extract the silver by the Ziervogel method (see Silver). The liquation process is 
based upon the fact that lead and copper may be melted together, but do not remain 
alloyed on cooling, so that a compound is formed containing much more copper than 
lead, the remainder of the lead separating and, while taking up the silver, settling 
down in consequence of its specific gravity. When the molten mass is slowly cooled, 
the lead combined with the silver runs off after the solidification of the copper; but 
if the molten metals are rapidly cooled, an intimate mixture of the two takes place. 
The mode of separating the silver from the lead will be referred to when treating 
of the former of these metals. 

It has been already mentioned that the refined copper resulting from the above processes 
contains suboxide of that metal, which, if amounting to a quantity of it percent., renders 
the copper unfit for use at ordinary temperatures, by impairing its ductility and mallea¬ 
bility while if the quantity of the 3 uboxide amounts to per cent., the metal is unfit for 


Fig. 23. 



use both cold and at a red heat—that is, becomes cold- and red.-short. This condition of 
the metal is, in Germany, termed “ over-cooked,” and the remedy is simply to melt the 
copper and submit it to what is, in England, technically known as poling; that is to say, 
a sufficiently long, stout, and green piece of wood, is used for thoroughly stirring up the 
molten mass. The rationale is that the carbon and hydrogen contained in the wood 
deoxidise the suboxide at the high temperature, rendering the metal very malleable and 
ductile, making it, as is technically termed, tough. A sample of Mansfeld refined and 
toughened copper was found by Dr. Steinbeck to contain in ioo parts :— 


Copper. 94-37 

Silver . 0-02 

Nickel . 036 

Iron. 0-05 

Lead .. .. . o-6o 

Oxygen. 0-58 

Sulphur. 0-02 


ioo-oo 

of copper smeufng. Owing chiefly to the possession of an enormous wealth of coal, th( 

fuel most suited for the reverberatory furnaces, a method of copper-smelting peculiai 




















48 


CHEMICAL TECHNOLOGY. 


to England is pursued, and a metal obtained of a very superior quality, although 
not so good as that extracted from particular ores in Eussia and Australia. Swansea 
is the chief and most important seat of this industry in the United Kingdom, and 
to it copper ores are not only carried from Cornwall, North Wales, Westmoreland, 
Anglesea, and other portions of the realm, Ireland included, but are imported from 
Chili, Peru, Cuba, Norway, Australia, and other parts of the world. The English 
ores are mainly pyritical. 

The chief processes of this mode of smelting consist in—i. Calcination of the ore; 
2. Smelting for coarse metal; 3. Calcination of coarse metal; 4. Making of white metal, 
a concentration process in which calcined coarse metal is smelted with rich ores ; 5. Prepara¬ 
tion of the blue metal by smelting together calcined coarse metal and calcined ores of 
medium richness; 6. Preparation of a red and white metal by smelting together the slags 
of the previous operations; 7. Calcination of the blue metal (5) and preparation of white 
extra metal; 8. Calcination of the white extra metal and preparation of the concentration 
metal; 9. Calcination of the ordinary white metal of cupriferous residues for the purpose 
of obtaining blistered copper. According to M. Gui-lt’s views, all these operations may be 
reduced to, at most, two calcinations and three smelting operations, viz. :—1. Calcination 
of the previously pulverised ores with the addition of common, salt, or of chloride of 
calcium, to form volatile chlorides ; 2. The smelting of calcined ores and obtaining a more 
liquid slag and a coarse metal; 3. The calcination of coarse metal by the aid of a blast 
for the production of blistered copper with or without the addition of chlorides; 4. Ke- 
fining and toughening the blistered copper. 

Calcining, nr Roasting This operation as carried on at Swansea does not materially differ 
the ores. from that pursued on the Continent. No very appreciable loss of 
weight is experienced, as the weight of the oxygen taken up compensates for the loss' 
occasioned by the more or less complete volatilisation of the sulphur, antimony, arsenic, 
&c. The roasted ore is black, this colour being due to the oxides of iron and copper. 
During the roasting heavy white fumes arc emitted, consisting of sulphurous and arsenious 
acids mixed with other substances; more recently, calcining furnaces have been con¬ 
structed on Gerstenhofer’s patent system, so as to admit of the utilisation of the sulphurous 
acid for the manufacture of sulphuric acid. 

smelting the Ores. This operation is effected at Swansea in a furnace of which Eig. 24 
exhibits a sectional view. K is a funnel intended for the introduction of the roasted ore ; 
o is an ash-pit filled with cold water. The object in view is to separate the ores from 


Fig. 24. 



the gangue as well as from oxides other than that of copper, by causing the sulphur of the 
sulphurets remaining undecomposed to act upon a portion of the oxides and sulphates in 
such a manner that these are either taken up by the slag, as, for instance, the oxide of 
iron, or are again reduced to sulphide, as the oxide and sulphate of copper. At a higher 
temperature the oxide of copper is reduced to the metallic state by the action of the 
sulphurets of iron and copper, oxide of iron forming, and the metallic copper being partly 

























COPPER. 


A 9 


taken up by the regailus, partly converted into suboxide again by the peroxide of iron, 
which is converted into protoxide and dissolved by the siliceous matter. The product of 
the first stage of the smelting is a coarse metal, regulus. 
itcmtins? or Calcining The roasting of the coarse metal is performed in the reverberatory 
the coarse Metal, furnace used for the first calcination of the ores. The objects in view 
are the oxidation of any metallic iron present, and the partial volatilisation and combus¬ 
tion of the sulphur, partial only, for otherwise the smelting for white metal would be 
impeded or not performed without serious loss of copper. 

Smeitinfr for White This operation consists in mixing the previously calcined coarse 
MetaL metal with rich copper ores containing hardly any sulphuret of iron, 

but consisting chiefly of the sulphide and oxide of copper mixed with quartz in such pro¬ 
portion that the pyrites (copper) is oxidised by the oxygen of the oxides present, the result 
being that all the copper combines with the coarse metal, while the protoxide of iron 
forms with the quartz silicate of protoxide. The white metal, almost entirely consisting 
of (L U 2 S), run into cakes in sand-moulds. 


niistrmi, or Crude _ The white metal obtained is converted into blistered copper by placing 
it on the hearth of a reverberatory furnace, and causing the fire to act at 
first rather gently, but afterwards so as to fuse the mass, the total duration of the 
process for each charge being 12 to 14 hours; the result is the volatilisation of the 
sulphur in the form of sulphurous acid, and the elimination, partially by volatilisation, 
partially by their being taken up in the slag, of such impurities as arsenic, cobalt, nickel, 
tin, iron, &c. When the mass becomes fused, suboxide of copper and sulphide of copper 
mutually decompose, the result being the formation of sulphurous acid and metallic 
copper (2 Cu 2 0 -f- Cu 2 S = S 0 2 -f 6Cu). 

The. molten coarse metal, impure copper as yet, is run into moulds, and its surface 
becoming covered with black-coloured vesicles, due to the escape of gases and vapours 
from the molten metal, it is termed blistered copper. On being broken, after cooling, it 
exhibits a honeycombed structure, due to the same cause that produces the blistered 
appearance on the surface. Blistered copper, as usually obtained, is comparatively pure. 
Refining: the The last operation in the English method of copper-smelting is the 
Blistered Metal, refining of the blistered metal in a reverberatory furnace, care being again 
taken to fire at first gently, so that the metal shall not become molten until after some 
six hours. As soon as the entire charge is thoroughly melted down, the slag, rich in sub¬ 
oxide of copper, is tapped off, and the molten metal covered with charcoal-powder. The 
operation of poling (sec above) is then performed, birch-wood being preferred for the 
purpose; this done, the copper having been run into moulds of a rectangular shape, is 
known as refined tough cake. 


M °from ()'xidised"orc' 3per Copper is readily obtained from oxidised ores by smelting them 
in a shaft-furnace with coke or coal, and such fluxes as will produce a slag which 
does not absorb copper. The crude metal obtained is refined in a low-blast-furnace. 
The smelting of oxidised ores is limited to a few localities, among which the Oural 
and Siberian works are the most important. Large quantities of excellent and 
very rich oxidised copper ore are found, but not as yet wrought, in the islands of 
Timor and Timor-Laout, and the adjacent islands of Polynesia, 
iiydromeuuu^caoiethcd This method owes its existence to the application of practical 
and analytical chemistry to metallurgy. As copper is very readily obtained, even 
from ores too poor to admit' of being treated by the dry process, in such a state of 
combination as to admit of its being dissolved in water, and thrown down from this 
solution by the simple presence of metallic iron, the hydrometallurgical process is 
often advantageously applied, One of the oldest of hydrometallurgical methods is 
that known as the cementation-process, performed by precipitating copper from a 
solution of the sulphate of the metal by means of metallic iron. Solutions of the 
sulphate occur naturally in some mines, and are also artificially prepared by treating 
poor oxidised copper ores with sulphurous acid, or by exhausting these ores with 
hydrochloric or dilute sulphuric acids, or by roasting pyritical ores and exhausting 
them with water. The copper obtained by this process is called cementation-copper. 
In the island of Anglesea the cementation liquid is conducted first into large basins 
in order that the oclirey and other suspended matters may subside, and afterwards 


5° 


CHEMICAL TECHNOLOGY. 


is nin into the cementation tanks containing old scrap-iron intended to serve as a 
precipitating agent. This scrap-iron is occasionally stirred up, so as to renew the 
metallic surface presented to the solution. The muddy liquid, containing spongy 
metallic copper and impurities, is run into reservoirs intended for the deposition of 
the spongy mass, which, after the supernatant liquid is run off, is dried in a furnace. 
The material contains on an average only 15, but may contain from 50 to 65 per 
cent, of copper. The main body is usually composed of basic sulphate of iron, 
which is effectually removed by the application of stirring machinery, such as is 
used in breweries in the mash-tubs. At Rio Tinto, Spain, and at Schmollnitz, 
Hungary, cementation-copper is prepared on a very large scale. In'Norway, copper 
solutions are treated, according to Sinding’s plan, with sulphuretted hydrogen, and 
the precipitate either worked up for metallic copper, or for sulphate of copper. 

Instead of sulphur, large quantities of iron pyrites containing more or less copper arc 
burnt, and the sulphurous acid obtained applied in the manufacture of sulphuric acid. 
The spent pyrites is frequently treated hydrometallurgically with a solution of chloride of 
iron, the copper being precipitated by means of sulphuret of iron. Poor ochrey copper 
ores are often worked up to obtain sulphate of copper, by some method suitable to the 
locality; for instance, roasting with iron pyrites or with copperas. It pays in some 
instances to roast pyritical copper ores, and after roasting to treat them for obtaining 
cementation-copper. 

copper obtained by Copper electrolytically precipitated is, provided pure materials are 

voltaic Electricity, operated upon, and the galvanic current not too strong, the purest 
obtainable. This method has been proposed and even tried on a large scale in Italy, in 
order to save time and iron, and to throw down the copper of the cementation-tanks. 
It is a generally known and daily applied fact that copper, as a coherent mass, can be 
separated from sulphate of copper electrolytically. 

Properties of Copper. The peculiar and really beautiful red colour of copper, the only metal 
so distinguished, is too well known to need mention. It is, although a hard and tough 
metal, so ductile and malleable that it may be drawn out to the very finest wire, and 
beaten to extremely thin leaves. Its malleability is increased by increase of temperature, 
and at a low red heat it can be hammered, rolled, and beaten into any required shape. Its 
fracture is granular. Its sp. gr. is z= S - 9 ; one cubic metre weighs about 8900 kilos. Its 
melting-point, according to Pouillet, 1200°; to Daniell, 1400°. The latest and most 
careful researches on this topic have been made by Dr. von Riemsdijk at the Utrecht Mint, 
and he has found that chemically pure copper fuses in an atmosphere of hydrogen at 
1330°; that is to say, at a temperature higher than the melting-point of either gold or 
silver, as simultaneously determined by an extensive series of experiments made in 
atmospheres of hydrogen. If properly poled, as the term runs, or in other words, free 
from suboxide, copper, when molten, flows readily, but when mixed with suboxide the 
flow is sluggish. While in the molten state the surface of the metal exhibits a beautiful 
sea-green colour. Copper is not suited for the making of castings, and probably this 
is due to a peculiar effect of heat upon this metal, as many of its alloys, especially those 
with tin, are very suited for casting. Molten copper suffers great expansion on cooling, 
and becomes honeycombed and internally crystalline. This defect can only be remedied by 
either keeping the metal while molten under a layer of charcoal, or by cooling it to some 
extent before casting into moulds, which should be made of a good conducting material, so 
as to cause the rapid cooling of the metal. Iron moulds, internally coated with a layer of 
bone-ash, are the best. Small quantities, cr 1 per cent, of zinc, lead, potassium, and other 
metals added to the molten copper entirely deprive it of the property of expanding and 
becoming honeycombed on cooling; the same effect is observed when copper holds in 
solution a small quantity of snboxide, but this fact is not available for any practical use, 
as such copper is cold-short. Just before cooling the vessel exhibits the phenomenon of 
spirting, the flying about of small globules of copper, accompanied, if large quantities of 
the metal are treate l, by a distinctly audible report. This phenomenon appears to be 
due to a cause similar to that producing it when silver is operated upon, viz., the violent 
expulsion of previously absorbed oxygen. At a very high temperatme, and with free 
access of air, or under the influence of electricity, copper burns, giving a brilliant green 
flame. In countries where, as in Sweden, Russia, and Holland, the roofs of churches and 
other large buildings are covered with copper—the most expensive at the first outlay, but 
the most lasting material for roofing purposes—the phenomenon of the burning of copper 
is now and then witnessed on a very large scale when fires accidentally occur. Copper-filings 


COPPER. 


Si 


aro used in pyrotechny, for producing a green flame. Dry air does not affect copper, 
unless sulphuretted hydrogen and other sulphurous emanations are present; but moist 
air causes the copper to become covered with carbonate of hydrated suboxide of copper, 
verdigris, or rust. Experience has proved, in the case of copper roofs, that this material 
protects the subjacent metal, and adheres to it with great tenacity. When solid masses of 
copper are heated they at first assume an iridescent rainbow hue, and next become 
covered with a brownish-red coloured suboxide, which, if the heating is continued, becomes 
black oxide, technically known as copper-ash, or copper-forge scale. In order to remove 
this oxide, when the copper is to be rolled into sheets, &c., the metal is dipped into what 
is termed a pickle—a solution of ammonia and common salt, and on being taken out is 
brushed with a heather-broom. Copper, as usually met with in commerce, is not by any 
means pure, but contains variable quantities of other metals, among which are chiefly 
iron, antimony, arsenic, lead, tin, zinc, and sulphur; Dr. Reischauer found in perfectly 
malleable copper no less than 1*48 per cent, of impurities insoluble in nitric acid. If 
this quantity is only slightly increased, the quality of the copper is so impaired that it is 
not only unfit for being rolled and hammered, but also for casting statues (always alloyed), 
because such copper loses its peculiar colour, and does not withstand atmospheric influ¬ 
ences. Copper is largely used for various purposes, among which we name only a few— 
vacuum and other pans in sugar-works; distillery, brewery, and other apparatus; for 
covering wooden sea-going vessels, and for a variety of generally well-known purposes. 
Dr. Steinbeck found that refined Mansfeld copper, analysed 1868, contained in 100 parts— 


Copper.99*28 

Silver . 0*02 

Nickel . 0*32 

Iron . 0*06 

Lead . 0*12 


100*00 

The total annual production of copper over the entire globe amounts (1870) to 
1,300,000 cwts., of which England alone yields fully 350,000 cwts. 

Alloys of copper. There are several alloys of copper, among which bronze, brass, and 
German, or nickel silver, are the chief. 

Bronze. Alloys, consisting of copper and tin, or of copper, tin, and zinc, or of copper 
and aluminium, all bear the name of bronze. The addition of any of these metals 
to copper renders it more fluid when molten, and hence better suited for castings, 
a3 well as denser, and consequently more easily polished; alloys are harder, more 
sonorous, and (the aluminium alloy excepted), far cheaper than copper itself. 
The addition of from 0*12 to 0*50 per cent, of phosphorus to these alloys renders 
them more homogeneous and malleable. The chief varieties of bronze in use are 
known as (a) bell-metal, (/ 3 ) gun-metal), and (7) statuary metal. 

(a). Bell-metal consists on an average of 78 parts of copper and 22 parts of tin. 
It should be sonorous, hard, and strongly cohesive. Being a brittle alloy it cannot 
be worked on the lathe; hence the desired sound or musical note of a bell depends 
entirely upon the shape given in the casting, and upon the constituents of the alloy. 
In order to save tin, zinc and lead are sometimes added, but too much of these 
impairs the goodness of the alloy. It is an error to mix silver with this alloy, in 
order to render it highly sonorous; analyses made of bell-metal cast in the middle 
ages in various countries, prove the absence of silver from such metal, traces only 
being present as an impurity. 

(/8). Gun-metal consists on an average of 90 parts of copper and 9 of tin. This 
alloy should combine mechanical and chemical durability. As regards its mechanical 
properties, the metal should be:—1. Tough, so as to prevent the piece or gun 
bursting while the charge is being fired, during which operation the metal is 
exposed to a pressure of from 1200 to 1500 atmospheres. 2. Elastic, so that the gun 
may be able to yield to some extent to the smart shocks occasioned by the evolution 








5 2 


CHEMICAL TECHNOLOGY. 


of gas during firing. 3. Hard, so that the motion of the ball should not cause any 
damage to the interior of the gun. As regards chemical durability, the alloy must 
resist the action of air and of the products of combustion of powder and gun-cotton 
at high temperatures. Gun-metal answering these requirements is unfortunately 
subject to what is termed liquation; that is to say, while in the molten state it 
separates into two qualities of alloy, one more fluid and containing more tin than 
the other. This separation makes the casting of guns in this alloy a difficult matter, 
because the homogeneity of the mixture is uncertain. It appears, however, that the 
addition of from o’12 to 0*5 per cent of phosphorus remedies the defect. Gun-metal, 
however, is fast being superseded by steel in the manufacture of ordnance. 
MM. Maritz, at the Hague, have for several generations been renowned for the 
superiority of their gun-metal manufacture, which is still pursued by them. 
According to a statement in the “ Handworterbuch der Chemie ” (Art. “ Geschutz- 
metall,”) the alloy employed by them consists of 0*69 per cent. Ee, 88*6i per cent. Cu, 
and 1070 per cent. Sn; generally the quantity of tin amounts to from 9 to 11 per cent. 

(7.) Statuary-bronze for ornamental purposes consists of copper, tin, lead, and 
zinc. It is requisite that while molten this alloy should be very fluid, so as to fill 
every part of the mould. After cooling, the metal must admit of being chiselled, 
and by exposure to air it should assume what is termed patina—a peculiar greenish 
black hue. The statue of Louis XIY. at Paris, made 1699, consists of—copper, 
91*40; zinc, 5*53; tin, 1*70; lead, 1*37. The statue of Henri IY. on the Pont 
Neuf at Paris, consists of—copper, 89*62; zinc, 40*20; tin, 5*70; lead, 0*48. 
Aluminium-bronze (90 parts copper and 10 aluminium) is used for various orna¬ 
mental purposes, chiefly in imitation of gold. 

muss. This alloy has been known from a very remote period. Zinc and copper 
form various alloys, but brass only is technically applied, and contains on an average 
30 per cent, of zinc. The colour of the alloy is inclined to red, when the quantity 
of zinc is small, and to yellow or whitish-yellow when the quantity of zinc is 
increased. The ductility and malleability of the alloy 'increase with the quantity 
of copper. Brass maybe hammered, rolled into sheets, or drawn to wire while cold, 
but cannot be worked hot. The so-called yellow metal, Muntz’s patent, an alloy 
of 40 parts of zinc and 60 of copper, may be wrought while red-hot, rolled into 
sheets, and forged into bolts. It is chiefly used for marine purposes, including 
the internal lining of air pumps of marine steam-engines. Brass is not so readily 
oxidised as copper, being harder, tougher, more easily fusible, and more fluid while 
molten. It solidifies without becoming honeycombed, and hence is suited for 
making all kinds of castings ; while simply by the addition of from 1 to 2 per cent, 
of lead, it is capable of being readily worked on the lathe, and may be then filed 
without, as it otherwise does, clogging the teeth of the file. 

Brass is made by any of the following methods1. By melting together a mixture of 
calamine stone and black or blistered copper under a layer of charcoal. 2. By simply melting 
together zinc and refined copper. The first method is the oldest, and is still carried on 
in furnaces arranged so that they may contain from 7 to 9 fire-clay crucibles at the same 
time. These crucibles are filled with the necessary materials, viz., previously roasted 
zinc ore, or residues from zinc-smelting furnaces, and copper. As by the use of calamine 
stone, only some 27 to 28 per cent, of zinc can be imparted to the afloy, it is usual to add 
previously to pouring out the molten alloy, another quantity of calamine stone, rather to 
prevent any loss of zinc by ignition than to increase the quantity of that metal. In 
former times the manufacture of brass was carried on in two distinct operations* one 
being the preparation of an alloy containing only 20 per cent, of zinc, known as arco- 
smelting, and the other the conversion of the arco into brass by a second smelting, and the 


COPPER . 


53 


addition of zinc. At the present time the manufacture of brass consists in .simply placing 
alternate layers of copper and zinc in fire-clay or graphite crucibles, and then smelting 
the two metals under a thick layer of charcoal. The alloy is cast in granite moulds 
surrounded by a thick coating of clay and cow-dung, or sand-moulds. Occasionally sheet- 
copper is converted into brass by exposing the sheets to the fumes of metallic zinc. 
Among brass alloys we may notice the following :—Tomback, or red brass, consisting of 
85 parts of copper and 15 of zinc. Dutch-gold, a gross misnomer, as none of it is made 
in Holland, and as the term really applies to a very pure gold coin, the ducat, still made, 
although not current, in Holland, at the Utrecht Mint. The brass alloy thus named con¬ 
sists of 11 parts of copper and 2 of zinc, and is made chiefly at Niirnberg and Furth, 
Bavaria, for the purpose of being beaten into very thin leaves. The alloy termed Aich- 
metal, and consisting of 60 parts of copper, 38-2 parts of zinc, and r8 parts of iron, is in 
reality malleable brass. Sterro-metal, though very much harder, is similar to the fore¬ 
going in composition. 

The well-known yellow, or Muntz, metal, largely used in this country for marine pur¬ 
poses, coating ships, &c., is an alloy of copper and zinc in proportions varying from 50 per 
cent, of zinc and 63 of copper, to 39 per cent, of zinc and 50 per cent, of copper. The alloy 
in use for coins of small value in this country, France, and Sweden, consists of 95 parts of 
copper, 4 parts of tin and 1 of zinc. The alloy used for this purpose in Denmark consists 
of 90 parts of copper, 5 of tin, and 5 of zinc. Bath-metal, or white brass, consists.of 55 
parts of copper and 45 of zinc. An alloy used for buttons consists of 20 parts of copper 
and 80 parts of zinc. The bronze colours (powdered alloys of copper and zinc), now 
largely used for bronzing painted surfaces, as well as for lithochromy and various other 
purposes, are obtained from scraps of metal rubbed down with oil, tallow, or wax, and 
turpentine. The various beautiful colours, violet, copper-red, orange, gold-yellow, green, 
are due to partial oxidation. These bronze-colours are not to be confounded with a beau¬ 
tiful substance known as mosaic gold —aurum tnusivum —bisulphide of tin. Analyses show 
the proportions in these alloys to be— 

For bright colours. j * * 17 

For red or deeper colours .. j ' * ^4 _ 9 ° 

For copper-red colours .... 100 


Chemical analysis has also proved the quantity of copper to amount to— 


a. In French bronzes : Copper-red colour .. .. 97*32 per cent. 

Orange .94-44 „ 

Bright yellow.81-29 » 

/3. In English bronzes: Orange .90-82 „ 

Deep yellow .82-37 „ 

Bright yellow.80-42 „ 

7. In Bavarian bronzes: Copper-red . 98-92 „ 

Violet.98-82 „ 

Orange .95-30 ,, 

Deep yellow . 81*55 » 

Bright yellow. 82-34 „ 


Germ s 5 ver Nickel German, or nickel silver, also called Argentan, packfong, or white 
copper, is an alloy of copper with nickel and zinc, or tin, and may be considered as 
a brass to which from one-sixth to one-third of nickel has been added. This alloy 
appears to have been known in China from a very remote period; in Europe it has 
been more generally in use during the last thirty years. The colour is nearly 
silver-white; its fracture small-grained and compact; sp. gr. = 8*4 to 8*7. It is 
harder, but yet quite as ductile as ordinary brass, and takes an excellent polish. It 
is prepared by melting together the granulated metals, zinc, copper, and nickel; 
these metals are put into a crucible in such a manner that copper is at the bottom 
as well as the top, while a layer of charcoal-powder covers the whole. Care is taken 
to stir the mass with an iron rod. Nickel-silver of good quality has the appearance 
of a silver alloy, containing one-fourth of copper. Nickel-silver is capable of as¬ 
suming an excellent polish, and is not readily acted upon by vinegar and the ordinary 
acids in culinary use ; hence it is used for spoons and forks. 













54 


CHEMICAL TECHNOLOGY. 


Average German-silver consists of— 

Copper .50—66*o 

Zinc. 19—31*0 

Nickel . 13—18*5 

At Sheffield the following varieties of this alloy are made :— 

Copper. Nicke 

Common . 8 2 

■White. 8 2 

Electrum. 8 4 

Infusible . 8 6 

Tutenac ... 8 3 


Zinc. 

3’5 

3’5 

3'5 

3’5 


"When tried on the touchstone, nickel-silver is hardly distinguishable from the 
silver alloy just mentioned, but on applying nitric acid to the streak caused by the 
nickel alloy, it is more rapidly dissolved, and by adding a few drops of chloride of 
sodium solution no turbidity, or precipitate of chloride of silver, is produced on the 
stone. The alloy known as Alfenide, used for making tea-pots, sugar-basins, milk- 
ewers, and similar articles, is nickel-silver, thickly electro-plated with pure silver, the 
quantity of silver amounting to about 2 percent. The alloy, known as tiers-argent (one- 
third silver), consists, according to Dr. C. Winkler’s analysis (see “ Chemical News,” 
vol. xxii., p. 225), of—Copper, 59*06; silver, 27*56 ; zinc, 9*57; nickel, 3*42. 


Since 1850 the Swiss Confederation has brought into circulation a series 
(monnaie billon) which contain in 1000 parts :— 



Silver. 

Copper. 

Zinc. 

Pieces of 20 Happen .. 

150 

500 

250 

„ 10 ,, .. . • 


550 

250 

» 5 » .. .. 

50 

600 

250 


of small coins 

Nickel 

100 

100 

100 


These coins are not turned red by wear, but assume a yellowish hue. In Belgium the 
5, 10, and 20 centime pieces are made of an alloy of 25 parts of nickel and 75 parts of 
copper; while the United States’ cent pieces contain 12 parts of nickel and 88 of copper. 
The alloy known on the Continent as Suhler’s white copper, consists of 88 parts of copper, 
875 parts of nickel, and 175 parts of antimony. 


Amalgam of copper. By the name of metallic cement is understood an amalgam of 30 parts 
of copper and 70 parts of mercury. It is obtained by moistening pulverised copper, 
obtained in a spongy state, by reducing its oxide at a low red heat, by means of hydrogen 
with nitrate of suboxide of mercury, care being taken to incorporate this saline solution 
thoroughly with the copper, while adding hot water. This cement, at first soft, hardens 
in a few hours. It has been successfully applied in stopping decayed teeth. 


Preparations oe Copper. 

Sulphate of copper. salt is met with naturally in kidney-shaped masses, or as an 

outer covering of minerals containing copper, as well as in solution, as referred to 
under Cementation-copper. Sulphate of copper, blue- or Cyprus-vitriol, crystallises 
in the shape of triclinohedrical blue-coloured crystals, soluble in 2 parts of hot and 
4 of cold water, and insoluble in alcohol. 100 parts of the salt contain:— 

Sulphuric acid .32*14 

Oxide of copper.3179 

Water .36*07 

Formula :—CuS 0 4 + 5 H 2 0 . 

Pr o||ue° n Chemically-pure sulphate of copper is obtained by heating metallic copper 
with concentrated sulphuric acid; the metal is oxidised by a portion of the oxygen of 
the acid, while sulphurous acid escapes (Cu 2 H 2 S 0 4 = CuS 0 4 -|- 2H2O4-SO2). If 
the metal is previously converted into oxide of copper by exposure to a red heat, only 
half the quantity of sulphuric acid is required. Sulphate of copper is manufactured 
















PREPARATIONS OF COPPER. 


55 


on a large scale by any of the following processes :—i. By the evaporation of cemen¬ 
tation-water until crystallisation is attained. 2. By heating sheets of copper in a 
reverberatory furnace to the boiling-point of sulphur ; a quantity of that element 
being then thrown in, and the flues and other openings closed, the effect is the forma¬ 
tion of sulphide of copper (Cu 2 S), which is converted by a comparatively low heat 
and the action of the oxygen of the air into sulphate (Cu 2 S + 50 = CuS 0 4 + CuO). 
The mass is next placed in a suitable vessel, and as much sulphuric acid is added to 
it as is sufficient to saturate the oxide of copper. The clear solution, having been 
decanted from the insoluble residue, is set aside for crystallisation. 3. By treating 
the crude copper obtained by smelting the ores, and containing about 60 per cent, of 
metal, with sulphuric acid. The resulting solution is evaporated in leaden vessels, 
and the clear liquid left to crystallise in copper pans. From the mother-liquor of the 
crystals metallic copper is precipitated by means of iron, because the presence of a 
large quantity of sulphate of iron renders this mother-liquor unfit for the further 
making of blue-vitriol. This method of obtaining sulphate of copper is the least 
expensive, but the salt is not quite pure, containing, according to M. Herter’s analysis 
of Mansfeld blue-vitriol, about 3 per cent, of sulphate of iron, and 0*083 P er cent, of 
metallic nickel. Very frequently the scraps and refuse of copper smithies, copper- 
scale, and other residues of that metal, are used in preparing sulphate of copper. 

4. At Marseilles, malachite is dissolved in sulphuric acid to obtain blue-vitriol. 

5. In Norway, iron pyrites containing copper are roasted and treated with water, the 
copper contained being precipitated with sulphuretted hydrogen, and the sulphide of 
copper, when dry, converted into sulphate by exposure to a gentle heat. G. Large 
quantities of sulphate of copper are obtained as a by-product of silver-refining, 
especially when silver is treated for the purpose of extracting the gold it contains, by 
fioiling—usually silver coins, chiefly Mexican and Peruvian dollars—with strong 
sulphuric acid; sulphate of silver and, as the coins contain some copper, the 
sulphate of that metal, are formed, while the gold is left as an insoluble substance. 
The silver is reduced to the metallic state (Ag 2 S 0 4 + Cu= CuS 0 4 + 2Ag)bymeansof 
sheets of copper placed in the acid solution, which is previously diluted, and which, 
after having been. decanted from the sediment, spongy metallic silver, yields on 
evaporation a very pure sulphate of copper. 7. Sulphate of copper is also obtained 
as a by-product of the hydrometallurgical process of extracting silver, or Ziervogel’s 
process. In order to separate the sulphate of iron from the crude blue-vitriol, as 
obtained at copper-smelting works from various cupriferous refuse, the crude salt 
is roasted so as to bring about a partial decomposition. By this means the sulphate 
of iron is decomposed, and the oxide of that metal formed is insoluble in water. The 
saline mass is dissolved in water, and the clear solution, decanted from the sediment, 
evaporated to crystallisation. According to Bacco’s plan, the crude blue-vitriol is 
dissolved in water, and carbonate of copper added to the solution, to cause the pre¬ 
cipitation as oxide of all the iron present, while an equivalent quantity of oxide of 
copper is dissolved and converted into sulphate. The purified sulphate of copper 
solution having been filtered is evaporated and left to crystallise. 

Double-Vitriol. Under the name of double-vitriol, a mixture of the sulphates of copper and 
iron crystallised together, and sometimes containing white vitriol, is met with on the 
Continent. The Salzburg vitriol, known by the brand of a double eagle, contains about 
76 per cent., the Admont 83 per cent., and the double Adinont 80 per cent, of 
sulphate of protoxide of iron. Of later years, however, these vitriols have been less in 
demand. 


56 


CHEMICAL TECHNOLOGY. 


Applications of As the base of the pigments obtainable from copper, the sulphate is very 
Biue-Vitrioi. frequently used, and should be pure, or at least free from the sulphates of 
iron and zinc. Blue-vitriol also serves for the manufacture of acetate of copper, for 
bronzing iron, for bringing out the colour of alloys of gold. It is used in dyeing and 
printing in various ways, for galvano-plastic purposes, and during the last twenty years 
large quantities of this salt have been sent to Mexico and Peru to bo applied in the 
American amalgamation-process of extracting silver. 


copper pigments. Among the many pigments which owe their blue or green colour 
essentially to copper, we may treat of the following :—i. Brunswick-green. 2. 
Bremen-green and Bremen-blue. 3. Casselmann's-green. 4. Mineral-green. 5. 
Schweinfurt-green, also known as emerald-green. Many of the pigments men¬ 
tioned here by their German names are known in this country by other denomina¬ 
tions, hut are not for that reason any different in composition. 


p.runswick-Green. Under this name several compounds of copper are applied as oil-paints. 
The pigment now chiefly in use bearing this name is basic carbonate of oxide of copper 
(CuCCb-f- CuH„0 2 ), an imitation of mountain- or mineral-green, and obtained from either 
finely pulverised malachite or the sediment often met with in cupriferous cementation- 
liquids. Brunswick-green is prepared on a large scale by the decomposition of sulphate of 
iron by means of either carbonate of soda or carbonate of lime, and in other cases by the 
decomposition of chloride of copper by means of a carbonated alkali. The ensuing preci¬ 
pitate is washed with boiling water, and afterwards mixed with a smaller or larger quan¬ 
tity of sulphate of baryta, zinc-white, or gypsum, and frequently with Schweinfurt-green 
(aceto-arsenite of copper) in order to obtain the desired hue. Another variety of Bruns¬ 
wick-green, rarely met with in the present day, appears to be a kind of artificially-prepared 
atacamite, an oxychloride of copper, the formula of which is, according to Iiitthausen, 
CuC 1 2 ,3 CuO-|- 3H 2 0. 

Bremen-Blue, or These substances are essentially hydrated oxide of copper, and are 

Bremen-Green. _ y J ± i ’ 

met with as a very bright blue spongy mass with a greenish hue. The value is 
greater according to the finer blue colour and loose spongy texture. When used with 
water, gum, or glue, this pigment yields a bright blue colour, hence its first name; 
but when it is mixed with linseed-oil, the blue colour turns within twenty-four hours 
to green, in consequence of the saponification of the oxide of copper, which becomes 
oleate, palmitate, and linoxate of that base. Bremen-green occurs in various hues 
obtained by mixing the precipitate with well-cleansed gypsum. At the present time 
the pigment is generally obtained from oxychloride of copper (CuCL^CuO -f- 4H2O). 
This preparation may be made in various ways, provided care be taken that the 
light green paste—technically known as oxide—contains no protochloride of copper 
(Cu 2 Cl 2 ). Gentele’s method is as follows :— 

1. 112-5 ldlos. of common salt, and hi kilos, of sulphate of copper, both free from iron, 
are ground together with sufficient water to promote reaction. 2. 112 - 5 ldlos. of old 
copper sheeting is cut into pieces a square inch in size, and placed with water acidulated 
with sulphuric acid in rotating casks so as to remove all rust, oxide and oxychloride, from 
tins metal, which is next washed with water. 3. The clean metal thus obtained is next 
placed in what is known as oxidation-closets, and covered for a thickness of half-an-inch 
with the paste mentioned above. A mutual action, aided by that of the atmosphere, is 
set up, the result being that the chloride of copper first takes up copper, becoming proto- 
chloride ; this in its turn takes up oxygen from the atmosphere and water, and thus becomes 
converted into the green-coloured insoluble basic hydrated oxide of copper, the action benm 
greatly aided by the turning over of the mass with a copper spade every two or three 
days. As the treatment of protochloride of copper with alkalies or alkaline earths gives 
rise to the separation of red or yellow-coloured suboxide, the mass should not, on bein" 
tested and previous to further operations, yield even the faintest indication of the presence 
of suboxide, since the slightest trace would spoil the hue of the pigment to be obtained • 
consequently in seme works the pasty mass is left for years before it is used for further 
operations. The action is accelerated by causing the mass to become dry before turning 1 it 
over with the spade ; the consequence being that the air gets thorough access, and a com¬ 
plete oxidation is obtained in about three to five months time. The mass is then cleansed 
with the smallest possible quantity of water, and is thus separated from the non-oxidised 


PREPARATIONS OF COPPER. 


57 


metallic copper. 4. To some 6 gallons of this cleansed material are added 6 kilos, of 
hydrochloric acid, and this mixture is allowed to stand for about two days. 5. Into a 
tank or tub—the blue tub—are poured some 15 gallons clear colourless potassa-lye. This 
having been done, the acid mixture is first diluted with some 6 more gallons of water, and 
then, as rapidly and expeditiously as possible, poured into the blue tub, the mixture being 
continuously stirred. The result of this last operation is that the previously basic copper 
compound, converted by HC 1 into neutral cupric chloride, is, when brought in contact 
with the potassa, converted into blue-coloured oxyhydrate of copper or Bremen-blue, 
while chloride of potassium is also formed. 6. After the mass has become pasty, it is left 
to stand for a couple of days, and then thoroughly washed by decantation to remove the 
chloride of potassium. The cupric oxyhydrate is then put on cloth filters, kept moist, and 
exposed to the air for some time. It is next dried at a temperature of from 30° to 35 0 , 
since at a higher temperature the hydrate of the oxide by losing its water becomes 
blackish-brown coloured. It is clear that Bremen-blue can be differently obtained, but 
these differences of preparation do not bear so much upon the precipitation of the 
hydrated oxide as upon the means of obtaining chloride of copper; these means may of 
of course be varied in many ways; for instance, by causing a mixture of common salt, 
dilute sulphuric, and copper scraps to act upon each other, the mass being afterwards 
exposed to the action of the air; by the action of hydrochloric acid upon copper and its 
oxide; or by partly decomposing neutral nitrate of copper by means of carbonate of soda. 
In this case a precipitate of carbonate of copper is formed, which, while giving off its 
carbonic acid, becomes converted into basic nitrate of copper (CuN 0 6 -f- CuH 2 0 2 ), deposited 
as a heavy green powder. A solution of zinc-oxide of potassa (solution of zinc-white in 
caustic potassa), is next added, the result being the formation of a deep blue pigment, 
very spongy and very covering (a technical term in use by painters); consisting of zincate 
of copper, with a small quantity of basic nitrate of copper. A magnesia Bremen-blue is 
obtained by the precipitation of a solution of the sulphates of magnesia and copper, to 
which some cream of tartar is added, by means of potassa, care being taken to pour the 
saline solution into the alkaline, and to keep an excess of the latter. 

casseimann ’s-Green. In the year 1865 Dr. Casselmann discovered this pigment, a beau¬ 
tiful green free from arsenic. It is prepared by mixing together boiling solutions 
of sulphate of copper and an alkaline acetate ; the resulting precipitate is a basic 
salt of copper (CuS 0 4 -f- 3CuH 2 0 2 + 4H 2 0). After drying, this salt is, next to 
Schweinfurt-green, the finest of all colours obtained from copper, and being free 
from arsenic, is highly commendable, though yet poisonous, as are most prepara¬ 
tions of, and especially acetates of, copper. 

Mineral-Green This pigment, also known as Scheele’s-green, is not so frequently used 
and Blue. n0 w as formerly. It is essentially a mixture of hydrated oxide of copper and 
arsenite of copper, and does not cover very well. It is prepared by dissolving 1 kilo, of 
pure sulphate of copper in 12 litres of water, to which is added, whilst constantly stirred, 
a solution of 350 grms. arsenious acid and 1 kilo, of pui-ified potash (carbonate) in 8 litres 
of water. The resulting grass-green coloured precipitate is washed with boiling -water and 
dried. Another pigment, sometimes known as mineral-green, is obtained from pulverised 
malachite, or basic hydrated oxide of copper. By the term mineral-blue is generally 
understood a kind of Berlin-blue, rendered less deep coloured by the addition of pipe-clay 
or other white-coloured powders, but the term also applies to a pigment formerly obtained 
bv grinding and washing the purest pieces of lazurite of copper, a mineral 

( 2 CuC 0 3 -f CuH 2 0 2 ) 

found in the Tyrol and near Lyons. This pigment is artificially obtained in France, 
Holland, and Belgium, by precipitating a solution of nitrate of copper with caustic lime 
or caustic potassa, and afterwards mixing the previously washed precipitate with chalk, 
gypsum, or heavy spar. The pigment is sent into the trade for use chiefly as a water- 
colour. Under the name of lime-blue a similar preparation occurs in quadrangular 
lumps, obtained by precipitating a solution of 100 parts of sulphate of copper and 
124 parts of sal-ammoniac with a milk of lime containing 30 parts of caustic-lime.. The 
precipitate is a mixture of hydrated oxide of copper and sulphate of lime, according to 
the formula (2CaS0 4 ,2H 2 0'-|- 3CuH 2 0 2 ). This pigment exhibits a purer tint than 
Bremen-blue, but though it covers pretty well as a water-colour, it is almost useless as an 
oil-colour. 

oii-Biue. A pigment w'hich, when ground with oils and varnishes, yields a beautiful 
violet-blue, and is essentially composed of sulphide of copper (CuS), there being applied 
in its manufacture either the native mineral, known as cupreous indigo, or an artificially 


58 


CHEMICAL TECHNOLOGY. 


prepared sulphide, obtained by fusing finely divided metallic copper with hepar-sulphuris, 
a mixture of several sulphurets of potassium. The fused mass is treated with water, and 
the sulphide of copper remains in small blue-coloured crystals, which, after drying, are 
pulverised and mixed with oil. 

Sc Emcraid-Green n ’ or This pigment is by far the mo3t beautiful, but also the most 
poisonous, of all green-coloured copper pigments. In Germany this substance is 
known under a number of aliases derived from the peculiar dej)tk of hue as modified 
in various manufactories by means of su^liate of baryta, sulphate of lead, and 
chrome-yellow. The constitution and mode of preparation of this pigment remained, 
at least on the Continent, a trade secret until the researches of MM. Braconnot and 
J. von Liebig made the particulars known. According to Dr. Ehrmann, pure 
emerald- or Schweinfurt-green is an aceto-arsenite of copper :— 

( ° 2 Cu° )2 } 0 2 + 3 (CuO,As 2 0 3 ); 

in i oo parts—Oxide of copper, 3i’29; arsenious acid, 58 - 65; acetic acid, 10*06, 
Dr. B. Wagner states that this formula is only empirical, because a portion of the 
copper is present as suboxide, and a portion of the arsenic as arsenic acid. 

According to Dr. Ehrmann’s statement, this pigment is prepared by first separately 
dissolving equal parts by weight of arsenious acid and neutral acetate of copper in boiling- 
water, and next mixing these solutions while boiling. There is immediately formed a 
flocculent olive-green coloured precipitate of arsenite of copper, while the supernatant 
liquid contains free acetic acid. After a while the precipitate becomes gradually crystal¬ 
line, at the same time forming a beautifully green pigment, which is separated from the 
liquid by filtration, and after washing and carefully drying is ready for use. The mode 
of preparing this pigment on a large scale was originally devised by M. Braconnot, as 
follows:—15 kilos, of sulphate of copper are dissolved in the smallest possible quantity of 
boiling-water and mixed with a boiling and concentrated solution of arsenite of soda or 
potassa, so prepared as to contain 20 kilos, of arsenious acid. There is immediately 
formed a dirty greenish-coloured precipitate, which is converted into Schweinfurt-green 
by the addition of some 15 litres concentrated wood-vinegar. This having been done, the 
precipitate is immediately filtered off and washed. It thus appears that the preparation 
of this pigment aims first at the least expensive preparation of neutral arsenite of copper, 
which is next converted into aceto-arsenite by digesting the precipitate with acetic acid. 
The pigment is available as a water- and an oil-colour, but does not cover very well in oil, 
although it dries rapidly. The colour cannot be used for mural painting, as the bine 
absorbs the acetic acid, leaving a yellowish-green arsenite of copper. The Scliwcinfurt- 
green consists of microscopically small crystals; if these crystals are pulverised, the 
colour, previously grass-green, becomes paler. Air and light do not affect this pigment, 
which is insoluble in water, but becoming, when boiled with it for a length of time, 
brown-coloured, probably in consequence of the loss of some acetic acid. It is a well- 
known fact that paper-hangings containing this pigment, and pasted on damp walls, 
cause the inmates of the rooms to suffer from headaches, due in all likelihood to volatile 
arsenical emanations, among which is arseniuretted hydrogen. 

Stannate of Oxide This preparation, also known as Gentele’s-grecn, is obtained by precipi- 
of Copper, tating a solution of sulphate of copper with stannate of soda, washing and 
drying the precipitate, which forms a beautifully green, innocuous, at least as compared 
with the foregoing, copper pigment. 

verdigris. Under this name we meet in commerce with a neutral and a basic 
acetate of copper; the one, a crystalline substance is 

(C2 Cu 0)2 } 0 * + Il2 °’ 

a salt formerly only prepared in Holland, and designated as “ distilled verdigris,” 
in order to mislead as to its mode of manufacture. 

The basic salt, blue verdigris, is chiefly prepared at and near Montpellier, by employing 
the marc of the grapes, the skin and stems of the bunches after the juice has been squeezed 
out, which readily forms acetic acid by fermentation. Into the marc are placed sheets of 
copper previously moistened with a solution of acetate of copper. The metal becomes 
coated with a layer of verdigris, which is removed by scraping. It is next kneaded with 


LEAD. 


59 


water, after which the paste is put into leathern fcag 3 and pressed, so as to obtain 
rectangular cakes. The metal is treated in the same manner until it is entirely converted 
into basic verdigris, having a blue colour, and known as French-verdigris. Formula— 

(Cl S 0)l )°.' CnH A+sH I o. 

A green-coloured verdigris is obtained at Grenoble and elsewhere, by submitting sheets of 
copper to the action of vapours of vinegar, or by placing the metal between pieces of 
coarse flannel soaked with that liquid. The formula of the substance thus produced is— 

(Ua ci 0) “} °=> 2 C“ h a. 

Neutral acetate of copper, first made by the Saracens in Southern Spain, and since the 
middle of the fifteenth century by the Hollanders, is now obtained either by—i. Dissolving 
the basic salt in acetic acid. 2. Or by the double decomposition of sulphate of copper and 
acetate of lead :— 

CuS 0 4 + { (0 =pg 0) » } <X = PbS 0 4 + ( (C ^ 0) ’} 

By the first method the basic acetate is dissolved in 4 parts of acetum distillatum 
(purified vinegar) or in wood-vinegar, the liquid being placed in a copper cauldron and 
heat applied. The clear liquid is decanted, and then evaporated in copper pans until a 
saline crust makes its appearance, when the fluid is transferred to wooden vessels pro¬ 
vided with thin laths serving as a solid nucleus for the crystals. According to the second 
plan, the solutions of the two salts are mixed, the liquid decanted from the sediment of 
sulphate of lead, and next evaporated after the addition of some acetic acid, until a crust 
of the salt is formed. Instead of acetate of lead, the acetates of lime and baryta are now 
used. The neutral acetate of copper is met with in commerce in “bunches” (grappes), 
consisting of deep green-coloured, non-transparent crystals, soluble in 13‘4 parts of cold, 
in 5 parts of hot water, and in 14 parts of boiling* alcohol. This salt, like the basic 
acetates, is highly poisonous. 

Applications of Both basic and neutral are employed as oil-and water-colours. In Russia 
Verdigris, verdigris, mixed with white-lead, is frequently used as an oil paint, the 
result being the formation of carbonate of copper and basic acetate of lead. The former 
of these substances yields with the undecomposed white-lead a bright blue colour, which, 
after painting, turns to a peculiarly fine green, the usual colour of the iron roofs of the 
houses in Russia, more especially in Moscow and the interior of the country. In Holland 
the same mixture is frequently applied as a paint to outdoor woodwork, of which it is an 
excellent preservative. Verdigris is sometimes further applied in the preparation of other 
copper colours, for instance, Schweinfurt-green; also in dyeing and calico-printing; in 
gilding (see Gold). The neutral salt was formerly used in the preparation of acetic acid. 

Lead. 


(Pbr=207; Sp. gr. = 11*37.) 

occurrence of Lead. This metal has been known from a remote antiquity. It is only 
rarely found native; its chief ore is galena (PbS). It also occurs as Bournonite, 
or antimonial lead ore, consisting of—41*77 parts of lead; 12*76 copper; 26*01 
antimony; and 19*46 sulphur; formula (3Cu 2 S,Sb 2 S 3 -f 2[3PbS,Sb 2 S 3 ]). From this 
ore copper as well as lead is extracted. The other lead ores of more or less import¬ 
ance are—cerusite or white lead ore (PbC 0 3 ); green lead ore (pyromorphitc, 
phosphate of oxide of lead, 3[P 2 0 5 ,3Pb0] -f PbCl 2 ); mimetesite (arseniate of oxide 
of lead, 3[As 2 0 5 ,3Pb0] -j- PbCl 2 ); vitriol lead ore or Anglesite, sulphate of lead 
(PbS 0 4 ); yellow lead ore (molybdanate of lead, PbMo 0 4 ); and red-lead ore or 
krokoite, chromate of lead (PbCr 0 4 ). 

jicihodofobtamin^Lcud Galena is the chief lead ore, 98*9 of the metal produced being 
extracted from it. It contains 86*57 P or cent, of lead, and 13*43 per cent, of sulphur, 
with sometimes only mere traces, sometimes an available quantity of silver. Galena 
exhibits a lead-grey colour and a strong metallic lustre, crystallises in cubes, is 
brittle, and has a sp. gr. = 775. It is also employed, when finely ground, and known 
as Alquifoux, for the purpose of glazing coarse pottery ware; for the manufacture 
of Pattinson’s white-lead; instead of sawdust for covering the floors of rooms in somo 


6o 


CHEMICAL TECHNOLOGY. 


of the German mining districts; -for ornamental purposes; jewellery; and of late 
in a peculiar process of extracting platinum from its ores. 

Lead is obtained from galena either by the precipitation method or by roasting. 
The former process is based upon the behaviour of metallic iron at a high tempera¬ 
ture towards galena; for if these two substances are heated together the result is 
the formation of sulphuret of iron and metallic lead (PbS -f- Fe = FeS -j- Pb). Ac¬ 
cordingly, the precipitation method consists in smelting the galena, previously freed 
from gangue, with granulated iron obtained by pouring molten cast-iron in a thin 
stream into cold water. The operation is carried on in a shaft furnace; the result 
is the formation of metallic lead, and of a lead matte consisting essentially of sul¬ 
phuret of iron, undecomposed galena, and sulphuret of copper. Sometimes iron 
ores and slags of ironworks are applied, in which case the oxygen of these substances 
aids the desulphuration. 

The furnace in use for the smelting is represented in figures 25, 26, and 27. b is the 
shaft; c, d, the hearth and crucible, which, as exhibited by the cut, is partly outside the 
furnace. By means of a channel the molten metal can be run off from d into the tap 
crucible. The gases and vapours previous to their escape into the chimney, t, are made 
to pass through the flues, as indicated by the arrows, in order that any solid particles 
containing lead, which the blast at o might carry off, may be arrested. The ore and 
iron, previously washed, are placed in alternate layers in the furnace. The products of 


Fig. 25. Fm. 26. 



the smelting collected in' d, are lead, containing silver and lead matte, the latter containing 
about 30 lbs. of lead to the cwt., the former sometimes 3 lbs. of silver to the same 
quantity, while copper also may be present. This lead matte is, according to its con¬ 
stituents, either worked up for cementation-copper, or added to other slags containing 
lead and again smelted. 

° bt eai i cmatfo^ d . by This process is based upon the behaviour of oxide of lead and 
the sulphate of that oxide towards galena, and is effected on a large scale in a 
reverberatory furnace. By the action of the oxygen of the air at a high temperature 
upon galena, a portion of this mineral is converted into oxide of lead and sulphurous 
acid, while sulphate of lead is simultaneously formed. By the oxygen of the sulphate 
and of the oxide the sulphur of any undecomposed galena is oxidised and removed 
(3PbO -f- PbS = 4?b + S 0 2 -j- 0 ; PbS 0 4 -f- PbS = 2Pb -f- 2S0 2 ). If there is present 
during the roasting any excess of galena, there is formed a subsulphide of lead 














LEAD. 


61 


(Pb 2 S), from which a small quantity of metallic lead is obtained by liquation, while 
the residue becomes a higher sulphuret (2Pb 2 S=2PbS-f-2Pb). 

The English process of lead smelting by roasting and liquation is based upon the 
reaction just described, and is carried on in a furnace exhibited in Pig. 28. The hearth, 
constructed of slag and built upon a massive wall, is arranged to slope in all directions 
towards the tap-hole, through which the lead runs off into a cast-iron pan set in a niche. 
The figures 0 , 0 , 0 , indicate the openings for the doors, three on each side of the building. 
t is a funnel through which the ores are placed on the hearth. Every six or seven hours 
a charge of 16 cwts. of ore is worked off, while the consumption of fuel amounts to about 
half that weight in the same time. Care is taken to spread the ore uniformly over the 
hearth ; this having been done, the heat is gradually increased, the doors of the furnace 
being closed. After a lapse of two hours the doors are opened sufficiently to ventilate 
the furnace and dissipate the smoke, and are again closed, and the heat increased until 
the mass, from which lead everywhere exudes and runs off to the lowest level, becomes 
by stirring and the addition of fluor-spar, almost perfectly fluid. This point having been 
reached, the upper layer of slag is run off, at once cooled with water, and thus solidified. 

Fig. 28. 



This slag is termed white slag from its white or light grey colour, and contains about 
22 per cent, of sulphate of lead. Some small coal is now cast into the hearth in order to 
solidify the tough, pasty slag wliich covers the lead, after which the tap-hole is opened 
and the raw lead run off into the iron pan, previously heated so as to keep the metal in 
a molten state. 

Raw Lead. The metallic lead obtained as described is by no means pure, usually 
containing silver, copper, antimony, arsenic, and other metals according to the purity 
of the ore. The separation of the silver, when in sufficient quantity to repay the 
expense of extraction, will be spoken of under Silver ; but one of the by-products of 
some of the methods of extracting that metal is litharge, oxide of lead, which is 
either brought into commerce as such or reduced again to metallic lead by a process 
here described. 

ReV Lit fl h C ar<i°e n of This process is pursued in a reverberatory furnace by placing on 
the hearth a mixture of litharge and small coal. The lead resulting, known as hard 
lead, in contradistinction to the soft lead obtained from refined litharge, is usually 
not quite pure. In order to give some idea of the composition of the various kinds 
of lead as obtained at Freiberg, Germany, we quote the following results of analyses 
by Dr. Eeich:— 

Antimonial lead. 



Eaw lead. 

Eefined lead. 

Hard lead. 

Miilden. 

Ilaisbruck 

Lead . . 

. 9772 

99*28 

87*60 

90*76 

87*60 

Arsenic 

. 1*36 

0*16 

7-90 

1*28 

0.40 

Antimony 

. 0.72 

traces 

2.80 

7*3 * 

n*6o 

Iron . . 

. 0*07 

0*05 

traces 

0*13 

traces 

Copper. . 

. 0*25 

0.25 

0*40 

o *35 

traces 

Silver . . 

. 0*49 

°*53 

— 

— 

— 














52 


CHEMICAL TECHNOLOGY. 


Properties of Load The colour and general physical properties of this metal are too well 
known to require detailed notice. Lead assumes a crystalline form with difficulty, but it 
is obtained in that state in a combination of cubes and octahedra by some metallurgical 
processes, e. g., Pattinson’s method of silver extraction. Lead is, when refined, a very 
soft and tractable metal; its absolute cohesive strength is small. When freshly cut it 
exhibits a strong metallic lustre, but tarnishes rapidly on exposure to air. If handled it 
dirties the skin, and gives, when rubbed on paper, linen, or cotton, a plumbago-coloured 
mark. Its sp. gr. is 11*37 ; 1 cubic foot weighs about 600 lbs.; 1 cubic metre, 11,370 kilos. 
In addition to the metallic impurities usually present in lead and already alluded to, 
some of its oxide is commonly mechanically mixed with it, impairing its malleability and 
ductility, but, on the other hand, increasing its resistance to pressure. Lead belongs to 
the most readily fusible metals, fusing far below red heat, at 332 0 ; on cooling it contracts 
and assumes a concave surface. Lead is volatilised and boils at a strong white heat, air 
being excluded. It is not well suited for being worked with files or cold chisels, the former 
becoming clogged, and the latter blunt. Sheet lead is cut with knives of well-tempered 
steel. This metal does not take up more than about 1*5 per cent, of zinc ; croj per cent, of 
iron, and rather more copper, but alloys readily wuth tin, bismuth, and antimony. 

Applications of Lead is employed in a variety of ways in building. It is much used for 

Metallic Lead. the leaden chambers of sulphuric acid works, and for this purpose should 
be as free as possible from any impurities or foi'eign metals, all of which impair the 
resistance of the sheets of lead to the acid vapours, and cause the metal to become 
gradually perforated with holes and cracks. The metal is further employed for leaden 
pans and other apparatus in chemical manufactories, for gas- and water-pipes, for rifle 
balls, and for many other purposes too numerous to be here specified. 

Manufacture of Shot. This manufacture consists of five distinct operations, viz.—(1) the 
melting of the lead; (2) the granulation of the molten metal; (3) the sorting of the grain 
of various sizes; (4) separation of irregularly-shaped shot; and (5) the polishing of the 
shot. Lead intended for this manufacture is never required to be pure, and arsenic is pur¬ 
posely added, because experience has taught that this addition improves the spherical shape 
of the shot. The quantity of arsenic depends upon the quality of the lead, but varies from 
0-3 to o - 8 per cent. : too much causes an irregular shape, and too little has the same defect. 
The arsenic is added either as arsenious acid, in which case the lead is melted under a 
layer of pow r dered charcoal, or metallic arsenic wrapped in a piece of paper is introduced 
under the surface of the molten lead by means of a suitable pair of forceps. The 
granulation of the lead is obtained by the use of a shallow sieve-like iron vessel, 
technically termed a card, provided with holes of regular size. The dross and scrapings 
from former smeltings are not removed, as they prevent the lead running too readily 
through the holes. The operation of granulation is carried on in shot towers, the card 
with the molten lead being at the top, the metal assuming a spherical shape while falling. 
The small spheres or drops are collected in water, to every 100 parts of w r hich C025 parts 
of sulphide of sodium is added in order to coat the metal with a small quantity of 
sulphide of lead and prevent its oxidation. Shot is also made on an entirely different 
plan embodying the application of centrifugal force. The molten metal is forced -with 
great speed through openings in a centrifugal machine, making 1000 revolutions per 
minute, the shot or particles assuming a spherical shape by reason of the great force of 
impact with the air near the machine. The sorting of the shot is effected lay variously- 
sized sieves, and the separation of the imperfectly-shaped grains is obtained by causing 
the shot to run over a long slightly sloping table provided with ledges of wood to prevent 
the shot falling off sideways. Only the perfectly spherical grains of shot reach the 
lower end of the table. Lastly, the shot is polished by placing 100,000 parts by w r eight 
of shot and 6 parts by weight of graphite together in a cylindrical iron vessel made to 
rotate slowly on a horizontal axis. In this country some manufacturers prefer to use an 
amalgam of tin, or simply mercury, instead of graphite, for polishing. The loss of lead 
in the manufacture of shot amounts to about 2 per cent. The sizes and trade names of 
the several kinds of shot vary in. different countries; in Germany No. o is the largest and 
No. 10 the smallest size. 

Alloys of Lead. The following alloys of lead in daily use are made on a large scale :_ 

Soft lead solder as used by tinsmiths, equal parts of lead and tin ; the alloy used for 
organ pipes, usually 96 parts of lead and 4 of tin, but often more tin is added ; white 
metal alloy for domestic utensils, as coffee and teapots, consists of lead, antimony, 
and tin; alloy for ships’ nails, 3 parts tin, 2 parts lead, 1 part antimony. The lead 
used by the Chinese for lining tea-chests consists of 126 parts lead, 17-5 parts tin. 


LEAD. 


<’3 

1*25 parts copper, with a trace of zinc. Other alloys, such as type metal, will be 
spoken of presently. 

Preparations of Lead. 

oxide of Lead. This substance is commercially employed in two different forms, viz., 
as massicot or as litharge. 

Massicot. Massicot, or yellow oxide of lead, occurs as a yellow or ruddy-coloured 
powder, obtained either by heating carbonate or nitrate of lead, or by calcining 
metallic lead on the hearth of a reverberatory furnace. Before chromate of lead 
was known, massicot was used as a yellow pigment. At red heat this substance 
fuses and becomes glassy. In most instances it is not a pure oxide of lead, but 
mixed with silicate of lead, the fact being that oxide of lead at a red heat strongly 
attacks any material containing silica, dissolving the silica and combining with it. 

Litharge. Litharge is a fused crystalline oxide of lead, and is obtained as a by¬ 
product of the separation of silver from lead in the process to be fully described under 
Silver. Litharge always contains a larger or smaller quantity of oxide of copper, 
oxide of antimony, traces of oxide of silver, and, according to Dr. Wittstein, metallic 
lead, varying in quantity from 1*25 to 3*10 per cent. The oxide of copper can be 
removed by digesting the litharge with a solution, cold of course, of carbonate of 
ammonia. Litharge absorbs carbonic acid from the atmosphere, combines at a higher 
temperature with silica, forming with it a readily fusible glass, is soluble in acetic 
and nitric, and also in very dilute hydrochloric acids, and is equally soluble in 
boiling solutions of caustic potassa and soda. It is insoluble in carbonate of am¬ 
monia and in the carbonates of potassa and soda. Litharge is largely used, entering 
into various compounds for glass, so-called crystal-glass, flint-glass, strass for 
imitating jewels, for glazing pottery and earthenware, as a flux in glass and 
porcelain staining, for the preparation of boiled linseed and poppy-seed oil, for 
the preparations of lead-plaster, putty, minium, red-lead, and acetate of lead. A 
solution of oxide of lead in caustic soda lye is applied in the preparation of stannate 
of soda; this solution is also used for imparting to combs and other toilet articles 
made of horn the appearance of tortoise-shell or of buffalo-horn. A very dilute 
solution is used as a hair-dye, and again in metallochromy to produce iridescent 
colours on brass and bronze. 

Minium. Red-Lead. Bed-lead is a combination of oxide of lead with a superoxide, the 
formula being Pb 3 0 4 . Bed-lead of excellent quality is largely manufactured near 
Newcastle-on-Tyne, by carefully heating oxide of lead in a reverberatory furnace 
expressly built for that purpose, the access of air being limited so as to prevent 
the fusion of that portion of the oxide which cannot then be converted into 
minium. Sometimes metallic lead is oxidised in a reverberatory furnace, the pro¬ 
cess, as, for instance, at Shrewsbury, being so arranged that at the hotter places of 
the furnace massicot, and at the cooler red-lead, is produced. The finest coloured 
minium, or Paris-red, is obtained from carbonate of lead by the same method. 
According to Mr. Burton’s plan, sulphate of lead is heated with Chili saltpetre, 
and after the mass has been exhausted with water the red-lead is left, while sul¬ 
phate and nitrite of soda are dissolved. Bed-lead is used for a variety of purposes, 
many similar to the applications of oxide of lead. Besides being applied as a 
cement, when mixed with linseed-oil and mastic, for the flanges of steam-pipes, it 
chiefly enters the market as a pigment, being for that purpose either mixed with 
water or with linseed-oil, in both instances covering extremely well. 


CHEMICAL TECHNOLOGY. 


64 

superoxide of Lead. When red-lead is treated with moderately strong nitric acid, there are 
formed nitrate of protoxide of lead and superoxide of that metal, Pb 0 2 , a brown-coloured 
powder largely used in the composition of the phosphorus mixture for lucifer matches. 
The mixture known in lucifer match works as oxidised minium, is a dried composition, 
consisting of nitrate of protoxide of lead, superoxide of lead, and undecomposed red-lead, 
and obtained by drying a magma of minium and nitric acid. 

combinations of oxide Among the salts of lead employed industrially, the following 

are the most important:— 

icetate of Lead. This Salt, 


(C‘ H A)} o 2 + 3 H a o 


consists in 100 parts of:—Oxide of lead, 5871; acetic acid, 27*08; water, 14*21. 
It crystallises in four-sided columnar figures; is soluble in 1 *66 parts of water and 
8 parts of alcohol. When submitted to dry distillation it yields neutral carbonate 
of lead and aceton, which volatilises. When heated with sulphuric acid it yields 
acetic acid, sulphate of lead remaining in the retort. Acetate of lead is prepared 
by heating litharge or massicot with rectified vinegar, or with wood vinegar, in 
leaden or in tinned copper pans. The clear liquid is decanted and evaporated, and 
then left to crystallise in porcelain basins or in wooden tubs : 100 parts of litharge 
yield 150 of acetate of lead. This salt is largely used in dyeing and calico 
printing, in obtaining red liquor or acetate of alumina; and for the preparation of 
varnishes, white-lead, and chrome-yellow. We shall speak of sub-acetate of lead, 
tribasic acetate of lead, when considering the manufacture of white-lead. 


Chromate of Lead. 


The basis of chromate of lead, and indeed the substance from which 
all chromium preparations are derived, is the chrome-iron ore, consisting mainly of 
protoxide of iron and oxide of chromium (FeO,Cr 2 0 3 , or Cr 2 Fe 0 4 ). It is a magnetic 
iron ore 4 isomeric sesqui-, or per-oxide of chromium having been substituted for the 
peroxide of iron, but the mineral varies, in composition, often containing consider¬ 
able quantities of aluminia, magnesia, and protoxide of chromium. It is met with 
interspersed through very hard metamorphic rocks in some parts of Scotland, in 
colour a steel-grey or pitchy black. Its value for industrial purposes depends upon 
the quantity of oxide of chromium it contains; and according to M. Clouet’s analysis 
(1869) the following chrome-iron ores contained the quoted quantities per cent, of 
chromic oxide:— 


Chrome-iron from Baltimore 
Norway 
France 
Asia Minor 
Hungary 
Oural (Russia) 
California 


45 

40 

37—51 
53 
3i 
49-5 
42*5 


Neutral, or Yellow Chromate 
of Potassa. 


This salt, 

C K 2 } °* °rK 2 Cr0 4 , 

is prepared by heating chrome-iron ore, previously pulverised and cleansed, with 
carbonate and nitrate of potassa on the hearth of a reverberatory furnace. The 
oxygen of the saltpetre cause the higher oxidation of the protoxide of iron and 



CHROMIUM. 


65 


sesquioxido of chromium, the latter being converted into chromic acid. The 
thoroughly sintered, not molten, mass, is, after cooling, again ground up and 
lixiviated with boiling water, and also boiled for a time to extract the neutral 
chromate of potassa. Wood vinegar is added to the solution to precipitate the 
alumina and silica, after which the clear liquid is evaporated, until a film of saline 
material begins to form, when it is left to crystallise. The crystals take a 
column-like form, and are of a lemon-yellow colour, readily soluble in water, but 
insoluble in alcohol, and having a great tendency to become converted into bichro¬ 
mate or red chromate of potassa. This conversion of the neutral salt into the bi-, or 
acid salt, is at once effected by the addition to its solution of sulphuric or nitric acid. 
The bichromate of potassa or acid chromate, K 2 Cr 2 0 7 , crystallises in anhydrous, 
aurora-red coloured prismatic crystals, soluble in io parts of water. This solution 
is highly caustic and poisonous. When heated to redness the salt gives off oxygen, 
leaving oxide of chromium and neutral chromate of potassa in the retort; the 
bichromate is prepared from the neutral salt by the addition to its solution of either 
sulphuric or nitric acid, preferably the latter on account of the formation of nitrate 
of potassa, which may be either sold or used in the manufacture of the neutral 
chromate. 


M. Jacquelain proposes that the clirome-iron should be mixed with chalk, and the 
mixture heated and frequently stirred, then cooled, pulverised, and put into water, with 
the addition of enough sulphuric acid to produce a weak reaction, the result being the 
formation, first of chromate of lime, which, by the addition of the acid, becomes the 
bichromate of that base. The sulphate of protoxide of iron present in this solution is 
precipitated by means of chalk. In order to convert the bichromate of lime into the cor¬ 
responding potassium salt, it is only necessary to add a solution of carbonate of potassa, 
the result being of course the precipitation of carbonate of lime, and the exchange of 
the chromic acid from the lime to the potassa. According to Tilglimann’s process 
chrome-iron ore is mixed with 2 parts of lime, 2 of sulphate of potassa, and heated 
for eighteen to twenty hours in a reverberatory furnace. The same inventor suggests 
the heating of chrome-iron ore with powdered feldspar and lime; Mr. Swindells ignites 
chrome ore with equal parts of either chloride of sodium or chloride of potassium to the 
highest possible white heat, at the same time exposing the mixture to a constant current of 
superheated steam, the formation of sodium or potassium chromate resulting. The most 
important improvement in the preparation of chromate of potassa is the substitution of 
carbonate of potassa for nitrate of potassa, and the use of a furnace so constructed as to 
admit of the proper access of air to the strongly heated mass, the oxygen of the air being 
made to oxidise the chromic oxide to chromic acid. Another improvement is, that in using 
lime instead of alkali, the oxidation of the chromic oxide is greatly accelerated, by reason 
that when lime is employed instead of potassa, the heated materials do not become semi- 
fused or pasty, but remaining pulverulent admit of the readier access of air, as well as 
preventing the sinking, on account of higher specific gravity, of a portion of the chrome 
ore to the bottom of the hearth,, and there becoming withdrawn from the action of the 
heat. 


Applications of the 
Chromates of .Potassa. 


Before the year 1820, the salts spoken of were only used for the pre¬ 
paration of chrome-yellow; it was then a very expensive process, 
viz., the calcination of the chrome-iron ore with nitrate of potassa only. At this date, 
M. Koechlin discovered the applicability of bichromate of potassa to the obtaining of 
what is technically termed “discharge” for Turkey-red—a madder colour—a discovery 
soon followed by others bearing upon the useful applications of this salt, among which are 
the formation of chrome-yellow and chrome-orange in calico-printing, the chrome-black 
in dyeing, the oxidation of catechu and Berlin-blue, the discharge of indigo-blue, the 
bleaching of palm-oil and other fatty substances, the preparation of mixtures for the heads 
of lucifer-matches, the preparation of chromate of protoxide of mercury and chromic 
oxide as green-coloured pigments in glass and china painting, and for the preparation of 
Vert Guignet, a peculiar hydrated oxide of chromium :—- 

(Cr 2 ) 5 





56 


CHEMICAL TECHNOLOGY. 


obtained by heating i part of bichromate of potassa and 3 parts of crystallised boric acid, 
and used as a pigment in calico-printing. As might be expected, all these discoveries 
gave a strong impulse to the manufacture of the chromates of potassa, "which have 
recently found still further useful applications in the obtaining of colours from coal-tar, in 
the manufacture of chlorine gas, in defuseling brandy and other spirits, and in the purifi¬ 
cation of wood-vinegar made from the crude pyroligneous acid. 

According to M. J. Persoz, there exist, America excepted, only six manufactories of the 
chromates of potassa, viz., two in Scotland, one in France, one at Trjondhem, Norway, and 
one at Kazan, near the Oural, Russia; the total production of these works amounted in 
1869 to 60,000 cwts. 

chromate of iJa<L r There are in technical use three different compounds of lead and 
chromic acid, viz., neutral chromate of lead or chrome-yellow, basic chromate or 
chrome-red, and a mixture of these two salts constituting chrome-orange. The first 
of these substances is obtained by two methods:—(1) By the precipitation of a 
solution of chromate of potassa with a solution of acetate of lead; or (2) by 
the use of sulphate or chloride of lead. According to the first plan, the operation 
begins with the preparation of a solution of lead, for which purpose granulated lead 
is put into wooden tubs placed one above the other, and the taps each tub is provided 
with being turned off, vinegar is poured into the upper tub. In about ten minutes 
the tap at the bottom of the tub is opened, and the contents let into the second tub. 
The operation is repeated with all the tubs, four to eight in number, the object 
simply being to moisten the lead thoroughly with the vinegar, so as to cause rapid 
oxidation on its subsequent exposure to air. The metal soon becomes coated with 
a bluish-white coloured film, and when this is apparent, vinegar is again poured 
into the topmost tub and left for about an hour, after which it is run off into the 
second tub, and the operation continued until there is obtained a saturated solution 
of basic acetate of lead. To prepare chrome-yellow, enough vinegar is added to 
obtain a reaction, and the fluid left to deposit any suspended sediment. At the same 
time, in another tub, a solution of 25 kilos, of bichromate of potassa in 500 litres of 
water is kept in readiness. The clear lead solution is next poured into the bichro¬ 
mate solution as long as any precipitate ensues. This precipitate is well washed, 
and usually mixed with gypsum, or sulphate of baryta, to obtain the lighter chrome 
colours; finally it is dried. According to Liebig, chrome-yellow is obtained from 
sulphate of lead, an almost useless by-product from calico-printing- and dye-works, 
by digesting it with a warm solution of neutral chromate of potassa. The depth of 
colour of the ensuing yellow pigment depends upon the quantity of sulphate of lead 
which is converted into chromate of lead. 

Dr. Habich states that there exist two binary compounds of chromate and sulphate of 
lead, the formulae of which are PbS 0 4 PbCr 0 4 and 2PbS0 4 -\- PbCr 0 4 . The former is 
obtained when a solution of bichromate of potassa, previously mixed with enough sul¬ 
phuric acid to cause its dissociation, is precipitated with a solution of lead; while the 
second compound is formed if the quantity of sulphuric acid is doubled. According to 
M. Anthon a beautiful chrome-yellow is obtained by the digestion of 100 parts of freshly 
precipitated chloride of lead with 47 parts of bichromate of potassium. 

Chrome-Bed. The basic chromate of lead, known as chrome-red and Austrian-cinnabar, 
PbCr 0 4 -f- PbH 2 0 2 ,* is a red-coloured pigment much in demand, and obtained from the 
yellow or neutral chromate of lead, either by boiling* it with a caustic potassa solution, or 
by fusing it with nitrate of potassa, the effect being that half of the chromic acid is with¬ 
drawn from the neutral chromate. Drs. Liebig and Wohler state that chrome-red is best 
obtained by fusing together, at a very low red-heat, equal parts of potassium and sodium 
nitrates, gradually pouring into the fused salt small quantities of chemically pure yellow 

* According to Dr. Duflos, see “Handbuch der Angewandten Pharmaceutisch-Technisch 
Chemische Analyse, &c.” Breslau, 1871, p. 293, the formula of this substance is 2PbQ,CrO,, 
and the dried salt does not contain any water as a component part. ’ 3 ’ 




LEAD. 


67 


chromate of lead. After cooling 1 , the insoluble chrome-red is well washed and dried. It 
is then a magnificently-coloured cinnabar-like crystalline powder. Professor Dulong 
prepares chrome-red by precipitating a solution of acetate of lead with a solution of 
chromate of potassa to which caustic potassa has been added. The various shades and 
qualities of chrome-red, from the deepest Vermillion to the palest red, are caused by the 
difference in size of the constituent crystalline particles. This fact is proved by experiment, 
for when several samples are uniformly ground to a fine powder the result is the production 
of a uniformly deep-coloured hue. In preparing chrome-red of a deep colour, everything 
which might interfere with or injure the crystallisation has to be avoided. The pigments 
commercially known as the chrome-orange colours are mixtures, in varying - proportions, of 
the basic and neutral chromates of lead, and are usually made by boiling chrome-yellow 
with milk of lime. M. Anthon recommends for the preparation of a good chrome-orange 
the treatment of 100 parts of chrome-yellow with 55 parts of chromate of potassa and 
12—18 parts of caustic-lime made into milk of lime. 

Chrome-Oxide, or This substance, Cr 2 0 3 , is used in glass- and porcelain-staining as a 
Chrome-G.een. couleur grand feu , that is to say, it stands the most intense heat provided 
no reducing materials are allowed to affect it. It is commercially known under the name 
of chrome-green as an indelible pigment for printing, being especially employed for bank¬ 
notes. It is prepared in various ways, the finest being obtained by heating chromate of 
protoxide of mercury, but this method is far too expensive to admit of any extensive appli¬ 
cation. Dr. Lassaigne heats equal molecules of sulphur and yellow chromate of potassa, 
and exhausts the mixture with water, leaving the insoluble green sesquioxide behind. 
Professor Wohler prefers to mix the yellow chromate of potassa with sal-ammoniac, to heat 
that mixture, and afterwards treat it with water, leaving the insoluble chrome-green as a 
fine powder. 

Among other methods of preparing the anhydrous sesquioxide is the heating of an 
intimate mixture of bichromate of potassa and charcoal. The hydrated oxide of chro¬ 
mium, according to the formula Cr 4 H 6 0 9 , is met with in the trade under a variety of 
names, and often contains boric or phosphoric acids, not, however, as an. essential consti¬ 
tuent (See Dr. P. Schiitzenberger’s formula on p. 65 for Guignet’s-green), but as a remnant 
of imperfect preparation. This hydrated oxide, the preparation of which to ensure a good 
colour is rather a difficult matter, requiring very careful manipulation, is known as 
Emerald-green, Pannetier-green, Matthieu-Plessy-green, and Arnaudon-green. The pig¬ 
ment is used as an artist’s colour and in calico-printing as a substitute for Schweinfurt- 
green, but is very expensive. 

Or 1 

chrome-Alum. This salt, y 2 > 4SO4 + 24H2O, is obtained in rather large quantities as a 

by-product of the manufacture of aniline-violet, aniline-green, and anthracene-red. It is 
a deep violet-coloured, octahedrically crystallised substance, now used to some extent as a 
mordant in dyeing, for rendering gum and glue insoluble, for waterproofing woollen 
fabrics, and for the preparation of chromate of potassa. 

Chromic Chloride. This compound, Cr 2 Cl 6 , best prepared by the decomposition of sul- 
phuret of chromium by means of chlorine, constitutes a crystalline violet-coloured mica¬ 
like material, employed in the manufacture of coloured paper and paper-hangings. 

White-Lead. This very important preparation obtained from lead is the basic car¬ 
bonate of the oxide of that metal, its formula being, 

PbOCOa + a@ QIIQ ). 

x 

According to the method employed, white-lead is commercially known as of 
Holland or Dutch, Trench or English manufacture. The Dutch mode of making 
white-lead is founded on the fact that when metallic lead comes in contact with 
the vapours of acetic acid, carbonic acid, and oxygen, at a sufficiently high tem¬ 
perature, the metal is converted into basic carbonate of the oxide of lead. It is 
quite evident from this brief statement that the chief conditions being fulfilled, the 
methods of operation may be more or less varied. In Holland, Belgium, and some 
parts of Germany, the lead—as pure as possible and free from silver, which, even in 
small quantities greatly impairs the good colour of the white-lead—is cast into 
thin strips, which are wound in a spiral and placed in coarse earthenware pots. 
(Fig. 29.) Common vinegar is poured into the lower part of these pots, some beer- 
yeast being added. The lead is then placed on a perforated piece of wood, so ns to 



68 


CHEMICAL TECHNOLOGY. 


prevent direct contact with the vinegar. After this the pots are covered with leaden- 
plates and buried (see Fig. 30) in a mass of horse-dung or spent-tan and dung. The 
fermentation of the dung causes the requisite increase of temperature, and the 
vinegar evaporating, aided by the oxygen of the air, converts the lead into basic 
acetate, which in its turn is converted into basic carbonate of lead by the carbonic 
acid resulting from the fermenting manure. This rather clumsy process has given 
place in Germany to the chamber method, consisting essentially in the following 
arrangement. Instead of the pots being made the receptacles for the lead, the strips 
of that metal are bent and suspended on a series of laths run lengthwise through the 
chamber, on the floor of which is placed a layer of spent tan, marc of grapes, or other 
fermentable material, saturated with vinegar. An improvement upon this arrange¬ 
ment is to have the chamber constructed with a double flooring, one water-tight, the 
other a light planking perforated so as to admit of the vapours of. vinegar being 
carried into the compartment. The action upon the lead is in each case the same; 
it is converted chiefly into white-lead, and this crude product is purified from any 
adhering acetate of lead by washing with water before being brought into the market. 
There is still in use in this country a modification of the method practised by the 
Dutch, who, by-the-bye, are not the inventors of white-lead manufacture, the true 


Fig. 29. Fig. 30. 



origin being Saracenic, the trade being successfully carried on by these semi-savages 
in Southern Spain, whence the Dutch brought over the art in the sixteenth century 
to Holland. This modification consists in the following arrangement:—Granulated 
lead is first moistened with about 1*5 per cent, of vinegar, the metal being previously 
placed on hurdles in a wooden box, the interior of which is heated by means of steam 
to 35 0 , some steam being introduced to keep the lead moist. If care is taken to 
supply carbonic acid, after from ten to fourteen days the operation is finished, and 
the product having been lixiviated with water and dried, is ready for use. 

English Method of According to this plan the metal is melted in a large iron cauldron 

Manufacturing n „ , 

White-Lead, and then made to flow on the hearth of a reverberatory furnace so 
as to convert the lead, by proper access of air, into litharge, which is obtained in a 
very finely divided state by a peculiar arrangement of the furnace. The hearth is 
constructed with a gutter, into which the fusing mass flows; and the sides or walls 
of the gutter are perforated to admit of the passage of the molten litharge, while the 
heavier metal sinks to the bottom. The litharge is next mixed with i-iooth of its 
weight of a solution of acetate of lead, and then placed in a series of closed troughs 
communicating with each other and admitting of the passage of a current of impure 
carbonic acid, obtained by the combustion of coke in a furnace provided with a blast 
to give an impulse to the gas. The litharge is continually stirred by machinery to 
accelerate the absorption of the carbonic acid gas. White-lead made by this process 










LEAD. 


69 



covers very well, and is preferred to tliat prepared by the wet method. We may 
mention in passing that it is the custom in this country to bring white-lead into the 
market ground with linseed oil to a 
thick paste, packed in strong oaken 
kegs or iron canisters. 

French Method of This method, in- 
white-LcSd. vented by MM. The- 
nard the elder, and Board, is not 
only generally adopted in Prance 
but in all countries where it is 
desired to carry out a really sound 
and rational plan of white-lead 
manufacture. The method is as 
follows:—Litharge is dissolved in 
acetic acid to obtain a solution of 
basic acetate of lead, 

(C 2 H^) 2 j 02 + pbHA . 

and through the solution a current 
of carbonic acid gas is passed. Two 
molecules of oxide of lead are con¬ 
verted into white-lead, while neutral 
acetate of lead remains. Litharge 
is again added to the solution of 
this salt, and, by digestion, more 
subacetate of lead is obtained, which 
is applied as just described. 

Ap whlt“d in The machinery 
M T]ichy ureat and contrivances at 
Clichy, near Paris, for effecting the 
method just explained, are exhi¬ 
bited in Pig. 31. In the tub, A, the 
litharge is dissolved in acetic acid. 

B c is a stirrer, moved by means of 
the shaft shown in the engraving, 
bearing at the top a pulley for the 
strap.. The solution of basic acetate 
of lead can be run off through the 
tap into the vessel E, made of copper 
and tinned inside, the object being 
to let the impurities the solution 
might contain subside. Prom e the fluid is led into the decomposition vessel con¬ 
structed with 800 tubes, which pass from the top to a depth of 32 centims. beneath 
the level of the fluid. These tubes are in communication with the main-pipe, gg, which 
also communicates with the washing apparatus, p, answering the purpose of purifier 
for the carbonic acid gas generated in the small lime-kiln, G, by the ignition of a 
mixture of 2% parts by bulk of chalk and 1 part by bulk of coke with sufficient access 
of air. The decomposition of the basic acetate of lead being finished in from twelve to 
fourteen hours, the supernatant liquor, neutral acetate of lead, is run off into the 

V 


























7o 


CHEMICAL TECHNO LOG T. 


vessel, i, and the semi-fluid magma of white-lead passes into o. The pump, E, serves 
to again convey the neutral acetate to the tank, A, and the operation is re-commenced. 
The white-lead in 0 is well washed—the first wash-water being conveyed back to the 
tank, A— and after drying is ready for use. In order to obtain the carbonic acid 
cheaply, it has been proj>osed to ignite a mixture of chalk or limestone, charcoal, and 
peroxide of manganese (CaCC^ -j- C -j- 3M11O2 — M113O4 -j- CaO -f- 2CO2.) "W here ad¬ 
missible, the carbonic acid resulting from the fermentation of beer-wort, or of dis¬ 
tillery-wash, may be applied. Natural sources of carbonic acid sometimes occur in 
the neighbourhood of active or extinct volcanoes; and near Brohl, close to the 
Laacher Sea in Bhenish Prussia, a locality well-known to tourists, a very plentiful 
and continuous supply of carbonic acid is naturally obtained and actually applied 
for the purpose under consideration. 

Among the very various suggestions for improved methods of making white-lead, and 
for which an enormous number of patents have been taken out, especially in this country 
and in the United States, we briefly mention the following :— MM. Button and Dyer first 
slightly moisten litharge with water, next mix it with a small quantity of a solution of 
acetate of lead, place the mixture in a stone trough, agitating and passing hot carbonic 
acid over it. Pallu (1S59) causes finely-divided lead to be thrown with great force, by 
means of a centrifugal machine, on an inclined plane, care being taken to moisten the lead 
with acetic acid. After the lapse of an hour, the finely-divided lead is converted into 
acetate and carbonate. A solution of acetate of lead is then poured over the mass, and 
the acetate of lead it contains is dissolved, while the white lead is carried into a tank, and 
there forms a deposit. M. Griineberg (i860) prepares white-lead by submitting granu¬ 
lated lead to the simultaneous action of air, acetic, and carbonic acid, aided by the rapid 
motion of the metal. From private information obtained from the largest -wholesale house 
in London, whose connections and trade relations embrace literally the -whole world, dealing 
in white-lead, we have learned that not i-ioooth part of the lead, as it is technically termed, 
of good and saleable quality met with in the trade, is made by these new processes, since 
the products of most of them are deficient in some respect or other. 

White-Lead from It is well-known that sulphate of lead (PbSo 4 ) is a by-product of 

Sulphate of Lead, various chemical operations, especially such as are carried on in connection 
with dyeing and calico-printing. The salt of lead thus obtained is a refuse which it has 
been sought to utilise in many ways. As it does not possess covering pow r er, it cannot be 
used instead of white-lead as a pigment, and the difficulty of reducing it to metallic lead 
renders its metallurgical utilisation, if not impossible, at least highly objectionable. It 
has been used as a gas-purifier instead of, or in connection with, lime, and for this purpose 
it is a very fit material, and by becoming converted into sulphuret of lead it may be 
afterwards utilised as a lead ore. It is converted into white-lead by digesting it with a 
solution of either carbonate of ammonia or of soda. The best method for converting the 
sulphate of lead into metallic lead is to mix the air-dried salt with 67 per cent, of chalk, 
12 to 16 per cent, of charcoal, and 37 per cent, of fluor-spar, and to smelt this mixture in a 
furnace. The result is the formation of carbonate of lead, which is reduced to the metallic 
state by carbon, the sulphate of lead and fluor-spar combining as a slair— 

(PbS 0 4 + CaC 0 3 + 2C + «Fl 2 Ca = Pb -j- 3C0 -f CaS 0 4 -j- ^Fl„Ca). 

According to Dr. Bolley, sulphate of lead may be reduced by the moist method by placing 
the salt with zinc into water, the result being the formation of chloride of zinc (sic) and 
metallic lead.* M. Krafft proposes to convert sulphate of lead into acetate of lead by 
boiling the former with a solution of acetate of baryta, sulphate of that base (permanent, 
or Chinese-white) being simultaneously formed. 

Theory of Preparing Leaving out of the question the preparation of white-lead from sul 
White-Lead, phate of lead, the preparation of the pigment as regards all the other 
methods is dependent upon :— 

1. The formation of basic acetate of lead; 

2. The decomposition of that compound into neutral acetate of lead and white-lead. 
Viewing white-lead for this purpose simply as a carbonate of lead, although we shall 


* It reads in the original exactly as above translated, but whence the chlorine for the 
chloride of zinc is to come has been left in nubibus ; water, sulphate of lead, and metallic 
zinc do not act upon each other unless some acid be present. Should dilute , sulphuric be 
present there will be formed sulphate of zinc. 





LEAD . 


71 


presently see that the white-lead of commerce is not so simply constituted, the formation 
may be illustrated by the following formulae :— 


{ } O + 3 PbO = { } 0 2 ,2PbH,0 3 ; 


-y- 

Acetic acid. 


Basic acetate of lead. 


II. } 0 2 , 2 PbH, 0 3 + 2C0 3 + 2 PbOo 3 + {} O a . 


Basic acetate of lead. 


Carbonate Neutral acetate 
of lead. of lead. 


It is therefore evident that a comparatively very small quantity of acetate of lead can 
produce a large quantity of white-lead, and the manufacture of that material would be 
endless but for the fact that white-lead retains some neutral acetate of lead, and that the 
loss of acetic acid cannot be practically avoided. 

White-Lead from M. Tourmentin prepares white-lead from basic chloride of lead, obtained 
Chloride of Lead. Py the action of common salt upon litharge, by mixing that compound 
with water, passing through it a current of carbonic acid, and next boiling the fluid in a 
leaden-pan with powdered chalk until a test-sample, when filtered, does not become 
blackened by the addition of sulphide of ammonium. The white-lead thus formed is freed 
from salt by washing -with water. 

Lasic Chloride of Lead Mr. Pattinson, of the Felling Chemical Works, near Newcastle-on- 
85 White-Lead ful Tyne, has proposed that, instead of white-lead, a basic chloride (oxy¬ 
chloride) of lead should be used; and he prepares that substance by adding to a hot solution 
of chloride of lead (PbCl 2 ), containing from 400 to 500 grammes of the salt to the cubic 
foot, an equal bulk of saturated lime-water. This addition causes the throwing down 
of the compound (PbCl 2 -f- PbH 2 0 2 ), which after having been collected on a filter and 
washed, is dried and used as a pigment. The chloride of lead is obtained directly from 
galena, which is decomposed from leaden-vessels with strong hydrochloric acid. The sul¬ 
phuretted hydrogen thus formed is carried by suitable tubing to a burner in the sulphuric 
acid Ghamber, the resulting sulphurous acid from the combustion being used for the pro¬ 
duction of sulphuric acid. Pattinson’s white-lead is not so white as ordinary white-lead, its 
colour verging to yellow, but this is no objection where white-lead is to be used with other 
paints, and the less so as Pattinson’s oxychloride of lead covers well. 

Properties of When unadulterated and well-made, white-lead is an exquisitely fine wliite- 
White-Lead. coloured powder, void of taste and smell. The white-lead of commerce 
exhibits, according to the mode of preparation, different features; one preparation is met 
with in flakes, having been obtained by the corrosion of thin strips of lead placed in pots. 
The lead known as Krems-lead is pure white-lead made in thin cakes by means of gum- 
water. 

The variety of white-lead known as pearl-white is blued with either a small quantity of 
indigo or Berlin-blue. The white-lead of commerce has frequently been made the object 
of chemical analysis, especially by Dr. G-. J. Mulder and M. Griineberg. The results of 
the analyses of the under-mentioned samples prove the correctness of the formula given 
above. The numbers refer to:—1. Ivrems white-lead. 2. Precipitated by the Clichy 
method and manufactured at Magdeburg. 3. From the Harz. 4. Another sample from 
Krems. 5. A sample from a chemical laboratory by imitating the Dutch method on a 
limited scale. 6, 7. Samples from Klagenfurt, Carynthia. 8. English lead manufactured 
according to the Dutch method. 



1. 

2. 

J- 

4 - 

5 - 

6. 

7 - 

8. 

Oxide of lead . 

• 83-77 

85-93 

86-40 

86-25 

84-42 

86-72 

86-5 

86-51 

Carbonic acid . 

. 15-06 

11-89 

ii -53 

11-37 

M -45 

11-28 

1 1*3 

11-26 

Water . 

roi 

2-OI 

2-13 

2-21 

1-36 

2 "OG 

2-2 

2-23 


It is certain that the covering properties of white-lead are dependent upon its state of 
aggregation, because a loose crystalline white-lead does not cover nearly as •well as the 
perfectly amorphous lead prepared by the old Dutch method. It appears that the covering 
power increases with the amount of hydrated oxide of lead. This is proved by the fact that 
those who merely choose white-lead by its covering power are often misled, a fact lately 
tested by the translator of this work, by giving to a man, thoroughly acquainted with white- 
lead as commercially met with, a mixture of carefully-prepared and dried hydrated oxide 
of lead, to which white precipitate, subnitrate of bismuth, and carbonate of bismuth had 
been added. The man, after testing a series of samples of purposely-adulterated white- 
lead, all of which he detected as adulterated, was unable to speak with certainty of the 
above mixture, which he took for pure lead. 









n 


CHEMICAL TECHNOLOGY. 


■Adulteration of 
Wliite-Lead. 


It lias been, and is still, to some extent, the custom in the manufactories 
to add to white-lead a certain quantity of sulphate of baryta, either native 
or artificially prepared. Lead is often mixed with sulphate of lead, chalk, carbonate of 
baryta, sulphate of baryta, and pipe-clay; but these adulterations are most common in 
the retail trade. Not any of these substances ought to be present; they possess no covering 
power and needlessly absorb oil. Pure white-lead ought to be perfectly soluble in very 
dilute nitric acid, and in the resulting clear solution caustic potassa should not produce a 
precipitate, for if it docs chalk is present. An insoluble residue in the dilute nitric acid 
indicates the presence of gypsum, heavy-spar, or sulphate of lead. The sulphate of lead 
may be recognised by reducing the lead with the blowpipe. Sulphate of baryta can be 
made evident by ignition with charcoal in the blowpipe flame, treating the residue with 
dilute hydrochloric acid, and adding a solution of gypsum, which again yields a precipi¬ 
tate of sulphate of baryta. Gypsum does not yield an insoluble precipitate with dilute 
nitric acid, but does so with a solution of oxalate of ammonia. According to Dr. Stein 
the most simple method of estimating quantitatively a mixture of white-lead and 
sulphate of baryta, is to heat the weighed sample in a piece of combustion-tube, and to 
collect the carbonic acid in a Liebig’s potassa-bulb, a chloride of calcium-tube being* 
fastened by a perforated cork to the combustion-tube to absorb the moisture. The 
quantity of carbonic acid given off stands in direct proportion to the quantity of carbonate 
of lead present. Pure white-lead of good quality gives off about 14*5 per cent, of the 
gas, and, according to Dr. Stein’s researches, the undermentioned series of mixtures gave 
off the quantities of carbonic acid indicated. 

33'3 parts of white-lead and 66*6 parts of heavy-spar lost by ignition 4*5—5 per cent. 

m 33*3 »> »* >> 6 *s 7 »> 

,, 20 o ,, ,, 13 o ,, 

,, . 5®'® . ” . ” . o 10'4 ,) 

The extensive applications of this material as a constituent of paints, 
“ to give body,” as the term runs, and as putty, and for various chemical 
operations, are well known. It has been experimentally proved by Dr. G. J. Mulder in 
his treatise “ On the Chemistry of Drying Oils and the Practical Applications to be drawn 
therefrom,” that the quantity of white-lead used in proportion to linseed-oil for painting 
purposes is far too great, being on an average from 250—280 parts of white-lead to 100 
parts of oil, while the author found that 52 parts of unadulterated white-lead, or 44 parts 
of oxide of lead (PbO) to 100 parts of raw or boiled linseed-oil are amply sufficient 
quantities. White-lead, however useful, is very sensitive to the action of sulphuretted 
hydrogen, by which it is blackened and discoloured, causing not only all the white paint 
to be spoiled, but also all pigments and paints of which white-lead is a constituent, as 
may be seen to a very large extent every summer at Amsterdam, where from the stagnant 
canals sulphuretted hydrogen is abundantly given off. The action, however, of the sea 
air in autumn has the effect of somewhat restoring the blackened and discoloured painted 
surfaces to their primitive hue. The late Professor Thenard suggested that pictures which 
had become blackened shoidd be cleaned by means of peroxide of hydrogen, the oxygen 
of which present as ozone converts the blackened lead colours into white sulphate of 
lead. 


66*6 
So*o 
50*0 

Applications of 
White-Lead. 


In this country it has become an almost universal custom to sell white-lead ready 
ground with linseed-oil into a thick paste. This practice certainly saves painters a 
great deal of trouble, but is also pregnant with the difficulty of detecting adultera¬ 
tion, while there is a chance of an inferior oil, rosin oil, being added. The oil 
almost entirely prevents the action of any acid upon the paste ; even if very strong 
nitric acid be taken, and heat applied, the decomposition and disintegration are 
very slow and incomplete, and, besides, owing to the insolubility of nitrate of lead 
in nitric acid, the action of strong nitric acid upon oil thus mixed gives rise to a 
variety of compounds, which interfere with the usual modes of testing the white- 
lead. To remove the oil in order to test white-lead, the best plan is to thoroughly 
incorporate some of the sample with a mixture of chloroform and strong alcohol in 
equal parts, and to wash the mass by decantation or on a filter with a fluid com¬ 
posed of 2 parts of chloroform and 1 of strong alcohol. The quantity of the oil 
may then be ascertained by the evaporation of this solvent. After washing once 
or twice with boiling alcohol and then drying, the white-lead can be readily tested 
by any of the known methods. 


TIN. 


73 


Tin. 

(Sn = 118 ; Sp. gr. = 7*28.) 

occurrence and Tin does not occur naturally in a metallic state : it is found as 

mode of obtainiug . . ^ . . 

the Metai. oxide in tinstone, or tin ore, fen0 2 , containing 79 per cent, of metal, 
and as sulphuret of tin in combination with other metallic sulphurets in tin pyrites, 
(2CU2S + SnS 2 ) + 2(FeS,ZnS),SnS 2 , with 26 to 29 percent, of tin. Tin ore occurs 
either interspersed in veins, in syenitic and similar rocks, or in secondary formations 
deposited from water, and consisting of various detritus, when it is known as seifer. 
These ores are not as a rule simply composed of pure oxide of tin, but contain various 
other metallic compounds, among which are sulphur, arsenic, zinc, iron, and copper. 
In some instances, in Cornwall, Malacca, Banca, and Billiton, tin ore is met with 
among the detritus of ancient river-beds in a very pure state, since the mechanical 
separation of the ore from impurities has been performed by nature itself, and as a 
consequence these ores yield a purer metal than the ore obtained from veins, which 
has to undergo dressing, washing with water, and roasting, previously to being 
smelted, in order to eliminate the arsenic, sulphur, and antimony. Tinstone occurs 
in Saxony in the earlier granitic formation. The ore is accompanied by, and partly 
mixed with, wolfram, molybdenum-glance, sulphur, and arsenical pyrites, and bears 
the name of Zinnzwitter. Fig 32, I. and II., represent the furnace in use at 
\ltenberg, Saxony, for smelting the roasted tin ore. It is built of granite upon a 



r~ ./ 

1 •. 

■ - /,-• . ^ • 


///,////// ///// //////:■ 
m//////////m '/A 



strong foundation of gneiss, and is about thrte metres in height. A is the shaft, b the 
fore-hearth, and D the bottom-stone, consisting of one single piece of granite scooped 
out in the direction of b. b is in communication with the iron cauldron, c; while the 
tuyere of the blast is placed at b. The ore, mixed with coke, coal, or charcoal, and 
with slag from former smeltings, is placed in A; the reduced tin collects first on the 
fore-hearth, b, and runs thence into c. The metal, however, is not pure, but contains 
iron and arsenic. It is separated from these impurities by a process of liquation ; 
the pure tin fusing more readily, oozes out and leaves behind an alloy of iron and 
tin fusible with greater difficulty. The metal thus obtained is very pure, containing 
hardly as much as o*i per cent, of foreign metals; it is known in the trade as refined 


















74 


CHEMICAL TECHNOLOGY. ' 


tin. The slags, as well as the alloy remaining, are smelted separately or together 
for tin, and the result brought into the market as block-tin. In Bohemia and Saxony, 
tin is cast either in ingots or in cakes. Banca and Billiton tin, a very pure metal, 
is cast in slabs. If tungsten ores occur with tin ores, there is great difficulty in 
obtaining pure metal. Tin ore found in Cornwall—and this county has yielded tin 
for at least 2,000 years—has to be smelted according to the ancient Stannary laws. 

Properties of Tin. Tin, as regards its colour, approaches the nearest to silver, only 
differing by a somewhat bluish hue, and it exhibits a high metallic lustre very 
similar to silver. It is, next to lead, the softest metal, yet is somewhat sonorous, for if a 
rod of tin be free to swing, and is gently tapped, a sound is produced; this is not the 
case under similar conditions with lead, thus proving tin to be considerably harder, also 
proved by the fact that it is not easily scratched with the nail. The bending of a rod of 
tin causes a creaking noise, which is the stronger the purer the tin. Tin is very malleable, 
and admits of being beaten to very thin foil, but it is not a very ductile metal. When 
rubbed between tho fingers it imparts to them a peculiar odour. The sp. gr. of pure tin 
is 7-28, and by hammering may be increased to 7-29 ; a cubic foot of tin weighs, according 
to its purity, from 375 to 400 lbs. Tin fuses at 228°, and becomes very brittle when 
heated to nearly that temperature. If the metal is intended for casting—it is, however, 
very rarely used in a perfectly pure state for castings, as it does not fill the moulds well— 
its metallic lustre and degree of cohesion after cooling entirely depend upon the tempera¬ 
ture of the tin at the time of casting. If too hot and exhibiting rainbow colours, its sur¬ 
face will appear striped and reddish-yellow after cooling, and the metal will be brittle 
if again heated to ioo° to 140° ; if not sufficiently heated, though in a fluid state, it is, after 
cooling, dull and brittle. The greatest metallic lustre is obtained, and simultaneously the 
greatest cohesive strength, when the surface of the metal while molten exhibits a high degree 
of lustre. At a white heat tin boils and volatilises, air of course being excluded; for 
if the metal be kept fused in contact with air, it becomes covered with a greyish coating 
of protoxide of tin and finely-divided metal, termed tin-ash, which substance when the 
heating is continued becomes converted into a yellowish-white stannic oxide, known as 
putty powder. Tin by exposure to air gradually loses its metallic lustre, but is by no 
means so readily affected by sulphuretted hydrogen and ammoniacal vapours as silver, 
and is used to imitate that metal in the construction of lustres for gas lamps, &c. 

Applications of Tin. Now that china and earthenware have become cheap, and other alloys 
are used for spoons, tin is not so frequently in demand as in former times for domestic 
utensils. Tin, though next to silver the dearest of metals, is met with in quantities 
measured by the ton, which of tin varies in price from £120 to £180—copper being 
from £95 to £105—and is largely used both as an alloy (for those with copper 
see under that metal), and in a pure state for various kinds of vessels for pharmaceutical 
and chemical operations, for worms of distilling apparatus, for the working parts 
for dry and wet gas-meters, and for block-tin pipes for conveying gas and water, &c. 
However, for many purposes, an alloy known in this country as pewter, of lead and tin in 
varying proportions, is preferred, because this compound is harder and stands wear and 
tear better than these metals separately. An alloy of lead and tin is called abroad 
two-pounclly when the metals are present in equal quantities, and three-poundly when 
consisting of 2 pounds of tin and 1 of lead. Tin, either pure or more or less alloyed with 
lead, may be beaten or rolled into thin sheets and foil, and applied in a great many ways ; 
among which, one of the chief, although gradually being superseded by a process of silvering, 
is tinning or amalgamating mirrors. Tin-foil is also used for the packing of chocolate, 
soap, cheese, fruit, &c., all of which keep very well under these conditions. Commercial 
silver-foil or leaf-silver is an alloy of tin with a littie zinc; in combination with other 
metals, viz. copper, antimony, and bismuth, in varying but small quantities, it constitutes 
a composition metal used for making teaspoons and other similar objects. Britannia metal 
consists of 10 parts of tin and 1 of antimony, its various applications are well known. 

As the specific gravity of those metals with which tin is purposely or naturally alloyed 
differs, the determination of the sp. gr. is a means of estimating the purity of the metal. 
The undermentioned figures illustrate this in the more commonly occurring alloys of tin 
and lead :— 

Sp. gr. 

10-183 
8-497 
8-226 
8-109 
7’994 


Parts Sn 

+ 

Parts Pb 

Sp. gr. 

Parts Sn 

+ 

Parts Pb 

1 

~k 

1 

8-8640 

1 

+ 

4 

2 

+ 

n 

J 

9-2650 

>-% 

0 

+ 

2 

i 

+ 

0 

9 - 553 c 

2 

+ 

1 

2 

+, 

5 

9-7700 

5 

-f 

2 

1 

+ 

3 

9-9387 

3 

+ 

1 

2 

- 4 - 

7 

10-0734 





PREPARATIONS OF TIN. 


75 

The material known as putty-powder and calcined tin-ash is used for polishing glass 
and metals, and for producing white enamels. 

Tinning. By this term we understand the covering of other metallic surfaces with a thin 
and adhesive film of tin. This operation only succeeds well when the surface of the metal 
to be tinned is quite free from oxide, and when during the operation the oxidation of the 
molten tin is prevented. The former requisite is attained by the action of dilute acids, 
rubbing and scouring with sand, pumice-stone, &c.; the latter condition by the use of 
either rosin or sal-ammoniac, both of which cause the reduction of any oxide that may be 
formed. 

Tinning of Copper. Brass, The vessels or other objects intended to be tinned are heated 
and Malleable iron. ne arly to the melting-point of tin; some molten tin is then poured 
into the vessel, and brushed about with a piece cf hemp over which some powdered sal- 
ammoniac is strewed. Pins, hooks and eyes, small buttons, and similar objects are tinned 
by being boiled in a tinned boiler filled with water, gTanulated tin, and some cream of 
tartar. The tinned objects are dried by being rubbed with sawdust or bran. 

Tinned Sheet-Iron. This well-known material, from which so many useful objects are made 
by the tinman, is not, as is frequently supposed, rolled out sheet-tin, but tinned sheet-iron. 
The iron previously to being covered with tin is thoroughly scoured, so as to present a 
clean metallic surface, and then immersed in baths of molten tin covered with a layer of 
molten tallow to prevent the oxidation of the metal. On being removed from the tin-bath 
the sheets are immersed in a bath of molten tallow to remove any excess of tin, wiped 
with a brush made of hemp, next cleaned with bran, and packed. In order to obtain iron 
covered with an alloy less easily fusible, MM. Budy and Lammatsch add about T lth of 
nickel to the tin. 

Moire-Metaiiique. When tinned sheet-iron, technically termed tin-plate, is washed over 
with a mixture consisting of 3 parts of hydrochloric and 1 part of nitric acid diluted with 
3 parts of water, and then cleaned with pure water, there will be observed a peculiar, 
somewhat mother-of-pearl-like appearance, due to the crystalline particles of tin, produced 
by the rapid cooling, reflecting the light unequally. 

Preparations of Tin. 

Aurum Musiyum; ^he substance known under that name is in reality a bisulphide of 

Mosaic -Gold. # \ x 

tin (SnS 2 ), prepared in the following manner:—4 parts of pure tin, with 2 of mercury, 
are amalgamated by the aid of a gentle heat, and introduced with 2^ parts of sulphur 
and 2 of sal-ammoniac into a flask, and heated on a sand-bath, at first gently and 
then gradually increasing to a full red heat. First the sal-ammoniac volatilises, and 
next mercury in the shape of cinnabar mixed with a trace of the sulphide of tin; while 
there is left the preparation known as mosaic-gold, forming the upper layer of the 
remaining contents of the flask, the lower portion being a badly-coloured sulphide. 
The rationale of the formation of this peculiar coloured sulphide, that is, peculiar as 
regards its physical appearance, is not quite clearly explained; the compound, more¬ 
over, may be prepared without mercury. When properly prepared, it appears as a 
golden-coloured metallic substance, greasy to the touch, and soluble in the alkaline 
sulphurets. It is chiefly used for imitating gilding on painted surfaces, but its 
employment is very much restricted from the fact that the bronze-colours are more 
satisfactory in result. Indeed, in the English market, mosaic-gold is almost obsolete. 

Tinsait. By the name of tinsalt the trade understands chloride of tin (SnCl2), but 
the commercial article, being prepared by dissolving granulated tin in hydrochloric 
. acid and evaporating the solution, is really (SnCU + 2H 2 0). According to M. Nollner 
* hydrochloric acid gas should be caused to act on granulated tin placed in earthenware 
receivers, and the concentrated tinsalt solution thus obtained evaporated in block-tin 
vessels. The salt occurs in the trade in colourless, transparent, deliquescent 
crystals, of course very soluble in water. The aqueous solution, unless acidulated 
with more hydrochloric or tartaric acid, soon deposits a basic salt. Tinsalt is used 
chiefly in dyeing and calico-printing. 


76 


CHEMICAL TECHNOLOGY. 


N o? physic in ' Under this name dyers use a solution of refined block-tin in aqua 
regia, and usually this substance is a mixture of perchloride and protochloride of tin. 
The material known as pinksalt is a double chloride of tin and ammonium— 

(SnCl 4 +2NH 4 Cl). 

A concentrated aqueous solution of this salt is not decomposed by being boiled, but, 
when diluted, the oxide of tin is thrown down. Pure chloride of tin is used in Prance 
in the preparation of fuchsine; while as a solution it is used by M. Th. Peter, at 
Chemnitz, for dyeing in iodine-green, 

stannate of soda. This salt is now very largely used in dyeing as well as in calico 
printing, and is prepared in various ways, sometimes by fusing tin-ores with caustic- 
soda and lixiviating the molten mass with water; or, according to Mr. Brown, by 
boiling soda-lye with metallic tin and litharge, the effect being the formation ot 
stannate of' soda and metallic lead. Dr. Haffely somewhat modifies this process by 
digesting litharge with soda-lye at 22 per cent, in a metallic vessel. Into the solution 
of plumbate of soda thus obtained, granulated tin is placed and heat applied. Some¬ 
times a stannite of soda is used and made by dissolving tinsalt in an excess of caustic 
soda, but this preparation is unstable, and does not answer well in dyeing and print¬ 
ing; it is only extemporaneously used on a limited scale by small dyers. 


Bismuth. 


(Bi = 2io; Sp.gr. = 979). 

0cC ofobtaiui n ng Mode Bismuth is a rather rare metal. It occurs in Peru and Australia, 
chiefly native, and with cobalt and silver ores in granite-gneiss and metamorphic 
rocks. It is also found as oxide, the ore being known as bismuth-ochre, Bi 0 3 , con¬ 
taining 89*9 per cent, metal; as sulphide, or bismuthine, BiS 3 , with 80*98 per cent. 

Pig. 33 - 





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metal; and as bismuth-copper ore, with 47*24 bismuth. As bismuth is chiefly found 
in the native metallic state, and is a readily fusible metal, its extraction from gangue 
is not a difficult matter, and consists in a process of liquation. 

Bism F^rna i ce Uation Tiie contrivance in use near Schneeberg, in Saxony, for the smelt¬ 
ing of bismuth is exhibited in Pig. 33. The ore, containing on an average from 
4 to 12 per cent, metal, separated as much as possible by mechanical means from the 
gangue, is broken up to the size of hazel-nuts and placed in the cast-iron tube, A, 












ZINC. 


77 


heated by means of the furnace. The fluid metal runs out into b, an iron-pot kept 
sufficiently hot by means of charcoal to prevent the solidification of the metal, and 
partly filled with charcoal-powder to prevent the oxidation of the metal. The 
residue in the iron tube is discharged into the water which fills the box, d. By 
this method of liquation about two-thirds of the bismuth contained in the ore is 
reduced. Bismuth, as has been stated (see Cobalt), is obtained as a by-product, 
and from the refuse of the refining of certain silver ores, which are treated with 
dilute hydrochloric acid, the basic chloride of bismuth being precipitated by water, 
afterwards dried, and reduced by means of soda. 

Properties of Eisimr.h, Bismuth possesses a reddish-white colour, strong metallic lustre, 
and crystalline texture. It is hard, but «o brittle that is readily pulverised, yet 
with careful treatment proves to be somewhat ductile. Its fusion-point is variously 
given by different authors, the latest determination of pure metal in an atmosphere of 
hydrogen is by Dr. van Riemsdijk, who found bismuth to melt at 268*3°. On cooling 
bismuth expands very considerably. 

a is Saxony, Peruvian bismuth; composed in 100 parts:—c. Bismuth, 96731 ; anti¬ 
mony, 0*625; arsenic, 0-432; copper, 1-682; sulphur, 0*530. 0. Bismuth, 93-372; 

antimony, 4-570; copper, 2-058. 

Applications of Bismuth in the metallic state is chiefly used for certain alloys. Its oxide 
Bismuth, enters with boric and silicic acids into the composition of some kinds of 
glass, and is used for porcelain- and glass-staining. The basic nitrate, or magisterium 
bismuthi , and the carbonate are used in medicine, and the former, under the name of 
Blanc de fard , is employed by ladies for painting and beautifying their faces. Among the 
alloys of bismuth those with lead, tin, and cadmium (see that metal), are the most import¬ 
ant. Newton’s fusible alloy is composed of bismuth, 8 parts ; tin, 3 ; lead, 5 ; and melts 
at 94-5 0 . Posse’s fusible metal consists of 2 parts of bismuth, 1 of lead, 1 of tin, and 
fuses at 93-75. If a small quantity of cadmium be added to these alloys they are rendered 
still more easily fusible. An alloy composed of lead 3 parts- In 2 parts, bismuth 5 parts, 
fuses at 91-66, and may be used for stereotyping purposes, but is rather expensive. This 
alloy is also used for making the pocket-book metallic-pencil for writing on paper prepared 
with bone-ash. Alloys containing bismuth were used as safety-plugs in steam-boilers; 
these plugs were screwed into one or more of the plates exposed to the force of the steam, 
usually in or near the steam-chest or dome, the idea being that the plugs would melt if the 
temperature of the steam rose beyond certain limits. Experience, however, has suffi¬ 
ciently proved that these plugs, although carefully made, did not act as a real preventative 
to boiler-explosions. 


Zinc. 

Zn —65*2; Sp. gr. = 7*i to 7-3) 

occurrence of zinc. This metal, known only a comparatively short time, is never found 
native, but in combination with sulphur (ZnS), with 67 per cent, of metal, under the 
name of blende or black-jack, the ore sometimes containing traces of indium. It also 
occurs combined with oxygen as noble-calamine, carbonate of zinc, or zinc-spai 
(ZnC 0 3 ), with 52 per cent, of zinc; as ordinary calamine-stone, or hydrated silicate oi 
zinc, with 53*8 per cent of metal; as red zinc-ore or red oxide of zinc, frequently 
containing manganese; as Gahnite (AlZn 0 4 ); and further as an admixture with other 
ores. 

Extracting zinc The general plan is to roast the ore and then mix it with the requi¬ 
site quanty of carbonaceous matter and suitable flux, care being taken that the latter 
shall not give rise to the formation of any oxidising material; for instance, if the ore 
requires lime as flux to take up the gangue, calcined limestone, and not chalk or 
limestone is used. The action of the fuel is aided by a blast, best of dry air. The 
products of this mode of treatment are:—.1. Metallic zinc, the vapours of which 


CHEMICAL TECHNOLOGY. 


condense m properly constructed and cool channels. 2. Hot gases usually applied 
for heating steam-boilers or other purposes. 3. The non-volatile materials, gangue 
and flux, slag with some metal. 

Dist ii 1 i l M i u°ffle°8 fZillc With the exception of cadmium, zinc is the most volatile of the 
readily fusible metals, while its melting-point is nearly twice the number of degrees 
of that of tin, the most fusible of the commercially valuable rnetais; this property 
is utilised in extracting the metal from its ores. The mode of distillation varies in 
some particulars in the three chief zinc producing countries, Silesia, Belgium, and 
England. In Silesia and Germany the apparatus used for the distillation of zinc 
consists (see Eigs. 33, 34, and 35) of a muffle-shaped fire-clay retort, the front or 
mouth of which is provided with two openings, the lower, a, being closed by a door 


Eig. 34. Eig. 35. 



which is opened only when the residue of the distillation is taken out. At b , the 
other opening, a rectangularly bent tube is inserted, provided with a small hole at c, 
closed by a plug when the operation of distilling is proceeding, and by which the ore 
is introduced into the retort. At d the molten zinc runs off. The muffles are placed 
to the number of from 10 to 20 in a furnace (see Eig. 36) constructed internally 


Eig. 36. 



somewhat like gas-retort furnaces, and rest on what are technically termed benches. 
The arches of the furnaces are so constructed as to concentrate the heat from the 
hearths placed longitudinally. The metal is received in crucibles placed in the 
recesses, tt. As the first portion of the metal and oxide carried over contains nearly 
all the cadmium existing in the ore, that portion is kept separate for the purpose of 
extracting cadmium. At the outset of the distillation the condensation room, t, is so 
cool that the vapours of the zinc become solid without agglutination, that is, remain 
finely divided. This product, though of course containing oxide, frequently yields 
98 per cent, of metallic zinc. Afterwards the metal carried over is what is termed 
drop-zinc, that is to say, the liquid runs off in a molten state. This crude zinc is 
refined by another smelting, and comes in the market in slabs about 2 inches thick 
by 10 long and 5 to 6 wide. 










ZINC. 


79 


Distillation in Tubes. At the celebrated zinc-works of Vieille Montagne, near Lidgc, 
Belgium, zinc ore is distilled in tubes. These tubes are placed in ro ws in a slanting 
position; they are made of fire-clay, i metre in length by 18 centims. width and 5 
centims. thickness (see Pig. 37), and closed at one end; the open ends are flush 
with the front brickwork of the furnace, in order that the charge of ore, flux, and 
carbonaceous matter may be introduced. Pig. 38 exhibits a cast-iron conically- 
shaped tube, 25 centims. long, and Pig.^39 a sheet-iron tube^o centims. long, both 

Pig. 37. Pig. 38. Pig. 39. 




of which are fastened to the fire-clay tube to receive the volatilised metal. A vertical 
section of the Belgian furnace used for the distillation of zinc is shown in Pig. 40, 
with the mode of placing the tubes, the closed ends of which rest on a projection of 
the brick-work. The ore is first calcined in a shaft-furnace, and the charging of the 
tubes usually takes place every morning at six o’clock, when the fire is rather low. 

Distmationo^fzine The zinc-smelting as carried 
on near Sheffield, Birmingham, and in Wales and 
other localities, is performed by downward dis¬ 
tillation. The furnaces represented in Pig. 41 
are constructed to contain six or eight fire-clay 
crucibles, cc, access to which is obtained through 
holes made in the fire-arch of the furnace. The 
bottom of each crucible is perforated and fitted 
with a tube to carry off the volatilised zinc ; 
during the time of charging this tube is closed 
with a wooden plug, which is of course burnt 
during the strong ignition. At first the crucibles 
are left open, but as soon as a bluish flame be¬ 
gins to show itself, the covers are put on. The 
condensation-tube is then applied over a vessel 
containing water to prevent the spirting of the 
metal. The zinc is ultimately refined by smelt¬ 
ing in iron crucibles. 

Mode of obtaining zinc There are two modes of utilis- 
ing this zinc mineral. In one 
English Miners. pi an the sulphuret is first roasted 
so as to convert it into oxide, and then treated 
as before described; or the ore is directly applied 
by adding a quantity of iron ore sufficient to desul¬ 
phurise it, lime being used as flux. The iron ore, 
if containing water or carbonic acid, ought to be 
calcined previously to being used for this purpose ; 
but instead of iron ore metallic iron is often used. 

Mr. Swindells has proposed to calcine native 
sulphuret of zinc with common salt, the result being the formation of sulphate of soda 
and chloride of zinc. The mass being lixiviated with water, from which the sulphate of 
soda crystallises, the chloride of zinc remains in solution and is precipitated by means of 
lime, yielding oxide of zinc. This oxide is treated for metal in the ordinary manner. 

Properties of zinc. The colour of zinc is bluish-white or grey; its crystalline structure 
varies according to its purity, and according to the temperature at which it was cast and 
the more or less rapid cooling. When zinc is cast and rapidly cooled the specific gravity 





























8o 


CHEMICAL TECHNO LOG Y. 


is 7-178, but when slowly cooled it is 7-145, and by hammering-and laminating maybe 
increased to 7-2 and even 7-3. A cubic foot of zinc weighs, therefore, from 360 to 390 lbs. 
Zinc is slightly harder than silver, but like lead and tin it is not fitted for filing, as it 
chokes the teeth of the files. When pure, zinc is sonorous ; it is a brittle metal possessed 
of a very small absolute tenacity, but offers a great resistance to crushing weight, when 
not subjected to sudden blows. Very pure zinc may be hammered out at the ordinary 

temperature, but the malleability is greatest at tempera¬ 
tures between ioo° and 150°. Zinc melts at 412° in the 
open air, and perfectly pure zinc melts in an atmosphere of 
hydrogen at 42^°. According to MM. Troost and Deville 
zinc volatilises, air or oxygen being excluded, at 1040°, and 
may be distilled; when heated in contact with air to 5oo' J 
zinc burns, emitting a very strong greenish blue-coloured 
light, and forming oxide of zinc (zinc-white), which is not 
volatile. Of all the metals used on a large scale, zinc has 
the highest coefficient of expansion by heat, its longitudinal 
expansion for temperatures from o° to ioo°, being for cast 
zinc for sheet zinc g .i 2 , consequently molten zinc greatly 
contracts while cooling. The malleability, tenacity, and 
cohesive force of zinc are greatly impaired by temperatures 
ranging from 150° to 200°, at which zinc may be pulverised. 
Superheated steam oxidises zinc (H 2 0 -j- Zn = ZnO -j- H 2 ), 
and this property is made use of in the separation of this 
metal from lead. When exposed to a moist atmosphere 
zinc is superficially oxidised, but as the oxide adheres 
strongly to the metal further corrosion is prevented. Zinc 
is so readily oxidised and acted upon by water, weak acids, 
and alkalies, that it is not at all a suitable metal for vessels 
intended to hold potable liquids or moist solids, as these 
substances take up zinc and become poisonous. An addi¬ 
tion of 0-5 per cent, of lead renders zinc far more malleable ; 
but if the zinc is to be used for the preparation of brass, even 0-25 per cent, of lead is 
injurious, and for brass-making zinc containing lead is avoided. Zinc often contains 
some 0-3 per cent, of iron, but this does not impair the good quality; the iron is usually 
derived from the iron pots used for re-melting the crude metal; if, however, the quantity 
of iron increases the zinc becomes brittle and cracks. Zinc obtained from calamine is 
usually purer than that obtained from the native sulphuret. The black residue remaining 
when zinc is dissolved in acids; and often mistaken for a carburet of zinc, is a mixture in 
various proportions of iron, lead, and carbon. The more impure the zinc, the more 
readily it is dissolved in acids, but by careful distillation zinc may be almost entirely 
freed from any foreign metals. In contact with iron zinc prevents the oxidation of that 
metal. Zinc precipitates copper, silver, lead, cadmium, arsenic, antimony, and others 
from their solutions. 

Applications of zinc. This metal is very largely used for covering roofs, making water¬ 

spouts, tanks for holding water, and for various architectural purposes. It should be 
borne in mind that for roofing purposes zinc is in so far dangerous as to greatly increase 
. the intensity of fire should buildings covered with zinc become ignited; one instance of 
this danger was exhibited in March, 1866, when the huge wooden building then standing 
in Lower Kennington-lane, and used as a floor-cloth factory, caught fire, the burning of 
the sheets of zinc covering the roof producing a heat so intense as to ignite no less than 
sixteen adjacent houses, although these were from 20 to 30 yards from the burning shed. 
Zinc is used in galvanic batteries, in various alloys, in chemical laboratories, and for 
galvanising iron wires, as well as for the preparation of zinc-white, and for various 
ornamental castings, which are made in iron moulds previously thoroughly heated to 
prevent a too rapid cooling and contraction of the metal. The Prussians make use of zinc 
for cartridges. The total annual production in Europe of this metal amounted (1870) to 
2,154,000 cwts., of which England produces 150,000 cwts.; in the metropolis, Vieille 
Montagne (Belgium) zinc is almost exclusively used. 


Eig. 41. 



Preparations of Zinc. 

zinc-white. Under this name there has during the last fourteen years been brought 
into the market anhydrous white oxide of zinc, applied instead of white-lead as a 
pigment. Zinc-white is prepared for this purpose by oxidising metallic zinc in fire- 























PREPARATION'S OF ZINC. 


81 


clay retorts, placed to the number of 8 to 18, in a reverberatory furnace. As soon 
as these retorts are at a bright white-heat, cakes of zinc are placed in them, and the 
vapours of the metal on leaving the retort are brought into contact with a current 
of air heated to 300° ; oxidation results, and the oxide, a very loose, snow-white, 
flocculent material, is carried by the current of hot air into condensing chambers, 
and gradually deposited. The oxide thus prepared is immediately fit for use; it is 
of a pure white colour, and very light. Zinc-white is also prepared by exposing 
metallic zinc to the action of superheated steam, hydrogen being at the same time 
evolved, and used for illuminating purposes, as at Narbonne, St. Chinian, Ceret, 
and a few other places, where it is known as platinum-gas, because the flamo is 
used for imparting a white heat to small coils of platinum wire, thus producing a 
very steady and highly pleasant light. As regards the use of zinc-white as a 
pigment, it is rather more expensive than white-lead, yet according to some is 
a better covering material in the surface proportion of 10 to 13, that is to say, 13 
parts by weight of zinc-white cover as much space as 10 of white-lead; moreover, 
zinc-white is not affected by sulphuretted hydrogen. Like white-leaf, this com¬ 
pound may be mixed with other pigments. By mixing Pdnmann’s green with it a 
green colour may bo obtained; blue with ultramarine ; lemon-yellow with cad¬ 
mium orange-yellow (sulphuret of cadmium). 

white vitriol, Sulphate Zinc-vitriol (SZn 0 4 -f- 7IIJ, sulphate of zinc or white vitriol, is 

of zinc. found as a native mineral, as a product of the oxidation of zinc- 

blende ; it is also prepared by dissolving zinc in dilute sulphuric acid, and by roasting 
native zinc sulphuret. This vitriol occurs in white agglomerated crystals and in small 
acicular shaped crystals, as purified sulphate of zinc; it is used as a “ dryer ” in oil paints 
and varnishes; as a mordant in dyeing, for disinfecting purposes, and sometimes as a 
source of oxygen, since, on being submitted to a red heat, it gives off sulphurous acid and 
oxygen, oxide of zinc remaining. 

Chromate of zinc. This preparation, obtained by precipitating a solution of sulphate of 
zinc with bichromate of potassa, is a very fine yellow-coloured powder, used now and 
then in pigment printing, because it is soluble in ammonia, and thrown down again as a 
powder insoluble in water when that menstruum is volatilised. A basic chromate of zinc is 
used as a pigment in the paint trade. 

Chloride of zinc. This compound of zinc, ZnCl 2 , is obtained either by dissolving zinc in 
hydrochloric acid, or more cheaply by causing the hydrochloric acid gas given off in 
manufacturing soda to act upon native sulphuret of zinc. By this action sulphuretted 
hydrogen is formed, which can be burned to produce sulphurous acid for the sulphuric 
acid chambers. The solution of chloride of zinc thus obtained is evaporated to the con¬ 
sistency of a syrup. ' 

Anhydrous chloride of zinc is obtained by heating an intimate mixture of dried 
sulphate of zinc and chloride of sodium; chloride of zinc is formed which sublimes, and 
sulphate of soda which is left behind (ZnS0 4 -|-2NaCl:r:Na 2 S0 4 -|-ZnCl 2 ). This anhydrous 
chloride may be sometimes advantageously used instead of strong sulphuric acid, for 
instance in rape and colza oil refining, and perhaps, although it would be more expensive 
and less manageable, in the manufacture of garancine from madder. This chloride has of 
late been applied instead of sulphuric acid in the manufacture of stearic acid, and in the 
preparations of ether and parchment paper. Chloride of zinc in a strong and crude solu¬ 
tion is largely and very successfully used for preserving timber; in paper-making for the 
decomposition of bleaching powder for bleaching the half-stuff and rags, and also in 
sizing the paper. The disinfectants sold as Sir William Burnett’s Fluid and Drew’s 
Disinfectant are solutions of chloride of zinc. The salt used in soldering iron, zinc, 
pewter, &c., is a compound of the chlorides of zinc and ammonium (2NH 4 Cl-j-ZnCl 2 ); its 
solution is obtained by dissolving 3 parts by weight of zinc in strong hydrochloric acid, 
and adding, after the solution is complete, an equal weight of sal-ammoniac. Oxychloride 
of zinc, obtained by mixing oxide of zinc with a concentrated solution of chloride of zinc, 
or with solutions of chlorides of iron or manganese, has been recently proposed by 
M. Sorel as a plastic mass suited for stopping hollow teeth. 

1 


8 2 


CHEMICAL TECHNOLOGY. 


Cadmium. . 

(Cd:=ii2; Sp. gr. = 8*6.) 

This metal is rather rare, and as yet of very limited use; it is a constant com¬ 
panion of zinc in varying quantities, but is only found in the Silesian zinc oreS in 
sufficiency to repay the trouble of extraction. It was discovered as a distinct metal 
by Dr. Stromeyer, at Hanover, and Dr. Herman, at Schonebeck, in 1817. As 
regards its properties, cadmium stands between zinc and tin; the colour and 
metallic lustre of cadmium are similar to those of tin; it is ductile and malleable, but 
more readily acted upon by atmospheric oxygen and moisture than tin. The specific 
gravity of cadmium is 8*6 ; it melts when quite pure in an atmosphere of dry hydro¬ 
gen at 320°, and boils and volatilises (air and oxygen being absent) at 86o° to 746*2°. 
The cadmium sold by manufacturing and operative chemists and opticians is in small 
round bars, weighing from 60 to 90 grms. Silesian calamine ore contains about 5 
per cent, cadmium ; the same ore found near Wieslock 2 per cent.; the zinc-blende 
found at the Upper Harz contains from 0*35 to 0*79 per cent, cadmium ; zinc-blende 
from Przibram, Hungary, 1*78 per cent.; and the zinc ore of Eaton, in North 
America, about 3*2 per cent, cadmium. Such ores give off, while being heated in 
the zinc furnace, a brownish-coloured smoke, consisting of carbonate of zinc and 
metallic cadmium ; this smoke, condensed separately, is used as cadmium ore, and 
reduced by means of charcoal, the materials being placed in iron retorts and the 
metal distilled over, next refined, and cast in the small bars mentioned above. 
The annual production of cadmium in Belgium from Spanish zinc ores amounts to 
about 5 cwts.; while Silesia produces some 2 cwts. annually. 

Mixed with lead, tin, and bismuth, cadmium forms the so-called Wood’s alloy or fusible 
metal, consisting of cadmium, 3 parts ; tin, 4; bismuth 15; and lead 8 parts ; this alloy 
fuses at 70°, and is used for stopping teeth, and for soldering surgical instruments. 
M. Hofer-Grosjean used as stereotype metal an alloy consisting of lead 50, tin 36, and cad¬ 
mium, 22*5 parts. The only preparation of cadmium technically used to any extent is the 
cadmium-yellow, jaune brilliant (CdS), sulphuret of cadmium, applied as a pigment in oil 
painting, and in pyrotechny for producing blue-coloured flames. This preparation is best 
obtained by precipitating a solution of sulphate of cadmium with sulphuret of sodium, and 
then thoroughly washing, pressing, and drying the precipitate. Dr. Van Riemsdijk, of 
the Utrecht Mint, while experimenting with cadmium and zinc, both pure and kept fused 
in an atmosphere of pure dry hydrogen, found that these metals, though perfectly non¬ 
volatile at their point of fusion, and while kept fluid at that temperature, became percep¬ 
tibly volatilised at a few degrees above this point. 

Antimony. 

(Sb=i22; Sp. gr. = 6*712.) 

\ntimony. This metal, also named stibium, is chiefly found in combination w r ith 
sulphur as black antimonial ore, or glass of antimony, containing 71*5 per cent., of 
metallic antimony, formula (Sb 2 S 3 ), in veins interspersed among granite and 
metamorphic rocks. Antimony also occurs as oxide (Sb 2 0 3 ) in the minerals known 
as Yalentinite (rhombic) and Senarmontite (tesseral), this last variety being found 
in large quantities in Constantine, Algeria, and in Borneo. The black sulphuret 
of antimony is separated from the gangue which contains it by the application of 
heat, as the sulphuret is very fusible. 

The operation is carried on at Wolfsberg, near Harzgerode, Germany, by placing the 
broken-up ore and gangue in crucibles, b (Fig. 42), perforated at the bottom, and placed 
on a smaller crucible, c , surrounded with hot sand or ash. The walls are of 


ANTIMONY. 


83 



brickwork, so constructed with openings for causing a draught as to convey most 
heat to the upper crucible. Wood is used as fuel. In other localities, especially 
in Hungary, the apparatus exhibited in section and plan in Figs. 43 and 44 is used. As 
will be seen the principle is the same, 

but both the crucibles containing the Fig. 42. 

ore, and the receiving crucibles outside 
the furnace, and connected by means 
of tubes with the inside crucibles, are 
more conveniently placed. The liqua¬ 
tion of the rather fusible antimony 
ore is most readily and conveniently 
performed in the hearth of a peculiarly 
constructed reverberatory furnace, ex¬ 
hibited in Fig*. 45 ; the main point of 
the arrangement of the hearth being 
that the molten black sulphuret, col¬ 
lected at the lowest level, runs through 
the spout, c, to the receiver, / placed 
outside the furnace. At first a mode¬ 
rate heat suffices, but towards the latter 
part of the operation a strong heat 
is required to eliminate all the sul¬ 
phuret. The opening at f is now 
closed with a plug. Not until the gangue becomes semi-fused is the operation finished, 
when the heavier sulphuret collected under the slag is run off by the opening of the plug 
at/. 


Fig. 43. 


Fig. 44. 



Fig 45. 



Metallic antimony is obtained from the black sulphuret, either by roasting or by 
smelting it with suitable fluxes. In the former instance the sulphuret is placed on 
the hearth of a reverberatory furnace and continuously stirred, while a supply of air 
has access to the molten mass ; the calcination is continued until the bulk of the ore 
is converted into antimoniate of antimony-oxide. This material, also known as 
antimonial ash, is reduced to metal in crucibles, and for the reduction heat alone 


































CHEMICAL TECHNOLOGY. 


&4 

would answer, as the calcined ore always contains undecomposed sulphuret ot 
antimony (3Sb 4 08+4Sb 2 S 3 =2oSb+ i 2 S 0 2 ); but as some oxide of antimony would 
be lost by volatilisation, the crude antimonial ash is mixed with crude argol or 
with charcoal-powder and carbonate of soda. A strong red heat is sufficient for the 
reduction, and it is customary to allow the metal to cool slowly under the super¬ 
natant slag, in order to obtain the peculiar crystalline appearance desired in 
metallic antimony in the trade. 

By another mode of operation the sulphur is first removed from the black sulphuret by 
means of iron, but which, if used by itself, presents a difficulty arising from the almost 
equal specific gravities of the metallic antimony and sulphuret of iron, rendering the sepa¬ 
ration of these substances too imperfect to admit of the use of iron alone; consequently, 
either carbonate or sulphate of soda or potassa is added, which tends also to increase the 
fluidity of the slag, ioo parts of black sulphuret of antimony, 42 parts of malleable 
iron, 10 parts of dry sulphate of soda, and 3^ parts of charcoal powder are the pro¬ 
portions. In order to eliminate the arsenic from the metallic antimony thus obtained, 16 
parts are taken, and there are added 2 parts of protosulphuret of iron, 1 of sulphuret of 
antimony, and 2 of dry soda; this mixture is kept fused for fully one hour’s time, 
the resulting metal is next fused with 1J parts of soda, and a third time with 1 part 
of soda, until the supernatant slag attains a bright yellow colour. 

properties of Antimony. The metallic antimony of commerce is never quite free from 
arsenic, iron, copper, and sulphur; the influence of these impurities on the physical 
properties of antimony is not well ascertained, as those of chemically pure antimony 
are not well known. 

Antimony may be purified by fusing it with oxide of antimony; the sulphur 
and iron are oxidized and some of the oxide of antimony reduced to metal. For 
pharmaceutical purposes antimony is purified by the addition to the molten metal of 
pure saltpetre, but this process is attended with a loss of antimony. Antimony pos¬ 
sesses a nearly silver-white but slightly yellowish colour, strong metallic lustre, and 
a foliated crystalline structure; it crystallises like arsenic and bismuth in rhomboidic 
crystals. The specific gravity of antimony is =6712; it melts at 430°, the pure 
metal fuses at 450°, and, according to Dr. Duflos, does not expand on cooling. 
Antimony is volatilised, air and oxygen being excluded, only at a bright white heat. 
It is a very brittle metal, neither ductile nor malleable, but harder than copper. 
Antimony forms alloys readily, imparting to them some of its own brittleness and 
hardness; it is, therefore, added to tin, lead, and pewter, in small quantities, 
to render these soft metals hard. As antimony is not readily acted upon by air, it 
has been suggested to electrotype copper with a thin layer of this metal. The 
powder sold as ironblack, and used to give to papier mache and plaster of Paris 
figures the appearance of polished steel, is finely divided antimony, obtained by preci¬ 
pitating that metal from its solution in an acid by means of metallic zinc; this 
powder is also used to impart a lustre to cast zinc ornaments. The chief use made 
of antimony is as an alloy for printing type, which usually consists of 4 parts of 
lead and 1 of antimony with a small quantity of copper. Antimony also enters into 
the hard so-called anti-friction alloys used for the bearings of machinery. 

Antimonial Peepaeations in Technical Use. 

oxide of Antimony. This substance (Sb 2 0 3 ), obtained by calcining sulphuret of antimony, 
or by the precipitation of a solution of chloride of antimony with a solution of carbonate 
of soda, finally washing and drying the precipitate, has of late been used as a substitute 
for white-lead, but does not cover so well and is more expensive, though it is not affected 
by sulphuretted hydrogen. As this oxide takes up oxygen in the presence of alkalies, and 
is converted into antimonic acid (Sb 2 0 s ), it has been lately proposed for use in the propa- 


ARSENIC : 


85 


ration, of aniline red and for the conversion of nitrobenzol into aniline; also for the 
preparation of iodide of calcium by keeping 1 antimonic oxide suspended in milk of lime, 
and adding iodine as long as the latter is taken up. 

Black Suiphuret of This compound (Sb 2 S 3 ), obtained by liquation, occurs in commerce in 
Antimony. the conical shape it has assumed 'while cooling; its colour is like that 
of graphite, but it has a stronger metallic lustre, is of a deeper black colour, fibrous, 
crystalline structure, and very brittle; it usually contains iron, lead, copper, and arsenic, 
and is employed for separating gold from silver, in veterinary surgery, pyrotechny, and in 
the preparation of the percussion pellets used in the cartridges of the now celebrated 
Prussian needle-gun. 

Neapolitan Yeiiow. This pigment, used as an oil paint and in glass and porcelain staining, 
is of an orange-yellow colour, and very permanent. It is antimoniate of oxide of lead, 
and is prepared as follows:—1 part of antimonio-tartrate of potassa (tartar emetic), 
2 parts of nitrate of lead, and 4 parts of common salt, are fused at a moderate red heat, 
and kept at that temperature for 2 hours. The molten mass is put after cooling into 
water and becomes disintegrated, the salt dissolved and the pigment precipitated. When 
required for staining glass or porcelain it is mixed with a lead-glass, and has recently 
been prepared by roasting a mixture of antimonious acid and litharge. 

Antimony cinnabar. Oxysulphuret of antimony (Sb 6 S 6 0 3 ), is a compound in colour similar 
to vermillion, and is obtained by causing dithionite of sodium or calcium to act upon proto¬ 
chloride of antimony in water, and boiling this mixture, a precipitate being* readily 
deposited; it is a soft, velvety powder, unaltered by the action of air and light, and suited 
for either oil- or water-colour. This substance may be prepared on a large scale by the 
following process:—(1.) Black suiphuret of antimony is calcined in a current of air and 
steam, antimonic oxide being formed as well as sulphurous acid, which may be employed 
for the preparation of calcium-dithionite from soda waste; the antimonic oxide is 
next dissolved in crude hydrochloric acid. (2.) Large wooden tubs which admit of being 
internally heated by steam, are for |ths of their capacity filled with the solution of 
calcium dithionite, and the solution of protochloride of antimony is gradually added, the 
liquid being stirred and heated to about 6o°; the reaction soon ensues, and the precipitate 
having subsided, is thoroughly washed and dried at a temperature not exceeding 50°. 
There are prepared on a large scale, by operative pharmaceutical and- manufacturing 
chemists, numerous varieties of antimonial preparations, among which are several 
sulphurets and one oxysulphuret, different from the preparation here mentioned. 

Arsenic. 

(As = 75 ; Sp. gr. = 5’6.) 

Arsenic. Arsenic occurs in the mineral kingdom either native or in combination 
with sulphur. Although a few minerals are found containing arsenic in a state 
of oxidation, the quantity is so small that their technical utilization for the obtaining 
of arsenical compounds is altogether out of the question. Metallic arsenic is a 
solid, cystalline, steel-grey coloured substance. It is prepared either by the subli¬ 
mation of the native metal, or by the ignition of arsenical iron pyrites (FeS 2 -{-FeAs 2 ) 
and of arsenical pyrites (Fe 4 As6), or by the reduction of arsenious acid 
(As 2 0 3 + 30=: 3CO -f- As 2 ). Metallic arsenic is met with in the trade in an impure 
state, often containing no less than 10 per cent, of suiphuret of arsenic, in the form of 
greyish-black coloured crusts and lumps, known as fly poison. Pure metallic arsenic 
is rarely employed; a small quantity is used in the manufacture of shot, and in pyro¬ 
techny for white Bengal fire, which gives a very brilliant light, but should only be 
ignited in the open air. Lastly, arsenic burnt in oxygen gas is used as signal lights 
in the Trignometrical Survey Service. 

Arsenious Add. The substance known as white arsenic is really arsenious acid, As 2 0 3 , 
and obtained as a by-product of a great many metallurgical operations, for instance, 
the roasting of cobalt ores for smalt, of tin and silver ores; the volatilised acid is 
condensed by conducting it through channels into wooden chambers. In some 
localities, as in Silesia, where fuel and labour are cheap, arsenical pyrites is 
purposely calcined, and the crude arsenious acid obtained is refined by another 


CHEMICAL TECHNOLOGY. 


86 

sublimation process. For this purpose the cast-iron vessels, a , Fig. 46, are used, upon 
which are placed iron rings or collars, b, c, d, and a hood e, communicating by means 
of tubes with a series of chambers, of which the first only is shown in i. The 
. flanges of the cast-iron collars and all other joints having been thoroughly luted, the 

fire is lighted and the heat so increased as to 
cause the semi-fusion of the arsenious acid, 
which after cooling exhibits a peculiarly 
porcelain-like appearance, at first being as 
transparent as glass and very similar to fused 
anhydrous phosphoric acid. 

This compound, like all arsenical prepara¬ 
tions is very poisonous; but it is a remarkable 
fact, proved by direct experiment, that pure 
metallic arsenic introduced into the stomach 
of rabbits and other small animals in a finely 
divided state, by the aid of pure water freed 
from air, does not act on them as a poison, 
being found in their fseces unaltered. The 
commercial article is sometimes more or less 
mixed with oxide of antimony and sulphuret 
of arsenic. Arsenious acid is used in dyeing 
and calico-printing, in glass-making, for the 
purpose of clearing the molten glass, for the 
preparation of other arsenical compounds and 
pigments, and further in arsenical soap for 
the preservation of stuffed animals. The air 
in museums is sometimes poisoned by ar- 
seniuretted hydrogen being evolved if the 
arsenical compound has not been properly 
prepared ; and in places where there are large 
collections of stuffed animals there should always be a good ventilation and a dry 
atmosphere. Arsenious acid is also employed in the manufacture of aniline. 

Arsenic Add. This acid (H 3 As 0 4 ) has become an article of large consumption, 
it is obtained by boiling 400 kilos, of arsenious acid in 300 kilos, of nitric or nitro- 
hydrochloric acid, and evaporating the solution to dryness. Recently it has 
been prepared more cheaply by passing chlorine gas into water wherein arsenious 
acid is suspended, and evaporating this solution. Arsenic acid is sometimes 
employed in calico-printing instead of tartaric-acid, and is very largely used in the 
preparation of rosaniline or fuchsine, some manufacturers of these dyes annually 
consuming 2000 cwts. 

The acid arseniate of soda, so-called dungsalt, now used instead of cows’-dung in 
certain calico-printing operations, and consisting of 25 parts of soda and 75 ot 
arsenious acid, is prepared by heating for a length of time, either 36 parts of 
arsenious acid, and 30 parts of nitrate of soda, or a mixture of arsenite of soda and 
nitrate of soda. This salt is obtained as a by-product of the preparation of aniline 
from nitrobenzol. 

suiphurets of Arsenic. There are two sulphurets of arsenic employed industrially, viz., 
realgar and orpiment. 


Fig. 46. 

































QUICKSILVER , OR MERCURY. 


87 

tieaigar. Red arsenic or realgar (As S 2 ) is found native in a crystalline state and among 
other ores. It is artificially prepared by fusing together sulphur and excess of either 
metallic arsenic or arsenious acid, or on a large scale by distilling arsenical pyrites and 
ores containing sulphur. Realgar is a ruby-red coloured substance, exhibiting a conchoidal 
fracture. Its use in pyrotechny is based upon its property of yielding, when mixed with 
saltpetre and ignited, a brilliant white light. This mixture is known as Bengal white 
light, and is best prepared with 24 parts of nitrate of potassa, 7 parts of sulphur, and 2 
parts of realgar. 

Orpiment. Anri pigmentum, yellow sulphuret of arsenic (As„S 3 ), is likewise found native, 
but is generally artificially prepared by fusing together either sulphur and arsenious acid 
or realgar and arsenious acid. This sulphuret is of a bright orange-colour, somewhat 
transparent; it contains, if prepared by the dry method, free arsenious acid, and may 
therefore be considered as arsenoxysulphuret. It is also prepared by precipitating a 
hydrochloric acid solution of arsenious acid by means of sulphuretted hydrogen, or by 
decomposing a solution of the double sulphuret of arsenic and sulphuret of sodium with 

liusma, dilute sulphuric acid. Orpiment is used in dyeing to reduce indigo, and to 
prepare what is termed rusma, a paste applied in dressing skins in order to remove the 
hair, and which consists of 9 parts of lime and 1 of orpiment mixed with water. This 
paste is also employed in the toilet to remove superfluous hair; but instead of this very 
poisonous compound, either the spent lime from the purifiers of gasworks, or the sulphuret 
of lime solution obtained by passing a current of sulphuretted hydrogen through milk of 
lime, may. be advantageously used. 

Quicksilver, or Mercury. 

(Hg = 2oo; Sp. gr. = i3*5.) 

occurrence and This metal is not met with so generally dispersed as silver and gold. 

Mode of Obtaining ~ . . .. . ... . 

Mercury it occurs in the following forms:—1. Sparingly m the metallic state 
interspersed in globules through the gangue, and in small quantities in mercury 
mines, sometimes containing silver. 2. As a sulphuret, known as cinnabar, HgS, con¬ 
taining 86*29 of metallic mercury an d 1371 of sulphur. This ore is met with among 
primitive as well as metamorphic and sedimentary rocks, and is often accompanied 
by sulphuret of iron, while the gangue or matrix is generally quartz, calcareous 
spar, or spathic iron ore. The richest mercury mines are those of Almaden and 
Almadenejas in Spain, which were worked at a remote period of antiquity, and next 
are those of Idria, Carynthia. Cinnabar is found also in the Rhenish Palatinate, 
at Olpe in Westphalia, Horzowitz in Bohemia, in various parts of Hungary, at 
YalTalta in Yenetia, in the Oural, in China and Japan, in Borneo, Mexico, at 
Huancavelica, in Peru, and in considerable quantities in California, where mercury 
is largely produced. 

Among the less important mercury ores is found the so-called liver-coloured ore, a clay 
mixed with cinnabar, bitumen, paraffine, and coal-slate. This ore is only met with in 
Caryntliia. There is also the fawn-coloured mercury ore, containing 2 to 15 per cent, of 
mercury, with sulphur, copper, and other impurities. The annual production of mercury 
throughout the globe amounted in 1870, to 84,500 cwts., of which California yields 56,000 
against 22,000 from Spain. 

Mercury is extracted from its chief ore, cinnabar, by :— 

1. Calcination in shaft furnaces, the mercurial vapours being condensed in chambers con¬ 
structed either of brickwork or boiler-plate, or in earthenware vessels (Aludels) joined 
together by flanges similar to earthenware drain-pipes. 

2. By decomposing cinnabar in closed vessels, the ore being mixed with either lime or 
forge scales. This method is usual hi Bohemia and the Bavarian Palatinate. 

Method of Extracting The contrivances in use in Idria for the extraction of mercury 

Mercury pursued , • • \ 

m idria. from its ores are illustrated m Figures 47, 48, and 49. a is a cal- 
ciantion furnace, which is flanked on each side by a series of condensation chambers, 
(! CD, communicating with the furnace. The ore is placed in lumps on the perforated 
arches, n 11 , of the furnace, and the space v completely filled. On the arch, p p\ the 


88 


CHEMICAL TECHNOLOGY. 


smaller lumps of ore are placed, and on r r, tlie dust, pulverulent ore, and residues 
of former operations. This having been done, the fuel, commonly dry beechwood, is 
ignited on the furnace-bars. The heat is gradually raised to and kept at a dark red 
heat for io to r 2 hours. The draught created carries into the furnace sufficient air 

Fig. 47. 



Fig. 48. 



to convert the sulphur of the volatilised ore into sulphurous acid and set the 
mercury free (HgS + 2 0 = S 0 2 -f Hg). The products of the combustion are carried 
into the chambers, c. The bottom of each chamber is made of strongly pressed clay 
shaped so as to form two planes inclined towards each other, and connected with 
gutters leading to a reservoir cut out of a solid block of porphyry in which the 
mercury is collected. A jet of water is made to play constantly in the last conden¬ 
sation-chamber, in order to keep it and the adjoining smoke-chambers, D D, quite 
cool, the last traces of mercury being condensed in D D. 

Very recently experiments have been made at Idria to distil he mercury continuously 
from its ore by the use of a reverberatory furnace, whereby both time and fuel are saved. 









































































QUICKSILVER, OR MERCURY . 


8 9 


Spanish Method or Tli 0 arrangement for condensing the mercurial vapours in use at 
Extracting Mercury. Almaden is exhibited in Fig. 50. It consists of a string of pearl¬ 
shaped vessels open at both ends. These vessels, locally known by the Arabian term, 
Aludels, are made of earthenware, and so constructed that the narrow end of one fits 
into the wider end of the other, care being taken to lute the joints with clay. The 
mode of arranging these rows or strings of aludels is delineated in Fig. 52, which 
represents the plan of the furnace shown in Fig. 51. This furnace consists of a 


Fia. 50. 



Fig. 51. 



Fig. 52. 



cylindrical shaft oven, which by means of a perforated v arch is divided into two 
parts. The fire is lighted in the lower part of the shaft, while on the perforated 
arch is first placed a layer of sandstone containing cinnabar, in quantities too small 
to admit of being otherwise advantageously treated. The rich ore is then placed on 
this layer of stone, and the openings in the arch of the furnace covered with tiles 
and tightly luted. The mercurial vapours are first conducted into the space c c, 
and thence through the twelve rows of aludels, each row having a length of from 
20 to 22 metres, and containing 44 aludels. The aludels are placed on a somewhat 
inclined plane as shown in the woodcut. At / the condensed mercury is run off by 























































90 


CHEMICAL TECHNOLOGY. 


the gutter, g , into the stone cisterns, h U; the vapours not condensed being carried 
on to the chamber, B, where they are completely liquefied. The smoke escapes 
through a chimney at b. As the mercury thus obtained is mixed with soot it has 
to be purified and cleansed; this is effected by causing the metal to flow down an 
inclined plane, to which the soot adheres. The sooty mass and the impurities 
collected in the room b, are submitted to distillation for the purpose of extracting 
the last traces of mercury. The quantity of ore operated upon at each calcination 
amounts to 250 to 300 cwts. Spanish mercury is met with in the trade packed in 
wrought-iron canisters or in sheepskin bags. The apparatus above described for 
separating mercury from its ores was invented by the Moors, who for several centu¬ 
ries were the only civilised inhabitants of the greater portion of southern Spain. 

ir th3°Ora f b° e t C hTa P id S of S Method of mercury distillation pursued at Horzowitz in Bohemia, 
other Substances. The sulphuret of mercury is mixed with from f to § of its weight of 
forge-scale, and the mixture placed on the iron plates, b b, Fig. 53. These plates are fixed to an 


Fig. 53. 



iron rod, and covered by the iron cupola, e e, which rests in a tank filled with water. The 
cupola is removable from the furnace by means of the frame g. The metal is collected 
in the water at d. Each cupola covers about £ cwt. of ore and 1 cwt. of foro- e -scale and 
there are generally six cupolas in one furnace. The operation lasts for 30 to ?6 hours 
In the Rhenish Palatinate mercury has been extracted from its ores since 1410 It 
there usual to mix the mercury ore with other metallic ores, that mainly worked beino- 
cinnabar interspersed m sandstone. The decomposition of the ore, which is a rather 
poor material, can be made to pay only by skilful management. The ore is mixed with 
ime and f la , ced m T on ^ etor ^ simda / to those used in gas-works, and heat ha™ 
been applied the cinnabar is decomposed, the result being the formation of metSlte 
mercury, which volatilises and is condensed in suitably-constructed receivers white the™ 
remains in the retorts a mixture of sulphuret of calcium and hyposulphite of lime Tb t 

operation lasts ten hours, after which the contents of the receivers are poured into 


























PREPARATIONS OF MERCURY. 


9i 


earthenware tanks filled with water; the mercury sinks to the bottom and the water is 
allowed to run off, carrying with it a blackish powder, consisting of finely-divided mercury 
mixed with a volatilised black sulphide, which is again submitted with lime to another 
distillation. 

Properties of Mercury. Mercury is the only metal remaining’ fluid at ordinary temperatures. 
It freezes at — 32’5°, and is in that state a malleable and ductile metal. At 360° it boils, 
and at a slightly higher temperature distils over, but is volatilised to some extent at all 
temperatures above its freezing-point, as may be proved by suspending a piece of gold-leaf 
in the neck of a bottle containing a small quantity of mercury. Mercury readily combines 
at ordinary temperatures with various metals, forming what are termed amalgams. The 
amalgams most readily formed are those of lead, bismuth, zinc, tin, silver, gold ; next is 
that with copper, while with iron, nickel, cobalt, and platinum, mercury will only amalga¬ 
mate with difficulty. The application of mercury in metallurgy in the extraction of gold 
and silver from their ores is based upon the property mercury possesses of readily combining 
with these metals. Amalgams of various kinds are industrially employed, as, for instance, 
with tin for covering mirrors and looking-glasses, with gold for the so-called process of 
fire-gilding. An amalgam of 4 parts mercury with 2 parts zinc and 1 part tin is used for 
the cushions of electrical machines. 

Applications of Mercury. J 3 y far the most extensive application of mercury is in the con¬ 
struction of various physical instruments, for filling the mercurial gauges of steam-boilers, 
and on the Continent these gauges are attached to all boilers, locomotive engine-boilers 
alone excepted. Mercury is employed in the preparation of a variety of compounds, 
among which is the fulminate of mercury; and, further, for various purposes in chemical 
and physical laboratories. More recently, an amalgam of mercury and sodium has been 
very successfully used by Mr. Crookes in the metallurgical extraction of silver and gold; 
and a solidified amalgam of the same metals is recommended to facilitate the transport of 
mercury, the amalgam admitting of being very readily decomposed by treating with dilute 
sulphuric acid. 

Preparations op Mercury. 

Mercurial compounds. The more important mercurial compounds which are manufac¬ 
tured on the large scale are the following :— 

Mercuric cworide. The substance commonly known as corrosive-sublimate is the per- 
chloride of mercury, HgCl, equivalents 135, consisting, in 100 parts, of 73*8 parts of 
mercury and 26*2 parts of chlorine. It is prepared either by sublimation from a 
mixture of sulphate of peroxide (red oxide) of mercury and common salt, or by dis¬ 
solving the same oxide in hydrochloric acid, and also by boiling a solution of 
chloride of magnesium with the peroxide (MgCLUIIgO==IICl-|-MGrO). When 
sublimed, this salt forms a white crystalline mass, w r hich fuses at 260°, boils at 290°, 
is soluble in 13*5 parts of water at 20°, and in 1*85 parts of the same liquid at ioo°. 
It is more readily dissolved by alcohol, 1 part of the salt requiring only 2’3 parts of 
cold and 1’i8 parts of boiling alcohol. Mercuric-chloride has been industrially 
employed as a preservative for timber by Mr. Kyan, and is used in the manufacture of 
aniline-red, in dyeing, and calico-printing, in etching on steel-plates, and for the 
preparation of other mercurial salts. Lately, the use of the double salt, HgCl 2 ,2KCl, 
obtained by boiling chloride of potassium with peroxide of mercury, has been sug¬ 
gested as a preservative for timber. It should be borne in mind that this prepara¬ 
tion of mercury is extremely poisonous, and easily absorbed by the skin of the hands. 

cinnabar. "Under this name is designated the mercuric-sulphide, HgS, which occurs 
native in crystalline or compact red-coloured masses, and was known in Pliny’s 
time by the term minium.* The cinnabar, or Vermillion of commerce, used as a 
pigment, is always artificially prepared either by the dry or wet way. By the former 
process 540 parts of mercury and 75 of sulphur are very intimately mixed. The 

* Eed-lead, afterwards called minium, was, as far as it appears, unknown to the ancients, 
being first prepared by the Arabs and Saracens. 


92 


CHEMICAL TECHNOLOGY. 


ensuing black-coloured powder is introduced into iron vessels, and exposed to a 
moderate beat so as to cause tbe fusion of the mass, which, after cooling, is broken 
up and then introduced into earthenware and loosely closed vessels, heated on a 
sand-bath. The sublimed mass is of a cochineal-red colour, exhibits a fibrous 
fracture, and yields when pulverised a scarlet powder, which is the more beautiful 
the purer the materials used in its preparation and the greater the care taken to avoid 
an excess of sulphur. Some chemists allege that a greatly improved vermillion is 
obtained if i part of sulphuret of antimony is added to the mixture of sulphur and 
mercury previously to the sublimation, and the sublimed and pulverised mass placed 
in a dark room for several months and treated with either dilute nitric acid or caustic 
potassa. According to Dr. J. von Liebig, vermillion is obtained in the wet process 
by treating the white precipitate of the Pharmacopoeia, or hydrargyrum amidato 
bichloratum , according to the formula, HgCl,HgNH 2 , which corresponds to the term 
used, but in Dr. A. W. Hofmann’s opinion, does not express the true composition of 
the compound. He considers white precipitate to be a chloride of ammonium, in the 
ammonium of which 2 equivalents of mercury have taken the place of 2 equivalents of 


hydrogen; formula N 


H a 

Hg 2 , 


Other chemists, again, hold different views as to the 


constitution of this body, which has been used in medicine since, if not before, the 
time of Paracelsus. Yermillion is generally obtained by precipitating a solution of 
corrosive-sublimate in ammonia with a solution of sulphur in sulphide of ammonium; 
or, according to Dr. von Martius, by agitating, in a suitable vessel, 1 part of 
sulphur, 7 of mercury, and 2 to 3 of a concentrated solution of liver of sulphur. 
According to M. Brunner’s method, by which decidedly the finest vermillion is 
obtained, 114 parts by weight of sulphur and 300 parts by weight of mercury are 
mixed, with the addition of a small quantity of caustic potassa solution, and incorpo¬ 
rated by being shaken by machinery. The resulting black compound is next treated 
with a solution of 75 parts caustic potassa in 400 parts of water, and heated on a 
water-bath to 45°. The mixture assumes a scarlet colour after a few hours, and as 
soon as this is apparent the semi-liquid mass is poured into cold water, next collected 
on filters, washed, and dried.. The vermillion of commerce is often adulterated with 
red-lead, peroxide of iron, chrome-lead, and more frequently with from 15 to 20 per 
cent, of gypsum. These adulterations are, however, readily detected, as they are left 
behind when the vermillion is sublimed. Bed-lead, one of the most usual adultera¬ 
tions of vermillion, can be readily detected either by treating a small quantity of the 
suspected sample with nitric acid, when in consequence of the formation of 
puce-coloured peroxide of lead, the mass assumes a brown colour, or by the addition 
of hydrochloric acid, when chlorine is given off. Pure cinnabar is completely and 
readily soluble in hydrosulphuret of sulphide of sodium (NaSH). 

Fulminating Mercury. . The compound known as fulminating mercury is a combination of 
fulminic acid, an acid unknown in a free state, and of oxide of mercury; its formula may 
be written C 2 Hg 2 N 2 0 2 . In 100 parts it consists of 77-06 of peroxide of mercury and 
23-94 of ful min ic acid. According to the late Dr. Gerhardt’s view, this body is a nitro¬ 
compound which may be regarded as cyan-methyl, the hydrogen of the methyl of which 

has been replaced by hyponitric acid and mercury; the formula is then: C | 2 j ^CIST. This 

substance was first discovered by Mr. Howard, and was known, until Dr. von Liebig gave 
the clue to its nature, as Howard’s detonating powder. It is prepared on a laro-e scale in 
the following manner. First, 2 lbs. of mercury are dissolved, by the aid of a gentle heat, 
in 10 lbs. of nitric acid (sp. gr. 1-33), and 10 lbs. more of nitric acid are then added. The 
resulting fluid is poured into six tubulated retorts, and to the contents of each retort is 


PREPARATIONS OF MERCURY. 


93 


added io litres of alcohol (sp. gr. 0-833). If the ingredients are mixed by measure instead 
of weight, for every volume of mercury, there is taken 7 1 volumes of nitric acid, and 
10 volumes of alcohol. After a few minutes a strong evolution of gas takes place, and at 
the same time a white precipitate, the fulminate of mercury, is formed. The retorts are 
fitted with tubulated receivers, from which glass tubes carry off the very poisonous gas 
and fumes, either to a flue or directly to the outside of the shed in which the operation is 
performed. The precipitate is collected on filters, and washed with cold water to 
eliminate the free acid. The fulminate is next dried, filtered, and all being placed on 
plates of copper or earthenware, heated by steam to less than ioo°. 100 parts of mercury 
yield in practice from 118 to 128 parts of fulminate, while, according to theory, 
142 should be obtained. The dried fulminate is, with cautious manipulation, divided into 
small portions, kept separately in a paper bag. The fulminate thus prepared is a crystal¬ 
line white-coloured substance, which, by being heated to 186 0 , or by a smart blow, explodes 
with a loud report. When placed on iron and struck with an iron instrument, the 
detonation is much increased. This substance also explodes by contact with concentrated 
sulphuric acid. When mixed with 30 per cent, of its weight of water, the crystalline 
fulminate may be rubbed to powder with a wooden pestle on a marble slab. The manu¬ 
facture of this substance on a large scale requires peculiar arrangements, into the particu¬ 
lars of which we cannot here enter. 

Percussion-Caps. The fulminate of mercury is chiefly used for filling percussion-caps. 
For this purpose 100 parts of the fulminate are rubbed to powder with 30 parts of water, 
50 to 62-5 parts of saltpetre, and 29 of sulphur. This mixture is dried sufficiently to 
admit of being granulated, after which it is forced, by means of machinery, into the 
copper caps, and simultaneously covered with either a layer of varnish or tin-foil, to 
protect it from damp. Tin-foil being more expensive is not used for military gun-caps. 
The best varnish for the purpose is a solution of mastic in oil of turpentine. The caps 
are finally dried by a gentle heat, and packed in boxes. One kilogramme of mercury 
converted into fulminate suffices for the filling of 40,000 gun-caps of the larger or military 
size, and for 57,600 caps of the size used by sportsmen. 

Platinum. 

(Pt= 197*4; sp. gr.=2i'o to 23*0.) 

occurrence of Platinum. This metal is only found native, and then not very abundantly, 

in platinum ore, more especially met with in the alluvial deposits of South America 
and the Oural, in grains of a steel-grey colour and metallic lustre. More recently, 
granules of metallic platinum have been found among the gold-washings in Califor¬ 
nia, the Brazils, Haiti, Australia, and Borneo. A very short time ago this metal was 
discovered in Europe, interspersed in rocks situated in the parish of Eoeraas, in 
Norway, and it is reported to have been found in the lead-mines near Ibbinbiiren, in 
Westphalia. Dr. Pettenkofer states that a proof of the far greater dispersion of 
platinum than is generally supposed lies in the fact that all silver contains a 
small quantity of platinum. The metal has also been found to accompany some of 
the copper and antimony ores of Timor and New Guinea. Platinum was discovered 
in South America by the Spaniards, who, believing it to be an inferior silver, gave it 
the diminutive platina of the Spanish name for silver, plata. It was brought from 
Jamaica and made known in Europe by a Mr. Wood in 1740, and somewhat investi 
gated in 1767 by Dr. E. Watson, then Professor of Chemistry at Cambridge 
Dr. Scheffer, Director of the Mint at Stockholm, was the first who thoroughly inves 
tigated the various physical and chemical properties of this metal in 1752; but as his 
researches were published in the Swedish language, they remained comparatively 
unknown in this country. 

platinum ores. The substance met with in commerce under the name of platinum ore, 

or crude platinum, is a mixture of a variety of metals, among which the following 
predominate:—Platinum, palladium, rhodium, iridium, osmium, ruthenium, iron, 
copper, lead, and frequently granules of osm-iridium, gold, chrome-iron ore, 


94 


CEEMICAL TECHNOLOGY. 


titanium-iron ore, spinel, zircon, and quartz. The reason why this ore is found in 
alluvial soil is, that the rocks originally containing the ore having been disintegrated 
by water, it is carried off by the streams and water-courses. Boussingault found, 
when travelling in South America, a seam of somewhat weathered syenite containing 
the platinum ore yet in situ; while, as regards the Oural, it has been proved by 
Pallas that the ore was originally imbedded in serpentine-rock which has been 
washed away by water, the water, however, leaving such minerals as chrome-iron 
ore, zircon, titanium-iron ore, &c. In the Island of Borneo, platinum ore is mixed 
with sesqui-Sulphuret of ruthenium, a mineral which has been named by Dr. Wohler 
(1866) Laurite. 


The composition of some platinum ores is exhibited in the following table:—Analysed 
by Dr. Berzelius, a , ore from the Oural; Dr. Svanberg, b and c, from Columbia and 
Choco; Dr. Bleekrode, d, from Borneo; Dr. Weil, c, from California. 



a. 

b. 

c. 

d. 

e. 

Platinum .. 

.. 86*50 

84*30 

86*i6 

op 

>—1 

57*75 

Rhodium .. 

.. 1*15 

3*46 

2*16 

— - 

2*45 

Iridium 

— 

1*46 

1*09 

7*92 

3*10 

Palladium .. 


1*06 

o *35 

1*28 

0*25 

Osmium 

— 

1*03 

0*97 

0*48 

o*81 

Osm-iridium 

.. 1*14 


1*91 

8*43 

27*65 

Copper 

.. 0*45 

0*74 

0*40 

o *43 

0*20 

Iron . 


5 * 3 i 

8*03 ) 



Lime. 

.. — 

0*12 

- 

8*40 

77O 

Quartz 


o*6o 

- 




According to Dr. H. Deville, the average quantity of platinum contained in the fol¬ 
lowing ores is:— 

Columbia.76'80—86*20 per cent. 

California. 76*50—85*50 „ 

Oregon . .. 50*45 „ 

Australia.59*80—61*40 „ 

Siberia . 73 *50—78*90 „ 

Borneo . 5775 — 7°' 21 » 

The annual production of metallic platinum amounts to from 35 to 50 cwts., of which 
quantity the Oural yields 28 to 49 cwts., Columbia and the Brazils, 6 to 8 cwts. 

Wollaston’s Method of The method originally devised by the late Dr. Wollaston, and still 
Ext from n & F ore 1 s? ura employed by the Parisian platinum-makers, Chapuis, Desmoutis, 
and Quennessen, is as follows:—The ore is first treated with cold aqua regia to 
dissolve any gold, and the liquid separated from the ore by filtration. The mineral 
is again treated with aqua regia in a retort, and heat applied; the distillate contains 
osmic acid, and the insoluble residue in the retort osm-iridium, ruthenium, 
chrome-iron ore, and titanium-iron ore. The acid liquid contains palladium, 
platinum, rhodium, and some iridium, in solution, and the acid having been neutral¬ 
ised with carbonate of soda, the fluid is mixed with cyanide of mercury, whereby 
palladium is separated as cyanide of palladium. That precipitate having been 
removed by filtration, the liquid, diluted with water, is next concentrated by evapo¬ 
ration, and then mixed with a concentrated solution of chloride of ammonium, the 
mixture resulting in a precipitate (PtCl 4 ,2NH 4 Cl), of the double chloride of platinum 
and ammonium, containing only a trace of iridium, which, as it imparts greater 
hardness to platinum, is not injurious. The platinum sal-ammoniac, as the precipi¬ 
tate is industrially named, is first dried and afterwards ignited, leaving spongy 
platinum, which is forced by means of properly fitting pistons into steel tubes heated 
to redness, the operation being repeated as often as is required to obtain the metal 
in a compact coherent state. According to MM. Descotil and Hess, platinum ores 
















PREPARATIONS OF MERCURY. 


95 


should be first fused with from 2 to 4 times their weight of zinc, the cooled brittle 
mass pulverised, and treated with dilute sulphuric acid to eliminate some of tho 
iron and zinc; the remaining substance is then treated with nitric acid, which 
dissolves the rest of the iron, copper, and lead. The ore is afterwards treated with 
aqua regia, which acts more readily on account of the fine state of division of the 
mineral. M. Jeannetty (Paris) found that platinum becomes readily fusible by 
the addition of metallic arsenic, which is afterwards volatilised. 

Me aad d Deb?ay nie The excellent method introduced by MM. Deville and Debray, in 
1859, is based upon the fact that metallic lead, while fusing with platinum ore, 
dissolves all the foreign metals, osm-iridium alone excepted. The platinum ore is 
consequently placed on the hearth of a reverberatory furnace, and having been 
mixed with its own weight of galena, a regulus is obtained, under which the osm- 
iridium is left, while a lead slag floats on the top, the iron decomposing a portion of 
the galena and producing metallic lead. The regulus is heated in a cupel furnace, 
whereby all foreign metals are volatilised or absorbed as oxides, leaving the metallic 
platinum, which is refined by being again melted in crucibles made of lime, which 
absorbs and eliminates all impurities, such as silicium, iron, copper, &c. The fuel 
used for this purpose is coal-gas, the combustion being kept up by means of oxygen. 
The smelting of 1 kilo, of platinum requires 100 litres of oxygen gas and 300 litres 
of coal-gas. The firm of Messrs. Johnson, Matthey, and Co., the most eminent and 
extensive platinum smiths in the world, exhibited at the International Exhibition 
of 1862 an ingot of pure platinum weighing no less than 2% cwts., valued at £4,000, 
smelted by the method of MM. Deville and Debray. The molten platinum is after¬ 
wards submitted to the action of a steam-hammer to render it dense, solid, and 
fully malleable. 

Properties of Platinum. This metal is nearly as white as silver, but with a steel-grey shade. 

It exhibits considerable lustre ; is very malleable and ductile, and so soft that it readily 
admits of being cut with a pair of scissors. It may be drawn in wire thinner than a 
spider’s web, an operation conducted by coating an already thin platinum wire with 
silver. The wire thus prepared is drawn out and the silver afterwards removed by nitric 
acid, which dissolves that metal but leaves the platinum. The specific gravity of platinum 
varies from 2i - o to 23 - o. This metal admits of being welded at a white heat, and may be 
melted by the oxyhydrogen flame, its melting-point, according to Dr. Deville, being 
between 1460° to 1480°. Platinum occurs in commerce as spongy platinum, black platinum, 
forged or hammered and cast platinum. 

Black Platinum. Black and spongy platinum possess the property of absorbing and con- 

Spongy Platinum, densing large quantity of gases, more especially oxygen. If a jet of hydro¬ 
gen is directed upon the spongy metal, black platinum being only an exceedingly finely 
divided spongy platinum, the gas combines with the oxygen absorbed by the metal, forming 
water; and this combination is attended with so great a development of heat that the 
platinum becomes red-hot and causes the ignition of the hydrogen. It is upon this property 
that the well-known Dobereiner lamp is based. Black platinum is prepared either by 
boiling sulphate of platinum with carbonate of soda and sugar, when the black platinum is 
precipitated as a very fine powder, or by melting platinum and zinc together, and treating 
the alloy with dilute sulphuric acid. Black platinum is industrially employed in the 
manufacture of vinegar directly from alcohol. 
h» ath'mtn 1 a°n tu ts' Platinum may be worked by hammering or by casting. The following 

Applications. 19 firms are platinum workers:—Heraeus, at Hanau; Freres Chapuis; Des- 
moutis and Quennessen, Godart and Labordenave, at Paris; and Messrs. J ohnson, Matthey, 
and Co., London. The chief use of platinum is for various apparatus in chemical 
laboratories. Although this metal withstands a very high temperature, and is proof 
against a large number of chemicals which attack or destroy other materials, it requires 
great care in its use, as it is readily acted upon by caustic alkalies, fusing nitrate of potassa, 
free chlorine, alkaline sulphurets, phosphorus, molten metals, and readily reducible metallic 
oxides. Crucibles, spoons, blowpipe points, the points of lightning conductors, tongs and 
forceps, and boilers for concentrating sulphuric acid are made of this metal. A boiler 


96 


CHEMIC A L TECH HOE OGT. 


capable of concentrating daily 8 tons of sulphuric acid costs about £2500, while a smaller 
but similar vessel for concentrating daily 5 tons of acid costs £1640, the value of the 
metallic platinum for this size exceeding £1000. Platinum is also used for galvanic 
apparatus, mustard-spoons, and now and then for ornamental work in watchcases, chains, 
&c. More recently platinum has been used in porcelain-staining to produce a greyish hue. 
In the year 1828, the Russian Government commenced coining platinum, 3, 6, and 12 
rouble pieces; but by a ukase of 22nd June, 1845, this coinage was discontinued, and the 
money made, 14,250 kilos, in weight, called in. In France platinum is used for making 
medals, especially prize medals for exhibitions. The first platinum coin ever made was 
struck at the Paris Mint in 1799, the dies having been engraved by M. Duvivier with 
the effigy of the first Consul, afterwards Napoleon I. In the year 1788 there was presented 
to Louis XVI. a watch, some of the works of which were made of platinum. Small 
caps or cylinders woven in platinum wire, are used to emit light when rendered liighly 
incandescent by the flame of burning hydrogen, the arrangement being termed a platinum 
gas lamp. According to M. Kraut, platinum frequently contains barium, or a combination 
of that metal. 

Platinum Alloys. As before observed platinum readily alloys with other metals. Among these 
alloys, that first made by Deville, consisting of 787 platinum and 21 *3 iridium, especially 
deserves notice, as it is not acted upon by nitro-muriatic acid, and is hard and malleable. 
An alloy of platinum containing 10 to 15 per cent, of iridium withstands fire and reagents 
far better than platinum alone and is harder; hence the vessels made with it are not so 
liable to be bent out of shape as those of platinum. According to M. Chapuis, an alloy of 
92 parts of platinum, with 5 parts of iridium, and 3 parts of rhodium, resists various 
reagents better than platinum alone. The alloy of 3 parts of platinum with 13 parts of 
copper is, according to M. Bolzani, equal in all respects to gold. Dr. Percy states that an 
alloy of platinum and gold for crucibles and other small vessels applied in chemical opera¬ 
tions, is best proof against alkalies. An alloy of equal parts by weight of steel and 
platinum is the best white speculum-alloy known ; its sp. gr. — 9-862. 

Eiayi Piatino-chioride. This compound (PtC 2 H 3 Cl 2 ) is obtained by repeatedly dissolving 
chloride of platinum in alcohol, and evaporating the solution to dryness. A very dilute 
solution when heated on a sheet of glass or a porcelain slate, yields a lustrous coating of 
platinum 

SILVER. 

(Ag = 108 ; Sp. gr. = io*5 to 107.) 

silver and its occurrence. Silver is a tolerably abundant metal, and is found partly in the 
native metallic state, almost always containing gold; partly in combination with 
other metals, as arsenic, antimony, tellurium, mercury, or combined with sulphur 
and other sulphurets. Silver rarely occurs as oxide or combined with acids. The 
chief ores are :—The sulphuret, silver-glance (Ag 2 S), containing from 84 to 86 per 
cent, of silver; the dark-coloured ruby ore (3Ag 2 S + Sb 2 S 3 ), with 58 to 59 per cent, 
of silver ; the light-coloured ruby ore (3Ag 2 S-f As 2 S 3 ), with 64 to 64-5 per cent, of 
silver; miargyrite (Ag 2 S -f Sb 2 S 3 ); and the brittle antimonial silver ore (6Ag 2 Sb 2 S 3 ), 
with about 67 to 68 per cent, of silver; polybasite [(Ag 2 S,Cu 2 S) 9 ,Sb 2 S 3 ], with 64 to 
72*6 per cent, ofsilver; and the white ore [(FeS,ZnS,Cu 2 S) 4 ,Sb 2 S 3 -f(PbS,AgS) 4 ,Sb 2 S 3 ], 
with 30 to 32-69 per cent, of silver. Galena frequently contains silver, usually 
between croi and 0.03 per cent., and sometimes as much as 0*5 to i*o per cent. 
This lead ore is the chief source of the silver produced in the United Kingdom. 
Some coj>per ores contain silver to an amount varying from 0-020 to i*ioi per cent. 
With regard to zinc ore the reader is referred to the statements under that head. 

Extractton of Silver The metallurgical process employed in the extraction of silver may bo 
fiom its ores. an y 0 f the following :— 

I. By the wet way. 

1 . By the aid of mercury. 

a. European method of amalgamation. 

b. American method of amalgamation. 

2. By means of solution followed by precipitation. 

a. Augustine’s method. 

b. Ziervogel’s method. 

c. Sundry methods. 


SILVER. 


97 


II. By the dry way. 

1. By concentrating- lead ores rich in silver. 

2 . Separation of the silver from the lead. 

a. Separation on the hearth. 

b. Concentrating- the silver in the lead by Pattinson’s method. 

c. Eliminating the silver from the lead by means of zinc. 

d. Refining the silver-glance. 

smelting tor silver Directly. i. It only rarely happens that silver ores are rich enough 
to admit of the metal being obtained by a direct smelting process. 

Ext Amaigaination? r by 2. The method of obtaining silver by the aid of mercury, or the 
amalgamation process, is chiefly applied to very poor ores, and to such metallur¬ 
gical products as contain only ioo to 120 grins, of silver to the metrical cwt. 

European Amalgamation This process—now obsolete—was conducted in four principal 
operations—viz., 1. The roasting; 2. Amalgamation; 3. Separation of excess of 
mercury from the amalgam by mechanical means ; 4. Volatilisation of the mercury. 
There was first added to the ores about 10 per cent, of common salt, and the mix¬ 
ture roasted to volatilise the antimony, arsenic, and other volatile minerals, the 
fumes being condensed in properly arranged rooms. By the reaction of the com¬ 
mon salt upon the pyrites, converted by the roasting into sulphate of iron, there is 
formed sulphate of soda, chloride of iron, and sulphurous acid, which escapes. The 
chloride of iron exchanges its chlorine with the silver, the result being the forma¬ 
tion of peroxide of iron. There are also formed sulphate of copper and persulphate 
of iron, which, while oxidising any sulphuret of silver to sulphate, become reduced 
to protosulphates. By the further action of the common salt, chloride of silver and 
sulphate of soda are formed, and the other metals converted into chlorides. The 
brown-coloured mass is next transferred to the amalgamation tuns; and after the 
addition of water, mercury, and iron, these tuns are made to rotate on their longi¬ 
tudinal axes for a period of 16 to 18 hours, the velocity being regulated to 20 to 22 
revolutions per minute. The iron while combining with the chlorine, causes the 
reduction of all the other metals to the metallic state, and as far as capable these 
then form an amalgam with mercury. 

In order to elucidate the amalgamation process we will, for example, take a silver ore to 
consist of— 

(Cu 2 S,AgS,EeS) + (As 2 S 3 ,Sb 2 ,S 3 ) 

from which the silver is to be separated, according to the method just described.* After 
the roasting with common salt (CINa), there being taken up in this instance 30 mols. 
of oxygen, the following substances are formed : 

[(Cu a Cl a ,AgCl,FeCl 2 ) + 3 Na,S 0 4 ] + [A 8 a 0 3 + Sb a 0 3 + 6SO J, 

V ■ " "Y~- 

Non-volatile substances. Volatilised substances. 

The changes which are effected by the action of the iron, mercury, and water in the amal¬ 
gamation tuns are exhibited by:— 

[ (C u 2 Cl 2 AgCl ,F eCl 2 ) + 3Na 2 S0 4 + 3 Ee + «Hg = 3Na 2 S0 4 + (Cu,Ag,«Hg) + ^eCl,]. 

' y ' 

Amalgam. 

At the end of the period destined for the rotation of the tuns, the amalgam is run 
off. The excess of mercury is strained through a coarse canvas bag, and collected 
in a stone trough or tank. The real amalgam, a thick pasty mass, remains in the 

* No attention is paid in this case to the volatile chlorides of sulphur, arsenic, and 
antimony which are simultaneously formed. The reader who desires more extensive 
information on the subject here briefly outlined, is referred to Mr. Crookes’s “ Metallurgy,” 







9 S CHEMICAL TECHNOLOGY. 

bag, which is next strongly pressed between planks to squeeze out any further 
excess of non-argentised Mercury. The solid amalgam* is then transferred to tho 
iron plates, bb, (Fig. 54), arranged as shown in the woodcut, and as already described 
under the article Mercury. By the action of the fire the mercury is separated from 
the amalgam, and being volatilised, is collected under the water contained in d, 
while the metallic silver and other metals mixed with it are left on the iron plates, t 


Fig. 54. 



At the present time, instead of the above contrivance, there is used an iron-dis 
tilling apparatus, not unlike cylindrical iron gas retorts, one end being fitted with a 
movable lid for the introduction of the amalgam, and the other end connected with 
an iron tube which dips into a trough filled with water to condense the volatilised 
mercury. Superheated steam is also advantageously used to separate the mercury 
from the amalgam. The crude silver left after the separation of the mercury is 
submitted to a first refining smelting, by being put into graphite crucibles, and the 
surface covered with charcoal powder. But even after this smelting the silver 
always contains a certain quantity of copper, from which it can only be separated 
by refining in a cupel furnace. 

American Amalgamation The American process is chiefly used in Mexico, Peru, Chili, and 
Process.” California. The ores to which it is generally applied are the ruby- 
silver ores and fahl ores. These are first pulverised in stamping mills, and are next 


* According to Dr. Karsten, the composition of the solid amalgam is:—Silver, n*o; 
mercury, 84-2 ; copper, 3-5 ; lead, ou ; zinc, 0-2. 

f The silver left on the plates at the Freiberg mines consists, according to Professor 
Lampadius, of-.—Silver, 75-0; mercury, 0-7 ; copper, 21-2; lead, 1-5. The refined silver 
of the same place contains, according to Professor Plattner:—Silver, 71-55 ; copper, 28*01. 































SILVER. 


99 


ground with water under granite or porphyry millstones, to a thoroughly impalpable paste. 
Tliis material is placed in a yard paved with flags, which are laid with a slight inclination 
sufficient to cause the rain-water to run off. After having been kept there for some days, 
there is added from g to 3 per cent, of what the miners locally designate as magistral, 
that is to say, roasted iron and copper pyrites (FeCJuSJ, which is thoroughly mixed with 
the finely-divided ore. Mercury is then added in quantity equivalent to about six times 
the amount of silver contained in the ore; this operation is termed incorporation. The 
kneading of the mercury is continued on alternate days for two to five months, and after 
that time the mass is washed with water in stone cisterns in order to separate the heavy" 
amalgam from the light gangue. The amalgam thus obtained is separated from any 
excess of mercury by being’ pressed in canvas bags ; the remainder of the mercury being 
separated by distillation. The rationale of this amalgamation process is :—The roasted 
copper-iron pyrites is essentially made up of mixed sulphates of copper and iron, which 
when reacting- upon the common salt, are converted into chlorides of the metals and sulphate 
of soda. The chlorides acting upon the silver convert it into chloride, and this becoming 
dissolved by the excess of salt, is converted by the mercury to the metallic state. Some of 
the mercury is converted into calomel, and the excess dissolves the silver, becoming amal¬ 
gamated with it. This American process requires a great length of time, and, moreover, 
occasions an enormous loss of mercury, as for every mol. of silver reduced from the chloride 
of that metal there is formed 1 mol. of calomel (Hg 2 Cl 2 ). On the other hand, this method 
admits of the extraction of silver from ores too poor to be treated in any other way, 
while a great saving of fuel, is obtained. 

A sfive t rExuaciion. of This hydrometallurgical method, invented by M. Augustin, is 
based upon the formation of a soluble double chloride of silver and sodium when 
chloride of silver is treated with an excess of a warm solution of common salt, and 
also upon the fact that copper is capable of precipitating all the silver from this 
solution. The ore is first reduced to a finely-divided powder, which essentially con¬ 
tains sulphurets of copper, silver, and iron. This powder is roasted, first without 
the addition of common salt, with the result that sulphates of the metals are formed, 
and excepting that of silver, again decomposed by a higher temperature. The mass 
is next roasted with common salt, whereby the sulphate of silver is converted into 
chloride. The mass is then treated with a concentrated hot solution of common 
salt, which dissolves the chloride of silver, and from this solution the silver is pre¬ 
cipitated by metallic copper, which becomes chloride of copper, and is, in its turn, 
precipitated by metallic iron. 

ziervogei’s Method. This method is to some extent similar to that just described, but 
no roasting with common salt takes place. The roasted ore, chiefly containing as 
essential ingredients sulphate of copper and sulphate of silver, is treated with boiling 
water to dissolve these sulphates, and yield a solution from which metallic silver is 
precipitated by means of copper, the sulphate of that metal being obtained as a 
by-product. When the ores happen to contain arsenic and antimony, this method is 
not applicable, as, by the roasting, arseniate and antimoniate of silver are formed, 
w’hich are insoluble in water. If lead is present, the ore becomes fluxed and the 
roasting a far more difficult matter. 

Sundry Hydrometallurgical j)r. Carl Ritter von Hauer suggests the treatment of the ores 
Methods of^Extiacting ag j n pp e European amalgamation process, and the extraction of 

the chloride of silver by means of a hyposulphite of soda solution, the metallic silver being 
next precipitated by the aid of copper or tin. Dr. Patera suggests the substitution in 
Augustin’s method of a hyposulphite of soda solution for that of common salt, the former 
being more manageable and applicable cold. Similar suggestions have been made by 
Dr. Percy, who also advocates the applicability of hypochlorite of lime, and of chlorine gas 
for converting the silver into chloride. MM. Rivero and Gmelin were the first to suggest 
the use of ammonia for. the purpose of extracting and dissolving the chloride of silver after 
the ores had been roasted with common salt; the precipitation of the chloride from the 
ammoniacal solution by means of sulphuric acid, and the smelting of the chloride with a 
suitable flux to obtain metallic silver. We must not omit to mention the method of 
extracting silver from copper regulus and mattes by means of hot dilute sulphuric 


IOO 


CHEMICAL TECHNOLOGY. 


acid, whereby the copper is dissolved and a residue left containing- the silver, which is 
further extracted in the dry way by means of lead. 

Extraction of silver The method of extracting silver from its ores by means of lead is based 

by the Dry W ay. -upon 

i. The property of lead to decompose sulphuret of silver, with the formation of sulphuret 
of lead and metallic silver; A ?£ 8 j yield { p^ Pb “ 


As lead hardly acts at all upon the other metallic sulphides, and least of all upon those of 
copper and iron, the products of the smelting are lead combined with silver, and a regulus 
consisting of the sulphurets of lead, copper, and iron. This method of extraction succeeds 
best with ores containing as small a quantity of copper as possible. 

2. Upon the decomposing reaction exerted by oxide of lead and sulphate of lead upon 
the sulphuret of silver, in consequence of which there are formed metallic lead containing 
silver and sulphurous acid :— 

yield / Pb * A - 


2PbO J 


\SO s 


and 


Ag 2 S 

Pb!SO, 


f PbAg 2 


J y ield Uao. 

3. Upon the reducing action of lead upon oxide of silver or upon sulphate of silver:— 

£o}*“{ 5 &b . 


and 


3 Pb 

Ag2S0 4 



( p bAg 
{ 2PbO 
(2S0 2 


4. Upon the greater affinity of the silver for lead than for copper. If copper that 
contains silver is melted with lead, the result is the formation of a readily fusible alloy of 
lead and a difficultly fusible alloy of copper and lead, the former metal being separable by 
liquation. 

Mode of preparing the Only genuine silver ores are submitted to the operation of 

Silver. smelting with lead, but these ores usually contain variable pro¬ 
portions of copper, lead, cobalt, sulphur, and other substances. The result of the 


Tig. 55- 



smelting with lead i3 the production of a metal containing silver, to be separated by 
any of the following operations 

1. On the refining-furnace ; 

2. By Pattinson’s process ; 

3. By means of zinc. 

Refining Process. This operation is as frequently carried on at lead-ore smelting-works 
as whero only silver is smelted. The rationale of the operation is that lead is 
readily separated from such metals as are at a high temperature either oxidisable 
with very great difficulty or not at all; whereas lead oxidises readily, its oxide 



o 


t) 


> > <. 
















SILVER. 


IOI 


becoming fluid. But it is requisite that the oxide of lead should be removed or ab¬ 
sorbed by a suitable medium, generally the porous substance composing the cupel or 
bottom of the hearth of the refining furnace. The operation is carried on as long as 
any oxide and metallic lead remain, so that only the silver is left. This operation is 
the exact counterpart on the large scale of the well-known lead-silver assay carried 
on in a muffle with bone-ash cupels. The refining furnace, see Fig. 55, is a circular 
reverberatory blast-furnace. The hearth, A, is covered with a dome of stout sheet- 
iron, lined inside with fire-clay, and removable by means of a crane, D. That por¬ 
tion of the hearth upon which the smelting is carried on is constructed of a porous 
substance, generally lixiviated wood-ash or marl of good quality. The cavity, c, is 
intended for collecting the silver; B is the space for the flame. In the circular wall 
which surrounds the hearth there'are:—(1). The door, not exhibited in the cut, which 
represents a vertical section intended for the discharge of the molten litharge. At 
the outset of the smelting this door is only partly closed with fire-clay to admit of 
the litharge being run off. The furnace is charged with lead to a little above the 
level of the lower sill of this door, and the fire-clay gradually removed as the level 
of the fused litharge sinks. (2). The door, p, opposite to the fire-place, and intended 
for the charging and construction of the hearth. (3). The openings, a a', admit¬ 
ting the tuyeres of the blast. 

The refining operation, is carried on at a gradually increased temperature until only a very 
thin layer of oxide of lead covers the surface of the silver. This is known by the peculiar 
display of colours, technically known as the brightening , more aptly expressed in German by 
a word which means lightening , for that is really the appearance. Tins being observed, the 
fire is slackened, and the silver having been cooled with water, is removed from the 
hearth. The litharge which runs off is, on cooling, a yellow or reddish-yellow crystalline 
mass (see Lead, p. 63). 

pattinson’s Method. The refining process just described is not suited, that is to say, 
does not pay, when the lead contains only cri2 per cent, of silver. Now it so happens 
that the various kinds of galena mbt with in England yield a lead which contains 
only 0*03 to 0*05 per cent, of silver. In 1833, Mr. H. L. Pattinson, of the Felling 
Chemical Works, near Gateshead-on-Tyne, instituted a series of experiments relative 
to a new method, applicable on the large scale, for separating lead from silver when 
the latter is present in small quantities. His efforts were successful, and have 
greatly benefited his own and other countries where his process is worked. 

Pattinson’s method essentially consists in a concentration process, based upon the pheno¬ 
menon that when a certain quantity of lead that contains silver is melted in iron cauldrons, 
and the fluid mass allowed to cool uniformly, there ensues a formation of small 
octahedral crystals which do not contain any silver at all, or, at any rate, are a great 
deal poorer in silver than the metal originally taken, while the portion of the metal 
rema inin g fluid is found to contain an increased quantity of silver. It is clear, there¬ 
fore, that if the crystals first obtained are again melted and cooled uniformly, another 
concentration will be obtained, and that the operation can be repeated until a lead is 
obtained rich enough in silver to admit of undergoing a refining process. Practically, 
Mr. Pattinson’s method admits of concentrating 2’5 per cent, of silver. In the execution 
of this process, the § and f systems are employed. If the first, at every operation two- 
thirds of the contents of the cauldron are removed with perforated ladles, while in the 
other case, seven-eighths is the quantity of crystals ladled out, leaving respectively one- 
third and one-eighth of the contents of the cauldron in the shape of fluid lead. The 
f system is better suited for the richer lead, the system for very poor lead. M. Boudchen 
has recently modified Pattinson’s process. Instead of ladling out the crystals, he 
diffuses them in the lead, and stirs them about to prevent them enclosing any lead 
likely to contain silver. The lead is withdrawn from the cauldron by means of a tap at the 
bottom. In all cases, however, the quantity of lead operated on at one time is always 
large, generally 200 cwts., to cause the cooling to proceed slowly. At the Freidrich Lead 
Silver Works, near Tamowitz, the enriched lead contains 1*28 per cent, of silver. 


CHEMICAL TECHNO LOG Y. 


102 

Reduction t>y Means This process, suggested by Mr. Parker, in 1850, has only recently 
been practically carried out by M. Cordurie, at Toulouse. This method, as far as 
we are now capable of judging, will probably supersede even Pattinson’s excellent 
method. The rationale of the process is based upon the facts :—1. That lead and 
zinc do not alloy together. 2. That the affinity of silver for zinc is much greater 
than for lead. 

The following is the manner of execution20 cwts. of lead, which may contain (per 
ton) only 0-25 kilo, of silver, is melted, and when properly liquefied there is added 1 cwt. 
of molten zinc. The zinc having been thoroughly mixed with the lead, the molten mass 
is left to stand until the zinc, which has risen to the surface, forms a cake that is easily 
removed. The zinc is then separated from the silver by distillation. The residue of the 
distillation is melted with lead, and the alloy thus obtained refined as above described. 
The zinc obtained by the distillation is used for another operation. According to a more 
recent improvement, the zinc is separated from the silver by oxidation by passing super¬ 
heated steam over the red-hot zinc (Zn -f H 2 0 = ZnO -f HJ. The lead, which of course 
after this operation contains traces of zinc, is purified by being melted with either chloride 
of lead, or a mixture of sulphate of lead and chloride of sodium, or with chloride of potas¬ 
sium from Stassfurt, the result being the formation of chloride of zinc, which collects at 
the surface or may be volatilised at a low red heat. 

The ultimate Refining In whatever manner silver may have been metallurgically obtained, 
of silver. "the metal is a crude material, very far from being cent-per-cent 
silver. The impurities, foreign metals, or, more correctly, base metals, often amount to 
7 and even 8 per cent. ; and in order to remove these, the silver is submitted to a process 
of ignition in, or rather on the surface of, vessels made of an absorbent material. This 
material is, for this ultimate refining, generally bone-ash, which is pressed into iron rings 
of convenient size, care being taken to fuse some lead with the silver, if there is not already 
sufficient. As regards this ultimate refining, there can be distinguished three different 
methods. The first has just been described. The second is carried on in muffles, the 
base metals burning off slowly. The third, and most advantageous method, is carried on 
in a reverberatory furnace. 100 parts of crude silver yield 96-8 parts of refined silver at 
99’9 P er cent, pure fine metal, which is cast in large-sized bars. The value of the annual 
production of fine silver amounts to £9,000,000. Of this, Mexico’s share is the largest, 
being half of the entire production. The bulk of this silver contains some gold and 
platinum. 

Chemically Pure silver. When for certain purposes metallic silver is required chemically 
pure, it may be obtained by dissolving any ordinary silver coin in nitric acid, and precipi¬ 
tating the "solution with an aqueous solution of common salt or hydrochloric acid. The 
chloride of silver thus obtained should be reduced by ignition in a crucible with dry car¬ 
bonate of potassa, to which a little resin may be added. But chloride of silver is now 
commonly reduced by the wet way, by causing it to be acted upon by metallic zinc and a 
dilute solution of either sulphuric or hydrochloric acid. 

(2AgCl -f Zn + C 1 H = ZnCl 2 -f Ag 2 -f C 1 H). > 

Properties of Silver. Silver obtained by smelting exhibits a pure white colour and a strong 
metallic lustre, which is greatly increased by polishing. Its fracture is compact rather 
than fibrous. It is softer than copper, but harder than pure gold ; when chemically pure 
its softness is greatest. It is not a sonorous metal, bearing a resemblance in this respect 
to tin and lead. Gold only excepted, silver is the most ductile of the metals, a property 
impaired by the presence of foreign metals other than copper and gold, by the latter of 
which the ductility is slightly increased. Lead and antimony render silver brittle. When 
silver contains an excess of carburet, produced by smelting the metal with an excess of 
carbon, the metal is rendered less ductile; but a small quantity of the carburet, as much 
as is found in coins of a high percentage of silver, is rather advantageous, increasing the 
hardness of the metal, and causing it to wear well. Smelting in plumbago crucibles does 
injure silver. Its specific gravity varies from io’5 to 107. The absolute strength is far 
less than that of copper. Its expansion by heat in o° to ioo° C. is ^ffith. According to 
M. Deville, the melting-point is 916°; but Dr. van Itiemsdijk states that the results of a 
series of experiments made at the Utrecht Mint in 1868, showed the melting-point to be 
1040°, the metal being kept in a slow current of pure hydrogen. At a very high tempera¬ 
ture, such as can be produced only by the oxyhydrogen flame or by electricity, silver is 
volatilised. When alloyed to other metals, especially to copper, the volatility is increased, 
and even at a lower temperature than the melting-point of copper, viz., 1330°, Dr. van 
Riemsdijk found such silver to be perceptibly volatile. M. Stas, of the Brussels Mint, in 
1869, distilled some 50 grms. of silver by means of the oxyhydrogen flame, in order to 


SIL VER . 


103 


obtain the metal perfectly pure. Molten silver absorbs oxygen, which is again expelled 
from the metal on solidification, and gives rise to the phenomenon known by silver-assayers 
as spirting, the escape of the gas causing the metal to be forced asunder in small drops. 
However, when the molten silver contains even 1 per cent, of either lead or copper, it 
solidifies without spirting. Silver is not acted upon by dilute acids, but is readily dissolved 
in the cold by nitric acid. Silver is very sensitive to the action of sulphuretted hydrogen, 
by which it is readily tarnished. 

auojs of silver. Silver alloys readily with lead, zinc, bismuth, tin, copper, and gold ; 
but the most important alloy, in an industrial point of view, is that with copper, 
pure silver being too soft for general application. All silver, therefore, whether used 
for plate, coin, or for ornamental purposes, invariably contains a certain amount 
of copper. In most civilized countries there exist laws regulating the alloy of silver 
to be used for coin or plate. Pure silver, or fine silver, is now generally indicated 
by {§£§. The alloy for the silver coins of Germany is indicated by $$; meaning 
that 1000 parts by weight of the coin contain goo parts of pure silver, the remainder 
being copper. Twenty-seven Union thalers weigh 1 half kilo., therefore a single 
thaler weighs 18*518 grms., and contains 16*666 grms. of pure silver. By an inter¬ 
national treaty with Prance, Italy, Belgium, Portugal, Switzerland, and Spain, 1 kilo, 
of ^ silver is to yield 200 franc pieces, t.e., 222! franc pieces to 1 kilo, of fine silver. 
The same alloy is employed for pieces of 2 and 5 francs, there being 200 of the 
latter to the kilo. In the Netherlands, where, by-the-bye, gold coin is no longer 
current, and silver is the standard, the alloy used is The silver coins of the 
United Kingdom are made of an alloy 7 P 0 2 & S 5; 1 lb. Troy, or 373'228 grms., of this 
alloy is coined into 66 shilling pieces. A pound Troy of fine silver would yield 
71^ shillings. 

Sil piate U &c fur nearly all European countries the laws have fixed the composition 
of the alloy of silver which, duly marked and stamped, shall be offered for sale as 
plate by gold- and silver-smiths, who, in Holland, Belgium, Prance, and Sweden, are 
not allowed to have in their workshops any electro-plated articles, or any alloys 
other than those fixed by law. The composition of these alloys varies; expressed in 
milliemes of fine metal, it is for Austria and Bavaria, 812; for Prussia and Saxony, 
750 ; for England, 925. Por Prance, Belgium, and the Netherlands, a double alloy 
is fixed, the higher being 950, the lower 800. The alloy lately brought into use 
under the name of tier 8 -argent, one-third silver, really consists of 27*56 per cent, 
silver, 59 per cent, copper, 9*57 per cent, zinc, and 3*42 per cent, nickel, though in 
the trade this alloy is alleged to consist of f nickel and \ silver. Tiers-argent sells 
at £3 12s. per kilo. This alloy is harder than silver ; its colour and polish are as 
good. It is extremely well adapted for all kinds of plate. 

Silver Assay. If it be desired to know the quantity of fine silver contained in an alloy of 
silver—which for our present purpose we will assume to contain only silver and copper 
there are three different methods by which this proposition can be solved, viz. 1. The 
assay by the dry way, termed cupellation. 2. The assay by the wet way, or titration pro¬ 
cess. 3. The hydrostatic assay. 

Dry Assay. Usually this assay is conducted by first testing the alloy by comparing the 
streak it makes upon touchstone—a piece of polished basalt or siliceous schist with the 
streak produced upon the same stone by test-needles ; that is to say, small bars of silver 
cf known composition. It should, however, be borne in mind that the surface of silver 
articles, as well as of coins, may have been blanched , as the term runs; that is to say, acted 
upon by hot, dilute sulphuric acid, to dissolve a portion of the copper of the alloy, and 
leave a film of alloy richer in silver. The alloy to be further assayed is next melted down 
with a piece of pure soft lead, or lead containing a known quantity of silver, in a capsule, 
technically called cupel, made of bone-ash. The cupel i3 previously well heated m a muffle, 
and the lead is placed in it. As soon as the lead has become quite liquid, the sample of 


104 


CHEMICAL TECHNOLOGY. 


silver to be assayed is added; the copper and lead are oxidised, and m that state absorbed 
by the porous substances of the cupel. As soon as the surface of the silver button appears 
quite bright, the operation is finished, and the cupel slowly cooled. The button of silver 
is then weighed. It is usual to make two assays of the same sample; these assays should 
agree in their results to within to be of any v alue. 

Wet Assay. This method of assaying silver was devised some sixty years ago by the late 
Professor Gay-Lussac, at the request of the French Government, in consequence of the 
o-reat irregularity of the results obtained by the dry method. The wet assay, having been 
very greatly improved in detail by Dr. G. J. Mulder, M. A. W. II. van Riemsdijk, Dr. Stas, 
and M. J. Dumas, is now generally adopted, and will remain to all time a masterpiece 
worthy of the ingenuity of its original inventor, who, by introducing this method, laid the 
foundation of volumetric analysis, now so usefully and completely applied. Gay-Lussac’s 
wet method of silver assay is more easily executed than the dry assay, while it is far more 
correct, admitting an accuracy of judgment within 2 ' 0 -th per cent. The method is based 
upon the property possessed by common salt of precipitating silver as chloride of silver 
from its nitric acid solution. As 5-4274 g rins - of P ure common salt exactly convert 1 grm. 
of pure silver, previously dissolved in nitric acid, into chloride of silver, it is evident 
that, from these data, and with the application of suitably constructed apparatus for the 
volumetric analysis, the fineness of any alloy of silver may be ascertained readily, rapidly, 
and with great accuracy. 

Hydrostatical Assay. This method is of course by no means so correct as either o± the 
foregoing, and, moreover, is impaired by the fact that, although alloys of copper and 
silver expand under pressure, they become denser, so that the hydrostatic weighing, that is 
to say, the estimation of the specific gravity of the alloy, is only admitted as a test of its 
relative value. With such alloys as have, like coins, to be rolled, pressed, or drawn, 
the hydrostatical results rarely differ more than from the results obtained by cupella- 
tion. The empirical rule for the estimation of the value of silver assayed by this method 
is the following:—The number 8-814 is subtracted from the specific gravity of the alloy, 
two cyphers are added to the difference, and the figure thus formed, considered as a whole 
number, is divided by 579; the quotient is the fineness of the silver alloy expressed in 
grains. For instance, let the specific gravity of the alloy be ~ 10*065, then the h- neness 
is — 216 grains, or ^ ; since— 

10-065-8-814= 1-251 
and 


125,100 


= 216 


silvering. The coating of metals with a film of silver can be effected by:—1, plating; 
2, the igneous process; 3, in the cold; 4, the wet way; 5, galvanically, or electro-plating. 

Silver-Plating. In order to coat metallic copper with a layer of silver, the sheet copper is 
first thoroughly cleansed, then treated with a moderately strong solution of nitrate of 
silver, and next covered with a sheet of silver. After having been made red-hot, the two 
metals are rolled out together. The silver then adheres so strongly to the copper as to admit 
of the metals being beaten or stamped into various shapes. Copper-wire is readily silvered 
by being covered with thin strips of silver, and passed through rollers. But tills method 
of plating is almost entirely superseded by electro-plating. 

igneous, or Fire- This method of silvering is effected by the aid either of a silver-amalgam, 

Silvering. or py applying to the well-cleansed surface of the metal intended to be 
silvered a mixture of 1 part of spongy precipitated metallic silver, 4 parts sal-ammoniac, 
4 parts common salt, and \ part corrosive sublimate. The metal to be silvered is rubbed 
with this mixture, and then heated in a muffle. Buttons intended to be silvered are covered 
with a paste consisting of 48 parts of common salt, 48 parts sulphate of zinc, 1 part of 
mercuric chloride, and 2 parts of chloride of silver. 

Silvering in the Cold. The metallic surface intended to be silvered, having been well cleaned, 
is rubbed by means of a smooth cork, with a mixture of equal parts of cldoride of silver, 
common salt, § of chalk, and 2 of carbonate of potash, made with water into a creamy 
paste. Professor Hein recommends that 1 part of nitrate of silver and 3 of cyanide of 
potassium should be rubbed together in a mortar, with the addition of sufficient water to 
form a thick paste. The paste is rubbed on the metal to be silvered with a piece of flannel. 
MM. Roseleur and Lavaux recommended a mixture of 100 parts of sulphite of soda and 
15 parts 01 any salt of silver. For silvering the dial-plates of watches, &c., M* Thiede 
recommends a mixture of spongy silver with equal parts of common salt and cream of 
tartar. In order to silver iron it is first covered with a layer of copper. 



GOLD. 


ic5 


Silvering by the This is effected by immersing- the metal intended to be silvered in a 
Wet way. boiling aqueous solution of equal parts of cream of tartar and common 
salt, with \ part of chloride of silver. The description of the methods of electro-plating 
will be given at the end of the chapter on Metals. 

Oxidised silver. The small ornaments met with under the name of oxidised silver are pre¬ 
pared with either sulphur or chlorine ; in the former case a bluish-black colour is imparted, 
in the latter a brown. The sulphur is applied simply by dipping the object into a solution 
of sulphuret of potassium, while for the chlorine colour a mixture of sulphate of copper 
and sal-ammoniac is used. 

Nitrate of silver. This salt (AgN 0 3 ) is now prepared on the large scale by dissolving silver 
containing copper in nitric acid, evaporating the solution to dryness, and igniting the 
residue until till the nitrate of copper is decomposed. The residue is next exhausted with 
pure water, the solution filtered and left to crystallise. For medical purposes the crystals 
are fused, and while liquid poured into moulds to form small round sticks. The most 
extensive use of nitrate of silver obtains in photography, a re-crystallised neutral and pure 
salt being preferred. Under the name of Scl Clement, there is now in use in photography 
a mixture of fused nitrates of silver, sodium, and magnesium, recommended as preferable 
to nitrate of silver alone. It is stated that the consumption of this salt for photographic 
purposes amounted, in 1870, to 1400 cwts. for Germany, France, England, and the United 
States ; the money value of this quantity being estimated at £630,000. 

Marking ink. A large quantity of nitrate of silver is also used for the purpose of making 
indelible ink for marking linen. This ink often consists of two different fluids, one a solu¬ 
tion of pyrogallic acid in a mixture of water and alcohol, being intended to moisten the 
linen previous to writing; the other, or writing fluid, consisting of a solution of ammo- 
niacal nitrate of silver thickened with gum. More recently aniline black has been applied 
in the marking of linen. 


Gold. 

(Au= 197 ; Sp. gr. 19-5 to 19-6.) 

° CC Ext e ractin- tl Goid le of Grold is found only in the native metallic state, sometimes in 
veins interspersed in rocks, and accompanied by quartz, iron pyrites, and iron ore. 
More frequently gold is found finely divided in sand, mixed with larger or smaller 
nuggets, and imbedded in quartz, with various other minerals, such as mica, syenite, 
chlorite slate, chrome-iron ore, and spinel. Native gold commonly contains some 
silver and other metals, among which are palladium and platinnm. According to 
recent analyses, the composition of samples of gold obtained from several countries 


is:— 

Gold 

Silver 


Iron and other metals 


Hungary. 
6477 
35-23 


S. America. 
88*04 
11*96 


Siberia. 

86*50 

13-20 

0*30 


California. 
89*60 
10*06 
o *3 + 


I. II- 

Australia. 
99*2 95-7 

o '43 3*9 

0*28 0*2 


Gold is found native with tellurium and telluride of silver, and among antimony, 
zinc, arsenic, and other ores. It is also found in galena and various kinds of clay ; 
indeed, gold is, next to iron, the most widely dispersed metal. The chief gold- 
yielding countries are Africa, Hungary, the Oural, Australia, and America, espe¬ 
cially Mexico, Peru, the Brazils, California, Columbia, and Victoria. 

The total value of the gold produced in the year 1869 is computed at £60,000,000, 
one-fourth of this representing the value of the production of California. The 
value of the joint production of the Australian Colonies is a little above another 
one-fourth. 

Mode of Extracting Gold. The mode of extracting gold is determined by the circum¬ 
stances of its occurrence. By far the largest portion of the gold in circulation is 
obtained by the washing process; that is to say, the elimination by means of water 
of the lighter minerals, the finely-divided gold being left behind. This process may 
be carried on in remote districts in a very primitive manner, by simply putting the 
sand into wooden bowls, and washing it gradually away with water. The gold 


CHEMICAL TECHNOLOGY. 


lob 

bo obtained is not pure, but contains titanic iron and other minerals. Wherever 
gold washing is a regularly established business, as in some parts of the Oural, 
properly constructed contrivances are applied. 

Extraction^means of ; lhe application of mercury to the extraction of gold is based 
upon the fact that mercury amalgamates with gold readily and very effectively. The 
operation is carried on with the gold-containing sand in peculiarly constructed 
mills. Mr. Crookes has shown that the addition of sodium to the mercury 
facilitates the extraction of the gold. The excess of mercury having been removed 
from the amalgam by pressure in leathern or stout linen bags, the remainder 
in amalgamation with the gold is volatilised by ignition in suitably constructed 
furnaces. 

smelting for Gold. By a far more perfect process than washing, gold is extracted from 
the gold sand by smelting with a suitable flux in a blast furnace. The object in 
view is to produce a rough or crude iron from which the gold is separated by means 
of sulphuric acid. This process yields from 25 to 30 times more gold than merely 
washing the sand. 

Treating 'with Aikaii. Mr. Hardings proposed to obtain the gold by treating the quartz 
or sand with caustic alkalies under a high pressure of steam, thereby forming a 
soluble silicate and leaving the gold. 

^th a er]^taUk: 0 o d re f 8 0m If gold happens to be interspersed through copper or lead ores, 
they are roasted and then washed. When the quantity of gold is sufficient such 
ores are treated with mercury, while sometimes they are treated for coarse metal; 
and this, containing all the gold, is smelted with litharge, which absorbs the gold, 
and is next separated from it on a refining hearth. 

ExfmcGon^of Gom from g 0 me minerals and metallurgical refuse containing only a very 
small quantity of gold have been treated at Beichenstein, in Silesia, by means of 
chlorine water, or an acidulated solution of bleaching powder. The gold is con¬ 
verted into chloride of gold (Au 01 3 ), and is precipitated from the solution by sul¬ 
phate of iron or sulphuretted hydrogen. This method has been severely tested by 
MM. Plattner, Th. Bichter, G-eorgi, and Dr. Duflos, and has been found to answer 
exceedingly well, even with very poor ores. This plan is of course generally 
applicable to gold sand and gold quartz. According to M. Allain, pyritical ores, 
having been roasted and treated with sulphuric acid to eliminate the iron, zinc, 
and copper, can be then treated with chlorine water so as to extract the gold present, 
to an amount only of 1 part of gold in 10.000 of mineral. 

Refining Gold. In order to separate any foreign metals from the gold obtained by 
the above process, the following methods have been employed, but only the last (5.) 
is now in general use. For that reason the other methods will only be briefly 
described:— 

1 Befining by means of sulphuret of antimony (Sb 2 S 3 ). 

2. By means of sulphur and litharge. 

3. By cementation. 

4. By quartation. 

5. By means of sulphuric acid. 

Jiy means of Sulphuret Tills process is effected by first smelting the alloy, which ought to 
of Antimony. contain at least 60 per cent, of gold, in a graphite crucible. Pulverised 

black sulphuret of antimony is added in the proportion of 2 parts to 1 of alloy and the 
molten mass is then poured into an iron mould, which is rubbed with oil. The mass on 
cooling will be found to consist of two separate layers—the upper, technically termed 


GOLD . 


107 

plagmct, consisting* of the sulphurets of silver, copper, and antimony; the lower, an alloy 
of antimony and gold, which is separated in a muffle or a wind furnace. The remaining 
gold is fused with borax, saltpetre, and some powdered glass. 

By the aid of Sulphur. This process does not aim at the entire separation of the gold from 
the other metals, but rather at its concentration in a smaller quantity of silver than was 
originally present in the alloy, so as to render it suited for quartation. The alloy, 
previously granulated, is mixed, with i part of powdered sulphur, put into a red-hot 
graphite crucible, and covered with charcoal powder. The crucible is kept at a low red 
lieat for 2 h hours, and then raised to the point of fusion. If the alloy contained gold in 
any considerable quantity, a layer of silver separates, which will be rich in gold, but if the 
original alloy was rather poor in gold, litharge is added to the molten mass, the oxygen of 
the litharge causing the combustion of the sulphur of a portion of the sulphuret of 
silver, the metallic silver combining with nearly all the gold. The reduced lead is taken 
up by the sulphurets of the other metals present. 

Cementation Process. The alloy containing gold having been either granulated or rolled 
into thin sheets suitably cut up, is placed in a crucible, in this instance technically termed 
a cementation box, and mixed with 4 parts of pulverised bricks, and 1 part each of 
common salt and dried copperas. The crucible is then gradually raised to a cherry-red 
heat. Chlorine is evolved in this operation by the action of the sulphate of iron upon the 
common salt; there is consequently formed chloride of silver, which is absorbed by the 
pulverised bricks, while the gold is left unattacked. After cooling, the mass is boiled in 
water in order to obtain the gold. Here must be mentioned Mr. F. B. Miller’s process of 
passing chlorine into molten gold in order to eliminate the base metals which render 
it brittle, while the silver, converted into chloride, floats to the surface. 

Quartation. This process has obtained its name from an opinion that, to ensure success, 
there should be three times more silver in the alloy than gold, i.e., the gold should amount 
to a quarter of the entire alloy. But Dr. M. von Pettenkofer has proved that if the 
amount of silver be double that of the gold, the separation of the two metals will 
be complete, provided sufficiently strong nitric acid be employed, and the boiling con¬ 
tinued for a length of time. Practically this method is as follows:—There is added 
to the gold a sufficient quantity of silver, and the two metals are smelted together. The 
alloy is next granulated, placed in a platinum vessel, and boiled with nitric acid of 1*320 
sp. gr., care being taken that the acid is free from any chlorine. The silver being dis¬ 
solved, the gold is left behind, and further refined by fusion 'with borax and saltpetre in a 
crucible. 

Kefi of i suiphunc AOd Aid This method of refining, which has been briefly alluded to 
under Copper, is preferable to any of the foregoing on account of its perfection, 
cheapness, and simplicity. By this method almost any alloy containing gold in 
addition to copper and silver can be treated, but the quantity of gold should not 
exceed 20 per cent., nor that of the copper 10 per cent., while the best proportions, 
according to Dr. Pettenkofer’s researches are, that in 16 parts of the alloy, the gold 
should not exceed 4 or be* much less than 3 parts, and the rest copper and silver. 
Usually the alloy intended for this mode of operation is first granulated, or if it 
happens to be in the shape of silver coins—Mexican dollars, for instance—they are 
cut to pieces. Formerly, platinum vessels were employed in the boiling of the 
alloy with thoroughly concentrated sulphuric acid (sp. gr. 1*848), but cast-iron 
vessels, or sometimes hard porcelain vessels, are now employed, the proportion 
being 2 molecules of acid to 1 molecule of the alloy. The heating is continued 
some twelve hours, until the copper and silver are completely dissolved. The sul¬ 
phurous acid evolved is employed in the manufacture of sulphuric acid, or is 
absorbed by a soda or lime solution to form sulphite or bisulphite of soda or bisul¬ 
phite of lime. The solution of mixed sulphates of silver and copper is poured into 
leaden pans, and becoming solidified on cooling, the pasty mass is dug out with 
iron sjmdes, and put into leaden tanks filled with boiling water, in 88 parts of 
which 1 part of sulphate of silver is soluble. The silver is precipitated from this 
solution by strips of copper, and the solution of sulphate of copper obtained, having 
been deprived of its excess of free acid by the addition of oxide of copper, is further 


CHEMICAL TECHNOLOGY. 


1 08 


treated for blue vitriol. The gold which has remained as a dark, insoluble, spongy 
mass, is first boiled with a solution of carbonate of soda, next with nitric acid, to 
free it from any adhering oxide of iron, sulphuret of copper, sulphate of lead, and 
other impurities; and after having been dried, is melted with the addition of salt¬ 
petre. By this process it has become possible to extract the i-ioth to i-i2th per 
cent, of gold contained in old silver coins; therefore this method of refining has come 
largely into use, as within the last thirty years nearly all European States have 
recoined the silver money in circulation. Still Dr. von Pettenkofer has observed, 
that nearly all the gold obtained by this process contains silver and platinum, 
in the proportion of 97*0 gold, 2*8 silver, and o*2 platinum. These metals are 
eliminated by fusion with saltpetre and bi-sulphate of soda. 

At Paris, Prankfort, London, and Amsterdam, this method of refining is carried on to a 
large extent by private firms. According to the Paris custom, the refiners return to their 
clients all the silver and gold, retaining only the copper, and being paid at the rate of 
from 5 to 5^ francs per kilo, of refined metal; but if the alloy contains less than i-ioth 
of gold, the refiners retain i-20ooth of that metal, paying a premium of f franc per 
kilo, of refined metal to their client. If the client desires all the gold and silver, to be 
returned to him, the refiner charges 2 francs and io to 68 centimes per kilo., according to 
the market price of silver, and retains all the copper. Usually, however, a charge of 
5 francs per kilo, is paid to the refiner. The value of the silver annually refined for gold, 
at and near Paris, amounts to about £5,500,000. 

Chemically Pure Gold. In order to obtain perfectly pure gold, that of commerce is dissolved 
in nitro-hydroehloric acid, the solution evaporated to dryness, the residue, chloride of gold, 
dissolved in water, and that solution precipitated by a solution of sulphate of iron :— 


Chloride of gold, 2(AuCl 3 ) 
Sulphate of iron, 6 FeS 0 4 


Chloride of gold, 2 (AuC 1 3 ) 
Oxalic acid, 3C 2 H 2 0 4 


yield 


l Gold, 2 Au. 

] Persulphate of iron, 2 Fe 2 3 S 0 4 . 

, ( Chloride of iron, Fe 2 C 16 . 

According to Mr. Jackson, gold may be readily obtained in a yellow spongy mass, by 
adding carbonate of potassa and an excess of oxalic acid, to a concentrated solution 
of chloride of gold, and rapidly heating this solution to the boiling-point:— 

Gold, 2Au. 

yield < Hydrochloric acid, 6 C 1 FI. 

( Carbonic acid, 6 C 0 2 . 

According to Mr. Reynolds, peroxide of hydrogen precipitates gold from its acid solution 
in beautifully lustrous metallic spangles :— 

( Gold, 2 Au. 

yield 


Chloride of gold, 2 (AuC 1 3 ) 
Peroxide of hydrogen, 3 H 2 0 2 


< Hydrochloric acid, 6 C 1 H. 

( Oxygen, 60 . 

Sometimes gold is precipitated by chloride of antimony or chloride of arsenic. 


The 


metallic gold obtained or precipitated by any of the above processes is next fused with 
borax in a graphite crucible. 


Properties of Gold. The peculiar colour of gold is too well known to require description. 
The richness of that colour is very much impaired by even small quantities of other 
metals. Many of the Australian sovereigns, for instance, are of a pale greenish 
yellow, due to the presence of a small quantity of silver. A small quantity of copper 
gives a red colour to the gold. Gold assumes a very high polish; is, when un¬ 
alloyed, but slightly harder than lead, and yet is the most malleable and ductile cf 
all metals. Its absolute strength is equal to that of silver. The specific gravity of 
gold varies from 19*25 to 19*55, an( l even 19*6, according to the mode of mecha'nical 
treatment. Its co-efficieut of expansion by heat = 682 per ioo° C., and its melting- 
point, according to Dr. Deville, is 1037°. Dr. Vim Riemsdijk, however, fixes the 
melting-point at 1240°, the metal being molten in quantities of several kilos, in an 
atmosphere of pure dry hydrogen. Molten gold exhibits a sea-green colour. The 
great value of gold is in a considerable measure due to its not being acted upon by 
air, water, ordinary acids, and alkalies; but, on the other hand, even very small 


GOLD. 


109 


quantities of lead, antimony, and bismuth impair its malleability to such an extent 
as to render it unfit for use either as coin or for ornamental purposes. The fol¬ 
lowing metals haye the same effect, but to a less extent: arsenic, zinc, nickel, tin, 
platinum, copper, and silver; the two latter being the only metals suitable to alloy 
with gold to make it sufficiently hard to resist wear and tear. Gold, of all the 
metals, is most readily affected by mercury, even to such an extent that the mer¬ 
cury present in the imperceptible perspiration of such individuals as have been 
treated medicinally with calomel for some length of time, is sufficient to act very 
perceptibly upon their jewellery, while gold coins kept for some days in their 
pockets become blanched. Gold-leaf imparts to transmitted light a blue-green hue. 

Alloys of Gold. Pure gold is used only for certain chemical processes, and beaten 
into leaf for gilding; the Staffordshire potteries consuming for this purpose alone 
£60,000 worth annually. All other gold, be it used for jewellery or for coinage, is 
always alloyed with copper or silver to produce the degree of hardness requisite for 
hammering, stamping, &c. Generally such alloys are considered as consisting of so 
many carats to the unit, the pound or half-pound being divided into 24 carats, each 
of which contains 12 grains. What is termed 18 carat gold is a unit of 24 carats of 
alloy, containing 18 carats gold and 6 of silver or copper. If the latter, the alloy is 
termed red; while if silver is used, it is termed white ; and if both metals are alloyed 
with the gold, the caratation is termed mixed . In most countries there are legally 
fixed certain standards for gold jewellery. In this country, 16, 18, and 22 carat gold 
is stamped, or, as it is termed, Hall marked; in Prance, 18, 20, and 22 carat; in 
Germany, 8, 14, and 18 carat, and also under the term of Joujou gold, a 6 carat gold, 
used for jewellery, to be electro-gilt. Among the coined gold of European States 
the term carat is almost everywhere replaced by the expression of so many parts fine 
per mille. Exceptionally fine ^old coins are the Austrian ducats, 23 carats 9 grains, 
986,11 of gold; the Dutch, or more correctly Holland, ducats, or 23 carats 6 to 
6'9 grains gold. Neither of these coins are at present a legal tender in Austria 
or Holland, but they are continually made at the Utrecht Mint, having been for many 
years the circulating medium in the North Baltic and White Seaports, as well as in 
the Black Sea, Levant, and Egypt. Originally they were coins of the Holy Boman 
Empire (Germany). The English sovereigns and half-sovereigns are coined from 
or 22 carat gold; or in thousands = ^; the Prussian Eriedrich d’Or = 7 9 0 o g 2 3 ; 
Wilhelm d’Or =213 carat; the 20-franc pieces of Prance, Belgium, Switzerland, 
and Italy = 21 carat 7! grain, or T 9 3 ° 5 0 a . According to the Vienna Treaty of 1857, 
current gold coins of Germany are made in 1000 parts of 900 of gold and 100 of 
copper, the relative value of silver to gold being taken as 1 : 15*3, or 1 : 15*5. 

colour of Gold. As all gold alloys, commercially or industrially used, exhibit colours 
different from that of pure gold, it is customary to produce superficially on such 
alloys the deep yellow of fine metal by boiling in a solution of common salt, salt¬ 
petre, and hydrochloric acid; the effect is the evolution of some chlorine, which 
dissolving a small quantity of the gold, again deposits it as a film of very pure gold. 
Electro-gilding is, however, frequently substituted for this colouring process. 

Testin ^Goid . Inenes8 Jewellers and goldsmiths generally use touch-needles made from 
varying gold alloys. The resistance of the streak made upon the touchstone to the 
action of the dilute nitro-muriatic acid is the test of the fineness of the gold; but 
it is clear that this method is only approximative, and it cannot be relied on, as 
jewellery is often superficially coated with a film of pure gold. The most reliable 


I IO 


CHEMICAL TECHNOLOGY. 


test is afforded by cupellation, for which purpose the gold alloy to be tested is ; 
according to its colour, fused with twice or three times, or an equal weight of silver, 
and about ten times its weight of lead. This compound alloy is submitted to cupel¬ 
lation in a muffle. The button which remains on the cupel is first flattened on an 
anvil, next annealed, and rolled into a thin strip, and then boiled with strong nitric 
acid to dissolve the silver, the remainipg gold being washed with boiling water, 
dried, re-ignited in the muffle, and finally, when cold, weighed. 

Applications of Gold. It is not necessary to speak of the well-known uses of gold, the 
most extensive being its application to coinage, and next that to gilding and 
jewellery. Gold in sheets | inch thick has been used to cover the large dome of 
Isaac's Church, at St. Petersburg, while three, at least, of the countless crosses on 
the domes of the Moscow churches are made of solid gold; a portion of one of the 
domes of a church in the Kremlin is likewise plated with gold. 

Gilding. This is done either with gold-leaf, or by means of the cold process, the 
wet process, fire-gilding, or electro-gilding. 

Gilding with Goid-ieaf. Gold-leaf, applied in gilding on wood and stone, is prepared 
in the following manner:—Fine gold is molten and cast into ingots, which are 
hammered and rolled into thin sheets about an inch in width, technically termed 
ribbon. The ribbon is cut into small pieces an inch in length, w'hich are placed 
between pieces of parchment, and beaten out to a moderate thinness. Goldbeaters’ 
skin— the exterior membrane of the intestina crassa of oxen—is then substituted for 


the parchment, and the hammering continued until the metal is of extreme tenuity. 
The refuse gold of this operation is used for the preparation of bronze-gold for 
painters. The articles to be gilded with gold-leaf are first painted over with a 
suitable varnish or size, and the gold-leaves pressed on gently with a piece of soft 
cotton-wool. Iron and steel, as, for instance, swords, gun-barrels, &c., are first 
bitten, as it is termed, with nitric acid, next heated to about 300°, and then covered 
with gold-leaf. 


Gilding by the Cold For this purpose fine gold is dissolved in aqua regia; clean linen rags are 
1 rocess. soaked in this solution, and then burnt to tinder, consisting of carbon and 
very finely divided gold. This tinder is rubbed on the article to be gilded with a cork 
moistened in brine ; the metallic surface to be gilded should be 'well polished. 

Gilding by the This process is carried out by placing the article to be gilded in either a 
v et w ay. dilute solution of chloride of gold in ether, which rapidly evaporates, or in 
a boiling dilute aqueous solution of the same salt, and adding to it carbonate of soda or 
potassa solution. Iron or steel should be first superficially coated with a film of copper 
by immersion in a dilute sulphate of copper solution ; or these metals, after being bitten 
with nitric acid, are painted over with a solution of cliloride of gold in ether. A solution 
of chloride of gold in solution of pyrophosphate of soda has lately been suggested as a 
suitable bath. 

Fire-giiding. Articles of bronze, brass, copper, silver, especially buttons and ornaments of 
military uniforms, are gilt with an amalgam of gold and mercury, 2 parts of the former 
and 1 of the latter being applied by means of a solution of nitrate of mercury. The 
articles being next heated in a muffle, the volatile metal escapes, leaving an adhering film 
of gold, which may either remain dull or be polished, the colour being preserved in the 
former case by a momentary immersion in a fused mixture of nitre, alum, and common 
salt, and immediately after in cold water. If it be desired to leave only some portions 
of the gilding dull, the portions to be afterwards polished are covered with a mixture 
of chalk, sugar, gum, and sufficient water to form a paste. The rationale of the action 
of the fusing mixture is that chlorine gas is evolved, winch, as the term runs, bites the 
gold. If it is desired to impart a red-gold colour, a paste of wax, bolus, basic acetate 
of copper, and alum is spread on the gilding, and the article held over a clear fire, the 
result being the reduction of the copper, which combines with the gold. As the use 
of the so-called quicksilver-water (nitrate of mercury) is very injurious to the opera* 
lives, M. Masselotte, of Paris, coats the articles with mercury, afterwards with gold, 


MANGANESE AND ITS PREPARATIONS. 


Ill 


and again with mercury, by means of galvanism. Finally, the mercury is volatilised by 
ignition in a muffle, so arranged that the vapours escape only in the flue. According to 
M. H. Struve, so-called fire-gilt articles are not really covered with a simple film of gold, 
but with an amalgam of gold and 13-3 to 16-9 per cent, of mercury. Electro-gilding will 
be treated in a separate section. 

Cassius's Purple. The preparation which bears this name was discovered by Dr. Cassius, at 
Leyden, in the year 1683. It is prepared by adding to a solution of chloride of gold a 
certain quantity of sesquichloride of tin. Dr. Bofley prescribes the following process :— 
First, 107 parts of the double chloride of tin and ammonium are digested with pure 
metallic tin until the metal is quite dissolved, 18 parts of water are then added, and the 
liquid mixed with the gold solution previously diluted with 36 parts of water. The result 
is the throwing down of a purple or black-coloured precipitate, about the chemical 
constitution of which nothing is certainly known. 'Well-prepared Cassius’s purple should 
contain 39*68 per cent, of gold. 

Saits of Gold. The double salts of chloride of gold and sodium (AuCl^NaCl-{- 2HO), and 
the corresponding potassium salt (2 AuC 1 3 ,KC1-f - 5HO), are employed in photography and 
medicine. 

Manganese and its Peepaeations. 

Manganese. Of all the ores of manganese met with in various degrees of oxidation, 
only the peroxide, mineralogically known as pyrolusite, polianite, and technically as 
glass-makers’ soap, is industrially of much importance. When perfectly pure this 
mineral consists of 63*64 per cent, of manganese, and 36*36 per cent, of oxygen, its 
formula being Mn 0 2 ; but the ore, as met with in commerce, frequently contains 
baryta, silica, water, and sometimes oxides of iron, nickel, cobalt, and lower oxides 
of manganese, viz., Braunite, Mn 2 0 3 ; Manganite, Mn 2 0 3 ,H 2 0 ; Hausmannite, 
Mn 3 0 4 ; and various other minerals, as potassa compounds, lime, &c. In Ger¬ 
many, the ore is purified by most ingeniously contrived machinery, which might be 
very advantageously applied to a great many other metallic ores and phosphatic 
minerals. Manganese is industrially employed in making oxygen, the preparation of 
bromine and iodine, glass-making, colouring enamels, for producing mottled soaps, m 
puddling iron, and in dyeing and calico-printing, for preparing permanganate of 
potassa ; but the largest consumers are the manufacturers of chlorine. The bulk of 
the manganese of commerce is derived from Germany, which supplies about 700,000 
cwts. to Europe annually. It is found also very largely and of excellent quality in 
Spain, as well as in Italy, Greece, Turkey, Sweden, and British India. 

Testing the quality yalue of manganese for technical purposes depends—i. On 

the quantity of oxygen it is capable of yielding, or the quantity of chlorine it will 
evolve, not taking into account the 0 of the MnO. 2. On the nature and quantity 
of the substances soluble in acids, such as the carbonates of lime and baryta, prot¬ 
oxide of iron, which, not yielding chlorine, saturate a certain quantity of hydro¬ 
chloric acid. But even if these impurities are absent, it may happen that, of two 
samples of manganese, one requires more acid than the other to evolve the same 
bulk of chlorine gas, as, for instance, when one of the samples contains in addition 
to peroxide of manganese (Mn 0 2 ) also the sesquioxide (Mn 2 0 3 ), especially if the' 
latter is present as hydrate. 3. On the quantity of water, which may amount even 
to 15 percent. 

According to the experiments of Dr. Fresenius, the most suitable temperature for drying 
a weighed sample of manganese, in order to estimate the water it contains, is 120°, no 
water of hydratation being expelled at that heat; but for commercial analysis the drying of 
a sample at ioo° is quite sufficient, provided it be kept at that heat for some hours con¬ 
secutively Among the many methods proposed for testing manganese, that originally 
invented by Drs. Thompson and Berthier, and improved upon by Drs. Will and Fresenius, 
is based on the fact that a molecule of peroxide of manganese treated with sulphuric 
acid is capable of converting, bf the 0 given off, 1 molecule of oxalic acid into 2 molecules 

of CO a . 


112 


CHEMICAL TECHNOLOGY . 


i mol. Peroxide of manganese, Mn 0 2 ) 
i mol. Sulphuric acid, H„S 0 4 > give 

1 mol. Oxalic acid, C 2 H 2 0 4 1 


1 mol. of Sulphate of protoxide of man¬ 

ganese, MnSo 4 . 

2 mols. of Carbonic acid, 2C0 2 . 

2 mols. of Water, 2H 2 0. 


Prom the weight of C 0 2 evolved is determined the quantity of peroxide of manganese con¬ 
tained in the sample. The operation is performed in the apparatus shown in Fig. 56. The 
flasks a and b are fitted with perfectly tight-fitting corks, perforated for admitting the glass- 
tubes, as seen in the woodcut. In the flask a is placed the mixture of previously dried 
manganese and oxalic acid, with enough water to fill about one-third of 
Fig. 56. the flask. The flask b is about half-filled with strong sulphuric acid; 

' the end of the tube c is plugged with a piece of wax and the apparatus 
weighed. Next some air is sucked out of b, by means of the tube d, 
so as to cause a small quantity of acid to run over into a ; thereupon the 
evolution of C 0 2 sets in, and the escaping gas passing through the acid 
in b is dried. The suction having been repeated, the wax plug at c, as 
soon as the evolution of C 0 2 ceases, is for a moment removed, and the 
suction again repeated to remove all the C 0 2 from the apparatus. The 
plug of wax is now replaced and the apparatus again weighed; the 
loss of weight gives by calculation the quantity of peroxide of man¬ 
ganese contained in the sample, if one holds in view that 2 molecules 
CO ,(C 0 2 “ 88) stand to 1 molecule Mn 0 2 as the quantity of carbonic 
acid found to x. If 2^98 grms. of dried manganese are taken, and the 
quantity of C 0 2 divided by 3, the centigrammes of C 0 2 lost express the 
proportion per cent, of pure peroxide of manganese contained in the sample ; to 1 part of 
manganese 1 4 parts of neutral oxalate of potassa should be taken for the experiment. If 
the sample of manganese happens to contain carbonates, it has, previously to being tested, 
to be treated with very dilute nitric acid, and of course well washed with distilled water 
and afterwards dried. For other methods of testing manganese, the reader is referred to 
Mr. Crookes’s work on “ Select Methods in Chemical Analysis.” 



Permanganate of Potassa. 

permanganate of Potassa. This salt (KMnOJ, used for disinfecting, bleaching, and 

other oxidising purposes, and constantly employed in chemical laboratories, owes its 
efficiency to the fact that, in contact with dilute sulphuric acid, it yields protoxide of 
manganese and oxygen (Mn 2 0 7 = 2MnO + 5O). The permanganate of potassa is for 
technical purposes prepared in the following manner:—500 kilos, of caustic potassa 
solution at 45 0 B. (=1*44 sp. gr.) are added to 105 kilos, of chlorate of potassa and 
the mixture evaporated to dryness, there being gradually added 180 kilos, of pow¬ 
dered manganese, and the heating continued to the fusion of the mass, which is 
stirred until cold. The powder thus obtained is heated in small iron crucibles to a 
red heat, and when semi-fluid is cooled; the mass is next broken up and put into a 
large cauldron filled with hot water, and left standing for about an hour. The clear 
liquid having been decanted from the sediment, hydrated peroxide of manganese, is 
evaporated to crystallisation; 180 kilos, of manganese yield 98 to 100 kilos, of crys¬ 
tallised permanganate. Approximately the process may be elucidated as follows:— 
a. By the fusion of the potassium manganate and chloride of potassium :— 
6 Mn 0 2 -{- 2KCIO3 12KOH = ( 3 K 2 Mn 0 4 ) -J- KC1 6 H 2 0 ; 

/ 3 . During the solution of the fused mass in water, the manganate of potassium is 
converted into hydrate of potassa, hydrate of peroxide of manganese, and perman¬ 
ganate of potassa:—3K 2 Mn0 4 -f 6 H 2 0 = 4 lK 0 H 4 - 2KMn0 4 -f Mn 0 2 -f- 4ll 2 0. Con¬ 
sequently one-third of the manganic acid is lost by the formation of peroxide of 
manganese. This also occurs when, according to M. Tessie du Motay’s plan, the 
conversion of manganate of potassa into permanganic acid is effected by sulphate of 
magnesia:—3K 2 Mn0 4 + 2MgS0 4 — 2KMn0 4 + Mn 0 2 + 2lv 2 S0 4 -J- 2MgO. Dr. 
Staedeler therefore suggests that the manganate of potassa should be converted into 





ALUMINIUM. 


H3 

permanganate by chlorine, accordingto the formula: —K 2 Mn0 4 -f- Cl==KCl-f IvMn0 4 . 
For disinfecting purposes a mixed permanganate of potassa and soda, or even the 
latter alone, is usual; the well-known Condy’s fluid is a solution of this salt in 
water containing per-sulphate, not proto-sulphate of iron. Permanganate of potassa 
is used to some extent in dyeing, and for staining wood. 

Aluminium. 

(Al = 27*4; Sp. gr. = 2* 5 ). 

Preparation of Aluminum. Aluminium, discovered at Gottingen, in 1827, by Dr. "Wohler, 
0 belongs in the shape of its oxide to the most widely dispersed as well as the most 
commonly occurring materials on our globe. The properties of this metal were more 
particularly studied in 1853 by Dr. Deville, who found that aluminium is far less 
readily acted upon in the molten state by oxygen, in the cold by dilute acids and 
by boiling water, than was at first thought to be the case, and this eminent author’s 
researches gave rise to the production of this metal for industrial purposes, two 
manufactories existing in France, viz., at Salyndres and Amfreville, and one in 
England, at Washington, county Durham. 

Aluminium is obtained from the double chloride of aluminium and sodium by the aid 
of the latter alkali-metal, which is prepared for this and other purposes by the ignition of 
a mixture of 100 parts of calcined soda, 15 parts of chalk, and 45 parts of small coal. 
Chloride of aluminium is best prepared from bauxite, native hydrate of alumina, which, 
having been previously mixed with common salt and coal-tar, is next heated in an iron 
retort with chlorine gas, the result being the formation of carbonic oxide and the double 
chloride of aluminium and sodium, which volatilises, and is condensed in a reservoir lined 
with giazed tiles. The salt so obtained contains iron, and consequently the aluminium 
derived from it is alloyed with that metal. The double chloride of aluminium and sodium 
is converted into metallic aluminium by being heated in a reverberatory furnace with 
sodium; while the aluminium is set free, a slag is formed consisting of the double salt with 
excess of chloride of sodium. Professor H. Rose, at Berlin, first used cryolite for his 
experiments on aluminium, the mineral bearing that name being a compound of the double 
fluorides of aluminium and sodium (A 1 2 F 1 3 -\- 6NaFl). This mineral being treated at a high 
temperature with sodium yields aluminium and fluoride of sodium, and the latter treated 
with quick-lime yields caustic soda and fluoride of calcium. 

properties of Aluminium. The colour of this metal is intermediate to those of zinc and 
tin; its hardness exceeds that of tin, but is less than that of zinc and copper, and 
about the same as that of fine silver; it is a very sonorous metal, rather brittle, 
malleable to some extent, readily rolled into thin sheets, and may be beaten into 
leaf; on the other hand, it is not ductile. Aluminium does notrust by exposure to 
air, and it may be even heated to redness without suffering much oxidation. When 
fused, however—it melts at 700°—it oxidises so much as to necessitate the use of a 
flux—best chloride of potassium—to absorb the alumina which is formed. It is very 
readily and rapidly dissolved by hydrochloric acid and solutions of caustic potassa 
and soda, hydrogen being copiously evolved; but the metal is not in ^he least acted 
upon by nitric acid. It does not amalgamate with mercury. With tin it yields an 
alloy of considerable hardness, yet to some extent malleable; with copper in the 
proportion of go to 95 per cent, of copper and 10 to 5 per cent, of aluminium, it 
forms aluminium-bronze. This alloy, in colour similar to gold, is used for artificial 
jewellery and small ornaments. Aluminium does not alloy with lead. The aluminium 
of commerce is never quite pure, always containing silicium, found by Dr. Ram- 
melsberg even to 10*46 per cent., and frequently present to 0*7 to 3*7 per cent.; 
while the quantity of iron varies from 1 *6 to 7*5 per cent. 

9 


CHEMICAL TECHNOLOGY. 


114 


Applications. Al uminium is now not so much in use : when first introduced aluminium 
jewellery was the order of the day. The metal is at present more usefully employed for 
small weights, light tubes for optical instruments, and to some extent for surgical instru¬ 
ments. The price, however, of this metal, £5 12s. per kilo., is too high to ad m it of its 
extended use; while great lightness combined with comparative strength are its only 
prominent qualities. 


Magnesium. 

(Mg=24; Sp. gr. 1743). 

Magnesium. As an oxide, and in combination with chlorine and bromine, as well as 
with other metalloids, magnesium is found in very large quantities, for instance, in 
sea-water and carnallite, as sulphate of magnesium, as kieserite, schoenite, kainite, 
in rocks as a pure carbonate, and as magnesian limestone; further as a silicate in 
meerschaum. Metallic magnesium has but limited commercial applications. It is 
silvery white in colour, somewhat affected by the oxygen of the air, but not more 
so than zinc; fuses at about the same temperature as that metal, and when heated 
a little above this point, burns with an intensely brilliant white light, and in oxygen 
gas the combustion is attended with a lignt almost equal to bright sunlight. Mag¬ 
nesium may be readily drawn into wire ; it is at the ordinary temperature of the 
air as malleable as zinc, and boils and distils over at about the same temperature as 
that metal. Magnesium is at present only applied to yield an intense light in 
photography, and for signals; for this latter purpose it was extensively used in the 
Abyssinian campaign (1868). It has been suggested to alloy magnesium instead of 
zinc with copper. 

Magnesium is prepared by a process very similar to that of aluminium manufacture :— 
Sodium is ignited with either chloride of magnesium—Bunsen, Deville, and Carron 
methods—or the double fluoride of magnesium and sodium—Tissier’s plan—or the double 
chloride of magnesium and sodium—Sonstadt’s method. Dr. H. Schwarz employs the 
double chloride of calcium and magnesium, and M. Beichardt carnallite, double chloride 
of magnesium and potassium. Several other suggestions have.been made as to the mode 
of preparing this metal, but it does not appear that they are available in practice. Mag¬ 
nesium is manufactured on the large scale by the Magnesium Metal Company at Man¬ 
chester, and the American Magnesium Company at Boston, the English firm producing 
about 20 cwts. annually. 


Electeo-Metalluegy. 

Application of Galvanism. It is one of the most prominent properties of the continuous 
electric current, that it is capable of decomposing compound substances in such a 
manner as to cause the constituents to be deposited on or near the place where the 
current leaves the body to be decomposed; this property is termed electrolysis , the 
body decomposed being termed electrolyte , and the places where the electric current 
enters and leaves electrodes; the positive pole of the battery being named anode , and 
the negative cathode. The constituents of the body decomposed by electricity are 
termed ions (from tcou, participle of «/n, to go); that deposited or separated at the 
anode (+ pole) being distinguished as the anion , and that making its appearance at 
the cathode the cation. An electric current strong enough to decompose a molecule 
of water is also capable of decomposing a molecule of a binary compound; accordingly 
the quantities by weight of a body decomposed by the electric current are propor- 
EiectroiyticLaw. tional to the chemical equivalents. The main laws of electrolysis 
were discovered by Earaday, who was the first to show that the constituents 
attracted by the anode (-f pole) are electro-negative, and those by the cathode 


ELECTRO METALLURGY. 


* n 5 

( — pole) electro-positive. As water is a common solvent, it frequently occurs that 
during electrolysis its elements are secondarily decomposed. For instance, sulphate 
of copper gives, at the anode oxygen gas, and at the cathode metallic copper, because 
the oxide of copper appearing at this pole is at once de-oxidised by the simultaneous 
appearance of hydrogen: the oxygen set free at the positive plate combines with the 
zinc, forming an oxide, converted by the acid into sulphate of zinc; so that for every 
equivalent (63*4) of copper deposited, one equivalent (65*2) of zinc is dissolved. If, 
instead of sulphate of copper, suitable solutions of gold, silver, &c., are employed, 
the electro-deposition of these metals can be effected. 

Electrotyping. The following are the chief technical applications of electrolysis:— 
Electrotyping. It has just been said that the copper separated electrolytically from 
the sulphate of that metal is deposited in a coherent state, and if the operation is 
continued for some time the layer of metal may become sufficiently thick to admit of 
being detached from the form upon which it was deposited. This principle of electro¬ 
typing was discovered in 1839, simultaneously at St. Petersburg by Dr. Jacobi, and 
at Liverpool by Mr. Spencer; among those who have laboured to improve this art, 
are Messrs. Becquerel, Eisner, Smee, Euolz, Elkington, and many others. The 
metallic solution applied for the preparation of casts to be electrotyped is always a 
saturated solution of sulphate of copper, and the form, technically termed the pattern 
or matrix, upon which it is desired to deposit the copper, should not consist of any 
metal, such as zinc, tin, or iron, acted upon by a solution of sulphate of copper. 
The matrix is usually, if it be a metal, made of copper; but more frequently it 
consists of gypsum or gutta-percha. In order to render the electric current uni¬ 
form, the zinc plate of the battery is amalgamated by dipping it in hydrochloric or 
dilute sulphuric acid, and then rubbing mercury over the surface with a brush or 
piece of soft rag. 

iiepioduction of Copper- The engraved ' copper-plate to be reproduced is placed at the 
Plate Engravings, bottom of a wooden trough lined with resin or ashphalte. Above the 
plate is fixed a wooden frame, on which is strained a sheet of bladder or parchment, to 
serve as a diaphragm; and on the top of the frame a plate of zinc is placed, and con¬ 
nected with the copper-plate by a strip of lead. A saturated solution of sulphate of 
copper is poured into the bottom of the trough, and in order to maintain the saturation a 
few crystals are added. Above the porous diaphragm a concentrated solution of sulphate of 
zinc is placed. This plan is also pursued in electrotyping woodcuts, stereotype-plates, &c. 

Deposition of Metals. To reproduce medals and other small objects a weak current only is 
required. The plate or object on which it is desired to cause the deposition to take place 
is suspended vertically from the cathode, and a plate of the metal to be deposited from 
the anode ; in proportion as the metal is precipitated at the cathode, it is dissolved at the 
anode, leaving the concentration of the fluid unchanged. Such substances as are 
non-conductors, wax, paraffine, and gypsum, are first superficially coated with some 
conducting material, as graphite, silver, or gold-bronze. Gutta-percha is an excellent 
material for casts, owing to its becoming plastic in boiling water. According to M. von 
Kobell, a tough malleable copper is obtained by adding to the copper solution some 
sulphate of soda and sulphate of zinc. Unless a rather weak current is applied, the 
copper is separated from its solution in a spongy state; on no account should the 
current be strong enough to decompose water. 

E1 Goi r d 0 and t s i uveJ. ith In order to apply a coating of gold or silver to copper, brass, 
bronze, or other metallic alloy, the surface should be first very thoroughly cleaned 
by boiling in a caustic soda solution. Smee’s battery—a platinised silver plate, and 
a plate of amalgamated zinc—is now generally used, the elements being placed in 
leaden vessels lined with asphalte. The solution of gold or silver in cyanide of 
potassium is employed as the decomposition liquid, in which the objects to be silvered 
or gilded are suspended by a wire connected with the negative pole of the battery ; 


\ 


lib 


CHEMICAL TECHNOLOGY. 


and to another wire, connected to the positive pole of the battery, is fastened a piece 
of platinum, which is also immersed in the liquid of the decomposition-cell. The 
whole process only lasts a few minutes, the cathode during the time being moved 
backwards and forwards by hand to render the deposit uniform. Plates of gold or 
silver are generally used instead of platinum at the anode, and become gradually 
dissolved by, and maintain, the cyanide solution at a constant strength. 

Gold solution. ioo grms. of cyanide of potassium are dissolved in i litre of distilled 
water, and 7 grms. of very fine gold in nitro-hydrochloric acid, this solution being 
evaporated to dryness on a water-bath, the residue dissolved in distilled water, 
and to the solution some cyanide of potassium added; or the gold salt obtained on 
evaporation may be dissolved in distilled water, and the solution carefully precipi¬ 
tated with sulphate of iron, the finely-divided gold being collected on a filter, next 
washed with distilled water, and finally dissolved in cyanide of potassium. 

suver solution. This solution is prepared by dissolving well-washed chloride of silver 
in the above solution of cyanide of potassium, so as to obtain a saturated solution 
of cyanide of silver, afterwards to be diluted with an equal bulk of water. 

Copper, bronze, brass, iron, and steel can be electro-plated directly; but polished steel, 
tin, and zinc have to be first coated with a film of copper. G-erman or nickel-silver is now 
generally electro-plated. The thickness of the film of silver may vary from i-42nd to 
1-450th, or even to 1-9400th of a millimetre, corresponding to 1-240 grms. of silver 
on 1 square metre of surface. Frequently the best electro-plated ware made in this 
country is afterwards coated with a very thin film of palladium to prevent the silver being 
affected by sulphuretted fumes. 

copper solution. For the purpose of electro-coppering, a solution of oxide of copper 
in cyanide of potassium is the most suitable fluid; this solution is prepared by first 
decomposing a solution of sulphate of copper in water, with the aid of caustic 
potassa and grape sugar, so as to obtain a precipitate of sub-oxide (red oxide) of 
copper, which, having been collected on a filter, and well washed, is next dissolved 
in a solution of cyanide of potassium. For the purpose of electro-coppering iron and 
steel, M. Weil, of Paris, prepares a fluid—350 grms. of cupric sulphate, 1500 grms. of 
potassio-tartrate of soda (sal seignette), and 400 to 500 grms. of caustic soda dissolved 
in 10 litres of water. 

M. Oudry’s method of depositing copper on iron candelabras, gas lamps, fountain 
ornaments, &c., is in some particulars quite different, the copper not being immediately 
deposited on the iron, which is first coated with an impermeable layer of a kind of red- 
lead paint, graphite being afterwards rubbed in for the purpose of rendering the surface of 
the object a conductor. To obtain a coating of copper 1 millim. in thickness, such articles 
as candelabra are left in the solution for 4^ days; the ornamental fountains of the Place 
la Concorde, Paris, have been for a period of two months in the solution. 

zinc and Tin Solution. To coat iron with zinc, a solution of the sulphate of the latter 
metal may be used, but the so-called galvanised iron of commerce is made by a 
different process, viz., by placing the iron to be coated in a bath of molten zinc, 
covered, for the purpose of preventing oxidation, with a layer of molten tallow or 
paraffin. For the purpose of electro-tinning, a solution of tin in caustic soda is 
employed, the anode being of tin. 

A so-called electro-steeling, really a deposit of iron on the copper plates used for engrav¬ 
ing, is effected by M. Meidinger in the following manner:—The bath is a solution of sul¬ 
phate of iron and chloride of ammonium: to the copper pole of the battery a plate of 
iron, and to the zinc pole the engraved copper plate, are connected. These steeled plates 
serve for as many as 5000 to 15,000 impressions. This method has been applied to 
stereotyping with great success, and indeed the deposition of iron electrolytically is 
a valuable addition to technology. 


ELECTRO METALLURGY. 


117 

Etching by Galvanism. This process is based upon the fact that, under certain conditions, the 
aubstances separated at, combine with the electrodes, the consequence being- that the 
electrode is gradually corroded and destroyed. The copper-plate intended to be etched is 
uniformly covered with a mixture of 4 parts of wax, 4 of asphalte, and 1 of black pitch; 
the design is then drawn or rather scratched with proper tools through this non-con¬ 
ducting layer, and the plate attached to the anode of a galvanic battery, and placed in 
a solution of sulphate of copper, containing also a copper-plate connected to the negative 
electrode of the battery. On this plate is deposited the copper of the solution, while the 
oxygen of the decomposed water, with the sulphuric acid, act upon the portions of metal 
not covered with the protective layer and produce the etching. 

Metaiiochromy, Or galvanic painting, consists in depositing thin films of oxide of lead in 
a coherent state on metal plates, thus producing Eobili’s colours. The oxide of lead is, for 
this purpose, best dissolved in caustic potassa or soda solutions. In England, this method 
of ornamenting is not much applied; but at Nuremburg, where toys are largely manufac¬ 
tured, this process is very simply carried out by placing the metallic object, previously 
connected with the cathode of a battery, in a concentrated solution of oxide of lead in 
caustic potassa, while to the anode is affixed a piece of platinum foil. 

Electro-stereotyping. Eor the purpose of reproducing printing-types by galvanic means, 
a wax impression of the type is placed in the deposition-cell. This operation is also 
employed for the reproduction of woodcuts, gutta-percha being used as a mould. 

Giyphography. By this name is understood a process for reproducing woodcuts, but it is 
now altogether obsolete, having been superseded by electro-typing. A further disadvantage 
was, that the glyphographic plates could not be printed from the same matrix as type. 

Gaivanography. At the suggestion of Dr. von Kobell, the reproduction of some kinds of 
drawings and pictures has been tried, in order to enable exact copies to be printed from 
plates electrolytically obtained from the original drawings; but this method, of very difficult 
and costly execution, is superseded by photography. 


DIVISION II. 


CRUDE MATERIALS AND PRODUCTS OF CHEMICAL INDUSTRY. 


Carbonate of Potassa. 


(E. 2 C 0 3 =: 138*2; in 100 parts, 68*2 potassa and 31*8 parts carbonic acid.) 

Source is^erived Potassa The substance known in chemistry as carbonate of potassa is 
generally termed potash, because it was formerly obtained from wood-ash, which, 
after lixiviation with water, was evaporated to dryness in cast-iron pots. Potassa 
occurs native in considerable quantities, but never free, being combined with silica in 
many minerals, also in combination as chloride of potassium, sulphate of potassa, 
and in various plants with organic acids. The following are the sources whence 
potassa is industrially obtained:— 

I. The salt minerals of Stassfurt and Kalucz; products- 

A. Inorganic sources 
of Potasssa. 


13 . 


carnallite, sylvin, kainite, and schoenite. 

II. Peldspar and similar minerals. 

III. Sea-water and the mother-liquor of salt-works. 

IV. Native saltpetre. 

V. The ashes of several plants. 

VI. The residue of the molasses of beet-root sugar after 
distillation. 

VII. Sea-weeds, as a by-product of the manufacture of iodine. 
v VIII. The suint of the crude wool of .sheep. 

I. The very abundant salt-rocks near Stassfurt, in Prussia, and 
Kalucz, in Hungary, chiefly yield carnallite, sylvin (C 1 K), and kainate, a compound 
of sulphate of potassa and magnesia with chloride of magnesium. Carnallite, so 
named in honour of Carnall, a Prussian mining engineer, consists, in 100 parts, 
leaving the bromine out of the question, of— 


Organic sources J 
of Potassa. ] 


Potassa Salts from the 
Stassfurt Salt Minerals. 


Chloride of potassium .. 

.. 27 

Chloride of magnesium .. 

•• 34 

"Water. 

• • 39 


100 


( Cl 

Formula—KCL, Mg J -f 6 H 2 0 . This salt is applied in the manufacture of- 

a. Chloride of potassium. 

/ 3 . Sulphate of potassa. 
y. Potash (carbonate). 




CARBONATE OF EOT ASS A. 


119 

a. Preparation of Chloride of Potassium.—According to the process originally 
patented (1861) by Mr. A. Frank, the abraum salts are ignited in a reverberatory 
furnace, with or without the aid of a current of steam, and next lixiviated with 
water, the resulting liquor yielding chloride of potassium. The rationale of this 
process is :—1. That the carnallite of the abraum salts is separated by the action of 
the water into chloride of potassium and chloride of magnesium. 2. The latter salt, 
on being ignited in a current of steam, is decomposed into hydrochloric acid, which 
escapes, and magnesia, which is practically insoluble in water, and which conse¬ 
quently remains. This process is not found to answer well on the large scale, 
because the abraum salts contain other chlorides, the chloride of sodium and tachy- 
drite, by the presence of which the decomposition of the carnallite is hindered. 
Dr. Griineberg, therefore, suggested that the abraum salts should be first mechani¬ 
cally purified, that is to say, the different components of the abraum salts should be 
separated from each other according to their varying specific gravity, which for— 
Carnallite is=i*6i8 

Chloride of sodium is = 2*200 
Kieserite is = 2*517 

The abraum salt having been ground to a coarse powder is passed through sieves, 
and treated as minerals are in metallurgical processes, with the difference that, instead 
of water, which of course would dissolve the salts, a thoroughly concentrated solution 
of chloride of magnesium is applied, this solution not acting upon the salts, and being, 
moreover, obtained as a by-product in enormously large quantities. The above- 
mentioned salts settle in layers according to their densities, the carnallite forming 
the upper, and the kieserite the lowest layer. The carnallite is at once applied to 
the preparation of chloride of potassium; the middle layer of common salt is so free 
from other foreign salts as to be fit for domestic use; the kieserite, after having been 
washed with cold water to remove any adhering chloride of sodium, is applied to the 

Fid. 57. Fig. 58. 




manufacture of sulphate of potassa, to be presently described. However, the greater 
number of manufacturers at Stassfurt prefer another plan, applying the five following 
operations to the abraum salts as delivered from the salt quarries :—1. Lixiviation 
of the carnallite with a limited quantity of hot water, sufficient to dissolve the 
chlorides of potassium and magnesium, leaving the bulk of the common salt and 
magnesian sulphate. 2. Crystallising the chloride of potassium by artificially 














120 


CHEMICAL TECHNOLOGY. 


freezing. 3. Evaporating and cooling the mother-liquor to produce a second yield 
of crystallised chloride of potassium. 4. Again evaporating and cooling the mother- 
liquor, which yields the double salt of the chlorides of potassium and magnesium, 
or artificial carnallite, which is next treated in the same manner as the native salt. 
5. Washing, drying, and packing the chloride of potassium. 

1. The carnallite is put into cast-iron lixiviation vessels and mixed with three-fonrths of 
its weight of water, previously employed for the washing of crude chloride of potassium, 
and, therefore, containing a large quantity of common salt and some chloride of 
potassium; steam, at 120 0 , and at a pressure of 30 lbs. to the square inch, is forced 
through the perforated circularly bent tube, t (Fig. 59) at the bottom of the vessel. In 

Mr. Douglas’s works the lixiviation vessels, Figs. 57, 
58, and 59, have a cubical capacity of 20 tons. They 
are closed with a tightly-fitting lid, an opening being 
cut for the escape of surplus steam. The stirrer, c, is 
kept in motion by steam-power. When the admission 
of steam and the stirring has been continued about 
three hours, the contents of the vessels are left at rest 
for two days, after which the saturated solution has a 
density of 32 0 B. = 1-286 sp. gr., and is forced by steam 
pressure into crystallising vessels; the residue in the 
lixiviation vessels, amounting to about one-third of the 
weight of the carnallite, is again treated as described. 

2. The crystallisation vessels are of wood or sheet- 
iron, 1-20 metres diameter, by 1-5 to 1-9 metres height. 
The chloride of potassium crystallises in combination 
with common salt, and is strongly impregnated with the 
very soluble and highly deliquescent chloride of mag¬ 
nesium; the salt deposited at the sides of the vessel 
contains upwards of 70 per cent, of chloride of potassium, while that collected at the 
bottom contains only 55 per cent. If shallow vessels are employed, the saline solution 
cools more rapidly, and a finer grained salt is obtained, mixed, however, with impurities, 
and requiring more washings, an operation which, with the coarse salt, has only to be 
performed once to yield 80 per cent, chloride of potassium. Most of the chloride of 
potassium sold by the manufacturers contains 80, and in some cases 85 and 90, per cent, 
of the pure salt. 

3. The evaporation of the first mother-liquor is carried on in iron pans of various 
sizes. As by the evaporation common salt is largely deposited, which has a tendency to 

Fig. 60, 



cake at the bottom of the pans, and check the conduction of heat, the pans are set so as 
to receive the action of the flame only on the sides (Fig. 61), and the liquid kept constantly 

















































































CARBONATE OF POTASS A. 


121 


stirred. When the liquor has been reduced to about two-thirds of its bulk, with a density 
of 33 0 B. = 1*298 sp. gr., it is run into the crystallising vessels. The mass remaining in 
the evaporating pan, consisting of 60 to 65 per cent, common salt, 6 per cent, chloride of 
potassium, and 30 percent, double sulphates of magnesium and potassium, is used as manure. 
Steam-heated evaporating pans, represented in Big. 60, are employed by some manu¬ 
facturers ; the four steam-tubes, t, are placed parallel to the sides of the vessel, and open in 
u, the waste steam being carried off by the tube t'. As might be expected, the concen¬ 
tration of the liquor is more rapidly performed by means of steam, but the crystallisation 
of the second crop of salt is poorer, yielding only 50 to 60 per cent, chloride of potassium, 
and requiring two to three washings to accumulate 80 per cent, pure potassium salt. 

4 and 5. The second mother-liquor is again concentrated by evaporation to 35 0 B. 
= sp. gr. 1 *299, yielding a saline mass similar to the residue of the first evaporation, and 
to which it is added and used as a manure. On being submitted to crystallisation, this 
last liquor yields artificial camallite, treated as the salt obtained from the native deposit, 
giving, however, with less labour 80 to 90 per cent, chloride of potassium. The chloride 
of potassium, after washing with pure water, is dried either in rooms heated by steam, or 
in a moderately-heated reverberatory furnace. The dry salt is then packed in casks, 
each containing about 500 kilos. 

13 . The preparation of sulphate of potassa may be effected:— 

a. From chloride of potassium and sulphuric acid. 

b. By Longmaid’s (see Soda Manufacture) roasting process, viz., the calcina¬ 

tion of chloride of potassium and sulphuret of iron, and in metallurgical 
processes where chloride of potassium is used instead of chloride of sodium. 

c. From chloride of potassium and kieserite. 

d. From kainite. 

The conversion of chloride of potassium into the sulphate of potassa by double 
decomposition with sulphate of soda is not practicable on tbe large scale, as the two salts 
have a tendency to form double salts; therefore, the methods a and b are practically 
available only under certain peculiar conditions. A small quantity of chloride of potassium, 
obtained in Scotland as a by-product of the preparation of kelp, is converted into sulphate 
of potassa by the means in use for the manufacture of soda {quod vide). The leading 
points in the manufacture of sulphate of potassa by the aid of the sulphuric acid contained 
m kieserite are the following:—First schoenite and camallite are prepared by dissolving 
chloride of potassium and kieserite in boiling water, and crystallising the solution thus 
obtained:— 

4 mols. Kieserite ’l (2 mols. Schoemte. 

3 mols. Chloride of potassium J \ I mol. Camallite. 

The schoenite and artificial camallite are separated by crystallisation, and the former 
decomposed by chloride of potassium :— 

4 mols. Schoenite 
3 mols. Chloride of potassium 

The sulphate of potassa crystallises first, and is simply purified by washing with water. 
As kainite is found in very large quantities among the saline deposits near Stassfurt, it is 
also used for the preparation of sulphate of potassa; by a simple washing with water, 
the chloride of magnesium contained in the kainite is removed, and the salt thus converted 
into schoenite:— 

t • ) — Schoenite. 

—Chloride of magnesium J 

The schoenite is then employed in the manufacture of sulphate of potassa by being 
treated with chloride of potassium; the sulphate of potassa thus obtained is used either 
in alum or potassa manufacture, or as a potassa manure. 

y . Preparation of Carbonate of Potassa or Mineral Potash.—'Very many sug¬ 
gestions have been made for converting by simple means chloride of potassium and 
sulphate of potassa into carbonate of potassa, industrially known as potash; but 
most of the plans proposed are unfit for use on the large scale, and even the method 
adopted by Leblanc for soda manufacture has not been in every case successful 
when applied to the production of chloride of potassium. At Kalk, on the opposite 


4 mols. 01 Sulphate 01 potassa. 
2 mols. of Schoenite. 

1 mol. of Camallite. 


122 


CHEMICAL TECHNOLOGY. 


bank of the Rhine to Cologne, a process, said to he based upon Leblanc’s method, 
is successfully in operation, but the real arrangements are carefully kept secret, no 
one being allowed to visit the works; however, it is stated that sulphate of potassa 
containing schoenite is mixed with chalk and small coals, and calcined, the cal¬ 
cined mass being lixiviated when cool, and yielding carbonate of potassa in 
solution, and a residue of sulphide of calcium. 

Mode of^ob^ning potassa n. Potassa-salts from feldspar. It has been found by the 
analysis of minerals entering largely into the constitution of rocks, that potassa is 
present in considerable quantities. The following may be taken as instances :— 
Orthoclase, or potash feldspar, contains from io to 16 per cent.; potash mica, 8 to 
io per cent.; trachyte, glaukonite, phonolithe, 7 to 8 per cent.; porphyry, granu- 
lite, and mica schist, 6 to 7 per cent.; granite, syenite, gneiss, 5 to 6 per cent.; 
dolerite, basalt, kaolin, and clay, 1 to 2 per cent. 

Before the discovery of the potassa-salt deposits at Stassfurt, Kalucz, and elsewhere, 
there were many suggestions made as to the obtaining of the potassa on the large scale ; 
but at present this branch of industry lies dormant, notwithstanding the theoretical value 
of Mr. Ward’s (1857) suggestion that feldspar should be mixed with fluor-spar, both finely 
pulverised—the fluorine being equal in quantity to the potassa contained in the fluor-spar 
—a mixture of chalk and hydrate of lime added, the mass ignited in kilns or gas-retorts, 
and finally treated with water to yield caustic potassa and a residue, which, after another 
calcination, yields excellent hydraulic lime. 

Pota s S eaiwaten° m HI* Dr. Usiglio found that the water of the Mediterranean contains 
in 10,000 parts by weight 5*05 parts of potassa ; and after the removal of the more 
readily crystallisable salts left by the spontaneous evaporation of the water by the 
sun’s heat, this natural mother-liquor is applied to the preparation of potassa- 
salts, according to the following method :— 

The process now in use near Aigues Mortes, and other localities in proximity to the 
Mediterranean, was invented by Professor Balard, the discoverer of bromine, and yields 
from 1 cub. met. of mother-liquor, equal to about 75 cub. mets. of sea-water, at 28° B. 
— 1*226 sp. gr. 40 kilos, of sulphate of soda, 120 kilos, of refined common salt, and 
10 kilos, of chloride of potassium. It has been found, however, that this method is rather 
costly, and the mother-liquor is generally left to spontaneous evaporation, yielding the 
three following kinds of salt:— a. The first salt separated from a liquor of 32 0 B. 
r= 1*266 sp. gr., only impure common salt. b. The second salt separated from a liquor, 
32 0 to 35° B. z=: 1.266 to 1*299 8 P* 8 T -> consisting of equal parts of common salt and Epsom- 
salt, and termed mixed salt. c. The third salt, 35 0 and 37 0 B. 1*299 to 1*321 sp. gr., 
termed summersalt. The second salt having been dissolved in fresh cold water, the 
solution is placed in Carre’s ice-making machine, and yields sulphate of soda by an 
exchange of its constituents. The third salt is dissolved in boiling water, yielding on 
cooling half its potassa as kainite. The mother-liquor, containing camallite, common 
salt, and bitter, or Epsom-salt, yields sulphate of soda, and, when treated with chloride 
of magnesium, all its potassa as camallite, which, by being washed with water, yields 
chloride of potassium. In this way it has become possible to obtain 45 per cent, of the 
potassa of the mother-liquor as chloride of potassium, and 55 per cent, of schoenite, which 
is converted into sulphate of potassa. 

Ash“ h of r pTants e TV• The residue left from the ignition of the organic matter, or wood, 
as it is usually termed, of plants, contains those mineral substances which the plant 
has taken from the soil, chiefly potassa, soda, lime, magnesia, small quantities of the 
protoxides of iron and manganese, combined with phosphoric, sulphuric, silicic, and 
carbonic acids, and also with the haloids. These combinations are not, however, the 
same as those existing in the living plant, because the high temperature of the 
ignition has the effect of changing the affinities. Plants growing near the sea gene¬ 
rally contain large quantities of soda, while those inland contain generally more 
potassa. The quantity of ash varies not only for different kinds of plants, but for 
various parts of the same plant, verv succulent plants and the most succulent parts 


CARBONATE OF BOTASSA. 


123 

generally yield the largest quantity of ash; herbs yield more ash than shrubs, 
shrubs more than trees, and the leaves and bark of these more than the wood. It 
is evident that the inorganic matter, chiefly alkaline salts, being contained in the 
juice ot plants in a soluble state, the quantity must of necessity be greatest in the 
juicy and succulent parts. 

Dr. Bottger found the ash of beech-wood to contain— 

21-27 P er cen t. of soluble salts, 

78'73 » » of insoluble salts. 

The soluble salts were found to be— 

Carbonate of potassa .. .. 15-40 per cent. 

Sulphate of potassa .. .. 2-27 „ „ 

Carbonate of soda. 5-40 

Chloride of sodium.0-20 / ” 


21-27 P er cent. 


The value of an ash for the manufacture of potash is chiefly dependent, in the first 
place, upon the quantity of potassic carbonate it will yield, upon the abundance of the 
wood or other vegetable product, and the cost of labour. The undermentioned woods 
yield, on an average, for 1000 parts, the following quantities of potash 


Pine . 

Poplar. 

Beech. 

Oak .. .... 

Box-wood. 

Willow. 

Elm . 

Wheat-straw . 

Bark from oak-knots.. ... 

Cotton-grass (Eriophorum vaginatum) 

Rushes. 

Vine-wood. 

Barley-straw . 

According to M. Hoss, 1000 parts 


0-45 Beech-bark.6-oo 

0-75 Dried ferns.6-26 

1 -45 Stems of maize (Indian com) .. .. 17-50 

1- 53 Bean-straw.20-00 

2- 26 Sunflower-stems.20-00 

2*85 Nettles.25*03 

3- 90 Vetch-straw .27-50 

3- 90 Thistles .35-37 

4- 20 Dried wheat-plant previous to 

5- 00 blooming.47-00 

5-08 Wormwood.73'0o 

5-50 Fumitory.79-00 

5-80 

of the following kinds of wood yield— 


Ash. Potash. Ash. 

Pine.3-40 0-45 Willow .28-0 

Beech . 5-80 1-27 Vine.34-0 

Ash.12-20 0-74 Dried ferns .. .. 36-4 

Oak.13-50 1-50 Wormwood .. .. 97*4 

Elm.25-50 3-90 Fumitory.219-0 


Potash. 

2-85 

570 

4*25 

73-00 

79-90 


The preparation of potash from vegetable matter is effected in three operations, viz.:— 

a. The lixiviation of the ash. 

b. The boiling down of the crude liquor. 

c. The calcination of the crude potash. 

The combustion of the vegetable matter should be so conducted as to prevent its 
becoming too violent, and giving rise to the ccmbustion of some of the reduced potassa- 
salt; nor should too strong- a current of air be admitted for fear of the ash being mechani¬ 
cally carried off. A distinction is made abroad—no potash from wood or other vegetable 
matter being produced in the United kingdom, nor wood used as fuel in sufficient quantities 
to yield ash for the preparation of potash—between the ash obtained by the combustion of 
the refuse wood of forests and the ash from wood used as fuel, the former being termed 
forest- and the latter yh^-ash. As ash from other fuel than wood may be mixed with fuel- 
ash, a sample may be roughly tested by lixiviation, and the density of the liquor taken by 
the areometer, the higher the specific gravity the larger the quantity of soluble salts. For¬ 
merly the forest ash was purposely prepared, and sold to potash-boilers. There is still 
known in Eastern Prussia and Sweden a material termed okras or ochras , holding a position 
intermediate to crude ash and potash. 

a. The lixiviation of the ash effects the separation of the soluble from the insoluble saline 
matter, the former amounting to about 25 to 30 per cent, of the entire weight of the ash. 
The operation is carried on in wooden vessels shaped like an inverted truncated cone, and 
provided with a perforated false bottom, which is covered -with straw; in the real bottom 
a tap is fixed for removing the liquor. If the lixiviation is systematically carried on, 


































124 


CHEMICAL TECHNOLOGY . 


several of these vessels are placed together, forming what is termed a battery, and under 
each a tank to receive the liquor. The ash to be lixiviated is first separated from the coarse 
particles of charcoal, next put into a small square water-tight wooden box, and thoroughly 
saturated with water for at least twenty-four hours. By this proceeding the lixiviation is 
greatly assisted, and the silicate of potassa to some extent decomposed by the action of 
the carbonic acid of the atmosphere. The next step is to transfer the wet ash to the 
lixiviation vessel, care being taken to press it tightly down on to the false bottom; cold 
water is then poured in, until the liquor begins to run off at the taps left open for that 
purpose. The liquor which runs off, after the water has remained some little time in 
contact with the ash, is found to contain about 30 per cent, of soluble salts, afterwards 
decreasing to about 10 per cent., when hot water is employed to complete the lixiviation. 
The insoluble residue left in the lixiviation-tub is of value as a manure, on account of the 
phosphate of lime it contains, and is also used in making green bottle-glass, and for 
building up saltpetre-beds. 

b. Boiling down the liquor. The liquor obtained by lixiviation is of a browm colour, 
owing to organic matter, humin or ulmine, "which the carbonate of potassa has dissolved 
from the small chips of imperfectly burnt charcoal. The evaporation is carried on in large 
shallow iron pans, fresh liquor being from time to time added, and the operation continued 
until a sample of the hot concentrated liquor exhibits on cooling a crystalline solid mass. 
"When this point is reached the fire is gradually extinguished, and as soon as the contents 
of the pan are sufficiently cold to handle, the solid salt mass is broken up; its colour is a deep 
brown. This crude product, containing about 6 per cent, of water, is known in the trade as 
crude, or lump-potash. It is evident that this method of boiling down may cause consider¬ 
able damage to the iron pans, therefore in many instances the operation is conducted in a 
somewhat different manner. The liquid is kept stirred with iron rakes, and the salt, instead 
of forming a hard solid mass, is obtained as a granular powder, containing upwards of 12 
per cent, water. Some manufacturers first separate the sulphate of potash, "which, being 
less soluble, crystallises before the carbonate, a deliquescent salt, is separated from the 
liquor; in most cases, however, this operation is only carried on where the sulphate of 
potash is required for alum-making. The pearl-ash or potash of commerce almost invari¬ 
ably contains a large quantity of sulphate of potash. 

c. In order to expel all the water and to destroy the organic matter, the saline mass is 
calcined, and as this operation was formerly performed in cast-iron pots, the salt has 
obtained the name of potash. A calcining furnace, Big. 62, is now used, distinguished 
from ordinary reverberatory furnaces by being provided with a double fire-place. These 


Big. 62. 



hearths, one of which is exhibited in section at a, Big. 62, are placed at right angles to 
each other, and the flame and smoke meeting in the centre of the furnace, pass off at 0 , 
the work-hole, into the chimney, k. "Wood is used as fuel, and as the heating of the 
furnaces requires a very large quantity, they are only in use when a sufficient supply of 
crude potash is ready for being operated upon. The furnace is thoroughly heated in about 
five to six hours, care being taken to fire gradually, and to bring the interior of the furnace 
to nearly red heat, so that the vapour due to the combustion of the wood may not condense 
inside the furnace, but be carried off by the flue. The crude potash, broken up to egg-size 
lumps, is next placed in such quantities at a time as may suit the size of the calcining- 
hearth ; for instance, if the hearth is roomed to contain 3 cwts., that quantity is divided 
into three portions and put in at intervals of a few minutes. The first effect of the heat 
is to expel the water from the potash, the escape of the steam being promoted by stirring 






































CARBONATE OF FOTASSA. 


125 

the mass with iron rakes. In about an hour all the water is driven off, and the mass 
takes fire in consequence of the burning- of the organic matter, the salt at first being 
blackened, but g-radually becoming white as the carbon bums off. As soon as this stage 
is reached, the potash is removed to the cooling-hearth, and when cold, packed in well- 
made wooden-casks, which, as this salt is very hygroscopic, are rendered as air-tight as 
possible. The heat of the furnace has to be well regulated to prevent the potash 
becoming semi-fused, in which case it would attack the siliceous matter of the fire¬ 
bricks ; the workmen from time to time take a small sample to test how far the calcination 
is complete. 

We, in Europe, obtain a considerable quantity of potash from the United States and 
Canada, known as American potash, of which there are three different kinds, viz.:—• 
1. Potash prepared as described. 2. Pearl-ash, or potash, purified by lixiviation, decan¬ 
tation from sediment, boiling down, and the calcination of the salt thus obtained. 
3. Stone-ash, a mixture of uncalcined potash (potassic carbonate), and caustic potash 
obtained by treating the crude potash liquor with caustic lime, and boiling down the mass 
to dryness; this article has the appearance of the crude caustic soda of this country, but 
is usually coloured red by oxide of iron; the lumps, stone-hard, are from 6 to 10 centims. 
in thickness, and contain upwards of 50 per cent, caustic potash. The under-mentioned 
analyses exhibit the varying composition of the potash of commerce:—Sample 1 is 
from Kasan (Russia) ; analyst, M. Hermann. 2. Tuscany. 3 and 4—the latter of a 
reddish colour—from North America. 5. Russia. 6. Yosges (France); analyst of 2, 3, 4, 
5, and 6, M. Pesier. 7 . Helmstedt, in Brunswick; analyst, M. Limpricht. 8. Russia; 
analyst, M. Bastelaer. 



1. 

2. 

3 - 

A. 

5 - 

6. 

7 - 

8. 

Carbonate of potash .. 

78-0 

74-1 

71-4 

68-o 

69-9 

38-6 

49-0 

50-84 

Carbonate of soda 

— 

3-0 

2*3 

5-8 

31 

4-2 

— 

12-14 

Sulphate of potash 

17-0 

135 

14-4 

I5-3 

14-1 

38-8 

40-5 

I7-44 

Chloride of potassium.. 

3-0 

o *9 

3-6 

8-i 

2T 

9-1 

10*0 

5-80 

Water. 

— 

7-2 

4'5 

— 

8-8 

5’3 

—- 

io-i8 

Insoluble residue .. 

0*2 

O-I 

2-7 

2-3 

2-3 

3-8 

— 

3-60 


The calcined potash varies in colour, being either white, pearl-grey, or tinged with 
yellow, red, or blue. The red colour is due to oxide of iron, the blue to the manganates of 
potash, a hard, light porous, non-crystalline mass, never entirely soluble in water. For¬ 
merly, a large quantity of potash was obtained from the residues of wine-making, and 
called vinasse, the semi-liquid left after the alcohol has been distilled from the wine, and 
containing, among other substances, argol, or crude bitartrate of potash; it was boiled 
down, and next calcined, yielding a kilo, of very good potash for every hectolitre of vinasse. 
The large quantity of potash thus formerly produced may be judged from the fact that 19 
of the wine-producing departments of France, those only where large quantities of wine 
are converted into alcohol, technically termed trots six and cinq huit, yield annually about 
9 to 10 million hectolitres of vinasse, at the present time employed for the preparation on 
the large scale of cream of tartar, glycerine, and tartaric acid. 

Potash from Molasses. Y. Of late years, the manufacture of potash salts from the 
vinasse left after the distillation of fermented beet-root molasses has been added 
as a new branch of industry by M. Dubrunfaut, and introduced into Germany by 
M. Yarnhagen, in the year 1840, at Mucrena, Prussian Saxony. 

Beet-root, on being subjected to ignition, yields an ash containing a large percentage of 
potash, a fact first observed in the early part of this century by M. Mathieu de Dombasle, 
a celebrated French agriculturist, who discovered that 100 kilos, of dried beet-root leaves 
weld io - 5 kilos, of ash, containing 5-1 kilos of potash; but this author’s idea that the 
leaves might be cut off and gathered for the purpose of potash manufacture, proved 
erroneous, in so far that the growth of the roots was greatly impeded. After the publica¬ 
tion of M. Dubrunfaut’s researches on this subject, in 1838, the vinasse of the beet-root 
molasses distillation was evaporated to dryness, next calcined, and the calcined mass refined 
for the production of potash and other salts of that base, an industry which has obtained 
a great development, as may be judged from the fact that the quantity of these materials 
produced on the European continent in 1865 amounted to 240,000 cwts. 

The reader who desires details on this subject is referred to the work, “ On the Manu¬ 
facture of Beet-Root Sug-ar in England and Ireland,” by Win. Crookes, F.R.S., &c., p. 25c 
et seq. 





126 


CHEMICAL TECHNOLOGY. 


The molasses from beet-root sugar consists, previous to the fermentation and 
distillation, of the undermentioned substances, as recorded by the several analysts 
whose names are subjoined:— 



Brunner. 

Fricke. 

Lunge. 

Heidenpriern. 

Water . 

15*2 

18*0 

18*5 

19*0 

197 

Sugar . 

49*0 

48*0 

507 

46*9 

49*8 

Salts and organic substances 

35-8 

34 '° 

30*8 

34 ’ 1 

30*5 


The following analyses by M. Heidenpriern exhibit the average composition of the 


ashes of molasses:— 

1. 

2. 

3 - 

Potassa . 

5172 

47*67 

50‘38 

Soda. 

8*00 

11 ‘43 

8*29 

Lime. 

5*04 

3*60 

3*12 

Magnesia. 

0*18 

0*10 

0*18 

Carbonic acid. 

28*90 

27*94 

28*70 

The remainder of the 100 parts consists 

of phosphoric and silicic acids, chlorine, 

oxide of iron, &c. The quantity of ash amounts to 10 or 12 per 

cent. According to 

Dubrunfaut the alkalimetrical degree of the ash of beet-root sugar molasses is a 


constant, as the ash obtained from ioo grms. of molasses neutralises on an average 
7 grms. of sulphuric acid (H 2 S 0 4 ). 

The molasses is generally treated in the following manner:—It is first diluted with 
either water or vinasse to 8° or ii° B=1*056 or 1*078 sp. gr., and mixed with 0*5 to 
1*5 per cent, of a pure mineral acid, the object of this addition being not simply the 
neutralisation of the alkali, but also the conversion of dextrine and such unferment- 
able sugar into fermentable sugar. Formerly, sulphuric acid was used, but upon the 
recommendation of M. Wurtz, hydrochloric acid is now generally employed, the 
advantage being the formation of readily soluble chlorides, instead of comparative 
insoluble alkaline sulphurets, the action of the organicmatter present in the molasses. 

The diluted molasses is next mixed with yeast, left to ferment, and the alcohol 
distilled off; the residue is a liquid of about 4 0 B. density [= 1 *027 sp. gr.] containing 
undecomposed yeast, ammoniacal salts, various organic substances, and all the 
inorganic salts of the beet-root juice. The potassa is present in this liquid as nitrate 
chiefly, although by the addition of hydrochloric acid a portion of this salt is decom¬ 
posed, red nitrous fumes sometimes being seen in the fermentation room. Evrard 
suggests that the saltpetre should be separated from the beet-root molasses by evapo¬ 
ration, and further purified by the aid of the centrifugal machine. The acidity of the 
vinasse is neutralised by chalk, and afterwards it is evaporated to dryness in an iron 
vessel, the total length of which is 20*3 metres, by an average width of 1*6 metre, 
extended at the top to 2 metres, the depth being 0*34 metre. The vessel is made of 
stout boiler plate, strengthened by stays and angle irons, and is divided into two 
divisions, the larger of which has a length of 14*3 metres, and is the real evaporating 
pan, while the other is used as a calcining furnace, and covered with an arch of fire¬ 
bricks o*6 metre high. The fire-place is 1*3 metre wide, and the fire-box has a 
surface of 3*3 square metres. The evaporation is effected by surface heating, that 
is to say, the flame and hot gases from the burning fuel, after passing across the fire¬ 
bridge are conducted over the surface of the vinasse, the calcining pan being nearest 
to the fire, while the evaporating pan is at its other extremity in contact with the 







CARBONATE OF TO TASS A. 


127 


flue or chimney. The vinasse, having been run off from the still, is kept in cisterns, 
from which it is forced by means of a pump into a reservoir so placed as to admit of 
the liquid running in a constant stream into the evaporating pan. At a first operation 
both the evaporating and the calcining pan are filled with vinasse, but afterwards 
the latter is filled regularly with concentrated thick liquor, which is simply carbon¬ 
ised, the organic matter being only destroyed. 

The daily average of carbonised vinasse is about 5 to 5^ cwts. The composition 
of that substance may be gleaned from the following approximate analysis:—• 
Insoluble matter — 23 per cent 

Sulphate of potassa = 11*07 ,, 

Chloride of potassium =z ii*6i ,, 

Carbonate of potassa =31-40 ,, 

Carbonate of soda =23*26 ,, 

Silicic acid and hyposulphite of potassa — traces ,, 


99-34 >> 

In Germany , the calcined vinasse is generally sold to saltpetre manufacturers, but 
in Belgium and Prance this material is calcined, lixiviated, and the salts it contains 
separately obtained. Por this purpose the vinasse is first evaporated to 38° or 40° B. 
(1*33 to 1*35 sp. gr.), and next carbonised and calcined in a furnace constructed 
as exhibited in Pig. 63. v is a reservoir containing the concentrated vinasse, which 
by means of a tube is gradually run into the furnace, of which G is the fire-place, m 
the calcination space, destined to contain the concentrated or carbonised vinasse, 


Pm. 63. 



which is evaporated to dryness and calcined in m'; a door is fitted to each com¬ 
partment, and at r, the end of the furnace opposite to the fire-place. The air required 
for the calcination is admitted partly through the ash-pit, partly through the 
openings, B, in the brickwork. The thickish liquid vinasse admitted into m' is 
constantly stirred, and, as soon as it is quite dry, it is shovelled across the brickwork 
ridge, A', into the calcining space, M, care being taken to again fill m' with concen¬ 
trated vinasse. The organic matter of the saline mass soon takes fire, emittins 
noxious fumes. The calcination is greatly aided by the access of air at B, and also 
to some extent by the nitrate of potassa present. The temperature has to be regulated 
to prevent the salts becoming fused and forming a hard compact mass, in which caso 
the sulphate of potassa would be reduced to sulphuret of potassium, a salt which 

























128 


CHEMICAL TECHNOLOGY. 


could not be removed. The calcined vinasse, technically termed salin , contains, 
•when removed from the furnace, io to 25 per cent, of insoluble substances, viz., 
carbonate and phosphate of lime, more or less charcoal, and in addition 3 to 4 per 
cent, moisture; the remainder consists of carbonates of potash and soda, sulphate of 
potassa, chloride of potassium, and sometimes cyanide of potassium in considerable 
quantity. The relative quantities of potassa and soda are, of course, not at all 
constant, but vary according to the soil on which the beets have grown; it has been 
observed in Prance that the molasses obtained from beets grown in the Departement 
du Nord are less rich in potassa than those grown in the Departements de l’Oise et 
de la Somme. The average composition of the salin is:— 

7 to 12 per cent, of sulphate of potassa. 

18 to 20 ,, of carbonate of soda. 

17 to 22 ,, of chloride of potassium. 

30 to 35 ,, of carbonate of potassa. 

The complete composition of the salin may be gathered from the following 
tabulated results:— 



a. 

b. 

c. 

d. 

Water and insoluble matter.. 

.. 26*22 

19*82 

I 7’47 

I 3‘36 

Sulphate of potassa 

.. iz ’95 

9*88 

2 ‘55 

3*22 

Chloride of potassium .. 

.. 15-87 

20*59 

18 ‘45 

l6*62 

Chloride of rubidium .. 

.. 0*13 

0*15 

0*18 

021 

Carbonate of soda. 

• • 25*52 

19*66 

19*22 

i 6*54 

Carbonate of potassa .. 


29*90 

42*13 

50*05 


100*00 

100*00 

100*00 

100*00 


The method of separating the soluble salts from each other, invented by M. Kuhl- 
mann, is generally executed as follows:—The saline mass is first broken up and 
granulated by the aid of grooved iron rollers, after which it is placed in lixiviation- 
tanks, each containing 26*4 cwts., and arranged precisely in the same manner as 
those in use in soda works. The liquor tapped from the tanks has a sp. gr. of 1 *229 
(= 27°B.); the insoluble resicfue is used as manure. The liquor having been col¬ 
lected in a large reservoir, capable of containing some 210 hectolitres, is concentrated 
by waste heat (abgangiger wdrme ) to a density of 1-26 ( = 30°B.); on cooling, the 
greater part of the sulphate of potassa crystallises, and is removed, care being taken 
to wash off the adhering mother-liquor. The sulphate thus obtained contains 80 per 
cent, pure potassic sulphate, the rest being carbonate of potassa and organic matter: 
this material is converted into potash by Leblanc’s process. The liquor at 30° B. is 
next poured into evaporating-pans, each capable of containing 90 hectolitres, and 
concentrated by means of heat and a steam pressure of 3 atmospheres (= 45 lbs. to 
the square inch) to a density of 42 0 B. (= 1*408). By this operation a mixture of 
carbonate of soda and sulphate of potassa is separated, which frequently exhibits 
30 alkalimetrical degrees; the liquor is transferred from the evaporating-pans tc 
crystallising vessels, in which it is cooled down to not less than 30°. If, by careless¬ 
ness, the temperature should fall below 30°, the chloride of potassium crystals 
become mixed with a layer of carbonate of soda. The liquor at a temperature of 
30°, and having a density of 42 0 B., is again transferred to evaporating-pans, each 
capable of containing 20 hectolitres, and evaporated 

In winter to a sp. gr. of 1*494 (=4 8 ° B.), and 
In summer to a sp. gr. of 1*51 (=r 49* B.) 











CARBONATE OF TOT ASS A. 


129 


By this operation sodic carbonate separates, the first and purer portions of which 
are of 82 alkolimetrical degrees, and the last of 50° only. After the separation of 
the salt, the remaining liquor is poured into small crystallising vessels, each capable 
of holding hectolitres, and having been left standing for some time, yields in 
each vessel about 130 kilos, of a crystalline salt, mainly composed according to the 
formula (K 2 C 0 3 + Na 2 C 0 3 -f- i2H 2 0). The remaining mother-liquor, when evapo¬ 
rated to dryness and calcined, yields a semi-refined potash, tinged with red by oxide 
of iron. This product is again lixiviated with water, and the liquor having been 
concentrated to 1*51 to 1*525 sp. gr. (= 49 0 to 50° B.), deposits a large quantity of 
sulphate of potassa and carbonate of soda. The mother-liquor having been again 
evaporated and calcined, yields a potash consisting in 100 parts of— 

Carbonate of potassa .. .. ..91*5 

Carbonate of soda .. .. .. 5*5 

Chloride of potassium and sulphate of potassa .. .. 3*0 


IGO’O 

The carbonate of soda possessing a strength of 80 to 85 alkalimetrical degrees is 
refined by being washed with a very concentrated aqueous solution of sodic carbonate, 
and thus brought to a strength of fully 90 alkalimetrical degrees. 

The sulphate of potassa, chloride of potassium, and the double salt of the two 
carbonates, are purified and re-crystallised. The following analyses exhibit the 
composition of refined potash obtained from beet-root sugar molasses :— 



a. 

b. 

c. 

Carbonate of potassa 

■■ 8873 

94*39 

89*3 

Carbonate of soda. 


traces 

5*6 

Sulphate of potassa. 

2*27 

0*28 

2*2 

Chloride of potassium .. 

I'OO 

2*40 

i *5 

Iodide of potassium 


0*11 

— 

Water .. .: . 

• • i -39 

1*76 

— 

Insoluble substances 

0*12 

— 

— 


a. 

b. 

c. 

d. 

e. 

53*9 

79 *o 

76*0 

43 *o 

32*9 

23*1 

14*3 

16-3 

17*0 

i 8*5 

2-9 

3*9 

1*19 

4*7 

14*0 

19*6 

2*8 

4*16 

i8*o 

16*0 


a and b are from Waghausel in Baden ; c is doubly refined French potash. The 
crude potash from beet-root sugar works, a product not to be confused with salin, 
is composed as follows:— 

Carbonate of potassa . 

Carbonate of soda 

Sulphate of potassa . 

Chloride of potassium. 
a is French product; b, from Yalenciennes ; c, from Paris; d, Belgian ; e, from 
Magdeburg, Prussia. 

Potassa Saits from yj. Potassa salts are obtained in ^ large quantities from various 
sea-weeds, as a by-product of the manufacture of bromine and iodine. The three 
following methods are employed for this purpose 

ci. The old calcination method, consisting in a complete reduction of the weeds to 
ash, and the methodical lixiviation of that product, so as to obtain various salts by 

crystallisation. 

b. The carbonisation, or Stanford’s method, consisting in the dry distillation of 
the weeds to convert them into a carbonaceous mass, afterwards lixiviated, while 
10 










130 


CHEMICAL TECHNOLOGY. 


products are simultaneously obtained, tbe sale of which considerably lessens the cost 
of the preparation of the potassa salts. 

c. A third mode of treatment, that of Kemp and Wallace, consisting in boiling the 
weeds with water, evaporating the solution, and carefully incinerating the residue. 

The oldest method is still the most generally employed in Erance, on the coasts 
of Brittany and Lower Normandy, especially in the neighbourhood of Brest and 
Cherbourg, and in Scotland and Ireland. 

The process is mainly conducted as follows:—After drying in the air, the plants are 
incinerated, the result of which is the formation of a black semi-fused mass,- which 
in Erance is termed Varech or Vraie, and in England and Scotland is known as Jcelp. 
A distinction is made between the kelp obtained by the incineration of the weeds, 
Fucus serratus and Fucus nodosus, found on rocks near the sea coast, and the kelp 
obtained from the plant botanically known as Laminaria digitata , thrown upon the 
coast during the storms. The latter is richer in potassa salts, but contains much 
less iodine; it is found plentifully on the western coast of Scotland and Ireland, 
while on the eastern coast of the British Isles the other weed is the chief source of 
kelp, having an average composition of:— 


Insoluble matters.57‘ooo 

Sulphate of soda.10*203 

Chloride of potassium. 13*476 

Chloride of sodium . 16*018 

Iodine .. .. 0 600 

Other salts . 2*703 


100*000 

The best kelp met with in commerce is tnat from the island of Bathlin, the value 
at Glasgow amounting to £7 10s. to £10 10s. per ton of 22^ cwts.; while Galway kelp 
is valued at only £2 or £3 per ton, owing to the large quantity of salt it contains. 


22 tons of moist sea-weed yield:— 

Medium kelp. 1 ton. 

Chloride of potassium.5 to 6 cwts. 

Sulphate of potassa .. . 3 cwts. 


The Scotch mode of treating kelp is briefly the following:—The material is 
first broken into small lumps, and put in large iron cauldrons, hot water being 
added to exhaust all the soluble matter. This operation follows the method of 
the manufacture of soda from common salt, to be presently considered. The water is 
first made to act upon nearly exhausted kelp, and at last with quite fresh kelp, 
until a liquid is produced marking 36° to 40° Twaddle = i* 18 to 1*20 sp. gr. The 
insoluble residue contains chiefly silica, sand, carbonate of lime, carbonate of 
magnesia, its sulphates and phosphates, and particles of charcoal, and is used for 
bottle-glass manufacture. The liquor from the kelp is evaporated in large cast-iron 
semi-globular cauldrons by the direct action of a coal fire, and contains chiefly 
chloride of potassium, a comparatively small quantity of chloride of sodium, sulphate 
and carbonate of potassa, carbonate of soda, some iodide of potassium, sulphuret ol 
potassium, and dithionite of potassium and sodium. The mode of separating these 
salts from each other is based upon their varying solubility in water, and is therefore 
conducted by alternate evaporation and cooling. As the sulphate -of potassa is 












CARBONATE OF TO TASS A. 


135 

the least soluble, it falls to the bottom of the cauldron during the first evaporation, 
and is collected by the workmen by means of perforated ladles, and brought into the 
trade as plate sulpha,te. After this salt has been collected the liquid is run 
into coolers, in which the greater bulk of the chloride of potassium crystallises ; the 
mother-liquor from these crystals is again transferred to the evaporator, and by 
the continued application of heat, and consequent concentration of the liquid, the 
common salt is separated. It should be borne in mind that common salt is scarcely 
more soluble in hot than in cold water, while the solubility of most other salts 
is greatly increased by a higher temperature; it is therefore possible to push 
the evaporation and concentration to the point of incipient precipitation of the 
chloride of potassium, the common salt being then ladled out of the cauldron, 
and the liquid again run into the coolers in order to obtain another deposit of 
chloride of potassium, always more or less contaminated with common salt. This 
operation is repeated four times; the first crop of chloride of potassium contains 
from 86 to 90 per cent, of this salt, the remainder is chiefly sulphate of potassa; the 
second and third crop yield a very pure salt, 96 to 98 per cent, of chloride of 
potassium; the fourth crop contains some sulphate of soda mixed with the chloride 
of potassium. The liquor left after the fourth crystallisation having a sp. gr. = 1 '33 to 
1-38 = 66° to 76° Twad., and containing among other compounds sulphate of soda, 
sulphurets and hyposulphites of the alkalies, alkaline carbonates, and iodide of 
potassium, is not submitted to further evaporation, but having been poured into 
shallow vessels placed in the open air is mixed with dilute sulphuric acid, sulphu¬ 
retted hydrogen and carbonic acid gases being largely evolved, while in consequence 
of the decomposition of the polysulphurets and hyposulphites, a thick foam of pure 
sulphur appears on the surface of the liquid. This sulphur is ladled off, and after 
having been washed on filters and dried, is sold. Almost as soon as the evolution of 
gas ceases, there is added to the liquid more sulphuric acid and some manganese, 
and the mixture treated for the preparation of iodine (quod vide). In order to guard 
against loss of valuable substances by volatilisation during the crude and imperfect 
mode of incineration, it has been tried to simply carbonise the weeds (Stanford’s 
method). The weeds are first dried and strongly pressed into the shape of peat 
blocks; these are submitted to dry distillation in retorts arranged similarly to those 
in gas-works. The products of the dry distillation collected in the usual manner 
contain in 100 parts of fresh weed:— 

68*5 to 73*5 parts of Ammoniacal liquor, 

4-0 „ Tar, 

7*0 to 7*5 ,, Carbonised weed, or coke-weed, 

2*0 to 3*5 ,, Illuminating gas. 

The coke contains 33 per cent, carbon, the remainder consisting of alkaline and 
earthy salts; the volatile products of the distillation are treated for paraffin, 
photogen, acetic acid, and ammoniacal salts, the gas being used for lighting 
purposes. Although Mr. Stanford’s mode of treatment is undoubtedly rational, 
there are difficulties in its practical execution which have prevented its adoption in 
Scotland as well as in Prance. The quantity of potash salts obtained from sea¬ 
weeds in the year 1865 amounted, according to M. Joulin, to a total of 2,700,000 
kilos., of which the United Kingdom produced 1,200,000 kilos., the remainder 
being produced by Prance. 

Since the production of chloride of potassium at Stassfurt and Kalucz has 


CHEMICAL TECHNOLOGY. 


(32 

become so extensive, the production of potassa salts from sea-weeds is of little 
consequence. 

Potassa Saits from Suint. "VTI. The fact is well known that sheep while browsing 

abstract a considerable amount of potassa, which, after having passed into the blood 
and tissues, is sweated through the skin, and deposited on the wool as suint. 
Professor Chevreul’s researches have proved that suint constitutes nearly the third 
part of the weight of crude merino wool, while the soluble portion of the suint 
consists of the potassa salts of a fatty acid, potassic sudorate (miniate de potasse). 
According to Messrs. Eeich and TJlbricht, the fatty acids of suint are compounds of 
oleic, stearic, and probably palmitinic acids. The better wool contains more suint 
than the coarser kinds; on an average the quantity of suint amounts to 15 per cent 
of the weight of the fleece. 

Since the year i860, and based upon the researches of MM. Maumene and 
Rogelet, the manufacture of potash salts from the wash-water of the crude wool has 
become, in the centres of the French woollen manufacture (Rheims, Elbceuf, Four- 
mies) an industrial branch. The wash-water is valued according to its degree of 
concentration; 1000 kilos, of wool yielding a liquid which, according to M. Chan - 
delon, has a sp. gr. of 1*03, is paid for at the rate of 5 francs 48 cents.; at a sp. gr. 
of 1*05, at the rate of 10 francs 45 cents.; sp. gr. 1*25, 18 francs 47 cents. The 
liquid is evaporated to dryness, the carbonaceous residue put into gas retorts, and 
heated to redness, the result being the formation of carburetted hydrogen gas and 
ammonia, which having been eliminated, the gas is used for illuminating purposes. 
The coke left in the retorts is lixiviated with water to obtain the soluble salts, 
chloride of potassium, carbonate and sulphate of potassa, which are separated 
from each other by methods already described. 

The residue left after the lixiviation with water contains earthy matter mixed with 
charcoal so very finely divided that it can be used as black paint. According to 
MM. Maumene and Rogelet, a fleece weighing 4 kilos, contains 600 grms. of suint, 
capable of yielding 198 grms. of pure carbonate of potassa; according to M. Fuchs, 
however, the quantity of suint only amounts to 300 grms., containing— 


Sulphate of potassa .. 

. .. 7*5 grms. = 

2*5 per cent. 

Carbonate of potassa .. 

. .. 133-5 » — 

44*5 >> >> 

Chloride of potassium 

. .. 9-0 „ = 

3 '° » >> 

Organic matter. 

. .. 150-0 „ = 

50*0 ,, ,, 


300-0 ,, = 

100.0 


It appears that the woollen industry of Rheims, Elboeuf, and Fourmies consumes 
annually 27 million kilos, of wool, the produce of 6,750,600 sheep. According to 
MM. Maumene and Rogelet this quantity of wool will yield 1,167,750 kilos, of 
potash, representing a money value of £80,000 to £90,000. According to M. P. Havrez, 
at Yerviers, Belgium, suint is more advantageously worked up for the manufacture of 
carbonate of potassa and yellow prussiate of potassa than for carbonate of potassa 
alone. Suint has been recently (1869) chemically investigated by MM. Marker and 
Schulze (see Journ. fiir Prakt. Chemie, vol. 103, pp. 193—208). It is clear that 
the production of potash from the wash-water of sheep’s wool can only be carried out 
in the centres of woollen industry; the sheep-farmers will always do better to return 
the wash-water and potash compounds it contains to the soil from which the animals 
have taken it. In an industrial point of view the extensive importation of foreign 




CARBONATE OF FOTASSA. 


r 33 

trool, especially from Australia and the Cape, is of great importance. In 1868 there 
were imported into the United Kingdom from those countries 63 million kilos, of 
wool, containing one-third of its weight of suint, from which between 7 and 8 kilos, 
pure potash could have been obtained, representing a money value of about £260,000. 

Preparation of Purified Potash.—The potash formerly obtained by the lixiviation 
of wood-ash was mainly a mixture of carbonate, sulphate of potassa, and chloride 
of potassium, the value of each of these salts being of course very different. At the 
present time, in consequence of the production of pure carbonate of potassa from 
vinasse, it has become necessary to treat the crude liquor obtained by the 
lixiviation of wood-ash methodically, so as to obtain the salts separately in as pure 
a state as possible. 

The carbonate of potassa used in chemical and pharmaceutical laboratories was 
formerly obtained by the ignition of cream of tartar or a mixture of that salt with 
nitre, as well as by the ignition of acetate of potassa; at the present time it is pre¬ 
pared by the careful ignition of nitrate of potassa with an excess of charcoal, or by 
the ignition of bi-carbonate of potassa. In England carbonate of potassa is manu¬ 
factured on the large scale, the pure salt being used in the manufacture of flint- 
glass, this glass owing its great superiority and perfect want of colour to the 
application of very pure materials in its manufacture. The preparation is pure 
crystallised carbonate of potassa, containing from 16 to 18 per cent, water, equal to 
somewhat less than 2 molecules, the second molecule being partly expelled by the 
heat applied in the manufacture. This salt is met with in the trade in small 
cubical crystals; the raw material used in its preparation is American pearl-ash, 
which, after having been mixed with sawdust for the purpose of converting the 
caustic alkali and sulphuret of potassium into carbonate of potassa, is ignited and 
fused in a reverberatory furnace, constructed like those used in the manufacture of 
soda. When cold the fused mass is treated with water, and the clear liquor having 
been decanted from the sediment, is evaporated to dryness in a reverberatory furnace; 
the grevish-black mass thus obtained is again lixiviated with water, and the opera¬ 
tion repeated. The white saline mass from the third ignition is again dissolved in 
water, and gently evaporated until the sulphate of potassa crystallises out; the 
mother-liquor left is next evaporated until a sample yields on cooling a salt of the 
composition mentioned above. If this salt is further ignited all the water is 
expelled, and a dry white granular mass left. The specific gravity of carbonate of 
potassa solutions at 150 is, according to Dr. Gerlacb— 


Percentage. 

Sp. gr 

Percentage. 

Sp. gr. 

1 

1*009 

30*000 

1*3010 

2 

1*018 

35 ‘ 000 

i*358o 

4 

1*036 . 

40*000 

1/4180 

5 

1*045 

45*000 

1*4800 

10 

1*092 

50*000 

i *5440 

15 

1*141 

51*000 

i* 557 ° 

20 

1*192 

52*000 

i *5704 

25 

i *245 

52*024 

1 *5707 

caustic Potassa. Preparation of Caustic 

Potassa.—Caustic potassa, hydroxide of 


potassium, KHO, consists in 100 parts of 83*97 of potassa or dry oxide of potassium, 
and 16*03 of water. Caustic potassa is prepared on the large scale in England. 


‘34 


CHEMICAL TECHNOLOGY. 


Tlio raw material for this preparation is always a crude carbonate of potassa 
obtained from chloride of potassium, camallite from Stassfurt, vinasse, or any 
other source. The crude carbonate is lixiviated with water, and the liquor rendered 
caustic with quick-lime. A more advantageous method of preparing caustic 
potassa is to mix sulphate of potassa with limestone and small coal, in sufficiently 
large quantities, and to ignite this mixture in a furnace. The crude material is, 
after cooling, lixiviated with water at 500, yielding at once raw caustic potassa 
liquor, which does not require any further addition of lime. The liquor is put into 
a steam-boiler and evaporated to a sp. gr. — 1*25 ; it is next evaporated to dryness 
in open pans, the foreign salts which separate being removed. Caustic potassa is 
employed for the conversion of soda-saltpetre into potassa-saltpetre, and with 
caustic soda for the manufacture of oxalic acid from sawdust. The following 
reactions, yielding caustic potassa, deserve a brief notice:—1. Decomposition of sul¬ 
phate of potassa by means of caustic baryta. 2. Conversion of chloride of 
potassium into silico-fluoride of potassium, and decomposition of that salt by means 
of caustic lime. 3. Ignition of potassic nitrate with thin sheet-copper. The fol¬ 
lowing table exhibits the quantity of potassa contained in solutions of that 
substance of varying specific gravity :— 


Sp. gr. 

Degrees Baume. 

Percentage of 

1*06 

9 

47 

1*11 

15 

9*5 

I ' I 5 

19 

13*0 

i*i 9 

24 

16*2 

1*23 

28 

I 9‘5 

1*28 

32 

23'4 

i *39 

4 i 

32-4 

1*52 

50 

42*9 

i*6o 

53 

46*7 

i*68 

57 

51-2 


Saltpetre, Nitrate of Potassa, 

(EN 0 3 = 101*2. In 100 parts, 46*5 parts potassa, and 53*5 parts nitric acid.) 
saltpetre. This salt is to some extent a native as well as a chemical product. The 
well-known flocculent substance often observable on walls, especially those of 
stables, is composed in a great measure of nitrates; a similar phenomenon is seen 
in subterranean excavations, and even in many localities the surface of the soil is 
covered with an efflorescent saline deposit, consisting largely of nitrate of potassa. 
These deposits are most common in Spain, Hungary, Egypt, Hindostan, on the 
banks of the Ganges, in Ceylon, and in some parts of South America, as at Tacunga 
in the State of Ecuador; while in Chili and Peru nitrate of soda, so-called Chili • 
saltpetre, is found in very large quantities under a layer of clay, the deposit 
extending over a tract of land some 150 miles in length. 

Occurrence of Native Although native saltpetre is met with under a variety of conditions, 
Saltpetre. they all agree in this particular, that the salt is formed under the 
influence of organic matter. As already stated, the salt covers the soil, forming an 
efflorescence, which increases in abundance, and which if removed has its place supplied 
in a short time. In this manner saltpetre, or nitre as it is sometimes called, is obtained 
from the slimy mud deposited by the inundations of the Ganges, and in Spain from the 
lixiviation of the soil, which can be afterwards devoted to the raising of com, or arranged 


SALTPETRE, NITRATE OF POTASS A. 135 

in saltpetre beds for the regular production of the salt. The chief and main condition 
oi the formation of saltpetre, which succeeds equally in open fields exposed to strong 
sunlight, under the shade of trees in forests, or in caverns, is the presence of organic 
matter, viz., Humus, inducing the nitre formation by its slow combustion ; the collateral 
conditions are dry air, little or no rain, and the presence in the soil of a weathered 
crystalline rock containing feldspar, the potassa of which favours the formation of the 
nitrate of that base. All the known localities where the formation of nitre takes place 
naturally, including the soil of Tacunga, formed by the weathering of trachyte and 
tufstone, are provided with feldspar. The nitric acid is due to the slow combustion of 
nitrogenous organic matter present in the humus, it having been proved that the nitric 
acid constantly formed in the air in enormously large quantities by the action of 
electricity and ozone, as evidenced by the investigations of MM. Boussingault, Millon, 
Zabelin, Schonbein, Froehde, Bottger, and Meissner, has nothing whatever to do with 
the formation of nitre in the soil, a fact also supported by Dr. Gfoppelsr oder’s discovery 
of the presence of a small quantity of nitrous acid in native saltpetres. 

Mod Saltpetre?* 11 ” The mode of obtaining saltpetre in the countries where it is naturally 
formed is very simple, consisting in a process of lixiviation with water, to which 
frequently some potash is added for the purpose of decomposing the nitrate of lime 
occurring among the salts of the soil, the solution being evaporated to crystallisation. 
Soils yielding saltpetre are termed Gay earth or Gay saltpetre. The process by 
which nitrate of potassa is naturally formed is imitated in the artificial heaps 
known as saltpetre plantations, formerly far more general than at the ])i’esent 
time, it having been found that the importation of Indian saltpetre, and the 
manufacture of nitrate of potassa by conversion from nitrate of soda, are cheaper 
sources. Thus, saltpetre beds are to be met with only under peculiar conditions, as, 
for instance, in Sweden, where all landed proprietors are required to pay a portion 
of their taxes in saltpetre. 

The mode of making these plantations may be briefly described as follows:—Materials 
containing much carbonate of lime—for instance, marl, old building rubbish, ashes, road 
scrapings, stable refuse, or mud from canals—is mixed with nitrogenous animal matter, 
all kinds of refuse, and frequently with such vegetable substances as naturally contain 
• nitrate of potassa, such as the leaves and stems of the potato, the leaves of the beet, 
sunflower plants, nettles, &c. These materials are arranged in heaps of a pyramidal 
shape to a height of 2 to 2./ metres, care being’ taken to make the bottom impervious to 
water by a well puddled layer of clay, the heap being in all directions exposed to the 
action of the atmosphere, the circulation of which is promoted through the heap by 
layers of straw. The heap is protected from rain by a roof, and at least once a week 
watered with lant (stale urine). The formation of saltpetre of course requires a considerable 
length of time, but, when taught by experience, the workmen suppose a heap ripe, the 
watering* is discontinued, the salt containing* saltpetre soon after efflorescing over the 
surface of the heap to 6 to 10 centims. in thickness; this layer is scraped off, and the 
operation repeated from time to time until the heap becomes decayed and has to be 
entirely removed. In Switzerland saltpetre is artificially made by many of the farmers, 
simply by causing the urine of the cattle, while in stable in the winter time, to be 
absorbed by a a calcareous soil purposely placed under the loose flooring of the stables, 
which are chiefly built on the slope of the mountains, so that only the door is level 
with the earth outside, the rest of the building hanging over the slope, and being supported 
by stout wooden poles; thus a space is obtained, which, freely admitting air, is filled 
with marl or other suitable material. After two or three years this material is removed, 
lixiviated with water, mixed with caustic lime and wood ash, and boiled down. The liquor 
having been sufficiently evaporated, is decanted from the sediment and left for crystalli¬ 
sation ; the quantity of saltpetre varying from 50 to 200 lbs. for each stable. 

Tr s a a\TpTtre°Ewth Ripe The crude salt from the heaps is converted into potassic nitrate 
by the following processes :— a. The earth is lixiviated with water, this operation 
being known as the preparation of raw lye. b. The raw lye is broken, that is to 
say, it is mixed with a solution of a potash salt in order to convert the nitrates of 
magnesia and lime present into nitrate of potassa. c. Evaporation of this liquor 
to obtain crude crystallised saltpetre, d. Defining the crude saltpetre. 


* 3 <> 


CHEMICAL TECHNOLOGY. 


Preparation ot 
Raw Lye. 


The ripe earth is lixiviated to obtain all the valuable soluble matter, 
it being expedient to use as little water- as possible in order to save fuel in the 
subsequent evaporation, for which the liquor is ready when it contains from 12 to 
13 per cent, of soluble salts. 

The raw lye, sometimes known as soil water, contains the nitrates 


Breaking up the 
Raw Lye. 


of lime, magnesia, potassa, soda, the chlorides of calcium, magnesium, and 
potassium; also ammoniacal salts and. organic matter of vegetable as well as of 
animal origin. In order to convert the nitrates of lime and magnesia into nitrate 
of potassa, the raw lye is broken up as it is termed, that is to say, there is added to 
it a solution of 1 part potassic carbonate in 2 parts water:— 


Nitrate of lime, Ca(N 0 3 ) 2 
Nitrate of magnesia, Mg(N 0 3 ) 2 
Carbonate of potassa, 2 K 2 C 0 3 


I f 

[ yield \ < 


Nitrate of potassa, 4KN0 3 . 
yield -j Carbonate of lime, CaC 0 3 . 

i Carbonate of magnesia, MgC 0 3 . 

The chlorides of calcium and magnesium are also decomposed, being converted 
into carbonates, while chloride of potassium is formed. The addition of the solution 
of potassa to the raw lye is continued as long as a precipitate is formed; in order, 
however, to have some approximative idea of the quantity of carbonate of potash 
which may be required, a test experiment is made with ^ litre of the raw lye. 

Sometimes sulphate of potassa is used instead of the carbonate, but in that case 
the magnesia salts of the raw lye have first to be decomposed by milk of lime, an 
operation which has to be followed by the evaporation of the fluid. If, after this, 
sulphate of potassa is added, sulphate cf lime is precipitated— 

[Ca(N0 3 ) 2 +E: 2 S04 = 2KN0 3 -j-CaS.0 4 ]. 

When chloride of potassium is used for the decomposition of raw lye, the salts of 
magnesia are first removed by the addition of milk of lime; and the clear super¬ 
natant fluid having been decanted from the sediment, there is added a mixture of 
equal molecules of chloride of potassium and sulphate of soda, the result being the 
formation of gypsum, while the sodic nitrate generated exchanges with the chloride 
of potassium, carrying over to the latter the nitric acid, and taking up the chlorine 
to form common salt. 

BoiI Raw d L7e. the The clarified raw lye decanted frem the precipitate of the earthy 
carbonates consists of a solution in which there are present the chlorides cf 

potassium and sodium, nitrate of potassa, 
carbonate of ammonia, excess of potassic 
carbonate, and colouring matter. The boiling 
down of this liquid is effected in copper 
cauldrons, Tig. 64, so set in the furnace as 
to admit of the circulation of the hot air and 
smoke from the fire-place, passing by c c 
below the heating pan, and thence by g into 
the chimney. In some works this waste 
heat is utilised in drying the saltpetre flour. 
As the bulk of the fluid in the cauldron 
decreases by evaporation, fresh lye enters by 
means of a pipe and tap from the pan, n. 
About the third day the alkaline chlorides begin to be deposited, and the workmen 
have then to take great care to prevent these.salts from becoming what is technically 


Fig. 64. 








SALTPETRE, NITRATE OF POTASSA. 


137 


termed burnt, which, might give rise to serious explosions, and for this purpose the 
liquid is stirred with stout wooden poles. After each stirring the loose saline matter 
is removed from the boiling liquid by means of perforated copper ladles. However, 
as a hard deposit is aKvays formed, a peculiar arrangement exhibited in Eig. 64, 
consisting of a shallow vessel, m, suspended by a chain, h, and weighted with a piece 
of stone, is lowered into the middle of the cauldron to about 6 centims. from the 
bottom, the object being to catch the solid particles, which would, when aggregating, 
form an incrustation, previously to their reaching the bottom of the vessel; and as 
no ebullition takes place at m, the particles once deposited remain there, and can be 
readily removed by raising the dish out of the cauldron, and emptying it into a box 
placed over the cauldron, the bottom of the box being perforated to admit of any 
liquor which may have been raised with the solid salt to return again to the 
cauldron. The deposit thus removed consists chiefly of gypsum and carbonate of 
lime. 

When a portion of the impurities contained in the boiling liquid have been 
removed, the raw lye still frequently contains some chloride of sodium, as this salt is 
not, as is the case with nitre, more soluble in boiling than in cold water. The 
abundant crystallisation of the saltpetre is a sign that the lye has been sufficiently 
evaporated; in order, however, to prove this, a small sample is taken, and if on 
cooling the nitre crystallises so that the greater part of the sample becomes a solid 
mass, the liquid is run into tanks and left for 5 or 6 hours, during which time 
impurities are deposited, and the liquid rendered quite clear. As soon as the 
temperature of the liquid has fallen to 6o°, it is poured into copper crystallisation 
vessels ; after a lapse of 24 hours the crystallisation is complete, and the mother - 
liquor being separated from the salt is employed in a subsequent operation. 

cruue n saitpetre The crude saltpetre is yellow-coloured, and contains on anaveiage 
some 20 per cent, of impurities, consisting of deliquescent chlorides, earthy salts, and 
water. The object to be attained by the refining is the removal of these substances. 
At the present day a large portion of the refined saltpetre met with in commerce is 
obtained by the refining of the crude saltpetre imported from India. It may be noted 
that this importation is steadily increasing, there being, in i860, 16,460,300 kilos., 
and in 1868, 33,062,000 kilos, of the salt brought to England; and, indeed, the 
production of saltpetre from natural sources in Europe is now limited to very few 
and unimportant localities. 

The method of refining saltpetre is based upon the fact that nitrate of potassa is 
far more soluble in hot water than are the chlorides of sodium and potassium. 
600 litres of water are poured into a large cauldron, and 24 cwts. of the crude saltpetre 
are added at a gradually increasing temperature; as soon as the solution boils, 
36 cwts. more crude saltpetre are added. Supposing the crude nitre to contain 
20 per cent, of alkaline chlorides, the whole of the nitre will be dissolved in this 
quantity of water, while a portion of the chlorides will remain undissolved even at 
the boiling-point. The non-dissolved salt is removed by a perforated ladle, and the 
scum rising to the surface of the boiling liquid by the aid of a flat strainer. The 
organic matter present in the solution is removed by the aid of a solution of glue— 
from 20 to 50 grms. of glue dissolved in 2 litres of water are taken for each hundred¬ 
weight of saltpetre. In order that the saltpetre may crystallise, the quantity of 
water is increased to 1000 litres, and as soon as this water is added the organic 
matter entangled in the glue rises as a scum to the surface and is removed. Tho 


CHEMICAL TECHNOLOGY. 


138 

operation haying progressed so far, and the liquid being rendered quite clear, it 
kept at a temperature of 88° for about twelve hours, and then carefully ladled into 
copper crystallising vessels, constructed with the bottom a little higher at one end 
than at the other. The solution would yield on cooling large crystals of saltpetre, 
but this is purposely prevented by keeping the liquid in motion by means of stirrers, 
as as to produce the so-called flour of saltpetre, which is really the salt in a finely- 
divided state. This is next transferred to wooden boxes termed wash-vessels, 10 feet 
long by 4 feet wide, provided with a double bottom, the inner one being perforated; 
between the two bottoms holes are bored through the sides of the vessel and when 
not required plugged with wooden pegs. Over the flour of saltpetre contained in 
these wooden troughs, 60 lbs. of a very concentrated solution of pure nitrate of 
potassa are poured, and allowed to remain for two to three hours, the plugs being 
left in the holes. The plugs are then removed, the liquor run off, the holes again 
plugged, and the operation twice repeated, first with a fresh 60 lbs., and next with 
24 lbs. of the solution of nitrate of potassa, followed in each case by an equal quan¬ 
tity of cold water. The liquors which are run off in these operations are of course 
collected, the first being added to the crude saltpetre solution, while the latter, being 
solutions of nearly pure nitre, are again employed. The saltpetre is next dried at 
a gentle heat in a shallow vessel, sifted, and packed in casks. 

Preparation of Nitrate During the last twenty years the preparation of nitrate of 
Chin-saltpetre. potassa from Chili-saltpetre has become an important branch of 
manufacturing industry. The product obtained by any of the following processes is 
called ‘ ‘ con verted-saltpetre,” to distinguish it from the preceding preparation. The 
method of procedure may be one of the following :— 

i. The nitrate of soda is decomposed by means of chloride of potassium— 

100 kilos, of sodic nitrate \ ( 119*1 kilos, potassa nitrate. 

87*9 kilos, of potassium chloride / [ 68*8 kilos, common salt. 

MM. Longchamp, Anthon, and Kuhlmann first suggested this mode of prepara¬ 
tion, which is now generally used on the large scale, as the decomposition of both 
salts is very complete, and as the common salt as well as the saltpetre can be utilised. 
The chloride of potassium is obtained by the decomposition of carnallite, or by means 
already mentioned. 

Equivalent quantities of nitrate of soda and of chloride of potassium are dissolved 
in water contained in a cauldron of some 4000 litres cubic capacity. As the nitrate 
of soda of commerce (Chili-saltpetre) does not, as regards purity, vary very much 
from 96 per cent., some 7 cwts. are usually taken, while of the chloride of potassium, 
which varies in purity from 60 to 90 per cent., a quantity is taken corresponding, as 
regards the amount of pure chloride, to the quantity of nitrate of soda. The chloride 
of potassium is first dissolved, the hot solution being brought to a sp. gr. = 1*2 to 1*21, 
next the nitrate of soda is added, and the liquid brought, while constantly heated, 
to a sp. gr. = i*5. The chloride of sodium continuously deposited is removed by 
perforated ladles, and placed on a sloping plank so that the mother-liquor may flow 
back into the cauldron, care being taken to wash this salt afterwards, so as to 
remove all nitrate of potassa, the washings being poured back into the cauldron. 
When the liquid in the cauldron has been brought to 1*5 sp. gr.—an aqueous solu¬ 
tion of nitrate of potassa at 15 0 , with a sp. gr. = 1*144, contains 21*074 per cent, of that 
salt—the fire is extinguished, the liquid left to clear, the common salt still present 
carrying down all impurities, and when clear it is ladled into crystallising vessels, 


SALTPETRE, NITRATE OF TO TASS A. 


*39 

which being very shallow, the crystallisation is finished in twenty-four hours. The 
mother-liquor having been run off, the crystals are thoroughly drained and covered 
with water, which is left in contact with the salt for some seven to eight hours, and 
then run off; this operation is repeated during the next day; the mother-liquor and 
washings are poured back into the cauldron at a subsequent operation. 

2. Nitrate of soda is first converted into chloride of sodium by means of chloride 
of barium, nitrate of baryta being formed, and in its turn converted into nitrate of 
potassa by the aid of sulphate of potassa:— 

a. 85 kilos, of nitrate of soda ) • ,, ( 130*5 kilos, nitrate of baryta. 

122 kilos, of chloride of barium j * tia » 58*5 kilos, of common salt. 

3- 130-5 kilos, of nitrate of baryta 1 87*2 kilos, of potassic sulphate, 

require for conversion into [ or 

nitrate of potassa ) 69*2 kilos, of potassic carbonate. 

When sulphate of potassa is used, permanent-white, baryta-white, or sulphate of 
baryta is obtained as a by-product, while if carbonate of potassa is used, carbonate 
of baryta remains, and of course may be readily re-converted into chloride of barium. 
In order to estimate the advantages of either process, the following points must be 
kept in view :— a. Taking into consideration that it is profitable to convert native 
carbonate of baryta into chloride of barium—for instance, by exposing witherite to 
the hydrochloric acid fumes produced in alkali works by the decomposition of salt— 
and to precipitate an aqueous solution with dilute sulphuric acid to obtain permanent- 
white, it may be inferred that it will also pay to obtain it as a by-product, b. Not¬ 
withstanding the complication of this process, it is advantageous as producing a far 
purer nitrate of potassa. 

3. Nitrate of soda is converted by means of potash into the nitrate of that base, 
pure soda being obtained as a by-product:— 

85 kilos. Chili-saltpetre ) • ( 101*2 kilos, of potassic nitrate. 

69*2 kilos, carbonate of potassa / ^ (53 kilos, of soda (calcined). 

This mode of manufacturing saltpetre was first introduded into Germany during the 
Crimean War (1854-55) by M. Wollner, of Cologne, who established large works to 
prepare saltpetre in this way, and very soon after, during the continuance of the war, 
five other manufactories of potash-saltpetre had been established on this method. 
In 1862 the production amounted to 7,500,000lbs. of potash-saltpetre, the carbonate 
of potassa required being obtained from beet-root molasses, the soda resulting as a 
by-product being even superior to that produced by Leblanc’s process. 

4. Nitrate of soda being decomposed by caustic potassa yields potassic nitrate and 
caustic soda. 

Accorcfing to M. Lunge’s description, this process, first suggested by MM. Land- 
mann and Gentele, afterwards modified by M. Schnitzel*, and practically applied by 
M. Nollner, is carried on in Lancashire in the following manner:—There is added to 
a caustic potash lye of 1 *5 sp. gr., containing about 50 per cent, of dry caustic potassa, 
an equivalent quantity of nitrate of soda, and the whole, after a short time, crystal¬ 
lised. The nitrate of potassa having been separated from the mother-liquor, that 
fluid, the density of which has been greatly decreased by the reaction, is by evapo¬ 
ration again brought to its former density, and yields on cooling another crop of 
crystals of potash-saltpetre. Usually there then only remains a solution containing 
caustic soda with saline impurities ; sometimes, however, a third crop of crystals is 
obtained. The deposit during the evaporation is chiefly carbonate of soda derived 


140 


CEEMICAL TECHNOLOGY. 


from the chloride of sodium contained in the potassium chloride from which the 
caustic potassa is made, this chloride being also converted into carbonate. The 
small quantities of undecomposed chlorides of potassium and sodium and sulphate of 
lime are retained in the mother-liquor, which is evaporated to dryness and ignited, 
yielding a dry caustic soda of a bluish-colour. The crystallised nitrate of potassa 
is now carefully refined to remove all impurities to about o*i per cent, of chloride of 
sodium, converted into saltpetre-flour, and treated as already described. Notwith¬ 
standing that the various operations have been carried on in iron vessels, the salt 
does not contain any of this metal, nor is the colour in any way affected. The flour 
is dried in a room 2 metres wide by 5 metres in length, built of brick-work, similarly 
to the chloride of lime rooms, and having a pointed arched roof 2 metres in height. 
The saltpetre-flour is spread on a wooden floor, under which extends a series of hot¬ 
air pipes, keeping the temperature at 70°, and very rapidly effecting the drying. 

Testing the Saltpetre. If, when perfectly pure, saltpetre is carefully fused, and allowed 
to cool, it becomes a white mass, exhibiting a coarsely radiated fracture ; even so 
small a quantity as g jjth of chloride of sodium causes the fracture to appear somewhat 
granular; with ^' 0 th the centre is not at all radiated, and is less transparent; and 
with jgth the radiation is only slightly perceptible at the edges of the fracture. 
Nitrate of soda has the same effect. This method of testing the purity of nitre, due 
to M. Schwartz, is employed in Sweden, where every landowner pays a portion of 
his taxes in saltpetre of a specified degree of purity. A great number of methods of 
testing saltpetre have been suggested by various authors for the purposes of the 
manufacture of gunpowder, not, however, in sufficiently general use to interest the 
reader. Werther’s test for chlorine and sulphuric acid is by solutions of the nitrates 
of baryta and silver; the silver solution is such that each division of the burette 
corresponds to 0*004 grm. of chlorine, and with the baryta solution to 0*002 grm. of 
sulphuric acid. According to Eeich’s plan, 0*5 grm. of dried and pulverised saltpetre 
is ignited to a dull red heat, with from 4 to 6 times its weight of pulverised quartz; 
the nitric acid is expelled, the loss of weight consequently indicating the quantity, 
the sulphates and chlorides not being decomposed at a dull red heat. If the loss 

d t we have 1*874 d nitrate of potassa, or 1*574 d nitrate of soda. 

Quantitative Estimation This method, due to Dr. A. Wagner, is based upon the fact 

of tlie Nitric Acid in , , ,. . .. 

saltpetre. that when saltpetre, or any other nitrate, is ignited, access of air 
being excluded, with an excess of oxide of chromium and carbonate of soda, the nitric 
acid oxidises the chromic oxide according to the formula Cr 2 0 3 -f-N 0 5 =2Cr0 3 -f-N 0 2 . 
76*4 parts, by weight, of oxide of chromium are oxidised to chromic acid by 54 parts 
of nitric acid, or of 1 of chromic oxide by 0*7068 of nitric acid. The operation is 
performed by taking from 0*3 to 0*4 grm. of the nitrate, mixing it intimately with 
3 grms. of chromic oxide and 1 grm. of carbonate of soda, introducing this mixture 
into a hard German glass combustion-tube, one end of which is drawn out, and a 
vulcanised india-rubber tube attached to it, which is made to dip for about a quarter 
of an. inch into water, while to the other open end, by means of a cork and glass tube 
bent at right angles, an apparatus is fitted for the evolution of carbonic acid gas, 
which is made to pass through the tube before igniting it, and kept passing through 
all the time until the tube is quite cool again after ignition. The contents of the 
tube are placed in warm water, and after filtration the chromic acid is estimated by 
Eose’s method. This process of estimating nitric acid has been found to yield very 
accurate results. 


SALTPETRE, NITRATE OF POTASSA. 


141 

uses of saltpetre. This salt is employed for many purposes, the most important 
being:—1. The manufacture of gunpowder. 2. The manufacture of sulphuric and 
nitric acids. 3. Glass-making, to refine the metal as it is termed. 4. As oxidant 
and flux in many metallurgical operations. By the ignition of 1 part of nitre and 
2 of argol, in some cases refined argol (cream of tartar), black flux is formed consist¬ 
ing of an intimate mixture of carbonate of potassa and finely divided charcoal. The 
ignition of equal parts of saltjjetre and cream of tartar gives white flux , consisting 
of a mixture of carbonate of potassa and undecomposed saltpetre; both these 
mixtures are often used. Black flux may also be made by intimately mixing 
carbonate of potassa with lamp-black and white flux. 5. When mixed with 
common salt and some sugar in the salting and curing of meat. 6. Bor preparing 
fluxing and detonating powders. Baume’s fluxing powder is a mixture of 3 parts 
of nitre, 1 of pulverised sulphur, and 1 of sawdust from resinous wood; if some 
of this mixture be placed with a small copper or silver coin, in a nutshell and 
ignited, the coin is melted in consequence of the formation of a readily fusible 
metallic sulphuret, while the nutshell is not injured. Detonating powder is a mix¬ 
ture of 3 parts saltpetre, 2 carbonate potassa, and 1 pulverised sulphur; this powder 
when placed on a piece of sheet-iron, and heated over a lamp, will explode with a 
loud report, yielding a large volume of gas:— 

Saltpetre, 6 KN 0 3 , ) (Nitrogen, 6N. 

Potassic carbonate, 2K 2 C0 3 , I = J Carbonic acid, 2C0 2 . 

Sulphur, 5S. / \ Sulphate of potassa, 5K2SO4. 

7. Por manure in agriculture. 8. In many pharmaceutical preparations. 9. For 
the preparation of Heaton steel. 

sodic Nitrate. This salt, also known as cubical saltpetre, Chili-saltpetre, nitrate 
of soda, NaN 0 3 , containing in 100 parts 36*47 soda, and 63*53 parts' nitric acid, 
is found native in the district of Atacama and Tarapaca, near the port of Uquique, 
in Peru, in layers termed caleche or terra salitrosa, 0*3 to i*o metre in thickness, and 
extending over more than 150 miles, nearly to Copiapo, in the north of Chili. The 
deposit chiefly consists of the pure, dry, hard salt, and is close to the surface of the 
soil. It is also found in other parts of Peru mixed with sand, in some places close 
to the surface of the soil, in others at a depth of 2*6 metres. Valparaiso being the 
great exportation depot for Peru, Bolivia, and Chili, both surface and deep soil salts 
are met with in tthe rade of that important port. The unrefined Chili-saltpetre is 
crystalline, brown or yellow, and somewhat moist; but the salt sent to the Euro¬ 
pean markets is commonly semi-refined by being dissolved in water and evaporated 
to dryness. The composition of a sample in 100 parts is 


Nitrate of soda. 94'°3 

Nitrate of soda . 0.31 

Chloride of sodium. 1.52 

Chloride of potassium. 0*54 

Sulphate of soda . 0*92 

Iodide of soda. 0*29 

Chloride of magnesium. 0*96 

Boric acid. •. .. .. traces 

Water . ■'1*96 


100*00 












142 CHEMICAL TECHNOLOGY. 

Being deliquescent tlie salt is not employed in the manufacture of gunpowder, 
but may be used for blasting powder. It is largely used for the preparation of 
sulphuric and nitric acids ; for purifying caustic soda; for making chlorine in the 
manufacture of bleaching powders; for the preparation of arseniate of soda ; in the 
curing of meat; glass-making; in the preparation of red-lead ; in large quantities 
in the conversion of crude pig-iron into steel, by Hargreaves’s and by Heaton’s 
processes; for preparing nitrate of potassa; and for the preparation of artificial 
manures and composts, it being used unmixed as a manure for grain crops. 

It may be seen from the analysis of nitrate of soda quoted above that that 
salt contains a small quantity of iodine, which at Tarapaca is extracted from the 
mother-liquor remaining from the re-crystallisation. According to M. L. Krafft 
the iodine amounts to 0*59 grm. in 1 kilo, of crude nitrate; 40 kilos, of iodine being 
prepared per day. M. Nollner thinks that the formation of the nitre deposits in 
Chili and other parts of South America has taken place under the influence of 
marine plants containing iodine. In order to give some idea of the large and 
increasing exportation of Chili-saltpetre, we quote from the published statistics, 
that in 1830, 18,700 cwts., and in 1869, 2,965,000 cwts., were shipped. 

Nitric Acid. 

Methodsof Manufacturing q^ g ac j£ (JsTH 0 3 ) is generally manufactured by decomposing 
nitrate of soda by sulphuric acid, and condensing the vapours set free. It is 
obtained on the large scale by placing in a cast-iron vessel, A, Fig. 65, the nitrate to 
be operated upon, to which is added by means of a funnel strong sulphuric acid. 
The lid is replaced, and the vessel connected by means of the clay-lined tube B, 
with the glass tube, C, dipping into the large stoneware flask, D, which serves the 


Fig. 65, 



purpose of a receiver. This flask is connected by means of a tube, a, to a similar 
vessel, D', and that to a third vessel, d", and so on, in order to completely condense 
the vapours which might have escaped through the first, second, and third vessels. 
The iron vessel, A, is heated by means of the fire placed in the hearth, f, the smoke 
and hot gases being carried off by G ir. At the outset of the operation the damper, 
d, is so regulated as to shut off the lower channel, and cause the smoke and hot 
gases to pass through E, heating the vessels D, d', and D", this precaution being 













NITRIC ACID. 


143 


required to prevent their cracking by the hot acid vapours entering from A. As 
soon, however, as the distillation has fairly commenced, the damper is altered to 
shut off E, and pass the hot air and gases through G. The nitric acid condensed in 
the first receiver is sufficiently strong for immediate use, but to facilitate the con¬ 
densation some water has been poured through the openings V b", into the other 
receivers, the acid from which is weaker and known in the trade as aquafortis. 

Very frequently the distillation of nitric acid is conducted in a series of glass 
retorts placed on a sand-bath; there are'generally two rows of retorts, the heating 
apparatus being a galley oven. If the acid is to be pure, the first condensations 
are collected in separate receivers, as the acid first condensed contains hydrochloric 
acid due to the chlorides contained in the nitrates under operation. 

Tlie proportion of materials employed is :— 

30 kilos, of Nitrate of potassa to 29 kilos, of strong sulphuric acid; or, 

17 ,, Nitrate of soda to 14*5 ,, ,, ,, ,, 

The bisulphate of soda which remains may either be used for the preparation of 
fuming sulphuric acid, or may be mixed with common salt, and ignited, to pro¬ 
duce hydrochloric acid and neutral sulphate of soda, available in the preparation 
of sodic carbonate. 

The nitric acid (NHO s ) resulting from the above operation is a colourless, trans¬ 
parent fluid, having a sp. gr. of 1*55, and boiling at 8o°. When diluted with water 
the boiling-point is higher. An acid containing 100 parts (NH 0 3 ) and 50 parts of 
water boils at 129 0 , but if the dilution with water is carried further the boiling-point 
is again lowered; consequently, when such an acid is heated above ioo° the result 
is that at first water with only a trace of acid distils over, and if the process be con¬ 
tinued the boiling-point gradually increases until it reaches 130°, when there distils 
over what is termed double aquafortis, sp. gr. =i’35 to 1-45, ordinary or single 
aquafortis having a sp. gr. = 1*19 to i - 25- Nitric.acid, when in contact with air, 
emits fumes, owing to the absorption of water from the atmosphere. 

meac Ac?ii Nitric The stronger acid manufactured as described is usually of a yellow 
colour, due to the presence of hyponitric acid. If a colourless acid is desired, the 
crude acid must be submitted to a bleaching operation, consisting of the follow¬ 
ing : _The coloured acid is poured into large glass vessels placed (Fig. 66) in a water- 

bath, heated to 8o° to 90°, and left in these vessels as long as any coloured vapours 


Fig. 66. 



are given off. The escaping hyponitric acid is carried by means of glass or glazed 
earthenware tubes either into a sulphuric acid chamber and there utilised, or into 
the flue of a chimney, and thus into the air. Any hydrochloric acid present in the 
nitric acid is also carried off as chlorine. In order to remove any sulphuric acid it 








144 


CHEMICAL TECHNOLOGY. 


is necessary to distil the nitric acid over pure nitrate of baryta, while the last traces 
of hydrochloric acid can be removed by distillation over pure nitrate of silver. 

condensatkm^of the Nitric More recently improvements have been made in the manu¬ 
facture of nitric acid, bearing especially upon the possibility of omitting the bleach¬ 
ing process, and a better mode of condensing the vapours of the acid. The first 
point is supplied by an arrangement introduced in the manufactory of M. Cheve, 
in Paris. Every practical chemist knows that the red vapours appear only at the 
outset and towards the end of the distillation of the nitric acid, and it is therefore 
only required to distil fractionally to obtain on the one hand a red-coloured acid, 
the acidum nitroso-nitricum or acidum nitricum fumans fortissime of the pharma¬ 
ceutists, and on the other a colourless acid, which can be forthwith delivered to the 
consumer. In order to practically effect the fractional distillation, a tap of porce¬ 
lain or hard-fired stoneware, constructed as exhibited in Pig. 67, is fixed by means 
of A, in communication with the iron distilling vessel, while the tubes B and B are 
connected with two different receivers. The tap is bored in such a manner, that 

at pleasure either the communication 
between A and b', or the communica¬ 
tion between A and B, can be esta¬ 
blished. By proper management, 
therefore, it is possible to separate the 
red-coloured acid entirely, and with¬ 
out any additional expense, from the 
colourless acid. 

A second improvement, contrived by MM. Plisson and Devers, Paris, bears upon 
the condensation apparatus, which consists in their works of a battery of ten pecu- 
Pig. 68. 


Pig. 67. 




liarly constructed bottles, six of which are open at the bottom and funnel-shaped, 
so as to fit in the necks of large carboys, G, Pig. 68. Prom a cylinder not shown 
in the engraving, being hidden by the wall, M, a stoneware tube is connected with 





































NITRIC AC IB. 


M5 


tiio bent glass tube, a, which communicates with one of the three tubulatures of 
the first carboy, A, which serves to collect the acid, that, by the boiling over of the 
mixture in the iron vessel, has been rendered more or less foul. The carboy A is pro¬ 
vided with a small tube, T, arranged to act as a hydraulic valve in such a manner 
that, when the fluid in the carboy has risen to a height of some centimetres, any 
additional fluid' entering A is carried off into the well-stoppered carboy A'. The 
second tubulature of the carboy A is fitted with a funnel through which wateir flows 
from the bottle f into A, thereby aiding the condensation. The acid vapours pass 
through the curved glass tube F, into the carboy B, from which, as likewise from the 
carboys B' and B 7 , the condensed fluid is carried by the tube T into the carboy a”. 
Any vapours which escape condensation in B are carried off to c, and thence to d, a 
portion of the acid being condensed in each of the vessels, and flowing back first to 
B and then to a". Any vapour not condensed in c and D is conducted by the glass 
tube G, first to d', next to c", and finally to B, where condensation takes place. Any 
vapours not now condensed are carried to b",c", d", and finally to the chimney stalk. 
The Mariotte botttles f' and f" contain water, which flows into the condensing 
vessels and dilutes the acid to 36° B. (= 1 ’31 sp. gr. = 42*2 per cent. N 2 0 5 ). In order 
to reduce any pressure arising in the vessels A' and A”, a tube H, and a similar one 
not represented in the cut, are connected with t and t', for the purpose of carrying 
any non-condensed vapour into b", where these vapours collect. 

Although this apparatus appears complicated, the working is very readily managed. 
The acid vapours issuing from the distillatory apparatus are partly condensed in the 
vessel A, and thence carried to a', the vapours still uncondensed continuing their 
course to b, b', b'', the fluid there collected flowing back to the general receiver A”. 
This apparatus when once well put together, has rarely to be repaired, saves much 
labour, and produces a larger quantity of acid than the ordinary apparatus, this 
being due to the more complete condensation ; while by the ordinary method only 
125 to 128 kilos, of nitric acid are obtained from 100 kilos, of nitrate, the quantity 
obtained by this apparatus amounts to 132 to 134 kilos. The following brief descrip¬ 
tion, illustrated by Figs. 69 and 70, will explain the internal construction of the 
bottles and of the syphon funnel. In each of the carboys of the lowest row is 
inserted a bent stoneware tube, T, Fig. 69, the opening, 0, of which is outside 
the bottle; a narrow space, L, admits the fluid to the interior of the tube, and it 
is clear that the acid can only attain a certain height in the carboy. The syphon 
funnel consists of a stoneware tube about 3 centims. in diameter, the side of which, 
Fig. 70, is perforated in a longitudinal direction ; any fluid therefore flowing into 
this tube from E can only reach to the opening 0. 

other Methods of Nitric Acid The following methods, differing from that above described, 

Manufacture. must here be mentioned; but the reader should not infer that they 

are actually in practice:—1. Action of chloride of manganese (chlorine preparation 
residues) upon nitrate of soda. When a mixture of these salts is heated to about 230°, 
nitrous vapours (N0 3 + O) are evolved, and there remains oxide of manganese, which can 
be again employed in the manufacture of chlorine. 

SMnCL ) ( (2MnO-f 3 MnO„), 

and yield ioNaCl, 

ioNaN 0 3 ) ( ioN 0 2 -J- 0 , 

By causing the mixture of hyponitric acid and oxygen to come into contact with water 
in the condensing apparatus nitric acid results, the excess of hyponitric acid being decom¬ 
posed into nitric acid and deutoxide of nitrogen. If the quantity of air in the apparatus 
is sufficiently large to oxidise the entire bulk of the nitrogen deutoxide into nitric acicf 
this process is continuous, but if there is not enough air, the deutoxide of nitrogen i» 

11 


CHEMICAL TECHNOLOGY. 


146 

dissolved in the nitric acid, any excess of that gas escaping. From the expci iinents on this 
process by Dr. Kuhlmann, who used clay retorts, it appears that 100 parts of nitrate of 
soda yield from 125 to 126 parts of nitric acid at 35 B. 5 this result almost agrees with 
that obtained by the ordinary process. Dr. Kuhlmann also instituted experiments with 
other chlorides, viz., those of calcium, magnesium, and zinc, the result being the formation 
of nitric acid and chloride of sodium with lime, magnesia, and oxide of zinc. 

2. Action of certain sulphates upon alkaline nitrates. Dr. Kuhlmann has pioved by a 
series of experiments that the sulphates, including only those having no acid properties, 
decompose the alkaline nitrates. Sulphate of manganese decomposes nitrate of soda, the 
result being the formation of products similar to those when chloride of manganese is 
employed; ^similar reactions take place when sulphate of zinc, sulphate of magnesia, and 
gypsum are used for this purpose. 

3. From nitrate of soda and carbon, yielding soda and nitric acid. 

4. From nitrate of soda and silica or alumina, yielding nitric acid, silicate of soda and 

c. From nitrate of baryta and sulphuric acid, without distillation,- the nitric acid 
(—*io° to ii° B.) decanted from the sulphate of baryta (permanent white) can be concen- 


trated by boiling to 25° B. 

Density of Nitric Acid. According to Kolb, the 
quantity of concentrated acid contained th( 
100 parts contain Density. 

specific gravity of nitric acid bears to the 
3 following relation:— 

100 parts contain Density. 

__A__ __A__ 

(—- 

8 ( 


( 


f 

1 

NH0 3 . 

N 2 0 5 . at o°. 

at i5°C. 

NH0 3 . 

n 2 o 5 . 

at o° 

at i5°C. 

IOO'OO 

857 1 1 *559 

1*530 

55*oo 

47*i4 

1*365 

1*346 

97*00 

83*14 1*548 

1*520 

50*99 

43*7° 

i*34i 

1*323 

94*00 

80*57 i *537 

1*509 

45*00 

38*57 

1*300 

1*284 

92*00 

78*85 1*529 

1*503 

40*00 

34*28 

1*267 

1*251 

91*00 

78*00 1*526 

1*499 

33*86 

29*02 

1*226 

1*211 

90*00 

77 * i 5 1*522 

i*495 

30*00 

25*71 

1*200 

1*185 

85*00 

72*86 1*503 

1*478 

25*71 

22*04 

1*171 

i*i57 

8o*oo 

68*57 1*484 

1*460 

23*00 

19*71 

i*i53 

1*138 

75-00 

64*28 1*465 

i*442 

20*00 

i7*i4 

1*132 

1*120 

69*96 

6o*oo i*444 

1*423 

15*00 

12*85 

1*099 

1*089 

65*07 

55*77 1 *420 

1*400 

II*4I 

977 

1*075 

1*067 

60*00 

5i*43 i'393 

T *374 

4*00 

3*42 

1*026 

1*022 

The following table exhibits comparator 

2*00 1*71 1*013 

r e data of density and degrees 

1*010 

according 

to Baume:— 

Degrees according Densit 
to Baume. J 

6 1 *044 

100 parts contain at 
o° 

100 parts contain at 

15 0 c. 

A . 

NH0 3 . 

67 

N 2 0 5 . 

5*7 


NH0 3 . 

7*6 

n 2 o 5 : 

6*5 

7 

1*052 

8*o 

6*9 


9*o 

7*7 

9 

1*067 

10*2 

8*7 


ir 4 

9*8 

10 

1*075 

11*4 

9*8 


12*7 

10*9 

15 

i * ii 6 

17*6 

i5*i 


19*4 

16*6 

. 20 

1*161 

24*2 

20*7 


26*3 

22*5 

*5 

1*210 

3i*4 

26*9 


33*8 

28*9 

30 

1*261 

39*i 

33*5 


4i*5 

35*6 

35 

1*321 

48*0 

4i*i 


50*7 

43*5 

40 

1*384 

58*4 

50*0 


61*7 

52*9 

'15 

i*454 

72*2 

61*9 


78*4 

72*2 

46 

1*470 

76*1 

65*2 


<83*0 

71*1 

47 

1*485 

80 *2 

687 


87*1 

7 1-7 


i 












NITRIC ACID. 


147 


47 0 B. correspond to 96° Twaddle. 

46° >1 

92 ° 

45 ° » 

88° 

43 ° » 

84° 

42 ° » 

8o° 

38 ° ,, 

7 °° » 

34 ° » 

6o° ,, 

29 0 } > 

50 ° 

25 0 >, 

4 °° »» 

20° „ 

30 ° 

14 0 » » 

20 ° „ 

7 ° » » 

10 ° ,, 


Nitric acid of 1*52 sp. gr. boils at 86° 


99 

1-50 

9 9 

99 ° 

99 

i -45 

99 

115 0 

99 

1*42 

9 9 

123 0 

99 

1*40 

99 * 

119 0 

99 

I *35 

9 9 

117 0 

99 

1*30 

99 

113° 

99 

I'20 

,, 

108 0 

99 


9 9 

104° 


Fuming Nitric Acid. When in the preparation of nitric acid there is taken for 1 mole¬ 
cule of nitrate of potassa 1 molecule of sulphuric acid, there is obtained by distilla¬ 
tion a reddish-yellow fluid, consisting of a mixture of nitric and hyponitric acids, 
known as red fuming nitric acid. When equal molecules of nitrate of potassa and 
sulphuric acid are taken, only one-half of the quantity of nitric acid is expelled, 
while the other half is decomposed into hyponitric acid and oxygen, the former 
combining with the nitric acid, and forming the fuming nitric acid. When in the 
preparation of nitric acid by the decomposition of the potassium or sodium nitrate, 
two molecules of sulphuric acid are employed, all the nitric acid in these salts is 
obtained, and there remains in the retort bisulphate of either base. When nitrate 
of soda is employed, it is, owing to the easier decomposition of this salt by sulphuric 
acid, not necessary to use exactly 2 molecules of sulphuric acid; 1*25 to 1*50 mole¬ 
cules of that acid have been found to be practically sufficient. 100 parts of Chili- 
saltpetre yield 120 to 130 parts of nitric acid at 36° B. 

The red fuming nitric acid is now generally prepared by adding to the ordinary 
concentrated nitric acid a substance which effects its decomposition. Sulphur 
has been employed for this purpose, but starchis generally used, and, according to 
M. C. Brunner’s recipe, in the following manner:—To 100 parts of saltpetre, 
3 1 parts of starch are added, and placed in a capacious retort, into which is poured 
100 parts of strong sulphuric acid, sp. gr.=1 -85. The distillation usually sets in with¬ 
out the aid of heat, but towards the end of the operation the application of a gentle 
heat is required. 100 parts of nitrate of potassa yield by this method about 60 parts 
of fuming nitric acid. The retort in this operation should not be filled to more than 
one-third of its capacity, owing to the very strong evolution of gas which takes place. 

Uses of Nitric Acid. The technical application of nitric acid is based on its property of 
oxidation when in contact with certain substances, the acid splitting up into deut- 






CHEMICAL TECHNOLOGY. 


14b 

oxide of nitrogen, hyponitric acid, and ozone, the latter forming with the body 
which caused the decomposition of the acid either an oxide or a peculiar compound, 
while the hyponitric acid, when organic substances are present capable of combining 
with it, forms the nitro-compounds, nitrobenzole, nitronapthaline, nitroglycerine, 
nitromannite, nitrocellulose, or gun-cotton, &c. A large number of metals are 
soluble in moderately concentrated nitric acid, but the strongest acid fails to 
act upon iron and lead. Proteine compounds, albumen, the skin of the hands, silk, 
horn, feathers, &c., are stained yellow by nitric acid, hence the use of this acid 
in dyeing silk. If the acid is in contact with these substances for any length of time, 
they are completely decomposed, and partly converted into picric acid. Starch, 
cellulose, and sugar are converted by the action of nitric acid into oxalic acid; 
but very dilute nitric acid converts starch into dextrine, and concentrated acid 
into xyloidine. Owing to the property nitric acid possesses of destroying certain 
pigments—for instance, indigo—itis sometimes employedin calico printing to produce 
a yellow pattern on an indigo ground. This acid is also used in dyeing woollen 
materials; in hat-making, to prepare a mercurial solution used in dressing felt hats; 
in the manufacture of sulphuric acid; in the preparation of lacquers; in the prepa¬ 
ration of nitrate of iron, a mordant used in dyeing silk black; for preparing picric 
acid from carbolic acid, and naphthaline-yellow from naphthaline; in the manufacture 
of nitrobenzol, nitrotoluol, and phthalic acid ; and for the preparation of nitrate of 
silver, arsenic acid, fulminate of mercury nitroglycerine, dynamite, &c. 

Technology oe the Explosive Compounds. 
a. Gunpowder , and the Chemistry of Fireworks , or Fyrotechny. 

vn Gunpowder in General. The substance known as gunpowder, or simply as powder, is 
a more or less finely granulated mechanical mixture of saltpetre, sulphur, and char¬ 
coal, the quantities of these materials being properly defined^ It ignites at 300°, 
also when touched with a red-hot or burning body, or under certain conditions by 
friction or a sudden blow. Powder under these conditions burns off rapidly but not 
instantaneously, yielding as the products of its combustion nitrogen, carbonic acid, 
or carbonic oxide, while there remains a solid substance consisting of a mixture of 
sulphate and carbonate of potassa. When the powder is ignited in a closed vessel, 
the sudden evolution of the large volume of gases causes a pressure impossible to be 
withstood; and even in guns and large ordnance, in which one side of the vessel is 
formed by the yielding shot, the metal forming the other sides must possess great 
elasticity. In guns and artillery the pressure only lasts as long as the ball is inside 
the gun, therefore the slower the combustion of the powder through its entire mass, 
the lower is the velocity of the projectile. 

Manufacture of Gunpowder. It is essential that the materials employed in the manufacture 
of powder should be very pure; the saltpetre should not contain any chlorides; the 
sulphur should be free from sulphurous acid, hence not flowers of sulphur but 
refined roll sulphur is used ; and lastly the charcoal requires very great attention. 
The wood from which it is intended to prepare a charcoal for gunpowder should be 
such as yields the least possible quantity of ash, while the charcoal should be soft 
like that used in pharmacy. The stems of the hemp and flax plants, especially the 
former, yield excellent charcoal, but in consequence of the limited supply, the wood 
of the wild plum tree (Prunus padus ) is largely used in Germany, Prance, and 


EXPLOSIVE COMPOUNDS. 


149 


Belgium; and in England the lime, willow, poplar, horse-chestnut, vine, hazel, 
cherry, alder, and other light white woods are employed for this purpose. All these 
varieties yield on being carbonised—effected in various ways, in retorts similar to 
those used in gas-works, in pits dug in the earth, by the aid of superheated steam, 
the wood being placed in boilers, &c.—from 35 to 40 per cent, charcoal. The tem¬ 
perature during the progress of carbonisation being kept as low as possible, there is 
obtained a very soft reddish-brown charcoal, known as charbon ronx. The charcoal 
prepared in cylindrically-shaped retorts is very inappropriately designated distilled 
charcoal. 

0?pSwdS 1 ffiSSSS. These operations include 

1. The pulverising of the ingredients. 2. The intimate mixing of these sub¬ 
stances. 3. The moistening of the mixture. 4. The caking or pressing. 5. The 
granulation and sorting of the grain, as it is termed. 6. Surfacing the powder. 
7. Drying. 8. Sifting from the dust. 

pulverising the ingredients. This operation can be performed in three different ways:— 

a. By means of revolving drums. 

b. By mill-stones; or 

c. In stamping-mills. 

a. The pulverisation by means of revolving drums is an invention due to the French 
revolution, and has the advantages of being very effective, rapid in execution, and of pre¬ 
venting the flying about of the ingredients in a fine dust. The drums are made of wood, 
lined with stout leather, and provided with a series of projections. The substance to be 
pulverised is put into the drum with a number of bronze balls of about 5 inch diameter, 
their action aided by that of the projections, when the drum is turned on its horizontal 
axis at a moderate speed, soon effecting a reduction to a fine powder. The charcoal 
and sulphur are separately pulverised; the saltpetre being obtained as a flour. (See 
Saltpetre.) 

b. Grinding by the aid of mill-stones. Two heavy vertical stones, similar to those in 
use for crushing linseed, revolve on a fixed horizontal stone. This contrivance is the most 
frequently used. 

c. Stampers are now employed only in small powder-mills. Frequently 10 to 12 stamps 
made of hard wood are placed in a row, each stamp being fitted with a bronze shoe, the 
entire weight being about 1 cwt. The stamps are moved by machinery, and make from 
40 to 60 beats a minute. The materials to be pulverised are placed in mortar-shaped 
cavities in a solid block of oak wood, each cavity containing 16 to 20 lbs. In Switzerland 
hammers instead of the stampers are employed. 

Mixing the ingredients. The mixing is performed by the aid of drums similar in size 
and shape to those used in the pulverisation, but made of stout leather instead of 
wood. The mixing of 100 kilos, of the ingredients, aided by the action of 150 bronze 
balls, takes fully three hours, the drum making ten revolutions a minute. It is 
usual to moisten the materials with 1 to 2 per cent, of water, supplied by fine jets 
regulated by taps. 

When stampers and mill-work are employed, the sulphur and charcoal are first 
separately pulverised by 1000 blows, and saltpetre having been mixed with these 
ingredients in the proper proportion, the machinery is again set in motion, and at 
first, after every 2000 blows, and then after every 4000 blows, the contents of the 
stamp-holes are removed from the one to the other, this operation being repeated 
some six or eight times. Where drums are used for the mixing operation, the 
moistening takes place after the mixture has been removed to a wooden trough, 
where 8 to 10 per cent, of its weight of water is added, care being taken to stir with 
a wooden spatula. 


CHEMICAL TECHNOLOGY. 


150 

Ca \iIe ? iNnvder SSlnp This operation, which in stamping-mills is the last of a continuous 
series, is separately performed where other machinery is employed. In the Trench 
and German powder-mills, the compression is effected in a rolling-mill, the rollers 
having a diameter of o*6 metre. The lower roller is made of wood, the upper of 
bronze; between the two an endless piece of stout linen is arranged, and upon this 
the moist powder is placed. The cakes are 1 to 2 centims. in thickness, with the 
hardness and very much the appearance of clay-slate. 

The operation of pressing is of great importance ; the stronger the pressure the greater 
the quantity of active material present in a given bulk, and hence the larger the volume 
of gas given off by the ignition of the powder. In many English powder-mills the 
pressing is effected by very powerful hydraulic machines, because, within certain limits, 
the more the materials are pressed, the more slowly the powder bums, when finished, 
while the temperature of ignition being lower, the expansion of the gases is less. If the 
powder were finished either without having undergone any pressure at all, or with only a 
slight pressure, it would act as a detonating-powder, the decomposition being instan¬ 
taneous throughout its entire mass. 

Granulation of the cake, >phe conversion of the cake into granules is effected— 

and Sorting the Powder. . 

1. By means of sieves. 

2. By means of peculiarly-constructed rollers, Congreve’s method; or 

3. According to Champy’s method. 

The granulation of gunpowder by the aid of sieves is carried on in the following 
manner :—The sieves consist of a circular wooden frame, across which a piece of parch¬ 
ment is stretched perforated with holes; the sieves are distinguished according to their 
uses, and by the size of these holes ; that employed for breaking up the cake having larger 
holes, and bearing a name different from the sieves used to produce the granules; this 
sieve again being distinguished from that employed for sorting the powder into the 
variously sized grain as commercially known. The sieves are provided 'with a so-called 
rummer, a lens-shaped disc made of hard wood, guaiac, box, or oak-wood, motion being 
imparted to the sieves by hand if they are small, or by suitably arranged machinery if 
they are large, in which case Lefebvre’s granulating-machine fitted with eight sieves in an 
octagonal wooden frame is generally employed. 

Congreve’s granulating-machine consists of three pairs of brass rollers, cr65 metre in 
diameter, provided with diamond-shaped projections 2 millimetres high, the projections 
of the upper rollers being coarser than those of the others. The broken-up cake is 
conveyed to the upper rollers by means of an endless canvas sheet. The mode of feeding 
this sheet is somewhat peculiar and ingenious : the loose bottom of a square box filled 
with coarsely-pounded cake is made to rise slowly upwards, and discharge the cake uni¬ 
formly upon the sheet through an opening in the side of the box. The cake while passing 
through the rollers is granulated, and then showered upon two sets of wire-gauze sieves to 
which a to-and-fro motion is imparted. Below these sieves again is a frame containing 
wire-gauze, the meshes of which are too small to admit of the passage of ordnance powder, 
while the dust and cartridge-powder readily fall through upon another wire-gauze, the 
meshes of which retain the rifle-powder but let the dust pass. The quantity of dust 
made by the Congreve machine is very small, owing to the fact that the rollers do not 
- crush but break the cake. Champy’s method, by which a very round-grained powder is 
obtained, is performed in the following manner :—Through the hollow axis of a wooden 
drum a copper tube, perforated with very small holes, is carried, and from these holes 
water spouts in a. fine spray upon the broken-up powder-cake placed in the drum, to 
which a comparatively rapid motion is imparted. Each drop of water forms the nucleus 
of a grain of powder, which is constantly increasing in size by being turned round in the 
midst of a mass of damp powder-cake ; the rotation of the drum is discontinued as soon 
as the grain has attained a sufficient size. The powder thus obtained is almost perfectly 
globular, but not of the same size; the sorting is effected by means of sieves, the over¬ 
sized grains being returned to the drum, as well as the undersized grains, which become 
the nuclei of proper-sized grain. According to the Berne method, round-grained powder 
is prepared by causing the angular-shaped powder to be rotated in stout linen-ba^s ; but 
by this plan much dust is formed. 

GranuliSdPowder. The aim of tllis operation is to impart symmetry to the grain, and 
to separate all the dust. It is performed in drums similar to those described above * 
5 cwts. of the powder is polished at a time, the drums rotating slowly for a few hours. 


EXPLOSIVE COMPOUNDS. 


151 

In some countries the polishing is effected by placing the powder in casks internally 
provided with quadrangular rods. In Holland, Dr. Wagner states that some black-lead 
is added to the powder during this operation to prevent ignition, but this is not generally 
done. Highly-polished powder does not readily attract moisture, and is to be preferred in 
a very damp climate. 

Drying the Powder. It is clear that this operation requires very great care in more 
than one respect. In small powder-works the powder is sometimes dried by 
exposure to the heat of the sun, being spread out on canvas sheets stretched in 
wooden frames ; or the drying-room is heated by a stove. In large powder-mills 
other methods of drying the powder are general. 

The quality of the powder very much depends on the care bestowed upon the drying. 
A too rapid drying entails the following disadvantages :— a. The powder may be very wet 
and not polished; coarse ordnance and ordinary military powder is never polished, and 
hence blackens the hands ; while, although the water is driven off, the nitre is carried to 
the surface of the grain, which thereby cakes together, b. By the too rapid evaporation of 
the water, channels and cracks are made in the grain, impairing its density, increasing 
its bulk, and rendering it more hygroscopic, c. Lastly, rapid drying entails a large 
amount of dust. For these reasons gunpowder, before being placed in the drying-rooms, 
is exposed for some time to a gentle heat in a well-ventilated room, the heat from a waste 
steam-pipe being sufficient. 

Sifli thep e owder from Having been dried, the powder is sometimes glazed, as it is 
termed; that is to say, again polished in the manner above described; but generally 
this second polishing is dispensed with, and the dry powder cleansed from the dust 
which adheres to it, by being placed in bags, made of a peculiar kind of woollen 
fabric, and arranged in frame-work to which a to-and-fro motion is given by 
machinery, the fine dust passing between the threads of the fabric into a box. The 
loss thus occasioned amounts on an average to 0*143 per cent., the dust consisting 
chiefly of charcoal. 

Properties of Gunpowder. Good powder is recognised by the- following properties :— 
1. Its colour should be slate-black; when blue-black it indicates that the powder 
contains too much charcoal, while a deep black colour shows the powder to be damp. 
If the charcoal employed was the so-called charbon roux, the colour of the powder 
will be a brown-black. 2. It should not be too much polished so as to shine like 
burnished black-lead. Small shining specks indicate that the saltpetre has crystal¬ 
lised on the surface. 3. The grains should be uniform in size, unless, of course, 
two differently-sized powders have been mixed. 4. The grain should crack uniformly 
when strongly pressed, should withstand pressure between the fingers, and should 
not be readily crushed to powder when pressed between the hands. 5. When pul¬ 
verised the mass should feel soft; hard sharp specks show that the sulphur has not 
been well pulverised. 6. Powder should not blacken the back of the hands or a 
sheet of white paper when gently rubbed. If it does so, there is either powder-dust 
or too much moisture. 7. When a small heap of powder is ignited on paper the 
combustion should be rapid, completely consuming the powder, and not setting fire 
to the paper. If black specks remain, the powder either contains too much charcoal, 
or it is an indication that that substance has been badly incorporated with the rest 
of the materials. Yellow streaks left after the ignition show the same defects for 
the sulphur. If no grains of powder remain, it is a proof that the powder was not 
well mixed; when any remaining grains of powder cannot be separately ignited, the 
saltpetre used was impure. If the powder on being ignited sets fire to the paper, it 
is a proof that it is either damp or of very inferior quality. 


152 


CHEMICAL TECHNOLOGY. 


The fact that different kinds of powder, although of the same weight to the cubic 
foot, do not have the same specific gravity, is shown by the following table :— 


, i cubic foot 

in pounds weight. 

Neisse’s ordnance powder.60 

„ „ „ (new mill) .. .. 60 

Berlin ordnance powder. 60 


Russian ordnance powder 


6o t 


Berne ordnance powder (No. 6) . 59! 

Berlin rifle powder (new mill). 60 

Berne rifle powder (No. 4).60 1 

Hounslow rifle powder . 59 

Berlin sporting powder (old mill).62 

Le Bouchet’s sporting powder.59! 

Very coarse-grained ordinary Dutch powder.. 60^5 

Very coarse-grained ordinary Austrian powder 64I 


Sp. gr 
177 
1-67 
1-63 
1 56 
1-67 
1-63 
1-67 
172 
177 
1-87 
1-87 
172 


Gunpowder can absorb more than 14 per cent, of moisture from the air; if the 
quantity of water thus taken up is not above 5 per cent., the powder, on being gently 
dried, reassumes its former activity; but if the quantity of water absorbed exceeds 
that amount, the gunpowder will not burn off rapidly, and when dried the single 
grains become covered with an efflorescence of saltpetre, of course impairing the 
composition and active qualities of the powder. Even what is termed dry powder 
contains at least 2 per cent, of hygroscopic moisture. Powder can be exploded by a 
heavy blow as well as by an increase of temperature, and as regards its explosion 
by a blow, very much depends upon the material upon which it is placed and with 
which the blow is imparted. The following list exhibits in decreasing order the 
materials between which a blow most readily ignites powder:—Iron and iron, iron 
and brass, brass and brass, lead and lead, lead and wood, copper and copper, copper 
and bronze. Eor this reason gunpowder magazines are provided with doors turning 
upon bronze and copper hinges, the locks also being of copper. When dry powder 
is rapidly heated to above 300° it explodes. Even if only a very small portion of the 
powder is thus rapidly elevated in temperature, the entire quantity, be it large or 
small, is exploded; hence, a very small quantity touched by a red-hot or burning 
body is sufficient to effect an explosion. It is generally held that the charcoal is 
first ignited, and that it spreads the ignition to the other materials. Although 
Mr. Hearder found by experiment that powder does not ignite when touched with 
a red-hot platinum wire while under the receiver of an air-pump, Professors v. 
Schrotter and Abel proved that gunpowder so placed ignited rapidly when heated 
by a spirit-lamp. 

composition of Gunpowder. Gunpowder consists very nearly of 2 molecules of saltpetre, 1 mole¬ 
cule of sulphur, and 3 of charcoal. Accordingly 100 parts of powder contain— 


Saltpetre. 74-84 

Sulphur . 11-84 

Charcoal (No. I.) 13-32 


The above figures approximately express the composition of the best kinds of sporting 
and rifle-powder. Ordinary powders, such as blasting-powder, consist of nearly equal 
molecules of nitrate of potassa and sulphur, with 6 molecules of charcoal. Accordingly 
100 parts contain— 0 ^ 

Saltpetre.66-03 

Sulphur . 10-4 5 

Charcoal (No. II.). 23-52 

















EXPLOSIVE COMPOUNDS 


5 53 

Products of the Drs. Bunsen and Schischkoff found the composition of a sporting and 
Combustion of Powder, rifle-powder to Le, in ioo parts, as follows:— 

Saltpetre .78-99 

Sulphur . 9-84 

! Carbon. 7*69 

Hydrogen. 0*41 

Oxygen . 3-07 

Ash .traces 

The residue of this powder after combustion was found to consist of— 

Sulphate of potassa .56’62 

Carbonate of potassa. 27-02 

Hyposulphite of potassa . 7-57 

Sulphuret of potassium. . 1 *06 

Hydrated oxide of potassa (caustic potassa) .. 1-26 

Sulphocyanide of potassium . o - 86 

Saltpetre. 5-19 

Carbon. 0-97 

Sulphur.| traces 


IOO-55. 

It appears from this analysis that the residue left after ignition of the gunpowder 
consists essentially of sulphate and carbonate of potassa, and not, as has been formerly 
stated, of sulphuret of potassium. The composition of the smoke of the powder was 
ascertained to be— 


Sulphate of potassa 

•. 65-29 

Carbonate of potassa 

•• 23-48 

Hyposulphite of potassa 

.. 4-90 

Sulphuret of potassium 

.. — 

Caustic potassa 

i -33 

Sulphocyanide of potassium 

•• o ’55 

Saltpetre. 

• • 3-48 

Carbon (charcoal). 

.. i-86 

Sesquicarbonate of ammonia 

Oil 

Sulphur. 





100-00 


From these figures it is clear that the smoke of gunpowder consists essentially of the 
same substances as the residue from the combustion, the only difference being that the 
sulphur and nitrate of potassa of the powder have been more completely converted into 
sulphate of potassa, while instead of the sulphuret of potassium, carbonate of ammonia 
makes its appearance. 100 parts by volume of the gaseous products of the combustion 


were found to consist of— 

Carbonic acid.52-67 

Nitrogen.41-12 

Oxide of carbon. 3-88 

Hydrogen . 121 

Sulphuretted hydrogen .. .. o-6o 

Oxygen. 0*52 

Protoxide of nitrogen. — 


ioo-oo 

The solid residues of combustion formed during the generation of the gases were found 


to be— 

Sulphate of potassa .62-10 

Carbonate of potassa. 18-58 

Hyposulphite of potassa .. .. 4-80 

Sulphuret of potassium .. .. 3-13 

Sulphocyanide of potassium .. 0-45 

Nitrate of potassa. 5-47 

Charcoal. I *07 

- Sulphur. 0-20 

Sesquicarbonate of ammonia .. 4-20 


10000 











































CHEMICAL TECHNOLOGY. 


154 


The decomposition of powder by its ignition may be represented by the following 
formulae:— 


1 gnu. of powder 


/ Saltpetre 

0-789> 

1 Sulphur 

0-098 / 

/ 

f C 0-076 > 

I Charcoal ■ 

Ho-oo4 i 

V 

(00-030/ 


yields after 
combustion 


/ 


/ 


Residue/ 
o - 68o 


Gases 

0-314 

0-994 


k 2 so 4 

k„co 3 

kao 3 

k 2 s 

KCNS 

KN0 3 

c 

s 

\(NH 4 ) 2 C 03 


Grm. 

0-0990 

0-2010 

0-0090 

0-0002 

0-0018 

0-0014 



Grm. 

0-422 

0126 

0-032 

0-021 

0-003 

0-037 

0-007 

O-OOI 

0-028 

C.c. 
79-40 
101-71 
7‘49 
2 '34 
1-16 
i-oo 


193-10 

According to the recent researches of Mr. Craig, and later investigations of M. Eedorow 
(1869), the products of the combustion of powder vary according to the pressure this 
substance is subjected to while being ignited. There has not hitherto been found any 
really effective substitute for gunpowder; fulminates and mixtures containing chlorate 
of potassa ignite too quickly and cause the bursting of the gun, while gun-cotton yields 
among its products of ignition water and nitrous acid, which act destructively on the 
metal, and also interfere with continued firing. 

New kinds of Blasting Under the name of pyronene there is sold a new kind of blasting- 

Powder. powder, consisting of nitrate of soda 52-5 parts, sulphur 20, and 

spent tan 27-5 parts. It is, of course, far cheaper than ordinary powder, but presumably 
not very useful nor active. Captain Wynands, of Belgium, has successfully introduced 
a substance, to which he has given the name saxifragine, consisting of nitrate of baryta 
76, charcoal 22, and nitrate of potassa 2 parts. Schultze’s (1864) wood-gunpowder consists 
of granulated wood treated with a mixture of nitric and sulphuric acids, and next 
impregnated with a solution of nitrate of potassa; this material is manufactured at 
Edgeworth Lodge, Hants. M. Bandisch has invented a process by which this wood- 
gunpowder may be compressed into a solid substance exerting great power, and free 
from danger by transport. Lithofracteur, a white blasting-powder used in Belgium, 
is a substance similar to gun-cotton. The haloxylin of MM. Neumeyer and Eehleisen is 
a mixture of charcoal, nitre, and yellow prussiate of potassa. Callou’s blasting powder 
is a mixture of chlorate of potassa and orpiment. Nitroleum is, in fact, nitroglycerine, 
which, with dynamite and dualin, will be spoken of presently. Picrate of potassa is used 
in France and in England for filling shells intended for the destruction of armour-plated 
ships, and for the manufacture of picrate gunpowder. 

Testing the strength In order to determine the streng-th or projectile force of gunpowder, 
of Gunpowder, and which for equality of composition is dependent on the mechanical 
treatment the powder has undergone, the following apparatus are used:—Test mortar, 
rod testing machine, lever testing machine, ballistic pendulum, and chronoscope. The 
first of these contrivances is a piece of heavy ordnance, charged with 92 gnus, of powder, 
and a ball weighing 29-4 kilos., the mortar being placed at an angle of 45 0 . The bore of 
the mortar is 191 millemetres in diameter by 239 in depth. Powder of good quality should 
propel the ball a distance of 225 metres, and frequently the ball is carried a distance of 
250 to 260 metres. The rod gunpowder testing apparatus consists of a mortar placed 
vertically, and which, when charged with 22 to 25 gtms. of powder, lifts a weight of 8 lbs., 
made to move between toothed rods; by the height this weight is raised, springs attached 
to the weight fastening in the notches of the rods and holding it, the quality of the powder 
is judged. 

White Gunpowder. In the year 1849 M. Augendre brought out a new kind of gunpowder, 
which, under the names of German white and American white gunpowder, has been 
occasionally employed. This powder consists of yellow prussiate of potassa, chlorate of 
potassa, and cane sugar. These materials, having been thoroughly mixed in a dry state, 
can be used in powder or in grains, igniting in contact with red-hot and flaming substances, 
but not by friction nor percussion. This white gunpowder may be preferred to the 








EXPL OSIVE COMPO UNDS. 


155 


ordinary powder for the following reasons:—Being composed of unvarying substances, 
this powder can always, by weighing out the proper quantities of each ingredient, be 
obtained of uniform strength and quality. The ingredients are not hygroscopic to any 
extent, and are not acted upon by exposure to the air. The manufacture requires but a 
very short time, the projectile force is far greater, and the powder need not be granulated. 
On the other hand, this powder acts, during its ignition, so very strongly upon iron and 
steel that it can only be used in bronze ordnance, and in the filling of shells, &c. It 
is more readily fired than ordinary gunpowder, although less so than other mixtures 
containing chlorate of potassa. Finally, its manufacture is very expensive. According 
to the experiments of J. J. Pohl (1861) on this subject, the following is the best recipe 


for this powder:— 

Yellow prussiate of potassa.28 parts 

Loaf Sugar .23 „ 

Chlorate of potassa.49 „ 

This mixture is approximative]^ equal to— 


1 molecule of Prussiate of potassa, 

1 „ Sugar, 

3 molecules of Chlorate of potassa ; 

corresponding in 100 parts to 28-17 of prussiate of potassa, 2278 of sugar, and 49-05 of 
chlorate of potassa. As no accurate and reliable analyses of the products of the com¬ 
bustion of this powder have been made, and as these products will vary with respect to 
the conditions under which the ignition takes place, whether in open air or in a close 
vessel, it can be merely calculated, that assuming complete combustion to take place, 
100 parts of this powder will yield :— 

Nitrogen. 1*865 parts 

Carbonic oxide .. .. 11-192 „ 

Carbonic acid .. .. 17*587 „ 

Water .16788 „ 


Total gaseous products .. 47*442 „ 

The solid residue will consist of— 

Cyanide of potassium .. 17*385 parts 
Chloride of potassium .. 29-840 „ 
Carburet of iron (FeC 2 ) 5*333 ,, 


Total non-volatile products 52*558 „ 

The bulk of gaseous matter evolved by the ignition of 100 grms. of this powder, taken 
at o° and 760 m.m. Bar., is as follows :— 

Nitrogen.. .. 1927-0 ciibic centims. 

Carbonic oxide 8942-9 „ 

Carbonic acid 8942-9 „ 

Aqueous vapour 20867-9 „ 

40680-4 „ 

As the temperature of combustion is estimated at 2604-5° the quantity of the gases is 
431162 c.c. 

Chemical principles of Under the name of fireworks we include certain mixtures of 

Pyrotechny. 

combustible substances employed as signals, as destructive agents (for instance, 
Congreve rockets), and for purposes of display. 

The various forms are, according to the end in view, so contrived as to burn 
off either rapidly or slowly, and with more or less emission of gaseous matter, heat, 
and light. These mixtures are mainly distinguished as heat-producing, ignition 
communicators (technically termed a match), and light-producing. The principle 
of the rational manufacture of fireworks, applying the word in its extended sense, is 
that neither any excess of the combustible nor of the combustion promoting and 
supporting agents should be employed, and that unavoidable accessory materials, 
viz., such as are intended only to keep the essential ingredients in a certain Required 
shape, the paper casings, &c., be in precisely the quantity required. The best 








CHEMICAL TECHNOLOGY. 


IS6 

proportions of the combustible and combustion-supporting substances can be readily 
ascertained by theoretical calculations; for instance, it will be evident that a 
mixture of 2 equivalents of saltpetre and 1 equivalent of sulphur (1), or a mixture 
of 2 equivalents of saltpetre and 3 equivalents of sulphur (2), is in each instance 
wrong; in the latter, too much of the combustible body is used; and in the former 
case, too much of the supporter of combustion is employed :— 

(1) . S can take tvp from 2KNO3 at most 3O, consequently 3O remain inactive. 

(2) . 3S and 2KNO3 yield either I£ 2 S and 2SO3, or a mixture of K 2 S 0 4 , K 2 S, 
and S 0 2 ; in each case some sulphur remaining unburnt. 

We have to bear in mind, however, that it is not always possible to elucidate 
theoretically the decomposition of firework mixtures, as the affinity of the substances 
which react upon each other is not well known, and depends on accessory con¬ 
ditions and comparatively unknown influences. It will require a more advanced 
knowledge of the products of the decomposition of the different substances and 
their specific heat before we can predict with some degree of certainty the best 
mixtures. As regards the existing mixtures, they are the result of a lengthy series 
of experiments, really made by rule of thumb, though with a certain correspondence 
with the best composition theory can give, that is to say, many of these mixtures 
have been somewhat modified and improved by modern science. 

The more commonly used These mixtures consist mainly of saltpetre, sulphur, and charcoal, 
Firework Mixtures, either in the same proportions as those in use for gunpowder, or 
with an excess of sulphur and charcoal. Some mixtures contain instead of saltpetre 
chlorate of potassa and other salts, not always essential to the combustion, but intended 
either to intensify the light evolved or impart to it a distinctive colour, as in signals 
and Bengal lights. 

Gunpowder Is used in fireworks when it is desired that there should be projectile force. 
A slower combustion of the powder is obtained partly by the use of the so-called flour of 
powder, that is pulverised, not gTanulated powder, partly by compressing the mixture. If, 
however, it is intended to produce loud reports, granulated powder is used. 

Saltpetre and Sulphur Mixture. This consists of 2 molecules (75 parts by weight) of saltpetre, 
and 1 molecule (25 parts by weight) of sulphur, and is used as the chief constituent of 
such firework mixtures as are intended to bum off slowly and evolve a strong fight. 
However, this mixture is not used by itself for two reasons, viz., it does not develope 
a sufficient degree of heat to support its continued combustion, and does not possess a 
sufficient projectile force, being capable of producing in the best possible condition of 
complete ignition only 1 molecule of sulphurous acid— 

2 KN 0 2 -f S = K 2 S 0 4 + S 0 2 + N; 

that is to say, 1 part by bulk of this mixture only yields 7-28 volumes of gas. For these 
reasons the saltpetre-sulphur mixture is employed with charcoal or floury gunpowder. 

Grey-coioured Mixture. Such a mixture, sanctioned by long use, is that known as grey- 
coloured mixture, consisting of 93*46 per cent, of saltpetre-sulphur, and 6*54 of floury 
gunpowder. This mixture is the chief constituent of other compounds intended to burn 
slowly, emitting at the same time a brilliant fight, owing to the fact that the sulphate of 
potassa formed by the combustion acts similarly to a solid brought to an incandescent 
state. All mixtures intended to emit fight, including coloured fights, are prepared upon 
the same principle, that the salt which is to give colour shall be non-volatile at the tem¬ 
perature of combustion. 

chlorate of Potassa Mixtures. This salt, IvC 10 3 , when in presence of combustible sub¬ 
stances, gives off its oxygen to the latter more readily, rapidly, and completely than salt¬ 
petre ; accordingly this salt is used in all mixtures in which it is desired to combine rapid 
ignition with combustion. Formerly a mixture of 80 parts by weight of clilorate of 
potassa and 20 parts of sulphur, was added to intensify and quicken the combus¬ 
tion of mixtures consisting of more slowly burning salts. A mixture of sulphur, char- 

Friction Mixtures. coal, and chlorate of potassa constitutes an active percussion 
Percussion Powders, powder. A mixture of equal parts by weight of black sulphuret of 
antimony and chlorate of potassa is used for the purpose of discharging ordnance by 
means of a percussion tube placed into the touchhole of the gam. Sir William Armstrong 
uses for this purpose a mixture of amorphous phosphorus and chlorate of potassa. 


EXPLOSIVE COMPOUNDS. 


157 


Mixture for igniting the This mixture consists either of chlorate of potassa and black sul- 
Cartridges of Needle-guns, phuret of antimony, or a compound containing fulminate of mercury. 
The following is a good preparation:—16 parts of chlorate of potassa, 8 parts of black 
sulphuret of antimony, 4 of flour of sulphur, 1 of charcoal powder, are moistened with 
either gum or sugar water, and about 5 drops of nitric acid added. A small quantity, 
technically known as the pill , is placed in the cartridge, and ignited by the friction pro¬ 
duced by the sudden passage of the steel needle through it. In this country either the 
above or a mixture of amorphous phosphorus and chlorate of potassa is used. Leaving 
the fulminates of silver and mercury out of the question, the explosive bodies and 
their applicability to warlike purposes and war pvrotechny have not been sufficiently 
investigated. Nitromannite or fulminating mannite, the picrates of the alkalies, 
and nitroglycerine, of which we shall presently treat more fully, especially deserve notice. 
M. Dessignolles, who suggests that instead of saltpetre, picrate of potassa should be used 
in the manufacture of gunpowder, states that quite different products are formed by the 
ignition of picrate of potassa, when effected in the open air (a), or under pressure ( 0 ):— 
a. 2C 6 H 2 K(N0 2 ) 3 0 = K 2 C 0 3 + 5 C + 2N -I- NO + N 0 2 + 4 C 0 2 + CHN. 


Picrate of potassa. 

a. 2C 6 H,K(Ncg 3 o= 


K 2 C 0 3 -f- 6C 3N -j- 5C0 2 -\- 2H 2 + 0 . 


Picrate of potassa. 

Fulminating aniline, chromate of diazobenzol, obtained by the action of nitrous acid 
upon aniline, and the precipitation of the product by the aid of a hydrochloric acid solu¬ 
tion of bichromate of potassa, is, according to MM. Caro and Griess, an efficient substitute 
for fulminating mercury. 

Heat-producing Mixtures. These consist chiefly of floury gunpowder and grey mixture, 
to which are added those organic substances, as pitch, resin, tar, igniting readily, but 
consumed more slowly than any firework. The heat generated by the combustion of 
fireworks is much higher than is required to ignite wood, but not of sufficient duration to 
cause the thorough burning of the wood, hence the addition of tar, &c. 

Coloured Fires. The salts employed to produce coloured flames are—the nitrates of 
baryta, strontia, and soda, and the ammoniacal sulphate of copper. The so-called cold 
fused mixture, composed of grey mixture, floury gunpowder, and sulphuret of antimony, 
moistened with brandy and then mixed, produces a white flame. The mixtures for 
coloured fires used in artillery laboratories are the undermentioned, calculated for 100 
parts of each mixture :— 

1. Chlorate of potassa . 3 1 2 7 

2. Sulphur. 

3. Charcoal . 

4. Nitrate of baryta. 

5. Nitrate of strontia . 

6. Nitrate of soda .. ... 

7. Ammoniacal sulphate of copper 

8. Saltpetre . 

9. Black sulphuret of antimony. 

10. Floury gunpowder .. .. _. . . 

It is hardly necessary to mention that great care is requiied in mixmj 
rials, and that each ingredient ought to be pulverised separately. . .. 

According to M. Uhden a beautiful white flame edged with blue is obtained by 
the ignition of the following mixture 20 parts of saltpetre, 5 of sulphur, 4 of sulphuret 
of cadmium and 1 part of charcoal. Chloride of thallium with other ingredients yields a 
beautiful oreen flame. Magnesium was used during the Abyssinian war in various ways 
when a brilliant light was required. The chlorates of the alkaline earth bases and the 
chlorate of soda would be preferable, were it not for the expense, and for the facts 
that these salts are rather hygroscopic and liable to spontaneous combustion. The car¬ 
bonates of baryta and of strontia are sometime^ used instead of the nitrate. According to 
MM. Dessignolles and Castelliaz, most brilliant coloured flames are obtained with picrate 

of ammonia in the following proportions:— 

v f Picrate of ammonia .. .. 50 

Yellow | pj[ cra t e 0 f protoxide of iron. 50 

( Picrate of ammonia .... 48 

Green j Nitrate of baryta. .. .. 52 

.p , j Picrate of ammonia .. .. 54 

lied. | Nitrate of strontia .. .. 46 


a. 

b. 

c. 

d. 

e. 

Green. 

Red. 

Yellow. 

Blue. 

White 

3 2 4 '7 

297 

— 

54'5 

— 

9-8 

17*2 

23-6 

— 

20 

5-2 

17 

3-8 

iS-i 

— 

52-3 

— 

— 

— 

— 

— 

457 


— 

— 

_ 

— 

9 5 6 7 8 9 10 

27-4 

— 

— 

— 

62’8 

— 

60 

— 

57 

— 

— 

5 

T V 

care is 

required 

0 

in mixing these mate- 












r 58 CHEMICAL TECHNOLOG Y. 

b. Nitroglycerine. 

.Nitroglycerine. This substance, also known as fulminating oil, nitroleum, trinitrine, 
glyceryl-nitrate, glonoine, was discovered in 1847 by Dr. A. Sobrero, while a student 
in the laboratory of Professor Pelouze, at Paris. Since the year 1862, M. Alfred 
Nobel, a Swede, has manufactured this liquid on the large scale. The formula of 

n tr \ 

nitroglycerine is C 3 H 5 N 3 0 9 or ^-q 5 ^ } 0 3 ; consequently it consists of glycerine, 
^ 3 H 5 } ^ 3 ’ * n which 3 atoms of IT have been replaced by 3 atoms of N 0 2 . 100 

parts of nitroglycerine yield on combustion— 


Water 

20 parts. 

Carbonic acid 

58 

Oxygen .. 

3*5 >> 

Nitrogen .. 

18*5 „ 


100*0 parts. 

As the sp. gr. of nitroglycerine is 1 

6, 1 part by bulk will yield on combustion— 

Aqueous vapour 

.554 volumes. 

Carbonic acid .. 


Oxygen .. .. 

. 39 

Nitrogen .. 

.236 


1298 

According to experiments made in 

Belgium, the -combustion of nitroglycerine 

does not yield free oxygen, but a large quantity of protoxide of nitrogen ; accord- 


ingly, the following equation will give some idea of the mode of explosion :— 

. - \ / Carbonic acid, 6 C 0 2 . 

2 molecules of / _ } Water, 5H 2 0 

Nitroglycerine, C 3 H 5 N 3 0 9 ( 1 Protoxide of Nitrogen, N 2 0 . 

V Nitrogen, 4N. 

M. Nobel states that the heat set free by explosion causes the gases to expand to 
eight times their bulk; accordingly, 1 volume of nitroglycerine will yield 10*384 
volumes of gas, while 1 part by bulk of powder only yields 800 volumes of gas ; the 
explosive force of nitro-glycerine is, therefore, to that of powder— 

By volume as 13 : 1, 

By weight as 8: 1. 

In order to prepare nitroglycerine, very strong nitric acid, density 49 0 to 50° B. 
4= 1*476 to 1 *49 sp. gr., is mixed with twice its weight of concentrated sulphuric acid. 
3300 grms. of this mixture, thoroughly cooled, are poured either into a glass flask 
or into a glazed earthenware jar, placed in a pan of cold water, and there is nex L 
gradually added 500 grms. of concentrated and purified glycerine, having a densit] 
at least of30° to 31 0 B. — sp. gr. 1*246 to 1*256, care being taken to stir constantly 
According to Dr. E. Kopp’s recipe (1868) the acid mixture should consist of 3 parts 
of sulphuric acid at 66° B. = 1767 sp. gr., and 1 part of fuming nitric acid. To 350 
grms. of glycerine 2800 grms. of the acid mixture are added ; and in performing this 
operation care should be taken to avoid any perceptible heating for fear of con¬ 
verting by a violent reaction the glycerine into oxalic acid. The mixture is now left 
to stand for five or ten minutes, and afterwards poured into five or six times its bulk 








EXPLOSIVE COMPOUNDS. 


159 


of very cold water, to which a rotatory motion has been imparted. The newly- 
formed nitroglycerine sinks to the bottom of the vessel as a heavy oily liquid, which 
is washed by decantation; but if not intended for transport—and experience has 
proved the transport of nitroglycerine to be highly dangerous—the washing may be 
dispensed witl\, as neither any adhering acid nor water impairs the. explosive 
properties. Nitroglycerine is now generally made on the spot in America and else • 
where by those whom experience in mining, quarrying, and engineering matters 
has taught the real value of this very powerful agent. 

Nitroglycerine is an oily fluid of a yellow or brown colour, heavier than and 
insoluble in water, soluble in alcohol, ether, and other fluids; when exposed to 
continuous cold, not of great intensity, it becomes solidified, forming long needle- 
shaped crystals. The best means of exploding nitroglycerine is a well-directed 
blow, neither a spark nor a lighted body will cause the ignition, which even with a 
thin layer takes place with difficulty, only part being consumed. A glass bottle filled 
with nitroglycerine may be smashed to pieces without causing the contents to explode. 
Nitroglycerine may even be gently heated and volatilised without decomposition or 
combustion, provided violent boiling is carefully prevented. When a drop of nitro¬ 
glycerine is caused to fall on a moderately hot piece of cast-iron the liquid is quietly 
volatilised; if the iron is red-hot the liquid bums off instantaneously, just as a grain 
of powder would do under the same conditions; if, however, the iron is at that heat 
which will cause the immediate boiling of the nitroglycerine, it explodes with great 
force. Nitroglycerine, especially if sour and impure, is liable to spontaneous decom¬ 
position, which, accompanied by the formation of gas and of oxalic acid, may have 
been the proximate cause of some of the dreadful explosions of this substance, it 
being surmised that the pressure exerted by the generated gases upon the fluid in 
hermetically closed vessels had something to do with the occurrences. On this 
account M. K. List advises that vessels containing nitroglycerine should be only 
loosely stoppered, or if being transported provided with safety-valves. Nobel 
secures nitroglycerine from explosion by dissolving it in pure wood-spirit, from 
which it may be again separated by the addition of a large quantity of water. Mr. 
Seeley on this score observes that:—1. The wood-spirit is expensive, and lost in the 
large quantity of water required for precipitating the nitroglycerine; 2. Wood-spirit, 
being volatile, may evaporate, and leave the nitroglycerine unprotected; 3. There 
is a change of chemical action between these bodies; 4. The vapour of wood-spirit 
i3 very volatile, and forms with air an explosive mixture. Many suggestions have 
been made as to rendering nitroglycerine safe to warehouse; among them may be 
noted the mixing with pulverised glass in a manner similar to Gale’s process foi 
o-unpowder. Wurtz recommends the mixture of nitroglycerine with equally dense 
solutions of either of the nitrates of zinc, lime, or magnesia, so as to form an 
emulsion, the nitroglycerine being recovered simply by the addition of water. The 
taste of nitroglycerine is sweet, but at the same time burning and aromatic; it is a 
violent poison even in small doses, and its vapour is of course equally virulent, hence 
great care is required in working with this substance in localities where, as in mines 
and pits, the supply of fresh air is limited. Instead of manufacturing nitroglycerine- 
in works specially arranged for that purpose, and transporting, this dangerous 
compound, it is better, as advised by and executed under the direction of Dr. E. 
Kopp, at the Saverne quarries, to have the quantity required for daily use prepared 
on the spot by intelligent workmen. Notwithstanding the very serious accidents 


i6o 


CHEMICAL TECHNOLOGY. 


which have been caused by the explosions of nitroglycerine in this country as well 
as abroad, and the consequent prohibition of its use, there is no reason why this 
powerful agent should not be employed according to Kopp’s suggestion. Instead of 
the acid mixture used in the preparation of nitroglycerine, M. Nobel suggests the 
following:—In 3J parts of strong sulphuric acid of 1*83 sp. gr. is dissolved 1 part 
of saltpetre, and the fluid cooled down; the result is the separation of a salt consisting 
of 1 molecule of potassa, 4 molecules of sulphuric acid, and 6 molecules of water, 
and which at 320 F. is altogether eliminated from the fluid, leaving an acid which, 
by the gradual addition of glycerine, is converted into glonoine, afterwards separated 
by water, as already described. 

Nobel’s Dynamite. Under the name of dynamite, Nobel, in 1867, brought out a new 
explosive compound, consisting of 75 parts of nitroglycerine absorbed by 25 parts 
of any porous inert matter, as finely-divided charcoal, silica. As evidenced by the 
experiments of Bolley and Kundt, dynamite has the advantage over nitroglycerine 
of not being exploded even by the most violent percussion, therefore requiring a- 
peculiarly-arranged cartridge. The explosion is attended with such force that 
large blocks of ice are shattered to atoms. Dynamite burns off quietly in open 
air, or even when loosely packed, the combustion being accompanied by an evolution 
of some nitrous acid; but when dynamite is exploded there are generated only 
carbonic acid, nitrogen, and aqueous vapour, no smoke being formed, and only a 
white ash left. Dynamite is not affected by damp, and undoubtedly offers great 
advantages as regards its* use in mining, quarrying, and similar operations, for 
although the price exceeds four times that of powder, dynamite performs eight times 
as much work with less danger, and less labour in boring blast holes. The dynamite 
is placed in cartridges of thick paper, and ignited by means of a fusee, which passes 
through the sand serving the purpose of a wad. Dynamite can be transported 
without danger of explosion. Dittmar’s dualin is a mixture of nitroglycerine with 
saw-dust or wood-pulp as used in paper mills, both previously treated with nitric and 
sulphuric acids. 

c. Gun-Cotton. 

Gun-cotton. This substance, also known as pyroxylin and fulmicotton, was discovered 
in 1846, simultaneously by the late Professor Schonbein, at Balse, and by Dr. R. 
Bottger, at Frankfort-on-Main. The mode of preparing this substance is as follows:— 
Equal parts of strong concentrated sulphuric acid, sp. gr. = 1*84, and fuming nitric 
acid are poured into a porcelain basin; as much cotton-wool is steeped in the fluid as 
the acid is capable of thoroughly moistening, and the vessel covered with a glass 
plate, and left for a few minutes. The cotton-wool is then removed from the acid, 
immediately transferred to a vessel containing a large quantity of water, and washed 
with care, the water being renewed until no more acid adheres to the gun-cotton, 
which is next dried in a current of warm air, and finally combed to remove all the 
lumps. The cotton should not be left too long in the acid, as it might become 
entirely dissolved. According to experiments instituted at Paris, in one of the 
powder mills—for in France no one is allowed to manufacture powder or gun-cotton 
except the Government—the following are the conditions under which the best results 
are obtained:—1. Equal parts of sulphuric and nitric acids and well-cleansed 
cotton. 2. Time of immersion in acid mixture from 10 to 15 minutes. 3. The same 
acid may be used once again, but then the time of immersion of the cotton 


GUN COTTON. 


161 


should he longer. 4. The gun-cotton haying been thoroughly washed should be dried 
slowly at a gentle heat. 5. Impregnating with nitre increases the strength of the 
gun-cotton. 

Properties of Gun-Cotton. In its outward appearance gun-cojfcton does not differ from ordinary 
cotton, neither is any difference perceptible by microscopic investigation. It is insoluble 
in water, alcohol, and acetic acid, difficultly soluble in pure ether, but readily soluble in 
ether which contains alcohol, and in acetic ether. Gun-cotton is liable to spontaneous 
decomposition, which may even induce its spontaneous combustion; this decomposition is 
attended with the evolution of aqueous vapour and of nitrous acid fumes, the remaining 
substance containing formic acid. As regards the temperature at which gun-cotton 
ignites statements differ; it has in some instances been dried at 90° to ioo° without 
any dangerous consequences, while it has been found to ignite at 43 0 . Instances are 
on record of serious explosions of gun-cotton having taken place under conditions 
which leave no doubt that the greatest care is required in handling and warehousing 
this substance; for instance, a small magazine, filled with gun-cotton, situated in the 
Bois de Vincennes, Paris, was exploded by the sun’s rays; and at Faversham the Le Bouchet 
drying-rooms, which could not possibly be heated above 45 0 to 50°, exploded with great 
violence. Gun-cotton explodes by percussion, leaving no residue after its ignition. Good 
gun-cotton may be burned off when placed on dry gunpowder without igniting the latter. 

It is very hygroscopic, but may be kept for a length of time under water without affecting 
its explosive properties. 

According to the best chemical analysis, gun-cotton is trinitro-cellulose, 

C 6 H 7 (N 0 2 ) 3 0 5 , 

consequently it is cotton considered in a pure state as cellulose, C6 H io 0 5 , 3 atoms ot t 
the hydrogen of which have been replaced by 3 atoms of hyponitric acid. 100 parts 


of gun-cotton contain— 

Carbon .24*24 

Hydrogen. 2*36 

Oxygen .59*26 

Nitrogen. 14*14 


100*00 

The conversion of cotton into gun-cotton may therefore be expressed by the following 
formula:— 

CgH^s + 3HN0 3 =: C6H 7 (N0 2 )305 + 3H 2 0 ; 

Cotton. Gun-Cotton. 


the sulphuric acid being employed only for the purpose of absorbing water. 
Assuming that the cellulose is entirely converted into trinitro-cellulose, 100 parts of 
cotton ought to yield 185 parts of gun-cotton, and when the conversion forms binitro¬ 
cellulose, 100 parts of. cotton ought to yield 155 parts of gun-cotton. The under¬ 
mentioned are the results of direct investigation. For 100 parts of cotton— 


Pelouse (in ten experiments, 1849) found 168 to 170 parts of gun-cotton. 

Schmidt and Hecker (1848) ,, 169 

Van Kerckhoff and Beuter (1849) ,, 176*2 

W. Crum (1850) ,, 178 

Bedtenbacher, Schrotter, and Schneider (1S64),, l, 'c> 

V. Lenk (1862) ,, 155 

Blondeau (1865) ,, 165*25 

By the explosion of gun-cotton in vacuo , carbonic oxide, aqueous vapour, and 
nitrogen are evolved. The same products, with the addition of nitrous acid and 
cyanogen, are generated by the explosion of gun-cotton in closed vessels. 1 grm. of 
12 








CHEMICAL TECHNOLOGY. 


162 

gun-cotton yields, according to Schmidt, 588 c.c. gases, these gases consisting in 


too parts by volume of— 

Carbonic oxide.30 

Carbonic acid.20 

Marsh gas. 10 

Deutoxide of nitrogen .. .. .. 9 

Nitrogen. 8 

Aqueous vapour .23 


100 

1 part by weight of gun-cotton is equal in projectile power to 4^5 to 5 parts of gun¬ 
powder. 

Gun ' c f °r fc Gu^owder! titute Gun-cotton has not yet been adopted in practice as a good 
substitute for gunpowder; its large bulk, coupled with the fact that the explosion is 
attended with the evolution of much water and nitrous acid, render it inconvenient 
as a substitute for powder. 

other uses of Gun-Cotton. Gun-cotton is advantageously employed in blasting, and has been 
used as a substitute for fulminating mercury in gun-caps when mixed with chlorate of 
potassa. The experiments of Professor Abel, of Woolwich, have led to great improve¬ 
ments in the manufacture of gun-cotton, carried into practice by Messrs. Prentice, of 
Stowmarket, and consisting chiefly in mechanical operations. The cotton, either by 
spinning and weaving, by pulping, or the aid of suitable solvents, is brought into a con¬ 
dition in which it has been found an excellent and cleanly substitute for gunpowder, 
having the advantages of not giving off smoke, exploding with less noise, and not fouling 
the guns. The detailed description of the method of these operations is not necessary 
here. Gun-cotton in many cases may serve the purpose of asbestos for filtering strong 
acids and other concentrated fluids which cannot be filtered through paper. 

collodion. Maynard employs a solution of gun-cotton in ether as a kind of glue or 
varnish, and gives it the name of collodion. This solution has the appearance of a 
syrup, and a thin film poured on the skin, leaves, by the evaporation of the ether, a 
strongly adhesive compact layer; hence collodion is applied in surgery, photography, 
and as a waterproof coating instead of varnish, especially to protect the composition 
of lucifer-matches from the effects of damp. The film of pyroxylin, deposited after 
the evaporation of ether, is insoluble in water and alcohol, becomes highly negatively 
electric when rubbed with the dry hand, and may be obtained so thin as to exhibit 
the colours of the Newton rings. Legray prepares in the following manner a gun¬ 
cotton quite soluble in ether 80 grms. of dried and pulverised nitrate of potassa 
are mixed with 120 grms. of concentrated sulphuric acid, and in the pulpy acid mass 
are thoroughly immersed by the aid of a glass rod or porcelain spatula 4 grms. of 
cotton, which is stirred about for a few minutes; next the vessel containing acid and 
cotton is placed in a large quantity of water, and the converted cotton washed until 
all the acid is eliminated, when it is dried. Soluble cotton may be made with 
nitrate of soda, 17 parts; sulphuric acid, sp. gr. = r8o, 33 parts; cotton, \ part. 
The converted cotton is soluble in acetic ether, acetate of oxide of methyl, wood- 
spirit, and aceton ; the usual solvent is a mixture of 18 parts of ether and 3 parts 
of alcohol. 








COMMON SALT. 


163 


Common Salt. 

Occurrence. Common salt, or .chloride of sodium, consists of— 

Chlorine, Cl . 35-5 60*41 

Sodium, Na .23*0 39*59 

58*5 ioo-op 

and is found on our globe in the solid, as rock-salt, as well as dissolved in sea-water 
in enormously large quantities. It occurs as rock-salt in extensive layers alternating 
with those of clay and gypsum at an average depth of 100 metres. The following are 
a few of the localities “where rock-salt is met with in the tertiary formation :— 
Wieliczka, Poland; the northern slopes of the Carpathian mountains, and in several 
districts of Hungary; in the chalk formation of Cardona, Spain; in the Eastern 
Alps, Bavaria, Salzburg, Styria, and the Tyrol. Among the trias formation are the 
salt deposits of the Teutoburg-wood, Germany, and a great many others, among them 
the celebrated Stassfurt deposits. In England rock-salt is found in Cheshire, this 
county being also plentifully supplied with saline springs, the water of which yields 
on evaporation an abundance of salt. Petroleum wells are found with salt in many 
parts of Asiatic Eussia, in Syria, Persia, and the slopes of the Himalaya. Salt 
occurs plentifully in several districts of Africa, America, and other parts of the 
world, and mixed with clay and marl, forming salt-clay. Salt occurs secondarily by 
having been dissolved, at a depth varying in Germany from 91 to 555 metres, by 
water, which carries it again to the surface, there forming salt springs and salt lakes, 
from which the salt is obtained by evaporation. Among the salt lakes may be 
noticed the lake near Eisleben, Germany, the Elton Lake, near the Wolga, Eussia, 
the Dead Sea, and the Salt Lake of Utah, United States. 

There can be no doubt that the common salt met with in salt springs owes its 
origin to the solvent action of water upon rock-salt, and as rock-salt is largely met 
with in sedimentary geological formations, the prevalence of this formation in 
Germany has ‘there given rise to a large number of salt springs. Common salt is 
also found in sea-water, and if obtained by its evaporation is often termed sea-salt; 
or if deposited, as is the case in the Polar regions, by intense cold on the surface of 
ice-fields, it is known as rassol. Common salt is largely obtained as a by-product 
of some chemical operations, as in the conversion of sodium-nitrate into potassium- 
nitrate by the aid of chloride of potassium. 

Met sai d t from r lea-water mmon The constituent salts of sea-water do not differ in any part 
of the world: even the difference in quantity is very small, and is generally due to 
local causes, as the dilution of the sea-water by river-water, melting icebergs, &c. 
The sp. gr. of sea-water at 17 0 , varies from 1*0269 to 1*0289, the sp. gr. of the water 
of the Eed Sea being as high as 1*0306. One hundred parts of sea-water contain— 



Pacific 

Atlantic 

German 

Eed 


Ocean. 

Ocean. 

Ocean. 

Sea. 

Chloride of sodium 

2*5877 

2 7558 

2*5513 

3*030 

Bromide of sodium 

0*0401 

0*0326 

0*0373 

0*064 

Sulphate of potassa 

o-i 359 

0*1715 

01529 

0*295 

Sulphate of lime 

0*1622 

0*2046 

0*1622 

0*179 

Sulphate of magnesia 

0*1104 

0*0614 

0*0706 

0*274 

Chloride of magnesium .. 

0*4345 

0*3260 

0*4641 

0*404 

Chloride of potassium 

— 

— 

•— 

0*288 


3*4708 

3*5519 

3*4384 

4*534 








164 


CHEMICAL TECHNOLOGY. 


The composition of the salt contained in the water of the several seas is shown 
by the following table :— 



03 



a 

0 ■ 

i 

<D 

§ 

CD 

• 

= 4-1 • 


<x> 

oj 


6 0 8 

| 0 1 

Oo» 

_ (-1 GC 

ea J.S 


d 

a 

QQ 

<D 

Xfl 

0 

d 

* 

6 

r d 

H S>*-2 

Id 2 «8 

a > r-H 

® *43 

O &Ol£j 

-§ g « 

^ 0 § 

© >3 

•rt 

pi g si 

J g § 

> r— < 

§ 0)*43 

m 

2 0 
a p 0 

CD r-H 


O 

pq 

pq 


^4 N 

<! <1 CO 

A <3 T 

Average quantity of salt and water 







Solid salt . 

0*63 

177 

177 

3 * 3 i 

3*37 

3*63 

22*30 

Water. 

99'37 

98*23 

98*23 

96*69 

96*63 

96*37 

7770 

The dissolved solid matter consists in 100 parts of— 





Chloride of sodium 

58*25 

79*39 

84*70 

78*04 

77*°7 

77*03 

36*55 

Chloride of potassium. 

1*27 

1*07 

— 

2*09 

2*48 

3 * 89 

4*57 

Chloride of calcium .. 

— 

— 

— 

0*20 

— 

— 

11-38 

Chloride of magnesium 
Bromides of sodium and 

10*00 

7*38 

973 

8*8i 

876 

7*86 

45*20 

magnesium 

— 

0*03 

— 

0*28 

0*49 

1*30 

0*85 

Sulphate of lime . 

778 

o*6o 

013 

3*82 

2*76 

4*63 

o *45 

Sulphate of magnesia .. 
Carbonates of lime and 

19*68 

8*32 

4*96 

6*58 

8*34 

5*29 

" 

magnesia. 

Nitrogenous and bitu¬ 

3*02 

3*21 

0*48 

0*18 

0*10 



minous matter .. 

— 

— 

— 

— 

— 

— 

I‘OC 


One cubic metre (35*3165 cubic feet) of sea-water contains consequently about 
28 to 31 kilos, of chloride of sodium, and 5 to 6 kilos, of chloride of potassium. 
Chloride of sodium (common salt) is obtained from sea-water:— 

a. By the evaporation of the water by the aid of the sun’s heat.. 

b. In winter by freezing. 

c. By artificial evaporation. 

.^ethod^of obtaining common This method of obtaining common salt from sea-water is 
limited to certain of the coast-lines of Southern Europe, and is never effected 
beyond 48° N. latitude. The countries best situated for this industry are Erance, 
Portugal, Spain, and the coasts of the Mediterranean. The arrangement of the 
salines, or salt-gardens, is the following:—On a level sea-shore is constructed a 
large reservoir, which, by a short canal, communicates with the sea, care being 
taken to afford protection against the inroads of high tides. The depth of water in 
these reservoirs varies from 0*3 metres to 2 metres. The sea-water is kept in the 
reservoir until the suspended matter has been deposited, and is then conveyed by a 
wooden channel into smaller reservoirs, from which it is conducted by underground 
pipes to ditches surrounding the salines, where the salt is separated from the water. 
The salt is collected, placed in heaps on the narrow strips of land which separate the 
ditches from each other, and sheltered from rain by a covering of straw. As these 
heaps are left for some time, the deliquescent chlorides of magnesium and calcium 

* According to the experiments of Baron Sass, the water of the Baltic from the Great 
Sound between the Islands of Oesel and Moon only contains o*666 per cent, of solid matter, 
and is of a sp. gr. = 1*00474. 



COMMON SALT. 


*>5 

are absorbed in the soil, consequently the salt is comparatively pure. The mother- 
liquor is used in the production of chloride of potassium (see ante , p. 119), sulphate 
of soda, and magnesia salts, the process employed being that originally suggested by 
Professor Balard, and afterwards improved by Merle. 

By Freezing. This process is based upon the fact that when a solution of common 
salt is cooled to several degrees below the freezing-point, it is split up into pure 
water, which freezes, and a strong solution of salt. The solution becomes more 
concentrated by repeated freezing and removal of the ice, until at last a splution is . 
obtained which by a slight evaporation yields a crop of salt. In order to render the 
product purer, some lime is added to the solution before evaporation to decompose 
the magnesia salts. 

By Artificial Evaporation. Common salt evaporated from sea-water by the aid of fuel, 
or sel rgnifere, is chiefly prepared in Normandy, in the following manner:—The 
sand impregnated with salt is employed to saturate the sea-water, which is next 
evaporated. Very frequently an embankment of sand is thrown up on the shore, so 
as to be covered at high tides only; in the interval between two tides a portion of the 
salt dries with the sand, which in hot summer weather is collected twice or three 
times daily. The sand is lixiviated in wooden boxes, the bottoms of which are con¬ 
structed of loose planks covered with layers of straw; the sand having been 
put in the boxes sea-water is allowed to percolate through them till the specific 
gravity of the water increases to 1*14 or to 1 ’17, the density being observed by means 
of three wax balls weighted with lead. The salt boilers at Avrauchin consider that a 
solution or brine of 1*16 sp. gr. is the most suitable for evaporation. The evapora¬ 
tion is carried on in leaden pans, and during the process the scum is removed and 
fresh brine added until the salt begins to crystallise out, when again a small quantity 
of brine is added to produce more scum, which is at once removed, and the evapo¬ 
ration continued to dryness. The salt thus obtained, a finely divided but very 
impure material, is put into a conical basket suspended over the evaporating pan, 
the object being to remove by the action of the steam the deliquescent chlorides of 
calcium and magnesium. The salt is next transferred to a warehouse, the floor 
of which is constructed of dry, well-rammed, exhausted sand, and here it is 
gradually purified by the loss of deliquescent salts, the consequent decrease in weight * 
amounting to 20 to 28 per cent. 700 to 890 litres of brine yield, according to the 
quantity of salt contained in the sand, 150 to 250 kilos, of salt. A very similar 
method is in use at Ulverstone, Lancashire. 

At Lymington and the Isle of Wight, sea-water is concentrated by spontaneous 
evaporation to one-sixth of its original bulk, the brine being then evaporated by the aid 
of artificial heat. In the neighbourhood of Liverpool salt is obtained by employing 
sea-water in refining crude rock-salt; in this way at least 2*3 per cent, of common 
salt results as a by-product. Luring a continuation of hot summer weather, salt is 
deposited from the water of many of the salt lakes in immense quantities, amounting, 
for instance, at the Elton Lake, Eussia, to 20 millions of kilos. 

Rock-salt. This mineral is frequently accompanied by anhydrite, clay, and marl, 
and is sometimes found in what are termed pockets of irregular shape, interspersed 
with clay. Again, in some cases saline deposits are separated by layers of marl. 
With rock-salt other minerals sometimes occur, as, for instance, brongniartine 
(Na 2 S 0 4 -j-CaS 0 4 ), near Villarubia, in Spain, and the remarkable minerals of the 
salt deposit near Stassfurt. Above the latter deposit is a layer 65 metres thick, 
of bitter, many-coloured, deliquescent salts, consisting of 55 per cent, of carnallite, 


i66 


CHEMICAL TECHNOLOGY. 


sylyin, and kainite; 25 per cent, of common salt; 16 per cent, of kieserite; and 4 per 
cent, of chloride of magnesium. As this saline layer contains 12 per cent, of 
potassa it is an important deposit in an industrial sense. 

The composition of rock-salt is as follows :— 

I. "White rock-salt from Wieliczka; II. White, and III. Yellow rock-salt from 
Berchtesgaden; IY. Prom Hall in the Tyrol; Y. Detonating salt from Ilallstadt; 
YI. Prom Schwabischhall. 



I. 

II. 

III. 

IY. 

Y. 

YI. 

Chloride of sodium 

IOO'OO 

99*85 

99*92 

99*43 

98*14 

99*63 

Chloride of potassium 

— 

— 

— 

— 

traces 

0*09 

Chloride of calcium 

— 

traces 

— 

0*25 


0*28 

Chloride of magnesium traces 

0*15 

0*07 

0*12 

— 

— 

Sulphate of lime 

— 

— 

— 

0*20 

i*86 

— 


100*00 

100*00 

100*00 

100*00 

100*00 

100*00 


The so-called detonating salt, found at Wieliczka in crystalline granular masses, 
has the property when being dissolved in water of giving rise to slight detonations 
accompanied by an evolution of hydrocarbon gas from microscopically small cells, 
the walls of which becoming thin when the salt is dissolved in water, give way, and 
cause the report. If the solution of the salt takes place naturally in the mine, the 
gas partly escapes, partly becomes condensed, forming petroleum, often met with in 
beds of rock-salt. The minerals of the salt deposit of Stassfurt are, according 
to MM. Bischof, Beichardt, Zincke, and others, the following:— 


Chemical 

Pormula. 


Anhydrite.. CaS 0 4 



Pi 

100 parts of 

In 100 parts are 

0 O 

water dis¬ 

contained: 

6g* 

solve at 


i8f°C. 

100 of Sulphate of lime 

2*968 

0*20 


Synonyms 
and Obser¬ 
vations. 


Karstenite. 


Boracite .. j 

l BjeOgoClj 
j M g 7 

26*82 Magnesia 

65*57 Boric acid ( 2 . Q I 

io*6i Magnesiumchlo- l y i 

ride / 

f Almost 

1 insoluble 

| Stassfurtite. 

• 

| 

( 

2676 Chloride of potas- x 



Carnallite.. . 

1 

| KMgCl 3 

1 + 6 H 2 0 

sium i 

34*50 Magnesium chlo -1 1*618 
ride \ 

64*5 

Contains 

Bromine. 

. 1 

{ 

38*74 Water ) 



Bed oxide of 
iron 

Pe 2 0 3 

100 of Oxide of iron 3*35 

Insoluble. 

— 

Kieserite .. * 

jMgS 0 4+ 

{ h 2 o* 

87*10 Sulphate of mag- 

nesia > 2*517 

12*90 Water ) 

40*9 

Martinsito P 

Poly halite. J 

! 2CaS0 4 
MgS 0 4 

k 2 so 4 

2 H 2 0 

45* 18 Sulphate of lime\ 

I 9*93 Sulphate of mag- I 

nesia 1 / 

28*90 Sulphate of po- ? 2*720 
tassa I 

5*99 Water J ' 

' Is decom- 
) posed while 
| being dis- 
< solved. 

! - 


* According to Rammelsberg it is probable that kieserite is originally an anhydrous 
meral, a conclusion which seems justified by the variable quantity of water found in 


mineral, a 
different analyses 








COMMON SALT. 


16? 


o 


Rock-salt ... 

Chemical 

formula. 

NaCl 

+3 

In ioo parts are o g 

contained: ^ Ph 

A 8 
c n 

ioo Chloride of sodium 2*200 

100 parts of 
water dis¬ 
solve at 
i8|° C. 

36*2 

Synonyms 
and Obser¬ 
vations. 

Sylvin ... j KOL 

100 Chloride of po- \ 

tassium j 2 02 5 

34*5 

— 

Tachhydrite ! 

1 

[ CaCl 2 
2MgCl 2 

I 2 H 2 0 

21*50 Chloride of cal- \ 
cium f 

36*98 Chloride of mag- > 1*671 
nesium 1 

41*52 Water / 

160*3 

— 

Kainite ... 

1 

' 

k 2 so 4 

MgSO + 

MgCl 2 

6H 2 0 

36*34 Sulphate of po- \ 
tassa I 

25*24 Sulphate of mag- | 

nesia \ — 

18 *95 Magnesiumchlo- ( 
ride 

19.47 Water / 

— 

Contains 

Bromine. 

Schonite or \ 
Pikromerite \ 

OOC 

4 . -*■ 

43* 18 Sulphate of po- . 

tassa j 

29*85 Sulphate of mag- \ — 

nesia l 

26*97 Water. ) 

— 

— 


Sylvin is also found in large quantities in the salt deposit near Kalucz, Galicia. 


Mode of working nock-sait. Rock-salt, like other minerals and according to its mode of 
occurrence, is either quarried or mined. If it happens, however, that the rock-salt 
is mixed with other minerals, clay, gypsum, dolomite, &c., a solution in water is 
effected, which is pumped up from the mine as a concentrated brine. In many, 
instances rock-salt is wrought in extensive and deep mines, as in the celebrated 
rock-salt mines of Wieliczka. 

Mode of working sait-springs. Natural salt-springs sometimes occur which have been 
imitated artificially by boring to a great depth into layers of earth containing saline 
deposits. In this manner a brine may be obtained sufficiently concentrated to 
be at once boiled down. The method of working the natural salt-springs is to form 
a convenient reservoir from which the saline solution is immediately pumped up for 
the purpose of being gradated (see p. 168). The solution previous to being boiled; 
down is left to allow the suspended matter to settle. The salt-springs obtained 
by boring either yield a native brine, or the borings are carried into solid rock-salt 
and water caused to descend into the salt deposit. This artificial brine is then pumped 
up, unless there is naturally an artesian formation. The brine previous to further 
operations is left for some time in reservoirs to deposit suspended insoluble matter. 

These saline solutions are not always free from impurities; in considering their admixture 
brine may be divided into two classes; the first containing sulphate of magnesia or soda, 
with chloride of magnesium; the other class embraces brine containing the chlorides 
of calcium and magnesium. If the brine happens to pass through peaty soil or layers of 
fignite, there often accrues organic matter, humic, crenic, and apocrenic acids. 



[68 


CHEMICAL TECHNOLOGY. 


prep aration of common operation is duplex and consists in— 

a. Concentrating tlie brine. 

a. By increasing the quantity of salt. 

/3. By decreasing the quantity of water. 

b. The boiling down of the concentrated brine. 

concentrating the Brine. Native brines or salt-springs seldom contain enough common 
salt to make it profitable to boil them down at once; it is consequently necessary to 
enrich the brine, and this may be done either (a) by dissolving in it rock-salt 
or crude sea-salt, neither being suited for culinary and many other purposes unless 
refined, or (/ 3 ) by decreasing the quantity of water without the use of fuel. 

Enriching by Gradation. The enriching or concentration of a brine by decreasing the 
quantity of water it contains is called a gradation process, and may be proceeded 
with by freezing off the water in winter time, or more generally by evaporating the 
water by a true gradation process; either— a. Gradation by the effect of the sun’s 
rays. b. Table gradation, c. Boof gradation, d. Drop gradation. 

Gradation by means of the sun’s rays is obviously the same method of procedure as 
that described under the treatment of sea-salt. Table gradation has been only experi¬ 
mentally tried at Beichenball, and consists simply in causing the brine to flow slowly 
from a reservoir down a series of steps, constructed so as to give as much surface as pos¬ 
sible, and thus hasten the evaporation. Boof gradation is effected by utilising the roofs 
of the large tanks containing the brine as evaporation surfaces, by causing the contents of 
the tanks to flow in a thin but constant stream over the roofs, which, of course, are 
exposed to the open air. 

Faggot Gradation. This operation, also known as drop gradation, is carried on by 
means of the following apparatus, termed gradation house, and consisting of a frame¬ 
work of timber, fitted with faggots of the wood of Frunus spinosa, which being 
thorny, presents a large surface. The entire construction is built over a water-tight 
wooden tank, -which receives the concentrated brine, and frequently the top of 
the gradation house is provided with a roof. Under the roof and above the faggots 
a water-tight tank is placed containing the brine to be gradated; this tank is 
provided with a number of taps, from which the brine trickles into channels provided 
with holes to admit of the brine falling on the faggots. These taps are placed 
on both sides of the gradation house, and are generally connected with levers to 
admit of being readily turned on and off from below. The gradation process is con¬ 
tinued until the brine is sufficiently concentrated to admit of being further evapo¬ 
rated by the aid of fuel; the brine may be gradated to contain 26 per cent, of salt, 
but the operation is rarely carried so far. 

The gradation process not only serves the purpose of concentration, but also that 
of purifying the brine, as some of the foreign salts are deposited on the faggots, this 
deposit of course varying in composition according to the constituents of the brine, 
but chiefly consisting of carbonate of lime, with the sulphates of potassa, soda, and 
magnesia. The deposit has in some instances been used as manure. In the tanks 
where the gradated brine is collected another slimy deposit is gradually formed, 
consisting of gypsum and hydrated oxide of iron. As in the present .day the brine 
obtained from bored wells is generally sufficiently concentrated to be at once boiled 
down, gradation is less frequent, being a. very slow process and involving a loss of 
the salt carried off by the wind. 

Bomng down the Brine. The obj ect is to obtain with the least possible expenditure of 
fuel the largest quantify of pure dry salt. Formerly the evaporation was carried on 


COMMON SALT. 


169 

in large cauldrons, but at the present time evaporating vessels are constructed of 
well rivetted boiler-plate, the shape being rectangular, the length 10 metres, depth 
o*6 metre, and width from 4 to 6 metres. These pans are supported by masonry, 
which also serves to separate the hues. Over the pans a hood is fixed and con¬ 
nected with a tube carried to the outside of the building to afford egress to the 
steam. The brine, concentrated to contain from 18 to 26 per cent, of salt, is poured 
into the pans to a depth of 0*3 metre. 

The boiling down process is in many salt works conducted in two different opera¬ 
tions :— 

a. The evaporation of water to produce a brine saturated at the boiling-point. 

b. The boiling down of the saturated brine until the salt crystallises out. 

The boiling down is generally carried on for several weeks, the scum being 
removed, and also the gypsum and sulphate of soda deposited at the bottom of the 
pan, with perforated ladles. As soon as a crust of salt is formed on the surface of 
the liquid, a temperature of 50° is maintained. At this stage the salt is gradually 
deposited at the bottom of the pan in small crystals, and being removed, is put into 
conical willow baskets, which are hung on a wooden support over the pan to admit of 
the mother-liquor being returned to it. Finally, the salt is dried and packed in casks. 

The quantity of mother-liquor collected after boiling for some two or three weeks is, 
compared with the quantity of brine evaporated, very small; it was formerly thrown away 
or used for baths, but is now employed for the preparation of chloride of potassium, the 
sulphates of soda and magnesia, artificial bitter water, and in some instances for pre¬ 
paring bromine. It is evident that by the boiling down all the salt contained in the brine 
is not reduced as dry refined salt, a portion being retained among the early deposit formed 
at the bottom of the pan, another portion remaining in the mother-liquor, and finally 
some loss accrues from the nature of the operations, amounting generally from 4 to 9-25 
per cent. As in some countries salt is an article upon which an excise duty is levied, 
in order that it may be employed duty free for certain industrial purposes, it is mixed in 
various proportions with substances rendering it unfit for culinary use. 

properties of common Chloride of sodium crystallises in cubes, the size of the crystals 
determining the varieties known in the trade as coarse, medium, and fine grained 
salt, and depending upon the rate of evaporation of the brine, a slow evaporation 
producing very coarse salt. Perfectly pure common salt is not hygroscopic, but the 
ordinary salt of commerce contains small quantities of the chloride of magnesium 
and sodium. Usually salt contains from 2*5 to 5*5 per cent, water, not as a constituent, 
but as an intermixture; hence the phenomenon called decrepitation, due to the 
breaking up of the crystals by the action of the steam when salt is heated. Ignited 
to a strong red heat chloride of sodium fuses, forming an oily liquid, and at 
a strong white heat is volatilised without decomposition. Common salt is readily 
soluble in water, and is one of the few salts almost equally soluble in cold and in 
hot water; 100 parts of water at 12 0 dissolve 35*91 parts of common salt. 

In order to express the quantity of salt contained in a brine, it is usual to saj T the 
brine is of a particular fineness, strength, or percentage; for instance, a brine at 
15 per cent, contains in 100 parts by weight 15 parts of salt and 85 parts of water. 
The Grddigkeit or degree of a brine means the quantity of water which holds in solu¬ 
tion 1 part by weight of salt; a brine-of 15*6 Grddigkeit contains, therefore, 1 part 
by weight of common salt in 15*6 parts of water. The poundage ( Pfiindigkeit ) of a 
brine indicates in pounds the quantity of salt contained in a cubic foot of brine. 

The following table shows the percentage of salt contained in brines of the several 
specific gravities:— 


170 


CHEMICAL TECHNOLOGY. 


per cent. 

Sp. gr. 

Salt per cent. 

Sp. gr. 

Salt per cent. 

Sp. gr. 

1 

1*0075 

7’5 

1*0565 

16 

1*1206 

i '5 

1*0113 

8 

1 *0603 

17 

1*1282 

2 

1*0151 

8-5 

1*0641 

18 

i*i 357 


1*0188 

9 

1*0679 

19 

i*i 433 

3 

1*0226 

9*5 

1*0716 

I 9’5 

i*i 5 IG 

3*5 

1*0264 

10 

1 ’0754 

20 

i*i 593 

4 

1.0302 

10-5 

1*0792 

21 

1*1675 

4‘5 

1*0339 

11 

1*0829 

22 

1*1758 

5 

1 ’0377 

ir 5 

1*0867 

23 

1*1840 

5*5 

1*0415 

12 

1*0905 

24 

1*1922 

6 

1*0452 

13 

1*0980 

25 

1*2009 

6-5 

1*0490 

14 

1*1055 

26*39 

1*2043 

7 

1*0526 

15 

1*1131 




tses ot common It is not necessary to enter into particulars on tliis subject. Salt is used 
Salt * as a necessary condiment to food; a man weighing 75 kilos, contains in his 
body 0-5 kilo, of common salt, and requires annually 775 kilos, to maintain this supply. 
Common salt is used in agriculture, and is as necessary for cattle and horses as for man. 
It serves industrially in the preparation of soda, chlorine, sal-ammoniac, in tanning, in 
many metallurgical processes, the manufacture of aluminium and sodium. Further, it is 
employed in the glazing of the coarser kinds of pottery and earthenware, from the fact that 
when common salt is fused with a clay containing iron, the sodium is oxidised at the 
expense of the iron, and forms soda, which, combining* with the alumina and silica, sup¬ 
plies a glaze, while the iron combining with the chlorine is volatilised. The uses of common 
salt for the preservation of wood, for curing meat, preserving butter, cheese, &c., are toe 
well known to require explanation. Among the salt-producing countries of Europe, Eng¬ 
land takes the lead, producing annually 32,400,000 cwts., while Germany only produces 
10, and Russia 20 million cwts. 

Manufacture of Soda. 

(Soda or Sodium carbonate, Na 2 C03 = 106. In 100 parts, 58*5 parts soda and 

41*5 parts carbonic acid.) 

soda. All the soda commonly used is derived from the three undermentioned 
sources:— 

a. Natural or native soda ; 

( 3 . From plants; 

■y. Chemical production. 

a. Native Soda. 

Occurrence of Native g 0 da is found in many mineral waters, as at Karlsbad, where the 
waters yield annually 133,700 cwts. of carbonate of soda, and at Burtscheid, Aix- 
la-Chapelle, Vichy, and the Geyser, in Iceland. Soda occurs as an efflorescence on 
some kinds of rocks, chiefly of volcanic origin, as trass and gneiss. Sesquicarbonate 
of soda,C 3 08Na4 -f 3H 2 0, is met with in large quantities in the water of the so-called 
soda lakes of Egypt, Central Africa, the borders of the Caspian Sea and Black Sea, 
in California, Mexico, and elsewhere. During the hot summer season a portion of 
the level country of Hungary is covered with an efflorescence of carbonate of soda, 
locally known as Szekso, which is collected and brought to market. The Egyptian 
name for soda is Tro-Na, hence the German term Natron. The soda locally known 
in Columbia as JJrao is obtained from a lake, La Lagunilla, distant 48 miles from 
the town of Merida. During the hot season the urao crystallises from the water, 


SODA. 


171 


and is gathered from the bottom of the lake at a depth of 3 metres by divers, with 
great risk of their lives; the annual quantity collected amounts to 1600 cwts. When 
the Spaniards were in possession of this territory the urao wa3 a government 
rponoply, and was brought to Venezuela for the preparation of Mo or inspissated 
tobacco juice. Very recently an inexhaustible supply of native soda has been 
found in Virginia.* 

Various theories have been proposed to explain the origin of native soda, but here 
as in other instances it is best to bear in mind that a posse ad esse non valet conclusio 
Native soda is rarely exported from the countries where it is found and collected, 
excepting the Egyptian Tro-Na, which is brought to Venetia for glass-making 
purposes and met with in the trade in the shape of bricks made up with sand. 

/ 3 . Soda from Plants, or Soda-ash. 

S0 and f from S Beet^root t . s ’ When treating in a former chapter of potassa we saw that the 
ash of plants, especially of those grown at a considerable distance from the sea, 
contains carbonate of potassa; likewise that plants grown near the sea-shore and in 
the localities known as salt steppes yield an ash which contains more or less soda 
in the living plant combined with sulphuric and organic acids, and which under the 
influence of the carbonate of lime is during the ignition of the plant converted into 
carbonate of soda. In addition to the species of Fucus growing in the sea itself, 
the genera known as Salsola, Atriplex, Salicornia, &c., are employed for the pre¬ 
paration of soda, and until lately were largely cultivated for this purpose. The 
process of obtaining soda from these plants simply consists in burning them in pits 
dug in the sand near the sea-shore, the heat of the combustion becoming so intense 
as to cause the ash to flux, so that after cooling the material forms a hard slag-like 
mass, termed in the trade crude soda or soda-ash, the quantity of carbonate of soda 
it contains varying from 3 to 30 per cent. This new material is refined by exhausting 
with water and evaporating the liquor. From the different plants and modes of 
preparation employed we obtain the following distinctions in kind 

a. Barilla, from Alicante, Malaga, Carthagena, the Canary Islands, and the Barilla soda 
(Salsola soda ) produced on the Spanish coast; contains on an average from 25 to 30 per 
cent, of carbonate of soda. 

b. Salicor, or soda from Narbonne, obtained by the ignition of the Salicornia annua, 
planted purposely, and gathered when the seed is ripe; contains about 14 parts of carbonate 
of soda. 

c. Blanquette, or soda from Aigues-Mortes, prepared from the plants growing wild on 
the tract of comparatively barren land lying between Aigues-Mortes and Frontignan, viz., 
the Salicornia Europea, Salsola tragus, Salsola Jcali, Statice limonium, Atriplex portulacoidcs. 
This soda only contains from 3 to 8 per cent of sodic carbonate. 

d. Araxes soda, of about the same value as the preceding, is largely used in Southern 

Kussia, and is obtained from plants of the mountain plateau of the Araxes in Armenia, 
where the soda is prepared. . x , _ _ ,, . , „ , 

e. Of less value even than the precedmg is the Yarec soda, obtained on the coasts of 
Normandy and Brittany from the goemon, Fucus vesiculosus. 

/. Kelp is obtained in Scotland and the Orkneys by the combustion of various sea-weeds, 
the Fucus serratus, F. nodosus, Laminaria digitata, and Zoster a marina. Notwithstanding that 
480 cwts. of dried plants only yield 20 cwts. of kelp, containing no more than from 50 to 
100 lbs. of sodic carbonate, 20,000 people are occupied in the Orkneys alone in the prepara- 

Among the varieties of soda derived from plants may be mentioned that obtained in 
considerable quantity from the vinasse of beet-root, but this soda, according to Tissandier’s 
analysis, always contains carbonate of potassa. 

* See “Chemical News,” vol. xxi., p. 129. 


172 


CHEMICAL TECHNOLOGY. 


Soda from Chemical 
Processes. 


y. Soda prepared by Chemical Processes. 

M. Leblanc, the inventor of the successful method of converting 
common salt into carbonate of soda, may indeed be considered as an immediate 
benefactor to his countrymen, who, until the latter half of the last century, annually 
paid 20 to 30 millions of francs to Spain for barilla. The war which broke out in 
1792 terminated the importation of soda, potash, and saltpetre into Prance, and 
hence the Comite du Salut Public decreed in 1793, amongst other measures, that 
all soda manufacturers should give the fullest particulars of their mode of working, 
and the processes they imagined might be used on the large scale to obtain soda 
equally good and cheap as that from barilla without the use of that or any similar 
material. The manufacturer' Leblanc was the first who sent in full particulars on 
this subject, and his process was declared by the committee to be the best and most 
suitable, the verdict standing unshaken to the present day, which witnesses the 
improvement of the recovery of the sulphur from the soda waste. 


Leblanc’s Process. This now consists in the following stages: 


b. 


The preparation of sulphate of soda from salt by the aid either of sulphuric 
acid or sulphates, or by the roasting of common salt with iron pyrites or 
other native metallic sulphurets. 

Conversion of the sulphate into crude soda by roasting with a mixture of 
chalk and small coal. 

c. Conversion of the crude soda into refined soda or caustic soda by lixiviation 
and evaporation. 

d. Eecovery of the sulphur from the soda waste. 

DecomposingFumace. a - Tlie most usual mode of converting common salt into sul¬ 
phate of soda is by the action of sulphuric acid. The condensation of the hydro¬ 
chloric acid gas is generally effected by a method introduced in 1836 by Mr. Gossage, 
and consisting in the use of a contrivance known as coke- or condensing-towers. 
These are square buildings from 12 to 14 metres in height, by an interior width of 
1*3 to i*6 metres, constructed of stone not acted upon by hydrochloric acid, the 
joints being cemented with a mortar made of coal-tar and fire-clay. To nearly the 
top these buildings are divided by a wall, each compartment thus formed being 
filled with pieces of coke resting on a perforated stone floor. Water is caused to 
flow constantly from the top of the tower on to the coke. The hydrochloric acid gas 
resulting from the decomposition of the salt by sulphuric acid is conducted by means 
of stoneware tubes to the bottom of the first compartment of the condensing-tower, 
and there meeting with the moist coke is condensed to within 95 per cent, of the 
entire quantity, the other compartment of the condensing-tower being usually in 
direct connection with the chimney-shaft of the alkali-works. The decomposition- 
furnaces at first in use were reverberatory furnaces so constructed that the smoke 
and gases from the combustion of the coals and the hydrochloric acid gas passed off 
together, and as a consequence the hot gases were not in the best condition 
for condensation. The furnace now in general use is that invented in 1836 by 
Gossage, and improved in 1839 by Gamble, who was the first to arrange the two 
phases or stadia of the decomposition in the separate compartments, g and E, of the 
furnace exhibited in Fig. 71. This arrangement has been used for a very Ion" 
period, the alkali manufacturers employing a reverberatory furnace which could be 
put into communication at pleasure with a kind of muffle, the bottom consisting of a 
stout cast-iron plate, the flame from the furnace-grate being made to play against 


SODA . 


173 


this muffle previously to entering the chimney. The muffle communicated with a 
condensing apparatus, M m\ According to this plan of working, the common salt 
was placed in g, and well warmed sulphuric acid made to flow over it; a very strong 
and violent reaction took place, and half or nearly two-thirds of the hydrochloric 
acid formed was readily condensed, as it was not mixed with the hot gases of the 
combustion. The product resulting from this mode of operation was a mixture of 
bisulphate of soda and common salt, 2NaCl + H 2 S 0 4 =^NaHS 0 4 -j- NaCl-f HC 1 . 
This mixture was next shovelled into the reverberatory furnace, E, the muffle being 
again charged with salt and acid. By the intense heat of the reverberatory furnace 
the mixture of bisulphate of soda and common salt was converted into neutral 
sulphate, NaHS 0 4 -f- ISTaCl = Na 2 S 0 4 -f- HC 1 ; the hydrochloric gas evolved in 
this operation was, however, condensed with difficulty, in consequence of being 
mixed with nitrogen, carbonic acid, and carbonic oxide; and besides the com 

Fig. 71. 

yr 



densing towers other and complicated apparatus were required to prevent the escape 
of acid fumes into the air. These defects have been remedied in the construction 
of an improved decomposition-furnace. 

New Decomposition-Furnace. This furnace consists of two muffles, one of cast-iron, the 
other of fire-bricks; the interior of the former is a segment of a hollow sphere of 
9 feet or 274 metres diameter, and 1 foot 9 inches or 0^52 metre deep, resting on 
brick-work. A cast-iron lid is provided, in shape also a segment of a sphere, having 
a depth in the centre of 1 foot or 0*30 metre; in this lid are arranged two openings 
with suitable doors, through one of which the common salt is introduced, while the 
other communicates with the second muffle. The hearth is placed obliquely, the 
flames first playing on the lid, and then passing under the muffle; accordingly the 
hydrochloric acid gas is unmixed with other gases, and its temperature being com¬ 
paratively low, condensation is more readily effected. The second or brickwork 
muffle encloses a space of 30 feet or 9*14 metres in length, by 9 feet or 274 metres 
in width; under the floor of this room a series of flues or channels are built, while 
the top is formed of a double vault to admit the circulation of the flames, which 
aro next conducted through the channels under the floor. 






















CHEMICAL TECHNOLOGY. 


174 

The mode of operation is as follows:—Into the iron muffle, previously well heated, 
half a ton of common salt is introduced, to which is added sulphuric acid of 17 sp. gr., 
the quantity of the acid being regulated so as to leave 1 to 3 per cent, of salt unde¬ 
composed in order to obtain a perfectly neutral sulphate. 100 parts of salt require 
for their complete decomposition 95 parts of an acid at 6o° B. — 17 sp. gr., or 
104 parts of an acid at 55 0 B. = 1*62 sp. gr. The mixture of acid and salt is occasion¬ 
ally well stirred, and after the lapse of hour has become sufficiently dry to be 
raked over into the brickwork compartment of the oven, which is kept at a bright 
red heat to assist the expulsion of the hydrochloric acid gas. If it is desired to 
obtain a concentrated hydrochloric acid solution, the escaping gas must be cooled 
down before entering the condensing-towers. There is generally a valve or damper, 
by which the communication between the two muffles may be closed, in order that 
the hydrochloric acid gas evolved in each may be separately collected and condensed. 
With these contrivances, and well constructed condensers supplied plentifully with 
water, the preparation of sulphate of soda may be carried on without any inconveni¬ 
ence to the neighbourhood in which the works are situated. Bor more than twenty 
years Messrs. Tennant, of Glasgow, have employed this kind of furnace, decomposing 
500 tons of common salt per week without receiving any complaints. On the Conti¬ 
nent, alkali-works are legally compelled to have the decomposition-furnaces con¬ 
structed according to a plan first brought out in Belgium, and which is very similar 
to the furnace already described. The assertion of Dr. Wagner, in his original text, 
concerning the many complaints now arising in England in reference to the escape 
of hydrochloric acid fumes from alkali-works, is altogether unfounded, the fact being 
that according to the published reports of the inspector, Dr. Angus Smith, under 
the Alkali Act, nearly all the manufacturers condense, instead of 95 per cent, of the 
hydrochloric acid, as required by the Act, from 97 to 98*5 per cent. 

conversion of^hesinph 4 ^ j n or q er to convert the sulphate of soda into crude or 
raw sodic carbonate, the former salt is mixed with chalk, or sometimes with 
slaked lime and small coal, and this mixture, fused in a reverberatory furnace. 
According to Leblanc’s directions, the proportions are— 

Sulphate. 100 parts 

Chalk. 100 ,, 

Slaked lime . 50 ,, 

but the quantities as employed in ten different works vary for 100 parts of sulphate 
from 90 to 121 parts of chalk, and the quantity of small coal from 40 to 75 parts* 


Fig. 72. 



In some alkali-works for a portion of the chalk is substituted the desulphurised and 
lixiviated soda waste. The reverberatory furnace generally used in English alkali- 
works, and technically known as a balling furnace , is shown in Fig. 72, and that 









SODA. 


»75 

employed in Germany in Fig. 73. In England, the materials haying been first 
heated on the upper stage of the furnace by the waste heat, only remain in the 
working furnace (see Fig. 72) for about half-an-hour; in German works the mixture 
of sulphate, chalk, and small coal is strongly heated in M (see Fig. 73), until the 
mass becomes fluxed and pasty, and lambent flames of‘burning carbonic oxide are 
ejected from the surface. When this is seen the semi-fluid mass is removed from 
the furnace through the openings P P, and transferred to an iron car, c, where it is 
left to cool. 

It is difficult to say whether the English or Continental method is the more 
preferable; viewed from a theoretical point of view, it would appear that the English 
method is tjie better of the two. As in English works, a smaller quantity of 


Fig. 73. 



materials, only about 7 cwts., while in Continental works from 30 to 70 cwts., is 
operated upon at a time, the labour is lighter; the materials, too, are not exposed to 
an intense heat’ for a long period; thus a loss of soda by the volatilisation of the 
sodium is less likely to occur. According to Wright’s investigations (1867), the loss 
of soda by the conversion of the sulphate amounts to 20 per cent, of the sodium 
contained in the sulphate, as shown by the following figures :— 


Undecomposed sulphate.3*49 

Insoluble sodium compounds.. . . 5 '44 

Yolatilisation of the sodium. 1*14 

Sodium retained in the waste .3*61 


Loss occasioned by the evaporation of the liquors .. 6*56 

20’24 

S KomoryHealth' 1 In 1853 Elliot and Bussell suggested a contrivance which dis¬ 
pensed with the stirring of the materials by manual labour, and consisted of a cylin¬ 
drical vessel made to rotate on a horizontal axis. Stevenson and Williamson im¬ 
proved upon this idea, and according to their plan of working (see Fig. 74) the 
mixture of sulphate, chalk, and small coal is placed in the iron cylinder, A, lined 
with fire-clay. Bibs or rails, B, cast on the cylinder, run on the wheels, c, receiving 
motion from machinery with which they gear, and causing the cylinder to rotate. 
The heated air of the hearth, D, flows through the opening E into the cylinder, and 
passing through p, reaches the vaulted compartment, G, and is carried off by the flue, 
K, to the chimney. The interior of the cylinder having been heated to redness, the 
materials are allowed to fall into it from the waggon, J, through the funnel, n. 
After the lapse of ten minutes the cylinder is caused to make a half revolution, and 
is then left for five minutes, the operation being continued until the mass inside the 



























i;6 


CHEMICAL TECHNOLOGY. 


cylinder fuses, which, takes place in about half-an-hour. The cylinder is then set 
continuously in motion so as to make one revolution every three minutes. The 
progress from time to time is watched through a door-way constructed in the 
cylinder, and as soon as the operation is complete the molten mass is run off through 
the opening b\ There can be no doubt that the rotatory furnace is a great improve¬ 
ment, and one which, besides saving labour, prevents a loss of soda by volatilisa¬ 
tion. A cylinder n feet long and 7*5 feet in diameter converts in two hours 14 
cwts. or 700 kilos, of sulphate at an expenditure of only 2s. id. 


Fig. 74. 



Lixi crude 0 so°d f a! he c - Conversion of crude into refined soda by lixiviation and 
evaporation, a. Lixiviation of the crude soda. When the crude soda is acted upon 
by water there results a solution containing chiefly carbonate of soda, and a mass 

remaining undissolved known as soda waste. 100 parts of raw soda yield :_ 

Soluble matter .. .. 45*0 parts 

Soda waste.587 ,, 

1037 » 

As a rule English ball soda has a deeper colour, and contains more carbon than 
the soda of Continental manufacture. Ball soda, previously to being lixiviated is 
usually exposed for at least two and sometimes for ten days to the action of the air, 
to gain in porosity, and hence be more readily" acted upon by the water. 

Of the several methods of lixiviation proposed, and in more or less successful use 
on the large scale, maybe mentioned the followingThe method of lixiviation by 
simple filtration is not to be recommended on account of the great labour it requires 
but the process consists in putting the crude soda, previously broken up into lumps 
of suitable size, into tanks provided with a perforated false bottom, upon which the 



























SODA. 


IT) 

crude soda is placed, water being poured on. This arrangement is represented in 
Fig* 75 > a j c, D. The perforated false bottom is about 25 centims. from the bottom 
of the tanks. The wooden channel, K, suspended from the ceiling of the shed by 
the iron bands, F r 1 , conveys water, 

whichbvmeansoftheplugs, t,t \and Fro 75. 

t", can be let into the tanks, these 
being provided with taps, r, r', and 
r", by which the liquid can be run off 
into the channel, k'. To illustrate the 
modus operandi three tanks, A, B, c, 
are sufficient; A is filled with fresh 
ball soda, B with ball soda once, 
and c with ball soda twice lixiviated. 

We then begin by filling each tank 
with the liquor which has been used 
for washing the soda waste the last 
time before throwing it aside; this liquid remains in each tank for a period of eight 
hours, and the alkaline ley, which then marks 30° B., is run off from A, and the 
operation repeated with weaker liquors in B and c, the leys being all conveyed to a 
large reservoir, the contents of which mark 25 0 B. Fresh liquor is poured into A 
and B, and into D, which is filled with ball soda. By this arrangement a constant, 
supply of ley at 25 0 B. is kept up. 

Desormes’s lixiviation apparatus, Fig. 76, consists of a series of twelve to fourteen 
tanks, of which only five, a, b, c, d, e, are exhibited in the woodcut. By means of 
the bent tubes, fitted about 15 centims. from the bottom of each tank, the liquor 
flows into the next lower tank of the series, and so to the tanks, F f', called the 
clearing or settling tanks, of which there are six connected together by tubes. The 
ball soda to be lixiviated is ground to powder, and placed in the perforated sheet- 
iron vessels, e e, a d , and so on. At the commencement the tanks are filled with 


Fro. 76. 




warm water, and two perforated vessels placed in E filled with 50 kilos, of ball soda; 
after twenty-five minutes these vessels are removed to D, and others filled with fresh 
soda placed in E. In this manner the operation proceeds, so that after eight hours, 
when fourteen lixiviation tanks are worked, there are found in A perforated vessels 
which have been gradually removed from the lowest to the highest tank, a, two 
13 































































I7S 


CHEMICAL TECHNOLOGY. 


vessels, //, having been removed, from that tank and placed upon the shelf, k, to 
drain, where having remained for about half-an-hour they are removed, the contents 
emptied, and other vessels placed to drain. Each time that two of the perforated 
vessels filled with ball soda are placed in the lowest tank, there is poured into the 
uppermost as much water as corresponds with the bulk of the fresh soda; this water 
displaces the heavy ley which runs through the tube from A to b, and so on, until at 
last the concentrated and nearly saturated liquor runs from E into F F, where any 
suspended matter is deposited. The temperature of the liquor in these tanks should 
be from 45 0 to 50°; but not higher, in order to prevent any decomposition of the 
sulphide of calcium. % The lixiviation tanks, as well as the clearing tanks, are 
provided with steam pipes for the purpose of keeping the liquor sufficiently heated, 
and to prevent any soda crystallising out by cooling. It is almost evident that this 
method of lixiviation is the best which can be adopted, as the concentrated liquo: 
cannot adhere to the solid substance which it is intended to dissolve, because in 
consequence of its high sp. gr. the liquor sinks to the bottom of the tank. Eig. 77 
represents two lixiviation tanks drawn to a larger scale, and of a somewhat different 
arrangement. Each tank is divided into three compartments by means of a double 
partition wall, communication between the two compartments being provided by the 


Fig. 77. 



ncles a and b and the space between the partition plates receiving the steam pipes, 
h h. g g are the tubes for conveying the liquor, and n n the perforated vessels, to 
which are rivetted iron bars serving the purpose of handles. Mr. James Shanks, of 
St. Helen’s, was the first to found a rational and economical plan of lixiviation, on 
what is termed methodical filtration, based upon the fact that a solution becomes more 
dense the more saline matter it has in solution, and that a column of weak ley of a 
certain height equilibrates a shorter column of a stronger ley. In accordance with 
this principle, the tanks, four or eight in number, are placed as shown in Eig. 78, 
and through them water is caused to flow, exhausting the crude soda in its passage, 
and becoming consequently denser in each consecutive tank of the series ; hence, 
the level of the liquid is lowered in each tank from the first, which contains pure 
water, to the last, from which a saturated ley runs off. The length of the tanks is 
2‘6 metres by 2 metres in depth; F is a perforated false sheet-iron bottom supported 
by iron bars. From the bottom of each tank an open tube, T, the lower opening 
being cut diagonally, and at the top a smaller tube, t, soldered on, connect the tanks. 
The water pipes, r r r r, fitted with taps are placed to admit of water being 
supplied to each tank; by means of the taps, R R', the ley can be run off into the 
channel, c\ Four lixiviations as a rule suffice. The working is as follows :—The 

































SODA. 


179 

first tank contains ball soda already three times lixiviated; the liquor added to it is a 
very weak soda solution from a former operation, which percolates into the second tank. 
The liquid there meets with soda which has been twice submitted to the lixiviation 
process, and next flows over into the third tank, the solid contents of which have 
been only once previously lixiviated. Finally, the lye arrives in the fourth tank, in 


Fig. 78. 



wnich fresh ball soda has been placed, and from this tank flows into a large reservoir. 
The first tank having been cleared of soda waste is now filled with fresh ball soda, 
and the succession of the operation reversed by the aid of taps fitted to the tubes 
connecting the tanks. The larger the number of tanks the more rapidly within 
certain limits a given weight of crude soda can be exhausted. The density of the 
■ ley ought to be from 1*27 to 1*286, a cubic foot, or 0*028 cubic metre, containing 
from 4*5 to 4*95 kilos, of solid matter. The advantages of this mode of lixiviation 
are—1. That the carriage of the crude soda from one tank to another is dispensed 
with, and consequently much labour saved. 2. The soda being always covered with 
liquid cannot cake. 3. As the current is always downwards the most concentrated 
portion of the fluid is conveyed forward, and consequently less water is required. 

4. By the continuity of the operation any reaction between the alkali and the 
insoluble calcium sulphuret is prevented, or, in other words, the formation of soluble 
alkaline and other sulphurets, entailing a loss of soda, is reduced to a minimum. 

5. The high degree of concentration of the ley effects a considerable saving in the 
expense of the evaporation. 

The nature of the ley after the suspended matter has been deposited, greatly 
depends upon the condition of the ball soda employed, the duration of the process, 
and the temperature of the water; it is, therefore, difficult to make any general 
observation. Kynaston, Scheurer-Kestner, and Kolb have proved that ball soda 
does not contain caustic soda, and that consequently the presence of this substance 
in the ley is due to the action under water of the lime upon the sodic carbonate. 
Sulphuret of calcium can only be present in the dry ball soda in very small quantities, 
but sulphuret of sodium may exist in the ley to a greater extent than caustic soda, 
the quantity varying with the mode of lixiviation. Commonly, only monosulphuret 
of sodium is present in the ley; even if a poly sulphuret were temporarily formed it 
would be immediately converted into monosulphuret by the presence of the caustic 
soda. The dry ball soda contains peroxide of iron, converted into sulphuret of iron 
by the action of the water; this sulphuret dissolving in the sulphuret of sodium 
causes the green- or yellow-brown colour of the ley. The quantity of water employed 












CHEMICAL TECHNOLOGY. 


I bo 

in the lixiviation has no effect upon the causticity of the ley, but the quantity 
of sulphuret of sodium increases •with the quantity of water, the duration of 
the lixiviation, the temperature, and the concentration; this is owing to the 
increased solubility of the sulphuret of calcium, which, when in contact with water, 
is converted into hydrosulphuret of calcium and hydrate of lime, the former yielding 
with caustic soda the more sulphuret of sodium the higher the concentration of the 
ley. The same reasoning holds good for carbonate of soda, which is also converted 
into sulphuret, but only in very dilute solutions, at a higher temperature after a 
lengthened contact. 

According to Kolb’s researches, ball soda should be lixiviated rapidly, with but a 
small quantity of water, and at a low temperature. If it were possible it would be 
a great improvement to contrive an apparatus in which ball soda could be lixiviated 
ir. a few hours with only so much cold water as would yield a very concentrated ley; 
the liquors obtained under such conditions would be free from sulphuret of sodium. 

The following analysis will give some idea of the composition of the crude ley. 
The sample was obtained from the alkali-works of Matthes and Weber, at Duisburg, 
the sp. gr. = 1*25, 1 litre containing 313*9 grms. of solid saline matter, consisting 


in roo parts of— 

Carbonate of soda. . .. 71*250 

Caustic soda.24*500 

Common salt.. .. 1 850 

Sulphite of soda. .. 0*102 

Hyposulphite of soda. 0*369 

Sulphuret of sodium .. .. .. .’. 0*235 

Cyanide of sodium .*.. 0*087 

Argillaceous earthy matter. 1-510 

Silica .. 0*186 

Iron..... .. .. traces 


100*089 

Another crude ley from some works near Aix-la-Chapelle was of a sp. gr. — 1*252, 
and contained 311 grms. of solid matter per litre. 

Evaporation of the Ley. / 3 . The clarified liquor contains essentially carbonate of soda 
and caustic soda, with common salt and other soda salts in smaller quantities. Owing 
to the presence of the double sulphuret of iron and sodium, the ley is coloured 
during the evaporation, if it be performed with the liquor immediately from the 
lixiviation tanks; to prevent this result it is necessary that the leys should stand for 
a considerable time in the clearing reservoirs to effect a slow oxidation of the com¬ 
pound salt, more rapidly attained by forcing a current of air through the ley, as 
suggested by Gossage. Bleaching-powder and nitrate of soda are used as oxidising 
agents; a lead-salt, oxide of copper, and spathose iron ore have been employed. As 
Kolb’s researches have proved that monosulphuret of iron is insoluble in caustic and 
in carbonate of soda solutions, an addition of sulphate of iron will have the effect of 
converting the double sulphuret of iron and sodium into monosulphuret of iron and 
sulphace of soda, the former salt settling rapidly and yielding a clear colourless 
liquid, and on evaporation a colourless salt. 

The ley is treated in either of the two following ways:— 

a. .Evaporated to dryness, the result being a homogeneous product which contains 
unaltered all the constituents of the ley, including the caustic soda. 











SODA. 


181 

( 3 . The ley is evaporated to a certain degree of concentration, the supersaturated 
solution depositing on cooling carbonate of soda as a crystalline powder, containing 
i molecule of water, Na 2 C 0 3 -f- H 2 0 ; the salt is gradually removed from the liquor 
by perforated ladles. During the evaporation fresh ley is run into the pan from a 
reservoir at a higher level, and in this way the operation is continued for several 
months. It is clear that by conducting the evaporation in this manner, the carbonate 
of soda collected becomes gradually less and less pure, being mixed with chloride of 
sodium and sulphate of soda; at last a mother-ley is left, containing chiefly caustic 
soda and sulphuret of sodium, and in a concentrated solution of these substances the 
other salts are insoluble. The crystalline carbonate of soda is first drained, an opera¬ 
tion sometimes performed in centrifugal turbines, and then calcined in a reverbera¬ 
tory furnace to oxidise any sulphuret of sodium that might be present; after this 
calcination the salt constitutes the calcined soda of commerce. The quality of the 
commercial article varies considerably, the difference being partly due to the care 
taken in the evaporation. The first crop of salt is always the best, that is to say, 
contains the largest percentage of sodic carbonate, sometimes amounting to 90 per 


Fig. 79. 



cent. When the ley is to be evaporated to dryness, the operation is carried on in a 
reverberatory furnace, Fig. 79. . The hearth is floored with fire-bricks, on to which a 
thick coating of carbonate of soda is well rammed. The fuel burning in A is coke; 
as soon as the furnace has become thoroughly red-hot, ley previously evaporated to 
33 0 B. in the pans D and E, is run into the furnace, effecting a very rapid evapo¬ 
ration to dryness, care being taken to stir the saline mass to keep the salt in a 
pulverulent state. By means of the dampers, F, G, and the flues, c c', the hot air and 
flame of the burning fuel may be conducted under the pans D and E or into the 
chimney. The composition of soda thus evaporated to dryness is, according to the 
analysis of two samples by Mr. J. Brown, as follows:— 



I. 

II. 

Carbonate of soda ,. 


65 ' 5 i 3 

Caustic soda. 


16*072 

Sulphite of soda .. - .. 


7-812 

Hyposulphite of soda .. 

2-231 

2-134 

Sulphuret of sodium .. 

.. 1*314 

1*542 

Chloride of sodium 

3-972 

3*862 

Aluminate of soda 

.. roi6 

1*232 

Silicate of soda 


o*8oo 

Insoluble matter .. 


0*974 


100-735 

99-941 



























CHEMICAL TECHNOLOGY. 


182 


The salt is next calcined, and the sulphuret of sodium converted into sulphite of soda, 
a portion of the caustic soda being 1 converted into carbonate of soda. The calcined salt 
is now ready for the market; but in some of the large alkali-works near Newcastle-on- 
Tyne it is re-dissolved in water, treated with carbonic acid, and again evaporated. A 
better product results from another method, namely, evaporating the ley to a known 
degree of concentration, and obtaining small crystals of soda-salt (Na 2 C 0 3 -f-H 2 0 ). In 
this case, as regards the methods of evaporation employed, the two following are most 
general:—Heat is brought to bear on the surface of the liquid contained in shallow 
rectangular iron pans fitted to the hearth of a reverberatory furnace ; the liquid rapidly 
boils at the surface, and a saline crust is formed, which is constantly broken up and 
collected with iron rakes by the workmen. Now and then the salt deposited at the bottom 
is removed and placed on a sloping ledge to drain. This method of evaporation is econo¬ 
mical, but attended with the disadvantage that the ley is constantly in contact with the 
carbonic and sulphurous acid gases arising from the combustion of the fuel, the conse¬ 
quence being that a portion of the caustic soda is converted into carbonate and sulphite 
of soda, the latter by the subsequent calcining operation being converted into sulphate. 
By the second plan of evaporation the heat is conveyed to the bottom of the pans, but 
then many precautions are required to prevent the bottom being burned in consequence of 
the settling down of a saline mass not conducting heat. Mr. Gamble, at St. Helens, 
employs a pan of a peculiar form, the section being like that of a boot; it is heated by the 
waste heat of the soda furnace, and the inclination of the sides of the pan greatly assists 
the removal of the salt, which, having been drained, is calcined, yielding a grey-coloured 
salt, afterwards purified by solution with the aid of steam in a small quantity of water, 
decanting the clear solution, and again evaporating it. Ralston obtains a purer product 
by washing the impure carbonate with a cold saturated solution of pure carbonate of soda, 
the chloride and sulphuret of sodium and the sulphate being thus removed. As already 
stated, the evaporation is not always continued to dryness, but to a degree of concentra¬ 
tion determined by experience. By varying the relative bulk of the liquid a more or less 
pure product may be obtained; when, for instance, the ley of the lixiviation tanks 
(= 1-286 ep. gr.) is evaporated to T 7 ths of its bulk, and the salt separated removed, this 
salt corresponds to a purified soda salt of 57 per cent.; by evaporating the remaining 
liquid to fths of its bulk, a salt of 50 per cent, is obtained. When the mother-liquor is 
evaporated to dryness, a very caustic and impure salt is obtained. Kuhlmann, at Lille, 
employs pans which are graduated so that the bulk of the liquid may be readily ascer¬ 
tained for the purpose of fractioned evaporation. The purification of the crude ley, 
containing sulphuret of iron dissolved by sulphuret of sodium, may be effected, as 
suggested by Gossage, in 1853, by filtering the liquid through a coke-tower (one of the 
towers used for condensing hydrochloric acid), a current of air being forced upwards to 
assist in oxidising the sulphuret of sodium. , 

The composition of refined soda, according to Tissandier’s analyses, is :— 


Moisture 

Insoluble matter.. 
Chloride of sodium 
Sulphate of soda 
Carbonate of soda 


I. 

2. 

'■y 

0 * 

4 - 

5 - 

. 2-22 

31 1 

115 

i-oo 

0-40 

. 0-12 

0-22 

0-08 

— 

0-06 

. 12-48 

6-41 

3-28 

2T I 

0-99 

. 8-51 

3-25 

2-15 

1-50 

°'35 

. 76*67 

87-01 

92-34 

95'39 

98-20 

100-00 

100-00 

100-00 

IOO'OO 

ioo-oo 


The composition of soda, containing caustic soda, is:— 


Moisture 
Insoluble matter 
Chloride of sodium 
Sulphate of soda 
Carbonate of soda 
Caustic soda 


1. 

2. 

■ 3 - 

4 - 

2-10 

1-50 

2-48 

1-38 

0-12 

O' I I 

0‘2I 

0-09 

4-32 

2-43 

3-50 

4 ” 11 

S-So 

1-62 

2-15 

2-50 

82-47 

88-09 

84-54 

81-67 

2"I I 

6-25 

7 - I 2 

10-25 

100-00 

100-00 

100-00 

100-00 


I11 order to obtain crystallised soda, Na 2 C 0 3 + ioH 2 0 , with 63 per cent, of water, 
a saturated solution of calcined soda in hot water is poured into large iron vessels, 
and yields crystals on cooling. The calcined soda is generally dissolved in conical 
vessels (Fig. 80), made of boiler-plate, c is a steam-pipe, e a water-pipe, D a per- 




















SOLA. 


i »3 

forated vessel to contain the calcined soda to be dissolved. The boiler is three- 
fourths filled with water, the perforated vessel filled with soda is then lowered into 
the liquid, and the steam turned on. The soda is rapidly dissolved, and when the 
solution marks 30° to 32 0 B. it is run into the crystallising vessels; the crystallisa¬ 
tion is complete in five to six days in moderately cool weather. The crystals are* 
broken up, and again dissolved in water in the vessel a (Fig. 81), heated by the fire 
at c. D d are flues carrying flame and heated air round the vessel; 33 is a water-pipe. 
The vessel having been filled with crystals, a small quantity of water is added, and 
as soon as the salt is completely dissolved, the fire is extinguished, the liquid being 
left to settle. The clear liquid is next syphoned into a reservoir, and from this poured 

Fig. 80. 



into cast-iron crystallising vessels. After seven or eight days the mother-liquor is 
removed, and the crystals are detached from the surface of the iron by placing 
the crystallising vessels for a few moments in hot water, the result being that by the 
incipient fusion of the crystals in their water of crystallisation, they are loosened 
from the metal to which they adhere. After, draining the salt is dried in rooms 
heated to 15 0 to 18 0 , and then packed in casks. Although a crystalline salt is gene¬ 
rally purer than a non-crystallised mass, yet the large quantity of water contained 
in crystallised carbonate of soda is an impediment to its extensive use, both on 
account of expense of carriage and the weakness of the alkali. In this country, 
however, owing to the great facility of water carriage, crystallised carbonate of soda 
is very largely used. 

Theory of Leblanc’s rrocess. The process of M. Leblanc has been best elucidated by the 
more recent researches of Gossage and Scheurer-Kestne . Formerly it was 
assumed that when a mixture of sulphate of soda, carbonate of lime, and carbon 
were calcined, the carbon while yielding carbonic oxide converted the sulphate of 
soda into sulphuret of sodium, in its turn decomposed by the carbonate of lime, the 
result being the formation of carbonate of soda, oxysulphuret of calcium, and the 
evolution of a portion of the carbonic acid; (a) Na 2 S 0 4 1 2C=Na 2 S-l-2CO2; 













i8 4 


CHEMICAL TECHNOLOGY. 


( 0 ) 2Na 2 S + 3CaC0 3 = 2Na 2 C0 3 -f CaO,2CaS + 00 2 . According to. Unger the car¬ 
bonate of lime loses its carbonic acid as soon as sulphuret of sodium is formed, 
there remaining a mixture of caustic lime, sulphuret of sodium, and carbon, which 
becomes converted into oxysulphuret of calcium, and caustic soda, the latter by 
‘taking up the carbonic oxide resulting from the combustion of the carbon becoming 
sodium-carbonate; this view appears to be nearest the truth, but as proved by 
Scheurer-Kestner, Dubrunfaut, J. Ivolb, and Th. Petersen, it is not necessary to 
assume the existence of oxysulphuret of calcium for the purpose of explaining the 
fact that the sulphuret of calcium does not act upon the sodium-carbonate, because 
sulphuret of calcium is almost insoluble in water, i2'5 parts of water dissolving at 
i2 , 6° only i part of sulphuret of calcium. This view is also confirmed by the 
results of experiments made by Pelouze. During the formation of soda in the cal¬ 
cining furnace the carbon is only converted into carbonic acid, viz. :— 
a. 5hTa 2 S0 4 + ioO = 5Na 2 S + ioC 0 2 . 

/ 3 . 5Na 2 S + 7CaC0 3 = 5Na 2 C0 3 + sCaS -f 2CaO -f 2 C 0 2 . 

However, as there is formed during the calcination process, especially towards the 
end of this operation, a not inconsiderable quantity of carbonic oxide which burns 
off with a bluish flame, this substance, although a secondary product, has to be taken 
into account in the formula; moreover, the formation of this gas is important, for 
as soon as it makes it appearance the chief reaction is being completed, proving 
the heat to be at its proper degree. 

The researches of Unger have undoubtedly proved that when the sulphat; 
is reduced by carbon there is only carbonic acid and not a trace of carbonic oxide 
formed, so that carbonic oxide is the result of the action of the excess of carbon 
upon the carbonate of lime ; this reduction of the carbonate of lime by carbon.takes 
place at a much higher temperature than that at which the sulphate is reduced, 
therefore the formation of carbonic oxide takes place after that of the carbonate 
of soda. Consequently there must be distinguished three phases in the formation of 
s xla, viz. :— 

a. The reduction of the sulphate, with evolution of carbonic acid gas— 

(Na 2 S 0 4 + 2C = Na 2 S + 2 C 0 2 ). 

/ 3 . Double decomposition of the newly formed sulphuret of sodium and carbonate 
of lime (Na 2 S 4 “ CaC 0 3 = Na 2 C 0 3 -{- CaS). 

y. The reduction of the excess of carbonate of lime by the carbon— 

(2CaC0 3 + 2C = 2CaO + 4 C 0 ). 

During the lixiviation the presence of caustic lime aids the formation of caustic 
soda. According to theory, ioo parts of sulphate only require 20 of carbon, but it 
is the practice to employ an excess of carbon, as much as 40 to 75 per cent., to pro¬ 
vide against incomplete mixture, the combustion of carbon without effect, and 
because of the necessity of obtaining the reaction of the carbonic oxide in order 
that the progress of the operation may be observed, as experience has proved that the 
mass should not be removed from the furnace until this combustion is nearly over, 
utilisation of Soda Waste. The greater part • of the soda now employed is obtained by 
Leblanc’s process, which, while it admits of lixiviating the soda readily and com¬ 
pletely, is defective, inasmuch as the residue, or waste as it is technically called, 
contains nearly all the sulphur used in the manufacture ; and that this is not a slight 
loss may be inferred from Oppenheim’s statement, that in the alkali works at Dieuzo, 


SODA. 


i$5 


Lorraine, tlie accumulated waste contains an amount of sulphur valued at £150,000. 
For every ton of alkali made there is accumulated 1J tons of waste, containing 
80 per cent, of the sulphur used in the manufacture; and this waste, until lately 
thrown on a refuse heap in some fields adjacent to the works, often proved a nuisance 
in hot weather, giving rise to fumes of sulphuretted hydrogen. For the last forty 
years much time and money have been spent in trying to recover the sulphur, 
but not until 1863 was any attempt successful. Three different processes are now 
resorted to, viz.—Guckelberger’s, modified and practised by Mond; Schaffner’s plan; 
and the process invented by M. P. TV. Hofmann, at Dieuze. Since the first suc¬ 
cessful experiment the methods have been so rapidly improved that, at the Paris 
Exhibition of 1867, no fewer than nine samples of recovered sulphur were sent in. 
All the methods mentioned above are based upon the same principle—the conversion 
of the insoluble sulphurets of calcium contained in the waste into soluble compounds 
by the aid of the oxygen of the atmosphere; the lixiviation of the oxidised mass, 
and precipitation of the sulphur contained in the leys by a strong acid, practically 
hydrochloric acid. 

Sctia ne}-ation U Proces?' ese * Schaffner’s plan for the regeneration cf sulphur from soda 
waste involves the following operations:— 

a. Preparation of the liquor containing sulphur 

/ 3 . Decomposition of the liquor. 

y. Preparation of the sulphur. 

a. The soda waste is submitted to a process of oxidation by the action of the air, 
and for this purpose is placed in large heaps, where heating takes place, together 
with the formation of polysulphurets and subsequently hyposulphites. After a few 
weeks the interior of the heap assumes a yellow-green colour, when the material 
is ripe for lixiviation; the heap is then broken up into large lumps, which remain for 
another twenty-four hours’ oxidation. These lumps are next submitted to lixiviation 
with cold water, and a concentrated liquor obtained. After this process follows 
another oxidation, effected by placing the lixiviated residues in a pit dug in the soil 
to a depth of 1 metre, and situated close to the lixiviation tanks; by this burying the 
heat generated by the oxidation suffers less dissipation than when the material is ex¬ 
posed on all sides to currents of air. The second oxidation proceeds more rapidly than 
the first in consequence of the greater porosity of the mass, so that besides poly¬ 
sulphurets more hyposulphites are formed. * Instead of effecting the second oxida¬ 
tion by burying, the waste may be left in the lixiviation tanks, and the oxidation 
accelerated by forcing the hot gases from a chimney under the perforated bottom of 
the tank; by these means both time and labour may be saved, the oxidation being 
complete in 8 to 10 hours. According to the quality of the alkali waste, this process 
of oxidation may be repeated three to four times; the gases accompanying the smoke 
of burning fuel are exceedingly well suited for effecting the decomposition of 
the sulphuret of calcium in such a manner as to cause the formation of poly¬ 
sulphurets and hyposulphites. The liquors resulting from the first lixiviation con¬ 
tain chiefly polysulphurets and hyposulphites ; but the liquors obtained after the 
second and third oxidation contain essentially hyposulphites; all the liquors are col¬ 
lected in one reservoir. 

Q. The decomposition of the lixiviation liquor by means of hydrochloric acid is 
carried on in a closed apparatus of cast-iron or stone, and is based upon the fact that. 


CHEMICAL TECHNOLOGY. 


186 


hyposulphites when treated with hydrochloric acid, evolve sulphurous acid gas, 
sulphur being precipitated (Ca 2 0 3 -f- 2HCI yields CaCl 2 -}- S 0 2 + S -f- II 2 0 ), and 
upon the reaction exerted by sulphurous acid upon the polysulphuret, which, while 
sulphur is deposited, is again converted into hyposulphite of lime— 

(2CaSx -f- 3S0 2 = 2CaS 2 0 3 4- Sx). 

The liquor is tested by titration to determine the quantity of polysulphuret and of 
hyposulphites contained, and according to the result the residue is more or less 
oxidised. 

The apparatus generally employed in the decomposition is shown in Fig. 82 ; a and b 
are the vessels to contain the liquor; l is the pipe by which the liquor is conveyed to 
a or b, regulated by a piece of elastic tubing entering at q into A, or q' into b. t and t' 
are earthenware tubes by which the hydrochloric acid is introduced, c and d are glass 


Fig. 82. 



tubes, c is fitted to the top of a, and has a longer leg dipping into the fluid at b ; the reverse 
is the case for d, the short leg of which is fitted to b, while the longer leg dips into the 
fluid in A. The tap, a, is closed when the gases should enter through c into the fluid 
contained in b, but the tap, b, is shut, and a opened, when the gases passsing through d are 
to enter the fluid contained in A. The excess of gas is carried off by the tube r. As soon 
as the decomposition by the action of the hydrochloric acid is effected, steam is injected 
through the valves, v V, to expel the last traces of sulphurous acid from the liquor. 
The liquor and finely divided sulphur are run off at o and o', care being taken to let the 
chloride of calcium solution run off by removing the wooden plug, p. In order to ascertain 
whether all the sulphurous acid is expelled, the wooden taps, h h', are opened, the smell 
of the gas being a sufficient indication of its presence. The taps, / and/', are employed 
as test cocks to ascertain the progress of the operation, and also to see whether "the 
vessels are properly filled with liquor. 

The sulphur obtained by this process is fine-grained, and mixed with some gypsum, 
chiefly due to the sulphuric acid contained in the hydrochloric acid. The sulphur and 
chloride of calcium liquor are conducted by the spout, g, to a vessel with a false bottom, 
perforated and covered with a flannel cloth, through which the liquor passes, the sulphur 
being retained. 

y. The sulphur is prepared for the market by a very simple process. It is mixed 
with sufficient water to constitute a paste, which is put into a cast-iron vessel, and 
steam at a pressure of if- atmospheres admitted to melt the sulphur, the water 
taking up any adhering chloride of calcium solution, and also the gypsum. The 
molten sulphur collects in the bottom of the vessel, and is tapped off into moulds ; 
the supernatant liquor does not mix with the sulphur owing to the greater specific 
weight of the latter. In order to perfectly saturate any free acid which might still be 











SODA. 


187 


present some milk of lime is added; by this addition another end is gained, viz., 
the removal of any arsenic, in the following manner:—If during the melting process 
an excess of lime be present, sulphuret of calcium is formed, and this sulphuret 
dissolves any sulphuret of arsenic which is thus removed to the supernatant liquor. 
The advantages of melting and purifying the sulphur by the above process are— 
the sulphur need not first be carefully washed and dried, fuel is saved, the sulphur 
freed from arsenic, and brought to the best state for pouring into moulds. Figs. 83 
and 84 represent the melting vessel; the cast-iron cylinder, B, is surrounded by a 
wrought-iron cylinder, A, and the whole inclined to admit of the molten sulphur 


Fig. 83. 



Fig. 84. 



collecting at the lower part of b. The sulphur paste is being stirred by an apparatus 
in gearing at e, with some motive power. The paste is poured into b at to ; at 
a steam is introduced, passing at 0 into the inner cylinder, and let off, when the 
melting is finished, through d and the valve, v ; the molten sulphur is run off at z ; 
s is a safety valve. By this process 50 to 60 per cent, of the sulphur contained in 
the soda waste is recovered, for every cwt. recovered 2 to 2\ cwts. of hydrochloric 
acid being employed. If this acid were too expensive, the residues of chlorine 
manufacture might be used, these residues consisting mainly of chloride of manganese, 
free hydrochloric acid, and chloride of iron; the first step would then be to free 
these residues from the chloride of iron by means of the lixiviated soda waste added 
in small quantities at a time; sulphuretted hydrogen would be given off, and 
Fe 2 Cl6 reduced to FeCl 2 , the changed colour indicating the end of the reaction. 
The dirty grey-coloured sulphur from this reaction should be burnt in the pyrites 
or sulphur-burning furnace. The prepared residue would now be fit for employment 
as a substitute for hydrochloric acid. Should, however, some monosulphuret of 
calcium be present in the soda waste liquor—not a very likely occurrence—some 
hydrochloric acid must be added before using the residues, 
sundry Methods of* Among the many methods which have been proposed for the 

Pr suiphafe of soda!” 1 preparation of soda the following especially deserve notice. Ac¬ 
cording to Kopp’s methods of soda manufacture sulphate of soda, oxide of iron, 
and carbon are smelted together in an ordinary soda furnace:— 








CHEMICAL TECHNOLOGY. 


ISS 


2 Fc 2 0 3 

3Na 2 S0 4 

16O 


yield by 
calcination 


( Fe 4 Na6S 3 . 

14CO. 

[ 2 C 0 2 . 


The crude soda absorbs from the air water, oxygen, and carbonic acid, becoming 
converted into carbonate of soda and an insoluble residue of suljihuret of iron 
containing sodium, Fe 4 Na6S 3 :— 


Fe 4 NaeS 3 \ 

2 0 ( yield 

zC0 2 ) 


( 2 Na 2 Co 3 . 

I Fe 4 Na 2 S 3 . 


The lixiyiation is effected with warm water at 30° to 40° ; the liquors yield alter 
twenty-four to twenty-eight hours, without any previous concentration, a large 
crop of beautifully crystallised soda. The insoluble residue of the lixiviation is dried 
and roasted to produce sulphurous acid, employed in the manufacture of sulphuric 
acid, used in its turn for the conversion of common salt into sulphate of soda. Thus 
the cycle of changes in the sulphur is complete :— 


Fe 4 lSra 2 S 3 ) • 
14 ^ f 


yield 


( 2 Fe 2 0 3 

Na 2 S 0 4 

US0 2 


The sulphate of soda present in the calcined residue is removed by lixiviation. 
It cannot be denied that this process presents certain advantages. 

riiroct conversion of A pl an for the direct conversion of common salt into soda has long 
Common Sait been sought, but hitherto not successfully carried into practice. W hen 
a concentrated solution of bicarbonate of ammonia is mixed with 
strong brine, or, better still, the pulverised bicarbonate stirred through a concentrated 
solution of salt, and this mixture left to stand, the result will be that after some hours 
bicarbonate of soda will be deposited in crystalline state, the supernatant liquid being a 
solution of sal-ammoniac. As bicarbonate of soda on being gradually heated to redness 
loses a portion of its carbonic acid, and is converted into monocarbonate of soda, this 
process has been suggested as suited for the manufacture of soda, and has been 
tried by Dyar and Hemming in England. Schloesing and Holland in 1855 took out a 
patent for some improvements on this method of soda manufacture, of which the following 
is an outline:—The first operation consists in the action of ammonia and carbonic 
acid upon a concentrated salt solution; to 100 parts of water 30 to 33 parts of common 
salt, 8^ to 10 of ammonia, and carbonic acid in excess are taken. The next step is the 
separation of the bicarbonate of soda, which is effected by a centrifugal machine. 
The third stage is the calcination of the bicarbonate of soda in cylindrical iron vessels, 
the carbonic acid gas given off being collected. The fourth and fifth operations aim at 
the recovery of the carbonic acid and ammonia from the liquid drained from the bicar¬ 
bonate of soda while in the centrifugal machine. The liquid is heated in a boiler, the 
result being the escape of the ammonia and carbonic acid, which are conducted to a 
cylinder filled with coke, through which a cold aqueous solution of carbonate of am¬ 
monia trickles, causing the condensation of the ammonia, the carbonic acid escaping 
into a gasholder. Next, milk of lime is added to the liquid, and the heating being con¬ 
tinued, all the ammonia is expelled. Lastly, the clear supernatant liquid is evaporated to 
recover the common salt. According to Heeren’s researches on this subject, this process is 
more suited for the preparation of bicarbonate of soda; it is stated, however, that the 
researches of Marguerite and Sourdival have resulted in improvements on this method 
which may in future lead to its being advantageously adopted in some localities for the 
manufacture of soda. 


soda from cryolite. Cryolite (Al 2 Flg,6NaFl) is largely employed for the manufacture 
of soda by decomposing the mineral by ignition with lime:— 


1 mol. of Cryolite') 

6 mols. of Lime / ^ 


c 


6 mols. of Fluoride of calcium, 
mol. of Aluminate of soda. 


This last compound being soluble in water is decomposed by carbonic acid, and 
alumina precipitated, soda remaining in solution. 100 kilos, of cryolite yield— 


SODA. 


189 


Dry caustic soda .44 kilos. 

Calcined soda.75 „ 

Crystallised carbonate of soda .. 203 ,, 

Bicarbonate of soda . 119*5 >> 


Bauxite (see under A lumina), on ignition with sulphate of soda and carbonaceous 
matter, yields in a similar manner soda and alumina. 

soda from Nitrate By the conversion of nitrate of soda into nitrate of potassa by the aid 
of soda. 0 f. carbonate of potassa (see under Saltpetre) not inconsiderable quantities 
of a strong solution of soda are obtained; the sodium of the sodium nitrate may be 
converted by any of the following means into soda or caustic soda :— 

a. By igniting nitrate of soda with carbonaceous matter. 

b. By igniting nitrate of soda with silica, and decomposing the silicate of sodium by 

carbonic acid. 

c. By igniting nitrate of soda with manganese. 

d. By the decomposition of nitrate of soda. 
a. By means of carbonate of potassa ; or, 

£. By.means of caustic potassa. 

In the latter case, besides nitrate of potassa, caustic soda is formed. 

caustic Soda. This substance, sodium hydroxide (NaHO), is met with in commerce 
as a highly concentrated solution, or more frequently as a solid mass, fused hydrate 
of soda, consisting in 100 parts of 77*5 parts of soda and 22*5 parts water. For 
many years a moderately strong solution of caustic soda was prepared by treating 
a carbonate of soda solution with caustic lime, but Dale was the first to use this 
solution instead of water in his boilers, and thus concentrate the lye to a sp. gr. of 
1*24 to 1*25, after which the ley was further evaporated in cast-iron cauldrons to a 
sp. gr. of 1*9, at which point it solidifies on cooling. 

Instead of using caustic lime, caustic soda is now directly produced by simply 
increasing the quantity of small coal added to the mixture of sulphate and chalk, 
the crude soda being at once lixiviated with water at 50°. After the liquor has 
cleared, it is rapidly concentrated to 1*5 sp. gr., when carbonate, sulphate, and 
chloride of sodium are deposited, the liquor assuming a brick-red colour, due to a 
peculiar compound of double sulphuret of sodium and sulphuret of iron. The ley 
is next strongly heated in large cast-iron cauldrons, and there is added 3 to 4 kilos, 
of Chili-saltpetre for every 100 kilos, of caustic soda required; by this operation the 
nitrate of soda reacts upon the sulphuret of sodium and cyanide of sodium present, 
causing an abundant evolution of ammonia and nitrogen. This somewhat com¬ 
plicated process may be elucidated by either of the two following formulae :— 
a. 2Na 2 S + 2NaN0 3 + 4 ll 2 0 = 2 Na 2 S 0 4 + 2 NaH 0 -f 2NH3. 

/ 3 . 5Na 2 S + 8 NaN 0 3 + 4H 2 0 = 5Na 2 S0 4 + 8NaHO + 8tf. 

According to Pauli, the kind of reaction depends chiefly on the temperature of the 
heated ley ; at 155° ammonia is largely evolved; above 155 0 and with greater con¬ 
centration of the ley nitrogen is given off. As for every ton of caustic soda produced 
this process absorbs 0*75 to 1 cwt. of nitrate of soda, the ley is in some works oxidised 
by filtering it through a column of coke, or by forcing air through it in minute jets. 

New Methods of Caustic Among these is the decomposition of sulphate of soda by means 01 

Soda Manufacture. caustic baryta, a rather expensive process, baryta white or permanent 
white being a by-product. linger uses caustic strontia instead of caustic baryta. Caustic 
soda may be prepared by treating cryolite for sulphate of alumina (see Alum), or by 
igniting nitrate of soda with manganese; or by decomposing silico-fluoride of sodium 
or fluoride of sodium with caustic lime. In England very pure caustic soda is prepared 
from sodium by carefully oxidising the metal with pure water in bright iron or sil ver 
vessels. 





CHEMICAL TECHNOLOGY. 


i?o 


According to Dalton’s researches :— 
A caustic soda liquor of the 
undermentioned sp. gr. 

2*00 

i-8 5 


Contains percentage of caustic 
soda (NaHO.) 

77-8 

6 3 ‘6 


172 
1-63 
1-56 
1*50 
I *47 
1 '44 
1*40 
1*36 
1-32 
1*29 
1-23 
1*18 


53 * 

46*6 

41-2 

36*8 

34 '° 

31-0 

29*0 

26*0 

23*0 

19*0 

i6’o 

i 3 *o 

9-0 


ro6 47 

Caustic soda is largely used in soap-making, paraffin and petroleum refining, and the 
preparation of silicate of soda and artificial stone by Ransome and Sims’s method. 


Bicarbonate of soda. This substance, NaHC 0 3 , called erroneously carbonate of soda 
in many of the London shops, consists in 100 parts of 36*9 soda, 1073 water, and 
5237 carbonic acid, and is prepared by passing a current of washed carbonic acid 
gas through a solution of carbonate of soda. If the solution is concentrated the 
bicarbonate is deposited as a powder, but from a dilute solution large crystals are 
obtained. It is, however, more advantageous to cause the carbonic acid to act upon 
crystallised and effloresced carbonate of soda; a suitable mixture consists of 1 part 
of crystallised and 4 parts of effloresced carbonate of soda. The sources of carbonic 
acid may differ, but in this country the gas is generally prepared by the action of 
weak hydrochloric acid upon chalk or limestone; of course the carbonic acid evolved 
during the fermentation of wort, or must, may be applied. 

When carbonic acts upon crystallised carbonate of soda there is first formed 
sesquicarbonate of soda ; the 9 equivalents of water which are displaced from each 
equivalent of crystallised carbonate of soda are collected in a reservoir, and this 
liquid having of course dissolved a portion of the bicarbonate is employed at a 
future operation for moistening the crystallised soda carbonate. The bicarbonate 
' is dried at 40° in a current of carbonic acid gas. The preparation of the bicarbonate 
by withdrawing from the monocarbonate by the aid of an acid one-half of the soda 
it contains has been suggested; for this purpose 28J parts of crystallised sodie 
carbonate are dissolved in twice their weight of warm water, and 4^ parts of 
sulphuric acid added, care being taken not to move the vessel. Being left to stand 
for several days the bicarbonate is deposited in crystals. It has been seen 
that when a solution of common salt is treated with bicarbonate of ammonia, the 
result is the formation of bicarbonate of soda and sal-ammoniac, which remains in 
solution. Bicarbonate of soda crystallises in monoclinical, tabular crystals; has a 
weak alkaline reaction; loses its carbonic acid at 70°, and becomes monocarbonate 
of soda; and by exposure to dry air is gradually converted into sesquicarbonate. 
The bicarbonate is employed generally in the preparation of effervescing drinks, and 


IODINE AND BROMINE. 


19* 

with hydrochloric or phosphoric acid in making bread without fermentation. The 
further uses of this salt are—the precipitation of the alumina from sodium- aluminate 
solutions, for the preparation of baths, for gilding and platinising, and for purifying 
and cleansing silk and wool. 1 grm. of the bicarbonate yields, when completely 
decomposed by an acid, about 270 c.c. of carbonic acid gas = 0^52 grm. by weight. 

The total production of soda in Europe amounted in 1870 to 11,850,000 cwts., of 
which Great Britain produced 6,250,000 cwts. 

Preparation of Iodine and Bromine. 

Preparation of Iodine. This element occurs in sea-water, from which it is taken up by 
various sea-weeds; from these sea-weeds iodine is derived industrially. Chili-salt¬ 
petre and some saline springs (for instance,- the Suiza, Sadiem Weimar) contain 
iodine in considerable quantity. Although iodine is found in the mineral kingdom 
(for instance, in the iodide of lead and phosphorites of Amberg, Bavaria, and Diez 
on the Lahn), it is not in this case industrially important. The chief seat of iodine 
manufacture is at Glasgow, where there are twelve factories ; there are two iodine 
factories in Ireland, and two at Brest, in Erance. 

Preparation from Keip. In order to obtain iodine from sea-weeds, the latter are first con¬ 
verted into kelp, that is to say, they are incinerated, the product broken to pieces 
and lixiviated with water, leaving an insoluble residue of 30 to 40 per cent., and 
yielding to the liquid 60 to 70 per cent. This solution, having a sp. gr. of 
1*18 to 1 *20, contains chlorides, sulphates, and carbonates of alkalies, sulphuret 
of potassium, iodide of potassium, and hyposulphites of alkalies; by evaporating 
and cooling the liquor, the sulphate of potassa and chlorides of potassium and 
sodium are removed. To the remaining mother-liquor, previously poured into 
shallow open vessels, dilute sulphuric acid is added, the result being, that while 
a strong evolution of gases, sulphuretted hydrogen, and carbonic acid takes place, 
there is formed a thick scum and a deposit of sulphur at the bottom of the vessel; 
the sulphur when washed and dried is sold. When the evolution of gas has 
completely ceased, more sulphuric acid is added, and, according to Wollaston’s 
method, the required quantity of manganese ; this mixture is poured into a large 
leaden distilling apparatus, C, Eig. 85. By this means the iodine is set free, carried 


Fig. 85. 



over in the state of vapour to the receivers, b, b', b", and Condensed as a solid 
crystalline mass. In Paterson’s large iodine works at Glasgow this operation is 
carried on in a cast-iron hemispherical vessel of 1*3 metres diameter, the cover 












192 


CHE MIC A L TECHNOLOG Y. 


being a leaden dome, to which, are fitted two earthenware stillheads, connected 
by means of porcelain tubing with two earthenware receivers, Fig. 85, each con¬ 
sisting of 4 to 5 parts. At Cherbourg, iodine is obtained, according to Barruel’e 
plan; by passing chlorine gas into the mother-liquor; by this plan the iodine is- 
separated from the iodide of magnesium, the latter taking up chlorine instead— 

(Mgl 2 -f Cl 2 = MgCl 2 + I 2 ). 

A more recent method, by which all the iodine present in the mother-liquor is 
obtained, consists in distilling the liquor with chloride of iron— 

( 2 NaI -f Fe 2 Cl 6 = 2I + 2 NaCl + 2 FeCl 2 ). 

As iodine is only very slightly soluble in water, 1 part of iodine requiring 55:24 parts 
of water at io° to i 2 ° for its solution, that is, 1 grain of iodine to i 2 ounces of water, 
it is carried over with the steam and deposited at the bottom of the receiver in the 
form of a black powder. When iodine is prepared by the aid of chlorine, the 
quantity of gas should be exactly sufficient to decompose the iodide of magnesium, 
for if the quantity of chlorine be too small no iodine is separated, and if too large 
chloride of -iodine is formed and free bromine, both of which being volatile escape. 
The iodine when removed from the receivers is drained on porous bricks or tiles, 
and dried between folds of blotting-paper. It need hardly be said that the iodine 

should not come in contact with a 
metallic surface. The iodine thus 
obtained has to be purified by sub¬ 
limation, an operation carried on in 
the apparatus represented in Fig. 86, 
consisting of stoneware retorts, c c, 
placed in the sand-bath, B, heated 
as shown in the woodcut. Each of 
these retorts is filled with upwards 
of 40 lbs. of crude iodine, and en¬ 
tirely surrounded by sand, in ordei 
to prevent the sublimation of any 
iodine in the necks of the retorts. 
These are then connected with the 


Fig. 86. 



receiver or condenser, R R, in which the crystalline iodine is deposited, the tubes, 
a b, a l, being for the purpose of carrying off the watery vapour. 1 ton of kelp 
yields on an average 4*07 kilos, of iodine. 


M S t t h n / 0 f d p ndMor i d T e ’r P I 11 1862, Mr. Stanford suggested that the sea-weeds should not 
fromCaibonised 1 sea-weed, be calcined, but simply distilled with superheated steam, so as to 
prevent volatilisation of the iodine, while the tarry and gaseous products should be sepa¬ 
rately utilised. This carbonised sea-weed, when quite cold, is lixiviated with water, and 
the solution treated for iodine and chloride of potassium (see p. 130). The volatile pro¬ 
ducts of the distillation are illuminating gas, acetic acid, ammonia, mineral oil, and 
paraffin. M. Moride, of Nantes, has modified this process: he prepares by evaporating 
the liquor from the lixiviation of the carbonised sea-weed, sulphate and chloride of 
potassium, &c. The mother-liquor is treated -with chlorine or hyponitric- acid, and then 
with benzine, in an apparatus so arranged that the benzine directly gives up the iodine it 
has dissolved to soda or potassa, the benzine thus acting as a continuous solvent. The 
liquor containing iodine is treated for the separation of iodine in the usual manner. 

Preparation of iodine from Crude Chili-saltpetre contains on an average 0-059 to 0-175 
ciiiii-saitpetre. p er cent, of iodine. According to Nollner, the iodine occurs from 
the formation of the Chili-saltpetre in the presence of decaying sea-weeds from shallow, 
stagnant, inland seas, which have dried up. The mother-liquors, left after the refining 
of the salt, or from its use for the conversion of chloride of potassium into nitrate of 
potassa, and containing 0-28 to 0-36 per cent, of iodine, are treated with sulphurous 











IODINE AND BROMINE. 


193 

acid until the iodine separated begins to re-dissolve. More recently nitrous acid has 
been used instead of sulphurous acid. The iodine thus obtained is refined by sublima¬ 
tion, while that remaining in the residual saline matter is removed by a further treat¬ 
ment with chlorine. 

Properties and Uses of iodine. Iodine (I = 127 5 Sp. gr. = 4*94) is a black-grey coloured 
crystalline substance, with a metallic appearance not unlike graphite. On being 
heated iodine is converted into vapours, which, according to Stas, when concentrated 
exhibit a blue colour, and a violet in a more dilute state. Iodine fuses at 115 0 , 
and boils above 200°. It is somewhat soluble in water, readily so in alcohol, 
ether, hydriodic acid, iodide of potassium solution, sulphide of carbon, chloroform, 
benzol, aqueous solution of sulphurous acid, and solution of hyposulphite of soda. 
A solution of iodine imparts a violet colour to starch. Adulteration of iodine 
with either pulverised charcoal or graphite may be at once detected by treating a 
sample with alcohol or a solution of hyposulphite of soda, in each of which the 
iodine, if pure, ought to dissolve completely, leaving no residue on sublimation. 
Sometimes the weight of iodine is fraudulently increased by the addition of water. 
Iodine is largely used in photography combined as iodide of potassium; for the 
preparation of other iodine compounds, for instance, iodide of mercury; also in the 
preparation of some of the tar colours, iodine violet, iodine green, and cyanine blue, 
the latter a compound from iodine and lepidin, a volatile base. The total produc¬ 
tion of iodine in Europe and Chili amounted in 1869 to 3453 cwts., more than half, 
or 1829 cwts., being produced in Scotland and Ireland. 

Preparation of Bromine. The element known as bromine occurs to a small extent in sea¬ 
water, a litre containing cro6i grms. bromine. The mother-liquors, however, of 
many salt works (for instance, those at Schonebeck, near Magdeburg, and the 
liquors left from many of the Stassfurt salts) are so rich in bromine, that its pre¬ 
paration is worth the cost and trouble. In order to avoid as much as possible the 
admixture of chlorine, there is added to the mother-liquor dilute sulphuric acid; 
this mixture is heated to 120°, and the hydrochloric acid set free by the sulphuric 
acid evolved, while the less volatile hydrobromic acid is left in the liquor, from 
which, on cooling, sulphates are deposited. The decanted liquor is distilled after the 
addition of more sulphuric acid and some manganese. Two Woulfe’s bottles serve 
as receivers; in the first are condensed water, bromine, bromoform, and bromide of 
carbon, while any bromine vapours which pass over to the second bottle are absorbed 
in the caustic soda it contains. The ley contained in this vessel is evaporated to 
dryness, the residue ignited in order to convert bromate of soda into bromide of 
sodium ; the saline mass being then mixed with sulphuric acid and manganese and 
distilled, yields pure bromine, best preserved under strong sulphuric acid. 

According to Leisler’s patent (1866) bromine is separated from the mother-liquor left by 
operations with kainite, or camallite, or from the water of the Dead Sea (containing, 
according to Lartet’s analysis, in 1 litre, taken from a depth of 300 metres, 7'093 
grms. =07 per cent, of bromine) by adding bichromate of potassa and an acid; heat 
being applied, the bromine is volatilised and collected in a condenser filled with metallic 
iron. From the bromide of iron thus formed, either the element itself or any of its com¬ 
pounds may be obtained. The apparatus employed by this patentee is a distilling ap¬ 
paratus ; the acid is hydrochloric diluted with four times its bulk of water ; to 100 parts 
by bulk of the bromine fluid, 1 part by bulk of acid is added. The bichromate is added 
in a saturated aqueous solution. The bromide of iron formed becomes dissolved by the 
aqueous vapour, and condensed in the receiver. Bromine is the only metalloid fluid at 
ordinary temperature. Seen in thick layers its colour is a deep brown-red, but in thin 
layers a hyacinth-red; its odour is strong and similar to that of chlorine gas. The 
aqueous solution of bromine—1 part requiring 30 parts of water for its solution—is of a 
yellow-red colour when freshly made, but like chlorine-water does not keep well, and is 
U 


194 


CHEMICAL TECHNOLOGY. 


soon converted, especially if exposed to light, into a colourless solution of weak k}-dro- 
bromic acid, ioo parts of bromine water contain at 15 0 , 3'226 parts of bromine ; bromine 
forms with water a solid hydrate at o°. It is readily soluble in ether, alcohol, chloroform, 
and hydrobromic acid. It yields with an aqueous solution of sulphurous acid hydro- 
bromic acid— 

(S 0 2 + H2O + 2Br = S 0 3 -f 2BrH). 

Bromine boils at 63°, giving off deep red vapours; at —7*3° it becomes a lead-grey 
coloured, foliated, graphite-like mass. Bromine acts upon colouring matters, dyes, and 
the colours of flowers as does chlorine, while organic matters, especially those of animal 
origin, are coloured brown. It is used in combination as bromides of potassium, ammo¬ 
nium, cadmium, and hypobromite of potassa, for photographic purposes and in medicine; 
and further as bromides of ethyl, amyl, and methyl, for the preparation of some of the tar 
colours, Hofmann’s blue, and the preparation of alizarine from anthracen. Bromine is 
also used as a disinfectant, and, according to Beichardt, may with advantage be sub¬ 
stituted for chlorine in the preparation of ferricyanide of potassium. Since the year 
1866 bromine has been manufactured at Stassfurt, now the chief bromine-producing 
locality. The total annual production of bromine in Europe and America amounts 
to 1150 cwts., of which 400 cwts. are obtained at Stassfurt, and 300 cwts. in Scot¬ 
land. 


Sulphur. 

sulphur. In combination with coals, rock-salt, and iron, sulphur is the mainstay of 
present industrial chemistry. It is often found native between gypsum, clay, and 
marl in tertiary deposits, more rarely in veins between crystalline rocks of the 
schistose and metamorphic varieties, and not unfrequently in coal and lignite 
deposits. Sulphur is an almost constant product of active volcanoes, being sublimed 
and deposited on surrounding objects. The largest sulphur deposits in Europe are 
met with in Sicily. It is also found in Egypt on the banks of the Bed Sea, espe¬ 
cially near Suez; at Corfu, one of the Ionian Islands; near the Clear or Borax Lake 
in California; on the slopes of the Popocatepetl, in the province of Puebla, Mexico, 
where yearly 2000 cwts. of sulphur are collected. Erequently, sulphur is deposited 
from the sulphuretted waters of mineral springs; for instance, the waters of Aix- 
la-Chapelle. Sulphur occurs in combination with metals, as in iron pyrites, PeS 2 , 
with 53*3 per cent, of sulphur; this mineral often contains thallium. The quantity 
of sulphur contained in the following minerals is, from 100 parts :—Iron pyrites 
(FeS 2 ), 53*3; copper pyrites (Fe 2 Cu 6 S 6 ), 34-9'; magnetic iron pyrites, mundic 
(Fe 7 S 8 , or, according to Th. Petersen, FeS), 39-5 ; galena (PbS), 13-45 ; black-jack 
(ZnS), 33-0; kieserite (MgS 0 4 -j-H 2 0 ), 23-5; anhydrite (CaS 0 4 ), 23*5; gypsum 
(CaS 0 4 + 2H 2 0), i8*6 ; gas coal, i*o. According to Dr. Wagner, the quantity of 
sulphur present in the coals used in the London gasworks annually, amounts to 
200,000 cwts., equal to 612,500 cwts. of sulphuric acid. 

Although sulphur occurs native as sulphuretted hydrogen and sulphurous acid, 
especially near active volcanoes, this is not of much industrial use. The regenera¬ 
tion of sulphur from soda-waste is decidedly one of the most important items in the 
sulphur industry. 

Smelti suiphu 1 ? eflning According to the comparative richness of the raw material, the 
sulphur is separated from its concomitant impurities by melting or by distillation. 
When the raw material is rather rich it is simply submitted to a process of melting 
in a cast-iron cauldron, b (Fig. 87), heated by a gentle coal or charcoal fire placed 
in A. During the melting the mass is stirred with an iron rod, and as soon as the 
sulphur has become quite fluid, the gangue and small stones are removed by means 
of the ladle, c. This done, the sulphur is poured into a wooden or sheet-iron vessel 
d, thoroughly wetted with water to prevent the adhesion of the sulphur to tho 


SULPHUR. 


195 


sides. The sulphur when cold and solid is broken into large lumps and packed ir. 
casks ready for the market. The stones and gangue are placed in heaps, or more 
commonly introduced into a shaft furnace (Fig. 88), and, a portion of the sulphui 
being sacrificed to serve as fuel, the greater part of the element is eliminated by th6 
following plan:—A small portion of the crude sulphur is ignited in the lower part oi 
the furnace, and the shaft, E, filled with large lumps of the earthy sulphur ore, from 


Fig. 88. 



which, rapidly ignited superficially, the molten sulphur trickles down. The 
openings, ///, give access to the air required for the combustion of a portion of the 
sulphur. The sulphur collects in the lower part of the furnace and is tapped off 
by the channel g into wooden or sheet-iron vessels. A far better method of pre¬ 
paring sulphur from the ore is by distillation, the apparatus being that exhibited in 
Fig. 89. A is a cast-iron cauldron, which is filled with raw material, and covered 


Fig. 89. 



with a tightly-fitting iron lid. The flues are so constructed as to heat the vessel D 
gently. The vapours of sulphur are carried by the tube m into the condenser, n, 
whence the molten sulphur runs off into the vessel k. The previously warmed ore is 
readily admitted to A by lifting the damper, p. From a suggestion made by E. and 
P. Thomas, sulphur is obtained from its ores by the application of superheated 
steam at 130°, this mode of working being the same as that employed by M. Schaffner 
for purifying the sulphur recovered from soda-waste. In passing, it may be men¬ 
tioned that very recently the extraction of sulphur from its ores has been attempted 










CHEMICAL TECHNOLOGY. 



by the aid of solvents, viz., sulphide of carbon and a light coal-tar oil of sp. gr. r= o*8S. 
M. Mene’s analyses of several samples of crude Sicilian sulphur obtained by smelting 
are— 



1. 

2. 

3 - 

4 - 

5 - 

Sulphur (soluble in CSj .. 

90-1 

96-2 

913 

coo 

88 7 

Carbonaceous matter. 

10 

°'5 

07 

II 

10 

Sulphur (insoluble in CS 2 ) 

2*0 


i -5 

21 

17 

Siliceous sand . 

2-3 

15 

3'3 

2-8 

5'5 

Limestone (sometimes ccelestin) 

4 *i 

i-8 

2-5 

3 '° 

2-8 

Loss . 

o *5 

— 

07 

1*0 

o *3 

The bottom portion of the blocks of crude sulphur 

often contains 25 per cent, of 

foreign substances. The crude sulphur 

is refined in 

order 

to eliminate all traces 

of earthy matter; and after this process it is 

brought into 

commerce 

in sticks or 


rolls or in powder. 

“Lamy’s Refining Apparatus. The apparatus for refining sulphur, invented by Michel and 
improved by Lamy, at Marseilles, consists mainly of two cast-iron cylinders, B 
(Fig. 90), used as retorts, and a large brick-work condensing-room, G. The cylinder B 

Fig. 90. 


is directly heated by the fire, the smoke of which is carried off by the chimney, E. 
The flues, C, however, surround D, where the crude sulphur undergoes a partial 
refining, and whence it flows by the tube F into the cylinder b. The cylinder B is 


























SULPHUR. 


197 


in communication with the vaulted room G. At the bottom of this room is placed 
a cast-iron plate in which a hole is bored, and fitted with a conical plug, j, con¬ 
nected with a rod, H, so as to admit of being shut and opened for the purpose of * 
tapping sulphur into the cauldron, l, whence it is ladled over into the moulds 
placed in ]\r. N is a box for the roll sulphur when it has become cold. 

aoii sulphur. If it is intended to prepare roll-sulphur, the mode of proceeding is the 
following:—Each of the cylinders is filled with crude sulphur, the lids firmly 
fastened, and the joints luted. Heat is at first applied to only one of the cylinders, 
and not until half of its contents are distilled off is the second cylinder heated. 
Gradually the heat at d increases to such an extent as to melt the crude sulphur; by 
this fusion the heavier earthy impurities settle down, while any moisture present is 
driven off. "When the distillation of the contents of the cylinder first heated is 
finished, that cylinder is filled with liquid sulphur from D by means of the tube F. 
The quantity of sulphur treated in twenty-four hours yields 1800 kilos, pure material 
collected in G. The temperature of this room being 112 0 , the sulphur is there kept 
in a molten state, and as soon as a sufficient quantity has collected at the bottom, it 
is tapped off into l, and cast in the moulds. When it is desired to prepare flowers 
Flowers of Sulphur, of sulphur, the mode of operation is the same, but the temperature of 
G should be kept at or rather below no 0 . This is effected by making the distillation 
interrupted instead of continuous, so that in twenty-four hours-there are only two 
distillations of 150 kilos, each. As soon as a sufficient quantity of flowers of sulphur 
has been condensed in the room G, the door of the room is opened and the sulphur 
removed. 

Dujardin improved upon this apparatus in 1854. By this process of distillation 
of sulphur a loss of 11 to 20 per cent, is incurred, partly due to combustion of a 
portion of the sulphur. The residue left in the cylinders and vessel d is known as 
sulphur-slag. The ordinary flowers of sulphur of commerce always contain some 
sulphuric and sulphurous acids, which can be removed by carefully washing with 
water. Sulphur so treated and gently dried is known in pharmacy as washed flowers 
of sulphur, Flores sulphur is loti. 

rrepanuion of sujpimr -Where fuel and labour are cheap, and a good quality of iron or 
other pyrites is found in abundance, sulphur may be prepared by the following 
process:— 

1. From iron pyrites, PeS 2 . As this mineral consists in 100 parts of 467 of iron 
and 53*3 of sulphur, it is clear that if half of the latter be removed by distillation, 
there will be left a compound of iron and sulphur yielding green copperas after 
oxidation. Accordingly iron pyrites might by distillation lose 26*65 parts of sulphur, 
and the residue still be fit for making green copperas; but if this quantity were to be 
driven off in practice, the temperature would require to be raised so high as to melt 
the remaining monosulphuret and lead to the destruction of the fire-clay cylinders. 
The quantity of sulphur actually distilled off on the large scale is only 13 to 14 per 
cent., leaving a pulverulent residue which does not attack the fire-clay cylinders. 

The process thus briefly outlined is carried on in the following manner :—The pyrites 
is put into conical fire-clay vessels, a a, Eig. 91, placed in a somewhat slanting position in 
the furnace ; the lower and narrower portion of these vessels is fitted with a perforated 
diaphragm preventing any pyrites falling down b, while the volatilised or fluid sulphur 
can pass readily through the holes into a receiver, c, filled with water. After the vessels 
a A have been filled with pyrites, the fire is kindled and the distillation set in progress. 
The sulphur collected in the receiver has a grey-green colour, and is purified by being 
re-melted, after which it is sent into the market in coarsely broken up lumps. In order to 


CHEMICAL TECHNOLOGY. 



free this land of sulphur from sulphuret of arsenic, it is submitted to distillation, the 
residue being 1 used in veterinary practice. The dark colour of the sulphur obtained 
from pyrites is due to an admixture of thallium far more than to the presence of 

arsenic. Mr. W. Crookes found in the 
Fig. 91. sulphur obtained from Spanish pyrites as 

much as 0*29 per cent, of thallium. 

Preparation of Sulphur by 2. Sulphur may be 
Roasting Copper Pyrites, obtained by the roast¬ 
ing of copper pyrites, and in this way 
becomes a by-product of smelting copper 
ores. Formerly this operation was carried 
on in peculiarly constructed furnaces in 
the copper-smelting works of the Lower 
ITartz, Germany; at the present time 
sulphur from this source is only obtained 
at Agordo in Italy, Wicklow in Ireland, 
and at Miihlbach, Salzburg, Austria. 
Sulphur obtained as a - 2 . Since Laming’s 
Manufacture. mixture has been em¬ 
ployed in purifying coal-gas, sulphur has 
to some extent been obtained as a by¬ 
product. Laming’s' mixture is hydrated, 
or any soft porous peroxide of iron mixed 
with sawdust; and in this mixture sulphur 
may accumulate to upwards of 40 per cent. 
(Fe 2 0 3 -f H 2 S = 2 FeO -f H 2 0 + S). Ac¬ 
cording to Hill’s patent the sulphuret of 
iron is calcined to obtain sulphurous acid, 
which is employed in the preparation of 
sulphuric acid. 

Sulphur from Soda waste. 4. "We havo already 
seen, while treating of the manufacture of 
soda (vide p. 1S5) that several processes 
due to MM. Schaflner,Guckelberger, Mond, 
F. W. Hofmann, and others, are in use for the regeneration of sulphur from soda waste; 
and that the quantities recovered are not small may be inferred from the fact that the 
Austrian Association for chemical and metallurgical products, under the management of 
M. Schaffner, at Aussig, produces annually 450,000 kilos, of sulphur in this maimer. 

Production of sulphur by 5. Dumas first made the observation that when one-third of 

Hydroge^up^Suiphuro^Acid, sulphuretted hydrogen is burned off, and the sulphurous acid 
produced conveyed with another one-third of sulphuretted hydrogen into a leaden or brick 
chamber, where moisture abounds, nearly all the sulphur is regenerated:— 

Sulphurous acid, S 0 2 ) • •, ( Sulphur, 3S. 

Sulphuretted hydrogen, 2H 2 S { c \ Water, 2H s O. 

By this reaction, by which, however, nearly half tlie sulphur is lost in the formation of 
pentathionic acid, it has been frequently attempted to obtain sulphur from gypsum, 
heavy spar, and soda waste. The process is briefly as follows :—For instance, heavy spar, 
native sulphate of baryta, is ‘reduced to sulphuret of barium, which is treated with hydro- 
chic ,‘ic acid, sulphuretted hydrogen and chloride of barium of course being formed. 
Either a portion of the gas is burnt and to the products of the combustion, sulphurous acid 
and water, the rest of the gas added, or the sulphuretted hydrogen is conveyed into water 
to which sulphurous acid is simultaneously conveyed from the combustion or roasting of 
iron pyrites. Mr. Gossage long since proved that, by conveying sulphuretted hydrogen into 
chloride of iron, the sulphur of the gas is deposited. Sulphur may be obtained by 
a similar reaction as a by-product of the manufacture of iodine and potassa salts from 
kelp. At Paterson’s iodine factory at Glasgow, 2000 cwts. of this sulphur are obtained 
annually. According to E. Kopp the incomplete combustion of sulphuretted hydrogen 
yields sulphur economically (H„S + OnH „0 -f- S). 

Sulphur obtained by the 6. When sulphurous acid gas is conveyed over red-hot charcoal, 

Ee AcM n onChareoai OUb the latter is converted into carbonic acid, while sulphur is set free. 
By this reaction the sulphurous acid from the roasting of zinc ores (black-jack) is con¬ 
verted into sulphur in large quantities at Borbeck, near Essen, Prussia. 

By Heating of Sulphuretted 7 - When sulphuretted hydrogen is passed through red-hot tubes 
Hydrogen. it is decomposed ; but this reaction is not industrially applicable to 

the preparation of sulphur. 





























SULPHUR. 


199 


Properties and Uses The yellow colour of sulphur is generally known ; at ioo° tliis colour 
of sulphur. deepens and nearly disappears. At — 50°, sulphur is very brittle and 
readily pulverised, becoming by the friction, especially in warm and dry weather, so highly 
electric as to cause the particles to adhere strongly to each other. The sp. gr. of this 
element varies from 1 ‘98 to 2'06. It melts at 115 0 , forming a thin yellow liquid, which, at 
160 0 , becomes thick and assumes an orange-yellow colour; when heated to 220°, sulphur 
is a tough, red, semi-solid; between 240° and 260° the colour becomes red-brown, but 
being heated above 340° the sulphur is again somewhat fluid, and at last boils at 420° -without 
having lost its deep colour, which also characterises the vapours. When sulphur heated 
to 230° is suddenly poured into cold water, it remains soft and so plastic that it may be 
advantageously employed for obtaining impressions of medals, woodcuts, and engraved 
plates, these impressions, as the sulphur again hardens after a few days, serving as 
moulds. On being heated in contact with air, sulphur bums, forming sulphurous acid. 
It is insoluble in water, very slightly soluble in absolute alcohol and ether, and rather 
more soluble in warm fixed and volatile oils, forcning the so-called sulphur balsam. The 
best solvents for sulphur are—sulphide of carbon, coal-tar oil, benzol, and chloride of 
sulphur.* It also dissolves in boiling solutions of caustic soda or potassa, in hot solutions 
of sulphurets of calcium and potassium, in the solutions of certain sulpho-salts; for 
instance, the compound Sb 2 S 3 ,Na 2 S, which is converted into Sb 2 S s ,Na 2 S, and in solutions 
of alkaline sulphites, converted thereby into hyposulphites. 

Sulphur is used in the manufacture of sulphuric acid, gunpowder, fireworks, for sulphuring 
hops and vines as a preservative against some diseases of these plants; the quantity of sulphur 
used for the purpose of sulphuring vines in France, Spain, and Italy, amounted, in 1863, 
to 850,000 cwts. of Sicilian sulphur, being about from 20 to 25 per cent, of the entire 
production. It is further employed in the manufacture of sulphurous acid, sulphites, and 
hyposulphites, sulphide of carbon, cinnabar, mosaic gold or bisulphide of tin, and other 
metallic sulphurets, ultramarine, various cements, and for vulcanising and ebonising 
india-rubber and gutta-percha. , 

The greater part of the total sulphur production of Europe comes from Sicily, whence, 
in 1868, 4,052,000 cwts., in value about £1,500,000, were exported. The total sulphur 
production in Europe in 1870 amounted to 7,012,500 cwts., but in this quantity the 
sulphur recovered from soda waste is not included. 


Sulphurous ahd IIyposulphurous Acids. 

Sulphurous Acid. This acid (S 0 2 , or hydrated H 2 S 0 3 ) ‘may be obtained— 

a. By oxidation of sulphur ; 

b. By reduction of sulphuric acid; 

c. By a combination of the processes a and b. 

The preparation of sulphurous acid by the oxidation of sulphur may be— a. By 
burning brimstone in the air; / 3 . By roasting or calcining iron and copper pyrites, or 
the product of Laming’s mixture from the purifiers of gas-works; y. By igniting a 
mixture of manganese and sulphur. The preparation of sulphurous acid by roasting sul- 
phuretswhen coupled with metallurgical operations, is, especially since Grerstenhofer’s 
furnace has been more generally introduced, the most advantageous plan of obtaining 
this acid, and also where the acid is required for the manufacture of sulphuric acid. 
"When, however, sulphurous acid is required for the purpose of preserving food, 
and as a raw material in the preparation of wines, hops, &c., it should not be 


* According to Cossa (1868)— 

100 parts of sulphide of carbon dissolve at 
100 „ » » 


100 

100 

100 

100 

100 

100 


benzol 


ether „ » 

chloroform „ „ 

aniline „ » 

According to Pelouze— 

100 parts of coal-tar oil, sp. gr. o*88, dissolve, at 


15*0° 

38-0° 

48 - 5 ° 

26*0° 

71-0° 

23 * 5 ° 

22 - 0 ° 

I30'0 0 

I30*0° 


31*15 parts of sulphur. 

94-57 

99 99 

146*21 

99 99 

0*96 

99 99 

4-37 

99 99 

0*97 

99 99 

1*20 

99 99 

85*27 

99 99 


43*0 parts of sulphur 




200 


CHEMICAL TECHNOLOGY. 


made from pyrites, but from sulphur, as, when obtained from pyrites, it is always 
mixed with arsenious acid. The Laming’s mixture saturated with sulphur from 
gas-works is largely used in the preparation of sulphurous acid in sulphuric acid 
works in and around London. The ignition in close vessels of metallic oxides and 
sulphur can only be advantageously used for the preparation of sulphurous acid 
under certain conditions. The oxides chiefly used for this purpose are those of 
manganese and copper ; the former yields, according to the weight of the materials 
employed, either only half the weight of the sulphur in the shape of sulphurous 
acid, or the whole of the sulphur may be converted into acid. Sulphurous acid is 
sometimes prepared by heating a mixture of sulphate of iron and sulphur— 

FeS 0 4 -f 2S = FeS + 2S0 2 ). 

When sulphate of zinc is calcined it yields sulphurous acid and oxygen— 

(ZnS 0 4 = S 0 2 + O + ZnO). 

Kieserite (MgS 0 4 -f- H 2 0 ), mixed with charcoal yields all its sulphuric acid as 
sulphurous acid. 


The preparation of sulphurous acid by the reduction of sulphuric acid is very frecpient; 
sulphuric acid is reduced by being strongly heated in contact with certain metals; for 
instance, copper, mercury, and silver :— 

Sulnhuric acid 2II SO ) ( Sul P hate of copper, CuS 0 4 , 1 

buipnunc acid, 2±i 2 bU 4 * ld Sulphurous acid, SO , 

Copper, Cu ) J (Water, 2H 3 0. 

A small quantity of sulphuret of copper is also formed. The dilution of sulphurous 

acid with carbonic acid and carbonic oxide does not interfere with its intended use. 

Sulphuric acid is decomposed and reduced by being boiled with charcoal-dust, sawdust, 

wood-shavings, &c. 

Sulphuric acid, 2 H S 0 4 { . ,. ( Sulphurous acid, 2 S 0 „ 

Charcoal, C | *"“( w”te“o.’ ^ 

This mode of operation may be made continuous by keeping up a supply of sulphuric 
acid and sawdust in the glass retort, as the decomposition of both these substances is 
complete, yielding sulphurous acid, water, and carbonic acid. When the vapours of 
sulphuric acid are passed through red-hot glass or porcelain tubes, the result is the 
formation of sulphurous acid, oxygen, and water (H 2 S 0 4 — S 0 2 -f- 0 H,, 0 ). The reduction 

and decomposition of sulphuric acid by the aid of sulphur may be viewed as a combined 
process of preparing sulphurous acid by oxidation and reduction:— 

Sulphuric acid, 2H„S0 4 \ j Sulphurous acid, aSO„, 

Sulphur, S ) > leld (Water, 2 H, 0 . ’ 

In practice, however, this operation is very difficult, owing to the fact that, long before 
the reaction begins to take place, the sulphur is molten, while as soon as the reaction sets 
in it becomes very tumultuous, and with the sulphurous acid gas vapours of sulphur are 
carried over, which solidify and obstruct the passage. At the ordinary temperature and 
pressure of the atmosphere, sulphurous acid is a gas having a pungent odour, and a 
sp. gr. =2-21. This gas dissolves readily and in large quantity in water, 1 volume 
absorbing at 18°, 44 volumes of gas. It is even more soluble in alcohol. When water is 
present all the higher oxides of nitrogen give up some of then* oxygen to the sulphurous 
acid, converting it into sulphuric acid, the oxides forming deutoxide of nitrogen. 
Chlorine also converts moist sulphurous acid gas into sulphuric acid, and similar 
results obtain with iodine. The mixture of sulphurous acid and sulphuretted hydrogen 
causes their mutual decomposition, water being formed, and sulphur deposited. Sulphu¬ 
rous acid is chiefly employed in preparing sulphuric acid, in the manufacture of paper, as 
so-called antichlorine, in the preparation of madder by E. Kopp’s process, the preparation 
of hyposulphite of soda, and the manufacture of sulphate of ammonia from lant (stale 
urine). Sulphurous acid is employed according to Laminne’s patent for the purpose of 
decomposing alum-shale in the manufacture of alum. 

It is further employed in some metallurgical processes, for preserving food, bleachino 
syrups, silk, wool, sponges, feathers, glue, isinglass, and other animal substances which 
do not admit of being treated with chlorine, and for bleaching straw hats, ’willow 
and wicker baskets, gum arable, &c. The bleaching property of sulphurous acid mav be 
considered as due to two entirely different causes: in some instances the pigment is only 


SULPHUR. 


201 


masked, not destroyed, as sulphurous acid enters with some pigments into a colourless 
combination; in other instances, however, a real decomposition of the pigment takes 
place. The former condition obtains with most of the blue and red flowers and fruits ; a 
red rose bleached by sulphurous acid has its colour restored by immersion in very dilute 
sulphuric acid. The pigments of yellow flowers are not affected by sulphurous acid; 
it also does not at first act upon indigo and carmine and the yellow colour of raw silk, but 
by the combined and continued action of this acid and direct sunlight, the oxygen of the 
acid acts as ozone and determines the bleaching. The avidity of sulphurous acid for 
oxygen may be utilised in extinguishing fires, especially in the case of the soot of 
chimneys catching fire, which may be very readily subdued by throwing a few ounces 
of flowers of sulphur into the fireplace or stove. 

Sulphite of Lime. Neutral sulphite of lime (SCa 2 0 3 -}- H„ 0 ), containing in ioo parts 
41 parts of sulphurous acid, deserves attention as a cheap, commodious, and very efficient 
substance for the development of sulphurous acid, the gas being readily set free by the 
action of hydrochloric or sulphuric acid. Bisulphites of lime and soda, the former 
in solution, the latter as a solid dry powder, are largely produced in some of the beet-root 
sugar manufacturing countries. 

Hyposulphite of soda. This salt (S 2 bTa 2 0 3 + 5 H 2 0 ) is largely used in photography, in 
metallurgy, as a mordant in calico-printing, and as antichlor in paper-making. 
Hyposulphite of soda may be prepared by several methods. According to Anthon, 4 
parts of calcined sulphate of soda are mixed with 1 to 15 parts of charcoal powder, 
the mixture is moistened and placed in an iron crucible, and calcined at red heat for 
6 to 10 hours; the cooled mass broken into small lumps is again moistened with 
water and then exposed to the action of sulphurous acid; the resulting product is 
dissolved in water, filtered, concentrated by evaporation, and left to crystallise. 
According to E. Kopp’s method, carried out industrially by Max Schaffner at Aussig, 
hyposulphite of lime is first prepared by causing sulphurous acid to act upon 
sulphuret of calcium (soda waste). The lixiviated mass is treated with sulphate of 
soda, the result being the formation of soluble hyposulphite of soda and practically 
insoluble sulphate of lime. Yery recently the pentathionic acid (S 5 0 5 ,H 2 0 ), 
obtained in large quantity as a by-product of the reaction between sulphuretted 
hydrogen and sulphurous acid in preparing sulphur, has been converted into hypo¬ 
sulphite of soda by boiling with soda lye (2S 5 0 5 ,H 2 0 + 3H 2 0 = 5 S 2 0 2 ,H 2 0 ). 

As hyposulphite of soda possesses the property of readily forming with oxide of silver 
a soluble double salt, hence dissolving easily such insoluble compounds as chloride and 
iodide of silver, it is employed in photography and in the hydrometallurgical extraction of 
silver. Being a solvent for iodine it is used in chemistry for purposes of volumetrical 
analyses. A mixed solution of sulphite and hyposulphite of soda dissolves malachite and 
blue copper ore, forming hyposulphite of protoxide of copper and sodium. Stromeyer 
has applied this reaction to the hydrometallurgical extraction of copper. Hyposulphite 
of soda is also used for preparing antimonial cinnabar and aniline green; the hyposul¬ 
phites of lead and copper have been proposed as a paste for lucifer matches. The 
property possessed by hyposulphite of soda of fusing at a comparatively low temperature 
in its water of crystallisation, and of readily solidifying on cooling, has been utilised by 
Fleck, in the sealing of glass tubes containing explosive compounds to be used under 
water in torpedoes. The enormous consumption of hyposulphite of soda may be readily 
inferred from the fact that the chemical factory near Aix-la-Chapelle produces 2000 cwts., 
and the factory at Aussig, Austria, 6000 cwts. of this salt annually. 

Manufacture of Sulphuric Acid. 

Sulphuric acid, H 2 S 0 4 , consists in 100 parts of 81 parts of anhydrous sulphuric 
acid and 18*5 parts of water. 

sulphuric Acid. There are in the trade two distinct varieties of this acid:— 

a. Fuming, or Nordhausen sulphuric acid (oil of vitriol), obtained by distillation 
from sulphate of iron, bisulphate of soda, sulphate of peroxide of iron, or by the 
decomposition of sulphate of soda by means of boric acid in the preparation of 
borax. 


E02 


CHEMICAL TECHNOLOGY. 


b. Ordinary sulphuric acid, known abroad as English sulphuric acid, prepared by 
the oxidation of sulphurous acid by means of nitrous acid, or, very rarely, separated 
from native sulphates. 

Faming sulphuric Acid. At a red heat all sulphates, except those of the alkalies and 
alkaline earths, are decomposed, and therefore may be employed in tLe preparation 
of fuming sulphuric acid; but on account of its cheapness sulphate of iron is pre¬ 
ferred. This salt, on exposure to red heat, is decomposed into anhydrous sulphuric 
acid and sulphurous acid :— 

l Peroxide of iron, Fe 2 0 3 , 

Sulphate of iron, 2FeS0 4 , yields \ Sulphuric acid, S 0 3 , 

\ Sulphurous acid, S 0 2 . 

Anhydrous sulphuric acid would indeed be obtained from sulphate of iron if it 
were possible to procure the salt perfectly anhydrous, but as this cannot be done 
without decomposition, some water is always retained, the result being the compound 
known as fuming sulphuric acid, that is to say, a mixture of anhydrous and ordinary 
acid (H 2 S 0 4 ), the former in very variable quantities. 

Fuming sulphuric acid is prepared on the large scale in the following manner:—The 
solution of sulphate of iron is first evaporated to dryness, and dried in open vessels 
as much as possible. The dry saline mass, vitriol-stone it is termed in G-ermany, is next 
transferred to fire- clay flasks, a, Fig. 92, placed in a galley-furnace, the necks passing 
through the wall of the furnace, and being properly secured to the necks of the receivers, 
b b. Into each of the flasks 2'5 lbs. of vitriol-stone are put: on the first application of 
heat only sulphurous acid and weak hydrated sulphuric acid come over, and are usually 


Fig. 92. 



allowed to escape, the receivers not being securely luted until white vapours of anhydrous 
sulphuric acid are seen. Into each of the receiving flasks 30 grms. of water are poured, and 
the distillation continued for 24 to 36 hours. The retort flasks are then again filled with 







SULPHUR. 


203 


raw material, and the operation repeated four times before the oil of vitriol is deemed 
sufficiently strong-. The residue in the retorts is red oxide (peroxide) of iron, still 
retaining some sulphuric acid. The quantity of fuming acid obtained amounts to 
45 to 50 per cent, of the weight of the dehydrated sulphate of iron employed; at 
Davidsthal, in Bohemia, 14 cwts. of vitriol-stone yield in thirty-six hours, 5^ cwts. of 
fuming sulphuric acid. 

It is preferable, however, to use sulphate of peroxide of iron instead of the dried 
protosulphate; the sulphate of the peroxide can be readily prepared by means of the 
peroxide and ordinary sulphuric acid. Frequently the fuming acid is prepared by passing 
anhydrous sulphuric acid, obtained by calcining perfectly dehydrated protosulphate of 
iron, or, better still, the persulphate of iron, into ordinary oil of vitriol. Fuming 
sulphuric acid is now and then prepared fi’om the bisulphate of soda left after the 
preparation of nitric acid from Chili-saltpetre. In France calcined sulphate of soda and 
boracic acid are intimately mixed and calcined, and the vapours of anhydrous sulphuric 
acid disengaged are absorbed by strong* ordinary sulphuric acid. Fuming sulphuric acid 
is an oily liquid of a brown yellow or deep brown colour; it emits the pungent smell of 
sulphurous acid, fumes on being exposed to air, and yields on being heated vapours of 
anliydric sulphuric acid: the sp. gr. varies from rS6 to 1-92. It is industrially hardly 
used for any other purpose than dissolving indigo, 1 part of the latter requiring for its 
solution 4 parts of fuming and 8 parts of ordinary sulphuric acid. 

0r buiphuric Acfd. sh The concentrated sulphuric acid (H 2 S 0 4 ), oil of vitriol of 
commerce, consists in 100 parts of 81*5 parts of anhydrous acid and 18*5 of water. 
The preparation of this acid on the large scale in leaden chambers dates from the 
year 1746, when Dr. Roebuck, of Birmingham, erected the first leaden chamber at 
Prestonpans, near Edinburgh. 

The rationale of the manufacture of sulphuric acid by the chamber process, in which 
sulphurous acid, nitric or nitrous acid, and water are employed, is, according to the latest 
researches of R. Weber (1866) and Winkler (1867), the following :—The oxidation of the 
sulphurous acid to sulphuric acid takes place in the leaden chambers under the influence 
of the vapour of water at the expense of the oxygen of the nitrous acid, which is con¬ 
verted into deutoxide of nitrogen. It is necessary, however, that the nitrous acid be first 
absorbed in plenty of water, which takes up the free nitrous acid, and decomposes the 
hyponitric acid, a process greatly promoted by the presence in the chamber of sulphurous 
acid purposely introduced. The water, usually in the form of steam, because practical 
experience proves that a certain elevation of temperature is required, acts in this process 
as in others wherein sulphurous acid effects reduction. By the presence of atmospheric 
air in the chamber the deutoxide of nitrogen is oxidised into hyponitric or nitrous acid, 
and this acid again decomposed by sulphurous acid; if the conditions are favourable 
the process is continuous. It occasionally happens that the nitrous acid in contact with 
sulphurous acid and excess of water forms protoxide of nitrogen, of course causing a loss 
of the efficient oxides of the nitrogen. The formation of the so-called chamber crystals, 
consisting according to R. Weber of (H 2 S 0 4 N 2 0 3 ,S 0 3 ) only takes place when the 

process is not well managed, and is chiefly due to want of water. 

Prt8 suiphSric Acid” ° f Although the use of leaden chambers is due to an Englishman, 
the present mode of manufacturing sulphuric acid was invented (1774) by a calico 
printer at Rouen, and improved by the celebrated Chaptal. The apparatus 
consists essentially of four parts, viz.— 1. A furnace, F, Fig. 93, where, by the com¬ 
bustion of sulphur or pyrites, sulphurous acid is formed; the sulphurous acid, 
carrying with it the nitrous vapours prepared in the sulphur burner by means of a 
peculiar contrivance, escapes from the furnace through the tube, T.* 2. An apparatus 
filled with coke through which mixed sulphuric and nitric acids percolate. 3. A 
number of leaden chambers, A, a', and A", wherein, under the influence of high 
pressure steam, the sulphuric acid is formed. 4. A large apparatus, K, known as 
* In order to convert 1 kilo, of sulphur into sulphuric acid, the following quantities of 
air are required:— 

When the sulphur is present in free state, 5275 litres of air, containing 4220 litres 
of nitrogen. 

When the sulphur is present as pyrites, 6595 litres of ah’, containing 5276 litres of 
nitrogen. 


*o 4 CHEMICAL TECHNOLOGY\ 

Gay-Lussac’s condenser, filled with coke, through which sulphuric acid of 66° B. 
(— 1*84 sp. gr.) percolates, the aim being to take up the nitric and hyponitric acids, not 
the deutoxide of nitrogen as -was believed before Winkler elucidated this point, 


Fig.'93. 




from the gases which flow into the last chamber previously to being discharged. 
The furnace or burner, as it is technically called (see Fig. 94), is built of bricks ; at a 
height of 80 centims. from the floor a stout cast-iron plate is placed so as to have 

a slight inclination towards the 
front. The walls are also covered 
with heavy cast-iron plates. In 
front of the burner are three or six 
large openings, p, p', p", which can 
be closed by iron doors fitted with 
wooden handles. On the bed or 
bottom plate three iron rails or 
ledges, each 10 centims. high, are 
placed to divide the bottom of the 
furnace into three or six compart¬ 
ments. At H, 11', and h" are the 
holes for the necessary supply of 
air. On the top plate is firmly 
fixed the tube, t, which conveys 
the gases generated in the burner to the leaden chamber of each section or com¬ 
partment. The burner is charged with about 50 kilos, of sulphur; this is kindled 
at the top, the draught of air through n, h', and n" being so regulated as to cause 


Fig. 94. 




























































































SULPEUR. 


205 


Fig. 95. 


the sulphur to be burnt off without becoming sublimed, for if any sulphur were 
volatilised it would cause the sulphuric acid to be turbid and milky.* Not only 
does the burner supply sulphurous acid, but also the nitric acid or nitrous 
vapours required in the leaden chamber; these are generated from a mixture of 
nitrate of soda and sulphuric acid at 52 0 B. (= 1-56 sp. gr.) placed in the cast-iron 
pot, N, which wdien filled is placed on the burning sulphur. 

The construction and arrangement of the denitrijicaieur is shown in Fig. 95. At G 
is placed an iron grating covered with thick perforated sheet lead; the vapours and 
gases generated in the burner pass through M into the 
space immediately below G, upon which a column of 
coke is placed, and kept saturated with sulphuric 
acid strongly charged with nitric acid, obtained by the 
condensation of the gases from the last chamber. This 
acid is forced by means of compressed air from the 
vessel Y into the Mariotte bottle, v, and passes thence 
through T into H, thence by T' to the coke, over wdiich 
it is delivered in fine jets by means of a perforated 
plate fitted to the lower part of the cover A. The acid 
coming in contact with the warm gases from the 
\hamber yields to them, in the state of vapour, all the 
nitrous compounds dissolved in the sulphuric acid, and 
charged with these vapours the gases pass through 
m, Fig. 93, into the leaden chambers. The denitrified 
sulphuric acid runs off through the tube t into a reservoir. 




The formation of sulphuric acid takes place in the leaden chambers or chamber. In manj 
cases, especially abroad, only one large chamber is worked, which is then, as shown in Fig. 93, 
divided by the .leaden plates it p/, technically termed curtains, into three or more compart¬ 
ments, these curtains reaching to the bottom into the acid collected there. If several 
chambers are worked, communication is maintained by means of leaden tubes. The 
tubes v v' v", convey steam to the chambers. The chambers are not usually all of the 
same size, one being considerably larger than the others; in the largest most of the acid is 
generated. The gases and vapours contained in the last chamber being almost free from 
sulphurous acid, and consisting mainly of atmospheric air and nitrous vapours, are 
conveyed through t' to the leaden reservoir, n, where the last traces of sulphuric acid are 
deposited. The action of Gay-Lussac’s condenser, k, is based upon the fact that concen¬ 
trated sulphuric acid absorbs and combines with nitrous acid. The apparatus consists 
essentially of a column of coke 8 to 10 metres in height, through which strong sul¬ 
phuric acid, 62° or 64° B., percolates, the flow being regulated by the apparatus shown in 
Fio\ 95. The acid saturated with nitrous acid is conveyed by the tubes h h into a 
reservoir, g, from which it is again forced by means of the monte-acid to the Mariotte 
flask, m. By the tube t'", the gases are conveyed to the chimney stalk of the works. As 
regards the cubic capacity of the leaden chambers, each 20 kilos, of sulphur consumed in 
twenty-fours hours requires 30 cubic metres (about 100 cubic feet) capacity; as this 


* According to theory, 1 molecule of sulphur requires only 3 molecules of oxygen, viz., 
2 to form sulphurous acid, and 1 to convert the latter into sulphuric acid; that is to 
say, 1 kilo, of sulphur requires 1500 grms. = 1055 litres of oxygen = 5275 litres of air, 
in which 4220 litres of nitrogen are contained. In order to regulate this supply of air 
many contrivances have been adopted, among them the anemometer invented by Combes ; 
this is fitted to the sulphur burner by means of a tube, through which the air supplied 
has to pass. In England reliance is placed upon the skill of the workmen who regulate 
the draught, as it is termed, simply by the slides in the doors of the burners. 

The air discharged from the chambers should not contain more than 2 to 3 per cent, of 
oxygen. By careful management and with good apparatus the maker may succeed in 
obtaining from 100 kilos, of sulphur 306 kilos, of strong acid at 1-84 sp. gr.; but the 
usual quantity from 100 kilos, of sulphur is seldom more than 280 to 290 kilos. 





























206 


CHEMICAL TECHNOLOGY. 


quantity of sulphur corresponds to 60 kilos, of hydrated sulphuric acid, a chamber of 
the capacity mentioned yields 2'5 kilos, of sulphuric acid per hour. One hundred parts 
of sulphur require from 6 to 8 parts of nitrate of soda, but if pyrites is employed this 
quantity is often increased. Also when pyrites is burnt larger chambers are used. Lately 
Gay-Lussac’s condenser has, in many cases, fallen into disuse, on account of the low price 
of Chili-saltpetre, and the expense of keeping the apparatus in working order. 

Use of oFC^!Sl paration Instead of sulphur native minerals containing that 
element are frequently employed for the preparation of sulphurous acid. Among 
these minerals, iron pyrites, bisulphuret of iron, FeS 2 , containing 53*5 per cent. 

of sulphur, is the most largely used. The pyrites are calcined 
in peculiarly constructed kilns, built with fire-bars, the 
spaces between which may be adjusted by means of a key, 
and the admission of the air required for combustion regu¬ 
lated with great nicety. The best pyrites oven known on 
the Continent is Gerstenhofer’s, invented in 1864; the prin¬ 
ciple of this oven, Fig. 96, is that the pyrites is made to 
fall through and meet the column of heated air sup¬ 
porting the combustion. In order to prolong the fall of 
the powdered pyrites, terraces or banks are built at intervals 
in the shafts. The broken up pyrites falls through the 
funnels a, provided with grooved rollers to pulverise it, on to 
the banks c, from one terrace, as they are termed, to 
another. As the furnace has been previously made red-hot, 
the sulphur ore ignites and bums off, aided by a moderate 
blast at c. The sulphurous acid formed is discharged by the channels d into the 
sulphuric acid chambers, sometimes being first conveyed to an ante-room, where 
the dust of the pyrites mechanically mixed with the gases is deposited. 

The nitrous acid vapours are generated in a manner similar to that used for 
sulphur. It will be seen that when pyrites is burnt, a far larger quantity of air is 
required for the same quantity by weight of sulphur, amounting for 1 kilo, of pyrites 
to 6595 litres of air. This excess is due to the oxidation of the iron of the pyrites, 
and the large bulk of nitrogen accompanying the excess of oxygen 
(2FeS 2 +110 = 4SO2+Fe 2 0 3 ). 

According to Fortman, the gases from the pyrites burners also contain vapours of 
anhydrous sulphuric acid. Among the substances found in the flue dust of the 
pyrites burners are selenium and thallium. Carstanjen found thallium to the amount 
of 3*5 per cent, in the flue dust of a sulphuric acid works near Berlin, where a 
pyrites from Mezzen was used. 

Chamber Acid. As soon as the acid formed in the leaden chambers has acquired a sp. gr. of 
1 -5 =50° B. = 104° Twaddle, it is run off into a reservoir, and is frequently used in that state 
of concentration for the purpose of preparing artificial manures or superphosphates in 
alkali works, for the preparation of nitric acid, and for other purposes. This acid may be 
freed from arsenic by treating with sulphuretted hydrogen. 

C suip e huric Acid! This operation is effected in two different stages, the first being car¬ 
ried on in leaden pans, the latter in platinum or glass retorts. Weak and cold sul¬ 
phuric acid does not act powerfully on lead, but as soon as the acid becomes concen¬ 
trated, and especially when hot, the lead is dissolved, sulphurous acid given off, and 
sulphate of lead formed. Many sulphuric acid makers concentrate their acid to 
6o° B.= 171 sp. gr., in leaden pans; others, however, concentrate in leaden pans to 
55 0 B.= i’59 sp. gr. only. 


Fig. 96. 


MA&AA 






SULPETJR. 


20 7 



concentration in Leaden Pans. The pans employed for this purpose are rectangular in 
shape, rather shallow, but long and wide, and supported by iron plates, so that the 
fire shall not strike the bottom directly. The modes of placing and construction are 
shown in Fig. 97; the acid is more strongly heated in the pan, m, while in n it is only 


Fig. 97. 


affected by the hot air. The depth of the acid in the pans varies from 24 to 36 
centims. As soon as the acid is of about 171 sp. gr., it is further deprived of its 
excess of water, in glass, porcelain, or platinum vessels. 

Platinum Retorts. Platinum retorts are now very frequently employed, although it is 
clear that these vessels, considering the high price of platinum, are expensive, 


Fig. 98. 



the price depending upon the weight, size, and workmanship. Messrs. Johnson, 
Matthey, and Co, Hatton Garden, London, are among the best makers of thes'- 
and other platinum apparatus. 

Fig. 98 is an enlarged view of the platinum retort, represented together with the 
leaden pans in Fig. 97. The hearth communicates with A. By means of the 






























208 


CHEMICAL TECHNOLOGY. 


syphon, x, the acid from n can be transferred to B ; the longer leg of x dipping into a 
leaden vessel, which admits of being lowered to d by the aid of the pulley. The acid 
then runs from the spout c into the channel d, and thence, through the funnel-tube, 
into the retort, B. The head, c, communicates by means of tubing, not shown in the 
cut, with a worm, where the water and very weak acid mechanically earned over 
with the steam are condensed. "When the temperature of the acid in the platinum 
still attains to 310° to 320°, strong acid comes over, and is condensed in the worm. 



Tig. 99. 
I 


In order to withdraw the acid from 
the still, when concentrated to 1 *78 to 
i-8o(=: 63 0 to 66° B.),the Breant syphon, 
Fig. 99, is used. It is made of platinum; 
the outer leg has a length of about 
5 metres, and is surrounded by a copper 
tube 15 centims.wideby36 centims. long, 
which can be filled at a from the tank m 
(see Fig. 97) with cold water, the outlet 
for the hot, water being at b. In order 
to increase the surface the main syphon 
tube is divided into four narrower tubes. 
The syphon is filled with sulphuric 
acid by cl and e after closing the tap c. 
The very hot acid cools while flowing 
through the platinum tubes, and is collected in jars, a, a', a", 


C< Giass Retons . 11 When glass retorts of good quality and sufficiently large size can be 
obtained at a cheap rate, they are very frequently employed, being placed to the 
number of ten or more (Fig. 100) in sand-baths. The retorts are connected to 


Fig. 100. 



earthenware balloons, in -which the acid fumes are condensed. 70 per cent, of the 
strong sulphuric acid sold in this country is concentrated in glass retorts. Yery 
recently cast-iron vessels have been used for concentrating sulphuric acid. 

other Methods of Sulphuric Many methods of preparing sulphuric acid have been suggested 
Acid Manufacture. but hitherto none have anywhere superseded the process generally 
adopted. For this reason it is necessary to mention a few only of the reactions upon 
which these methods are based. Haliner oxidises sulphurous acid with chlorine, care being 
taken that steam is present at the time :— 


Sulphurous acid, S 0 2 \ 
Aqueous vapour, 2H O > yield 
Chlorine, 2CI I 


{ Sulphuric acid, H 2 S 0 3 , 
Hydrochloric acid” 2OIH. 








SULPHUR. 


200 


Pcrsoz’s method is based upon the following reactions :—i. Oxidation of sulphurous 
acid by means of nitric acid, the latter being heated to ioo° and diluted with four to six 
times its bulk of water. 2. The vapours of hyponitrjc acid are again converted to nitric 
acid by the oxygen of the air and steam. In this process the leaden chambers are replaced 
by a series of large stone-ware Woulfe’s bottles. Although enormous quantities of gypsum 
are found native, all attempts to prepare sulphuric acid from this mineral on an industrial 
scale have failed. Gypsum is decomposed, by superheated steam and at red heat, into sul¬ 
phuric acid, oxygen, and sulphurous acid, leaving caustic lime in the retort. Shanks 
mixes gypsum with cliloride of lead and water at about 6o°. 

n _ n 1 tt ) ( Chloride of calcium, CaCL, * 

ClXride’o?fead,'pba; ) ( wlter^H O.^’ PbS ° 4 ’ 

The chloride of calcium solution having been withdrawn from the precipitate of 
sulphate of lead, the latter is heated with hydrochloric acid :— 

Sulphate of lead, PbS 0 4 *1 . ,, ( Chloride of lead, PbCl 2 , 

Hydrochloric acid, 2CIH j ^ 1C c \ Sulphuric acid, H 2 S 0 4 . 

Properties of Sulphuric Acid. The most highly concentrated sulphuric acid contains 18‘46 per 
cent, of water; its formula is H 2 S 0 4 ; sp. gr. = 1-848. In a perfectly pure state it is a 
colourless liquid, but commonly is more or less yellow or brown, owing to the presence of 
organic matter. It destroys many organic substances, leaving- a carbonaceous residue. 
This sulphuric acid does not fume on exposure to air; it is very hygroscopic, and when 
left exposed to air, gradually absorbs fifteen times its bulk of water. When mixed with 
water great heat is evolved. The boiling-point of the most highly concentrated acid is 338°. 

The following table gives the quantity of anhydrous sulphuric acid contained in sul¬ 
phuric acid at 15-5 0 C.:—■ 


Hydrated 
Sulphuric acid. 

Sp. gr. 

Anhydrous 

acid. 

Hydrated 
Sulphuric acid. 

Sp. gr. 

Anhydrous 

acid. 

100 

1-8485 

1*8475 

8 i *54 

76 

1-6630 

61-97 

99 

80-72 

75 

1-6520 

61-15 

98 

1 -8460 

79-90 

74 

1-6415 

60-34 

97 

1*8439 

79-09 

73 

1-6321 

59*55 

96 

1-8410 

78-28 

72 

1-6204 

58*71 

95 

1-8376 

77*40 

7 i 

1 -6090 

57*89 

94 

1-8336 

76-65 

70 

i *5975 

57*o8 

93 

1 -8290 

75*83 

69 

1-5868 

57-26 

92 

1-8233 

75-02 

68 

1-5760 

55*45 

9 i 

1-8179 

74-20 

67 

1-5648 

54*63 

90 

1-8115 

73*39 

66 

1*5503 

53*82 

89 

1-8043 

72*57 

65 

i* 539 o 

53 *oo 

88 

1-7962 

7 i *75 

64 

1-5280 

52*18 

87 

1-7870 

70-94 

63 

1-5170 

5 i *37 

86 

i *7774 

70-12 

62 

1-5066 

50*55 

85 

1-7673 

69-31 

61 

1 -4960 

49*74 

84 

1-7570 

68-49 

60 

1 -4860 

48-92 

83 

i *7465 

67-68 

59 

1-4760 

48-11 

82 

1-7360 

66-86 

58 

1-4660 

47-29 

81 

i *7245 

66-05 

57 

1-4560 

46-58 

80 . 

1-7120 

65*23 

56 

1 -4460 

45*68 

79 

1-6993 

64*42 

55 

1-4360 

44*85 

78 

1-6870 

63-60 

54 

1-4265 

45*03 

77 

1-6750 

62-78 

53 

1-4170 

43*22 


Comparative degrees of Baume and Twaddle, with the corresponding sp. gr. 


i Baume. 

Degrees Twaddle. 

Sp. gr. 

66 

168 

1-84 

63 

154 

i *77 

60 

140 

1-70 

57 

130 

1*65 

50 

104 

1-52 

45 

88 

1*44 

40 

76 

1*38 

35 

62 

1-31 

30 

52 

1-26 

25 

42 

1*21 


15 




210 


CHEMICAL TECHNOLOGY . 


The reader desirous of more information as to the specific gravities indicated by 
Baume’s hydrometers is referred to the “ Chemical News,” vol. xxiv., p. 28, et seq. 

The uses of sulphuric acid are so numerous that it would be impossible to mention all 
of them, sulphuric acid being to chemical industry what iron is to the mechanical. 
Sulphuric acid is employed in preparing a great many other acids, among them nitric, 
hydrochloric, sulphurous, carbonic, tartaric, citric, phosphoric, stearic, oleic, and palmitic. 
Further, sulphuric acid is used in making superphosphates, soda, sulphate of ammonia, 
alum, sulphates of copper and iron, in paraffin and petroleum refining, silver re finin g, 
manufacture of garancine, garanceux, and other madder preparations, manufacture of 
erlucose from starch, to dissolve indigo, &e. 


Sulphide of Carbon. 

sulphide of carbon. This compound, consisting iii 100 parts of 15*8 parts of carbon 
and 84*2 of sulphur, formula CS 2 , was discovered in 1796 by Lampadius, at Frei¬ 
burg. It is obtained by causing the vapour of sulphur to pass over red-hot coals, 
or by distilling an intimate mixture of native metallic sulphurets with charcoal or 
coke. The largest quantity of sulphide of carbon is obtained, according to Sidot 
and W. Stein, at not too high a red heat, that is to say, at what is termed in 
gas-works orange-red heat. 

Sulphide of carbon is best manufactured by means of Peroucel’s apparatus 
(Fig. 101). A is a fire-clay gas-retort, supported on the fire-clay block B; e and E 



Fig. ioi. 


•ire openings, one being that of a porcelain tube firmly cemented into the cover of a, 
serving for the introduction of sulphur; the other opening is for the introduction 
of pieces of coke, with which, before the operation commences, the retort is filled. 
The vapours of the sulphide of carbon pass through the tubes n and I into the 
vessel J, wherein part of the sulphide is condensed and flows through K into the flask, 
L, filled with water, thence through M into 0 , finally being run off by the tap, N. Any 
vapours not condensed in j pass through P P into the worm, t, the condensed sulphide 
being collected in s. The crude sulphide of carbon is rectified by re-distillation 
over zinc or over bichloride of mercury by means of steam or a water-bath. If the 
bichloride is employed, the crude sulphide should remain in contact with the salt for 
at least twenty-four hours before re-distillation. With the apparatus described, the 
retort being 2*1 metres in height and 0*3 metre in diameter, 2 cwts. of crude sulphide 















GLAUBERS SALT. 


211 


of carbon may be prepared in twelve hours. The quantity of sulphide resulting 
from a given weight of materials is always much less than the quantity theoretically 
obtainable; this is, of course, partly due to an unavoidable loss of liquid, and probably 
to the formation of monosulphide of carbon (CS), a compound corresponding to 
carbonic oxide. Crude sulphide of carbon contains usually io to 12 per cent, of 
sulphur in solution, and also sulphuretted hydrogen. To purify the crude sulphide, 
bleaching-powder solution is added to the liquid in the retort, into which steam at 
15 lbs. pressure is forced to effect the reaction between the chloride of lime and the 
impurities present in the sulphide of carbon. Sulphide of carbon is usually kept 
under water. When pure, sulphide of carbon is a colourless liquid, strongly 
refractive, exhibiting extremely bright colours when in the sunlight. Its odour 
somewhat resembles that of chloroform; the taste is aromatic. Its sp. gr. —1*2684; 
the boiling-point is 46*5°, consequently the liquid is very volatile at the ordinary 
temperature of the air. 

carbon. Sulphide of carbon does not combine with water or spirits of wine. It is not 
soluble in every proportion in water (see ‘ ‘ Chemical News,” vol. xxiv., p. 34); in ether 
and chloroform, however, it is freely soluble. Sulphide cf carbon is an excellent 
solvent for resins, essential and fixed oils, caoutchouc, gutta-percha, camphor, 
sulphur, phosphorus, and iodine. It is highly inflammable, burning with a red-blue 
flame; the products of complete combustion are sulphurous and carbonic acids. The 
vapour of sulphide of carbon with oxygen or air constitutes an explosive mixture; 
the light given by a mixture of deutoxide of nitrogen and sulphide of carbon is 
very intense, and has been employed in photography. To Mr. Fisher, of Birmingham, 
is duo the honour of having first prepared sulphide of carbon for industrial 
purposes. At the present day these purposes are very varied, but consist chiefly of 
the vulcanisation of caoutchouc, the extraction of fat from bones, and oils from oil 
seeds and olives, the extraction of sulphur from its concomitant rocks, and of fat 
from crude wool. Sulphide of carbon is also used in electro-plating to obtain by its 
addition to the silver-bath a bright and polished surface. It is highly valued for 
killing vermin in corn. 

chloride of Sulphur. Chloride of sulphur (C 1 2 S 2 ), important only in its technical use 
for the vulcanising of caoutchouc, is an oily fluid, sp. gr. i*6o, of a brown colour, 
fuming on exposure to air. It boils at 144 0 . On being mixed with water it is 
decomposed, yielding sulphurous and hydrochloric acids, a very small quantity of 
sulphuric acid, and sulphur. Chloride of sulphur converts rape-seed oil into a mass 
resembling caoutchouc, and linseed oil into a varnish. Chloride of sulphur is 
prepared by passing chlorine gas over sulphur heated to 125 0 to 130°; the product 
is rectified by distillation. 

Hydrochloric Acid and Glauber’s Salt, or Sulphate of Soda. 

Hydroehioric Acid. The commercial article known as hydrochloric or muriatic acid, 
or spirits of salt, is, as has been explained in the manufacture of soda, a solution 
of the gas given off during the decomposition of common salt by sulphuric acid. 
In order to effect this condensation, the gas is conveyed to the coke columns, or in 
many instances is prepared and condensed by the aid of the apparatus shown in 
section in Figs. 102 and 103, and in plan in Fig. 104. The apparatus consists of 
several cast-iron cylinders, 17 metres long by 0*7 metre diameter, closed similarly 




2I2 CHEMICAL TECHNOLOGY. 

to gas retorts by lids luted with clay. One of the lids is provided with an opening, 
o, into which is fitted the stoneware or leaden pipe, a, conveying the hydrochloric 
acid to the condensing apparatus. The other, or posterior lid, is also provided with 
an opening, d, through which is passed the tube of a leaden funnel, so that after 
the retort is filled with salt, sulphuric acid may be poured in. The construction of 

Fig. 102. 


required quantity of strong sulphuric acid is now poured into the retort, and the 
funnel having been withdrawn from d, the hole is closed by a clay plug. As soon 
as the reaction is over, the 180 kilos, of sulphate of soda produced are removed, and 
the operation repeated. The condensatioh apparatus, Figs. 102 and 104, consists of 


the furnace, in which two retorts are usually placed, allows the flame of the fire at 
0 to play round the cylinders before reaching the flue leading to the chimney, F. 
b is an arch covering the furnace. The first stage of the operation is to fill each 
cylinder with 150 kilos, of salt or chloride of potassium, in localities where the latter 
is abundant. The lids or covers are next luted on, and the fire kindled. The 


Fig. 103. 





































GLAUBER'S SALT. 


2J 3 


rows of Woulfe’s bottles partly filled with water, care being taken to place the first 
pair of these bottles in a tank of cold water. The condensation of the last portions 


Fig. 104. 



of the hydrochloric acid gas is effected either by the aid of coke columns, or in 
leaden chambers, into which fine jets of cold water are injected on all sides. 

properties ^Hydrochloric Crude commercial hydrochloric acid is commonly a yellow 
liquid, this colour being due to chloride of iron. It has a caustic sour taste, and 
fumes on exposure to air. At 20° water is capable of absorbing 475 times its own 
bulk of hydrochloric acid gas; a saturated solution contains 42‘85 per' cent, of 
gas, the sp. gr. being = 1*21. The following table shows the sp. gr. of hydrochloric 
acid at various degrees of concentration, and the quantity of pure acid (real gas) 
contained at 70° :— 


Specific 

gravity. 

Degrees 

Baume. 

Degrees 

Percentage 

Specific 

Degrees 

Degrees 

Percentage 

Twaddle. 

of acid. 

gravity. 

Baume. 

Twaddle. 

of acid. 

1*21 

26 

42 

42*85 

1*10 

i 4*5 

20 

20*20 

I'20 

25 

40 

40'80 

1*09 

12 

18 

18*18 

rig 

24 

38 

3 8'88 

1*08 

11 

16 * 

16*16 

ri8 

23 

36 

36*36 

1*07 

10 

14 

14*14 

1*17 

22 

34 

34‘34 

1*06 

9 

12 

12*12 

ri6 

21 

32 

32*32 

1*05 

8 

10 

10*10 

I * I 5 

20 

30 

30*30 . 

1*04 

6 

8 

8*o8 

i*i 4 

19 

28 

28*28 

1*03 

5 

6 

6*o6 

ri 3 

18 

26 

26*26 

I'02 

. 3 

4 

4*04 

1*12 

17 

24 

24*24 

1*01 

2 

2 

2*02 

i'ii 

i 5‘5 

22 

22*22 






uses of iiydrochioric Hydrochloric acid is very largely employed in the manufacture 
of chlorine, sal-ammoniac, chloride of antimony, glue, phosphorus, in the prepara¬ 
tion of carbonic acid for the manufacture of artificial mineral waters, in beet-root 
sugar works, bleach works, hydro-metallurgy, and alone or mixed with nitric acid 
for dissolving various metals. 

Glauber’s Sait. Sulphate of soda, or Glauber’s salt, consists in 100 parts of 19*3 soda, 
*24*7 sulphuric acid, and 56 water; formula, Na 2 S 0 4 + ioH 2 0 ; anhydrous, Na a S 0 4 , 
in 100 parts—soda, 43*6 ; sulphuric acid, 56-4. It is prepared as described under 
hydrochloric acid by decomposing common salt with sulphuric acid. It is also 
found native as Thenardite (Na 2 S 0 4 ), Brogniartine or Glauberite (Na 2 S 0 4 -j- CaS 0 4 ), 
and it occurs in sea-water and some mineral waters, as in those of Piillna and 
Carlsbad. • 




































214 


CHEMICAL TECHNOLOGY. 



Sulphate of soda is indirectly obtained by various processes, among which are— 

1. The double decomposition of common salt and sulphate of magnesia or kieserite from 
the mother-liquor of sea-water, or of salines when exposed to a low temperature either 
naturally in water or artificially by the assistance of Carre’s ice-making machine. 

2. Longmaid’s process of roasting sulphuret of iron or copper with common salt. 3. Cal¬ 
cination of kieserite or magnesian sulphate with common salt. 4. Kuhlmann’s process, 
the calcination of sulphate of magnesia and nitrate of soda, hyponitric acid and sulphate 
of soda being formed. 5. As a by-product of paraffin and petroleum refining. The 
sulphate of soda of the alkali works contains on an average 93 to 97 per cent, of the pure 
salt, the remainder being chiefly chloride of sodium. 

uses of sulphate This salt is extensively employed in the manufactures of soda, ultra- 
of soda. marine, and glass. In the last case the sulphate is mixed with coal and 
silica, and calcined, its sulphuric acid being reduced to sulphurous acid, which is volatilised, 
while a silicate of soda is formed. Sulphate of soda when thus employed should be 
purified from all traces of iron by being dissolved in water, some lime added to the 
solution, and the clear liquid evaporated to dryness. Sulphate of soda is used in 
metallurgy in the treatment of some kinds of antimonial ores, the sulphuret of antimony 
found near Bouc and Septemes, Trance, &c. It is also employed in certain processes of 
wool-dyeing. 

Bisuiphate of soda. This salt (NaHS 0 4 ) is obtained in large crystals when 1 molecule 
of sulphate of soda and 1 molecule of sulphuric acid are dissolved in water and the 
solution left to evaporate slowly. One of the chief uses of the bisulphate is in a 
mixture with abraum salt containing chloride of magnesium, employed for re¬ 
moving zinc from lead. As a by-product sulphate of soda is obtained in the manu¬ 
facture of nitric acid from nitrate of soda and sulphuric acid, and by heating cryolite 
with sulphuric acid. 

Bleaching-Powder and Hypochlorites. 
chlorine. It is one of • the most valuable properties of chlorine that it destroys 
organic pigments and miasmata, and is hence useful as a bleaching agent, and as a 
disinfectant. It is also employed as an oxidising agent in the extraction of gold 
from pyritical ores. 

At the ordinary temperature and pressure of the atmosphere chlorine h a 
greenish-yellow gas, its sp. gr. = 1*33 ; it possesses a peculiarly disagreeable, 
irritating odour, and is very soluble in water, 1 volume absorbing 2*5 volumes of 
gas, forming the well-known aqua chlorii, or acidum muriaticum oxygenatum aqua 
solutum of the pharmaceutists, and the chlorine water of the scientific chemist. 
The bleaching property of chlorine gas, possessed also by its solution, is due to the 
great affinity of chlorine for hydrogen, so that the chlorine while seizing upon the 
hydrogen of the organic body in most instances causes the simultaneous decomposi¬ 
tion of water, and by the formation of ozone destroys the organic colouring matter, 
hydrochloric acid being at the same time formed, a fact requiring attention in the 
use of chlorine as a bleaching agent. When linen, or rather flax, raw cotton, and 
paper pulp are bleached by chlorine, the fibre, really cellulose, is not acted upon, 
but only the colouring matter is oxidised by the ozone formed. Chlorine cannot be 
used to bleach animal matters, or such as contain nitrogen, these becoming yellow 
by its action. Chlorine is not suited for transport either as gas or in aqueous solu¬ 
tion, therefore one of its combinations with oxygen and a base, viz., a hypochlorite, * 
is used. Hydrated oxide of calcium or slaked lime is the chief constituent ol 
bleaching-powder. Usually the alkali manufacturers prepare bleaching-powder. 

preparation of Bleaching- Bleaching-powder is prepared on the large scale in the fol¬ 
lowing manner:—In works where soda and chloride of lime are to be manu¬ 
factured simultaneously, the chlorine is obtained by mixing the common salt to be 


BLEA CEING-PO WEEP. 


215 

converted into sulphate of soda by the action of sulphuric acid with peroxide of 
manganese, heat being applied. 

The process is as follows : 

Common salt, 2NaCl, \ / Glauber’s salt, Na 2 S 0 4 . 

Peroxide of manganese, Mn 0 2 , j yield | Sulphate of manganese, MnS 0 4 , 
Sulphuric acid, 2H 2 S0 4 ) * ( Chlorine, 2CI, and 2H 2 0. 

I11 some works chlorine is prepared by the reaction of hydrochloric acid and 
manganese, and sometimes with the addition of sulphuric acid. In the first instance 
only half the chlorine contained in the hydrochloric acid is given up, because tho 
other half forms chloride of manganese; for— 


Manganese, Mn 0 2 , | 

Hydrochloric acid, 4CIH, j 


yield 


{ Chlorine, Cl 2 , 

Manganic chloride, MnCl 2 , 
Water, 2H 2 0. 


In the second instance all the chlorine 
obtained — 

Manganese, Mn 0 2 , \ 

Hydrochloric acid, 2CIH, J yield 
Sulphuric acid, H 2 S 0 4 , ) 


contained in the hydrochloric acid is 

( Sulphate of manganese, MnS 0 4 
< Chlorine, Cl 2 , 

(Water, 2 H 2 0 . 


As proposed by Clemm, a chloride of magnesium solution, as largely obtained at 
Stassfurt, may be employed by concentrating the solution to 44 0 B (=1*435 S P* g r ->) 
and adding manganese, so that to 1 mol. of Mn 0 2 , 2 mols. of MgCl 2 are taken. The 
cooled, solid mass, when exposed to the action of superheated steam at 200° to 300°, 
yields chlorine gas. 

P M4th r out°ManganeTe ne The following methods are selected as being the most scientific 
and interesting:— 

1. Mac Dougal, Eawson, and Shanks’s process, consisting in the decomposition of 
chromate of lime by hydrochloric acid, the result being the formation of chloride of 
chromium, chloride of calcium, and the evolution of free chlorine— 


(2CaCr0 4 + 16HCI = Cr 2 Cl 6 + 2CaCl 2 + 3 H 2 0 + 601 ). 

158 parts of chromic acid yields 106 parts of chlorine. The chloride of chromium is 
again precipitated with carbonate of lime, and by ignition converted into chromate 
of lime. Only three-eighths of the chlorine contained in the hydrochloric acid is 
given up, while manganese yields one-half. 

2. Schlosing's method consists in acting upon manganese with a mixture of hydro¬ 
chloric and nitric acids, the degree of concentartion of the acids being so regulated by 
the addition of water that the mixture yields only chlorine, while nitrate of protoxide 
of manganese is formed: this salt being calcined yields manganese, peroxide, and 
nitric acid. The nitric acid aids the oxygen of the air in decomposing the hydro¬ 
chloric acid. The nitrate of manganese begins to decompose at 150°, and the decom¬ 
position is completed at 175 0 to 180°, yielding much peroxide, in some cases even 
93 per cent. 

3. Yogel’s method of decomposing chloride of copper by heat. 3 mols. of chloride 
yield 1 mol. of chlorine ; according to Laurens the process is 

2CuC1 2 = Cl 2 -1- Cu 2 Cl 2 . 

The chloride in crystalline state is mixed with half its weight of sand, and heated in 
earthenware retorts to 200° to 300°, yielding chlorine gas, while the remaining proto¬ 
chloride of copper is re-converted into perchloride by the action of hydrochloric 
acid. Mallet has constructed a peculiar rotating apparatus for the decomposition of 


2 l6 


CHEMICAL TECHNOLOGY. 


tliis salt, tlie same apparatus serving to prepare oxygen, ioo kilos of cupric 
chloride yield 6 to 7 cubic metres of chlorine gas. 

4. Peligot’s method. When 3 parts of bichromate of potassa and 4 jiarts of con¬ 
centrated hydrochloric acid are gently heated, the fluid yields on cooling crystals of 
bichromate of chloride of potassium, KCl,Cr 0 3 ; at ioo 0 this salt yields chlorine. 

5. Dunlop’s process is followed at Mr. Tennant’s works, Glasgow. Sulphuric acid 
is made to act upon a mixture of 3 mols. of common salt, and 1 mol. of nitrate of 
soda, the result being the formation of chlorine and hyponitric acid. The latter is 
absorbed by passing the mixed gases through strong sulphuric acid. 

6. Mr. Walter Weldon’s process is performed by means of an apparatus comprising 
five vessels arranged at successive elevations, so that after having been pumped up to the 
highest of them, the liquor operated upon can afterwards descend to all the others by its 
own gravity. The lowest of these vessels is a well, which is furnished with a mechanical 
agitator. The slightly acid chloride of manganese liquor with which the process com¬ 
mences runs from the stills in which it is produced into this well, and is there treated with 
finely divided carbonate of lime, the action of which is facilitated by the energetic 
agitation. When the neutralisation of the free acid which is at first contained in this 
liquor and the decomposition of the sesquichloride of iron and sesquiehloride of aluminium, 
which are also at first contained in it, are completed, the liquor is pumped up into 
settling tanks, placed nearly at the top of the apparatus, and known as the “ chloride of 
manganese settlers.” It now consists of a quite neutral mixed solution of chloride of 
manganese and chloride of calcium, containing in suspension considerable quantities of 
sulphate of lime, and small quantities of oxide of iron and alumina. These solid 
matters rapidly deposit in the chloride of manganese settlers, leaving the bulk of the 
liquor perfectly bright and clear, and of a faint rose-colour. The next step is to run off 
the clear portion of the contents of the settlers into a vessel immediately below, called 
the oxidiser. This is usually a cylindrical iron vessel about 12 feet in diameter, and about 
22 feet deep. Two pipes go down nearly to the bottom of the oxidiser, a large one for 
conveying a blast of air from a blowing engine, and a smaller one for the injection of 
steam. The latter is' for the purpose of raising the temperature of the contents of the 
oxidiser when necessary; for sometimes the chloride of manganese liquor reaches 
the oxidiser sufficiently hot—between 130° and 160° or i7o°F. immediately above the 
oxidiser is a reservoir containing milk of lime. The oxidiser having received a charge of 
clear liquor from the settlers, and this liquor having been heated up to the proper point, if 
it was not already hot enough, blowing is begun, and milk of lime is then run into 
the oxidiser as rapidly as possible, until the filtrate from a sample taken at a tap placed 
nearly at the bottom of the oxidiser, ceases to give a manganese reaction with solution of 
bleaching-powder. A certain quantity of milk of lime is then added, and the blowing 
continued until peroxidation ceases to advance. That point is usually attained when 
from about 80 to 85 per cent, of the manganese present has become converted into 
peroxide. The contents of the oxidiser are now a thin black mud, consisting of solution 
of chloride of calcium containing in suspension about 2 lbs. of peroxide of manganese 
per cubic foot, these 2 lbs. of peroxide of manganese being combined with varying quan¬ 
tities of protoxide of manganese and lime. This thin mud is now run off from the oxidiser 
into one or other of a range of settling tanks or “mud settlers,” placed below it, and is 
there left at rest until it has settled as far as it will, usually until about one-half of its 
volume has become clear. The clear part is then decanted, and the remainder, containing 
about 4 lbs. of peroxide of manganese per cubic foot, is then ready to be used in the stills. 
There it reacts upon hydrochloric acid, liberatin'? chlorine, with reproduction of exactly such 
a residual solution as was commenced with. With that solution the round of operations is 
begun again; and so on, time after time, indefinitely. 

Apparatus ^fo r re paring 'When hydrochloric acid and manganese are used, the apparatus 
is that delineated in Fig. 105. It consists of a large stoneware jar. A, provided with 
an opening, a, over which an air-tight cap is fitted when the apparatus is at work, 
and by which the jar is filled with manganese and acid ; b is another opening fitted 
with a leaden or earthenware gas tube ; c is a tube serving to run off the spent 
manganese liquor. B is a wooden box into which steam is admitted for the purpose 
of heating A and its contents sufficiently to promote the reaction between the hydro¬ 
chloric acid and the manganese. 


BLEACHING-PO JVPER. 


217 


When chlorine is prepared from a mixture of common salt, sulphuric acid, and man¬ 
ganese, the apparatus is required to withstand more heat, and is therefore constructed 
entirely of metal, a a, Fig. 106, is a shallow iron pan, fitted with the tube b for the purpose 
of emptying the contents of the leaden cylinder, d cl. This iron vessel serves as the lower' 
part of the leaden cylinder, d d, the top of which is provided with an opening for a funnel 
syphon-tube for the introduction of the acid, and another opening, f, for the manganese. 
The entire apparatus stands on a Hue leading from a furnace. 


Fig. 106. 



Condensing Apparatus. The chlorine passes from the generator through the tube, or, Fig. 107, 
into a room constructed of large blocks and slabs of sandstone joined by means of asphalt 
cement, or a mixture of coal-tar and fire-clay. Sometimes the room is built of bricks laid 
in a similar cement, the interior being lined with asphalt; leaden chambers also are used 
for this purpose. The room is fitted with several shelves upon which slaked lime is placed 
in layers of three to four inches and more in thickness. The chlorine gas is readily absorbed 


Fig. 107. 



heat being evolved. Care is to be taken that the temperature does not exceed 25°, because 
then chlorate of lime is formed; this is prevented by admitting the gas slowly. As soon as 
the absorption ceases, the bleaching-powder is removed with rakes from the shelves, and 
fresh lime introduced. Frequently the chloride of lime is somewhat diluted by an admixture 
of slaked lime. 

Wlien it is desired to prepare a solution of chloride of lime, the apparatus shown in 
Fig. 108 is employed. Two or four earthenware vessels, a, about 2 hectolitres capacity, are 
placed in the leaden trough, b, the bottom of which is protected by a cast-iron plate and a 
stoneware slab, f, from the direct action of the fire at d. b represents a concentrated solu- 


























































































218 


CHEMICAL TECHNOLOGY. 


lion of chloride of calcium serving the purpose of a bath, such a solution boiling at I 79 ’ 5 °- 
By the syphon funnel, k, the hydrochloric acid is poured into a. I is a perforated cistern 
filled with manganese, s is the leaden gas tube. The chlorine being first washed in n, 
passes through n into t, filled with pieces of manganese, to decompose any vapours of 
hydrochloric acid carried over, and lastly, the chlorine passing through m reaches the 
absorption vessel, s. This vessel is a lead-lined wooden cask, fitted with an axle bearing 
spokes to which are fastened gutta-percha floats. The bearing and plummer-blocks of the 
axle are made of guaiacum wood and ebonite. The axle, o, gears with a suitable motive 
power, the purpose being to keep the milk of lime in continuous motion while the gas is 
being admitted. 

Tig. ioS. 



The chlorine gas enters above the level of the fluid, which is kept constantly stirred, to 
assist in the absorption. From the vessel wherein the absorption takes place a small tube 
leads into another vessel filled with water to a depth of 18 to 24 centims.; a tube fitted to 
this vessel leads into the open air to convey away any unabsorbed chlorine. As in the 
preparation of solid chloride of lime, it is here necessary to guard against an increase in 
temperature and also saturation; Schlieper has proved that too concentrated solutions 
evolve oxygen, while too dilute solutions yield chlorate of lime. 

Ut produc n tion iies^dies ine As the chlorine required for the preparation of chloride of 
lime is generally obtained by the aid of manganese and hydrochloric acid, the resi¬ 
dues consist chiefly of free acid and protochloride of manganese. The principal 
suggestions as to the utilisation of these substances are :— 

a. Those aiming at the regeneration of peroxide of manganese; and 
/ 3 . Those not proceeding with this view. The former are of course the more 
important. 

Dunlop’s Process. This process is one of the oldest and the best, excepting perhaps, 
Balmain’s, in which the chlorido of manganese is neutralised with the ammoniacal water 
of gas-works, the supernatant liquor being employed for preparing sal-ammoniac, while 
the precipitate is ignited in a reverberatory furnace and converted into peroxide of 
manganese. Dunlop’s process, as practised at Tennant’s works at Glasgow, is based upon 
the fact, first observed by Forchhammer, that carbonate of manganese, when heated to 
260°, is converted into peroxide of manganese; that is, the carbonic acid is driven off, 
and the compound, • 2Mn0 2 MnO, obtained. The process consists in the following 
operations:— 

1. Conversion of the chloride of manganese into carbonate of manganese. 

2. Conversion of the carbonate into peroxide of manganese. 

To the chlorine preparation residues, when they have become clear, either chalk or milk 
of lime is added to neutralise the excess of acid and precipitate the oxide of iron. This 
precipitate having settled, the clear liquid, a rather pure solution of protochloride of man¬ 
ganese, is poured into shallow troughs and intimately mixed with finely powdered chalk. 
The magma thus formed is transferred for further decomposition to a large cast-iron 
trough, 27 metres long by 3 metres wide. Parallel to the length of this vessel, a stout 
wrought-iron axle is carried, to which are fitted cast-iron branches serving as stirrers. 


































ELEACHING-FO WEEK. 


219 


The axle passing through stuffing boxes at each end of the trough, gears with a motive 
power, whereby the stirrers are caused to keep the chalk constantly suspended in the 
manganese solution. High-pressure steam is conveyed into the trough and aids decom¬ 
position. The carbonate of manganese obtained is freed by washing from chloride of 
calcium, and having been well drained, is calcined in a peculiarly constructed furnace, in 
which the carbonate is first dried on a higher stage, and then is transferred to a lower and 
hotter stage, where oxidation is commenced. The oxidation is completed at the lowest 
stage of the furnace, to which plenty of air is admitted. The fire-place is constructed to 
admit of the regulation of the heat with great nicety, because too high a temperature would 
cause the formation of protosesquioxide, and too low a temperature would leave the car¬ 
bonate undecomposed. 

Gatty’s Process. In this process the residues are converted into nitrate of manganese, 
which is next decomposed by heat. The residues are evaporated to the consistency of a 
syrup, and mixed with nitrate of soda:— 

To 76 kilos, of protochloride of manganese ) 
and to 95 kilos, of sulphate of manganese j 
The mixture is dried, and then heated to a dull red heat in an iron retort, the fumes of 
nitric acid given off being used in the manufacture of sulphuric acid. The residue in the 
retort consists, according to the salt of manganese employed, of peroxide of manganese 
and chloride of sodium or sulphate of soda ; it may be lixiviated with water to obtain the 
peroxide of manganese in a pure state if sulphate of soda is present. 

Hofmann’s Process. The processes of regenerating manganese by the application of soda 
waste are more important than the preceding. In Hofmann’s process the protochloride 
of manganese is, by the addition of the yellow ley obtained from the lixiviation of soda 
waste converted into sulphuret of manganese. The precipitate, consisting of— 

Sulphuret of manganese . 55 '°° 

Sulphur.40’oo 

Protoxide of manganese . 5’oo 


106 kilos, of nitrate of soda are taken. 


IOO’OO 

is dried and calcined, the sulphurous acid given off being led into the sulphuric acid 
chambers. The remaining residue, consisting* of— 


Sulphate of manganese.44*5 

Peroxide of manganese. 18*9 

Protoxide of manganese.36*6 


100*0 


is next mixed with nitrate of soda and heated to 300°, yielding sulphate of soda and 
nitrate of manganese, the latter, however, being at once decomposed into peroxide of 
manganese and hyponitric acid :— 

* «. MnS0 4 + 2HaH03 = Mn(N 0 3 ) 2 -fNa 2 S 0 4 ; 

0 . Mn(N0 3 ) + Mn0 2 + 2N0 2 . 

After the mass has cooled, the sulphate of soda is removed by lixiviation, the residue 
yiel din g a material free from iron, and according to the inventor, equal to native manganese. 
* Weldon’s Process. To the residue, consisting of protochloride of manganese, are first added 
for every molecule of that salt 2 molecules of hydrate of lime. Into this magma, consist¬ 
ing of hydrate of protoxide of manganese, hydrate of lime, and chloride of calcium, air 
is forced, the effect being that the manganese is rapidly higher oxidised, and forms cal- 
cium-manganite (CaMn 0 3 , or Mn 0 2 ,Ca 0 ), which, having subsided, and the supernatant 
chloride of calcium solution being run off, is ready for chlorine making by the addition of 
hydrochloric acid. The same process is repeated, and even a change of vessels is not 
required. (See p. 216.) 

ether Methods of utilising 0 . Utilisation of the residues without regeneration of the 
the Residues. ° peroxide of manganese. M. Schaffner, at Aussig, precipitates the 
protochloride of manganese with lime, dries the precipitate, and calcines it in a rever¬ 
beratory furnace, obtaining protosesquioxide of manganese, employed with iron ore in the 
blast furnace. The solution of chloride of calcium simultaneously obtained is precipi¬ 
tated by sulphuric acid, yielding the material known as annaline; that is to say, the 
gypsum used in paper manufacture. In the process of soda-making from sulphuret of 
sodium and iron, as suggested by Malcherbe and improved upon by Kopp, for the oxides 
and carbonate of iron, the corresponding manganese compounds may be substituted. 
Carbonate of manganese may be used to convert sulphuret of sodium into soda, and may 
also serve for the preparation of permanganates. A. Leykauf suggests that the residues 










2 20 


CHEMICAL TECHNOLOGY 


of chlorine manufacture should be employed to form a violet-coloured paint, known as 
Nuremberg-violet, a compound of ammonia, oxide of manganese, and phosphoric acid. 
In England the residues are frequently employed in the purification of coal-gas and as 
disinfectants. 


T of°ni£achiiig^PoMder. n When chlorine gas and slaked lime (hydrated oxide of calcium, 
CaH 2 0 2 ) are brought in contact, a portion of the oxygen of the lime combines with 
the chlorine, forming hypochlorous acid, which, combining with the undecomposed 
lime, forms hypochlorite of lime, while another equivalent of chlorine combines 
with the deoxidised lime (calcium) forming chloride of calcium:— 

/ Hypochlorite of lime, Oa (Clo) 2 , 
yield / Chloride of calcium, CaCl 2 , 

(Water, 2H 2 0. 

This bleaching-powder consists in ioo parts of:— 

Hypochlorite of lime .49*31 

Chloride of calcium .38‘28 

Water . 12*41 


Hydrate of lime, 2CaH 2 0 2 , 
Chlorine, 2C1 2 , 


or of— 

Chlorine 
Lime .. 

Water 


100*00 

48*90 

38*69 

12*41 


100*00 

A bleaching-powder of this theoretical composition does not and cannot occur in 
the trade; a good sample, containing 26*52 per cent, of active chlorine was composed 


as follows:— 

Hypochlorite of lime .26*72 

Chloride of calcium .25*51 

Lime .2 3 . 05 


Water of composition and moisture .. 


100*00 


This analysis may be more intelligible by the following arrangement 


2672 

20*72 


Hypochlorite of lime 
Active chloride of calcium 

Excess of chloride of calcium . 4-79 

Hydrate of lime .30:40 

Water of composition and moisture .. .. 17*31 


100*00 

According to Dr. Eresenius (1861), bleaching-powder is a mixture of 1 molecule 
of Ca(C10) 2 and 2 molecules of basic chloride of calcium, CaCl 2 , 2 CaH 2 0 + 2H 0 . 

ropet powder. ° Bleaching-powder is a white, rather moist powder, consisting 
of hypochlorite of lime, chloride of calcium, and excess of slaked lime. 10 parts <5 
water dissolve the bleaching material, leaving the excess of lime ; the chlorine con¬ 
tained in the chloride of calcium also acts as a bleaching agent, as on addin» an 
acid to the bleaching-powder the hypochlorous acid set free reacts upon the hydro¬ 
chloric acid evolved from the chloride of calcium, forming water and chlorine 

(h}°+ci} -h|°+oi}) 



















BLEACEING-PO WEEP. 


221 


The bleaching power of chloride of lime does not come immediately into play 
unless an acid is added; this property is turned to account in the producing of white 
patterns upon fabrics dyed turkey-red, by printing the pattern in a thin paste of tar¬ 
taric acid, the fabric being afterw T ards immersed for a few minutes in a solution of 
hypochlorite of lime. Instead of employing acids for setting the chlorine free from 
chloride of lime, sulphate or chloride of zinc may be substituted, the result being 
that gypsum and oxide of zinc are precipitated, while hypochlorous acid remains in 
solution. * The various industrial uses of bleaching-powder have already been men¬ 
tioned. Chloride of lime, as bleaching powder is generally termed in this country, 
is sometimes used for the preparation of oxygen, i kilo, (of the formula Ca(C 10 ) 2 ), 
yielding 132*2 grms. = 92*4 litres of oxygen. 

chiorimetry. As the value of a sample of chloride of lime depends upon the quantity of 
of the really active chlorine and hypochlorous acid it contains, methods have been 
devised for ascertaining with a greater or less degree of accuracy the quantity of 
these active agents. Formerly the test was the discolouration of a certain quantity 
of indigo solution by a certain quantity of bleaching-powder solution, as compared 
with the action of chlorine upon indigo, but it is cleat that this method could 
not yield accurate results. 

Gay-Lussac^ chiorometric Th.is eminent savant makes use of the oxidising action of 
chloride of lime upon arsenious acid, a volume of dry chlorine gas dissolved in 
water being employed. The solution of chlorine is poured into a graduated tube 
divided into 100 parts, each of these divisions corresponding to one-hundredth of 
chlorine. A solution of arsenious acid in dilute hydrochloric acid is also prepared, 
the strength of the solution being such that equal bulks of the two liquids suffer 
mutual decomposition:— 

Arsenious acid, As 2 0 3 , 

Water, 2H 2 0, 

Chlorine, 2C1 2 , 

Water is decomposed; its oxygen combines with the arsenious acid, forming arsenic 
acid, w’hile the hydrogen combines with the chlorine. Usually 1 litre of dry chlorine 
gas is dissolved in 1 litre of distilled water. The normal solution of arsenious acid 
is so prepared that it is entirely decomposed by the chlorine Water to arsenic acid. 
The test is carried out as follows:—Take 10 grms. of the sample, and triturate with 
distilled w 7 ater, adding sufficient of the latter to make up a litre. Next take, by 
means of a graduated pipette, 10 c.c. of the arsenious acid solution, and pour it 
into a beaker, adding a drop of indigo solution to impart a faint colour; next add, 
by means of a burette, sufficient of the bleaching powder solution to cause the 
colour nearly to disappear, then add more of the indigo solution, and again bleaching- 
powder solution, until the fluid becomes quite colourless. The normal arsenious 
acid solutionis prepared by dissolving 4*4 grms. of this acid in 32 grms. of hydro¬ 
chloric acid, the liquid to be diluted to 1 litre. If 10 grms. of bleaching-powde • 
contain 1 litre of chlorine gas, it is of 100 degrees strength, 
penot s Test. Penot has modified Gay-Lussac’s method in the following particulars 
For the arsenious acid solution he substitutes arsenite of soda, and for the indigo 


j Arsenic Acid, As 2 0 5 . 
yield | Hydrochloric acid, 4 C 1 H 


* Explosions have occurred from bleaching-powder being kept in too tightly closed 
vessels, due to spontaneous decomposition, (Ca(C 10 ) 2 -f- CaCl 2 = 2CaCl 2 -f- 0 2 ). As a pre¬ 
vention it is suggested that the powder should be ground, packed in casks, and strongly 
pressed into a hard mass. 


222 


CHEMICAL TECHNOLOGY . 


solution a colourless iodised paper, which is turned blue by the smallest quantity of 
free acid. The paper is prepared in the following manner:—i grm. of iodine, 
7 grms. of carbonate of soda, 3 grms. of starch, and £ litre of water are mixed. When 
the solution becomes colourless, it is diluted to ^ a litre; in this fluid white paper is 
soaked. The arsenical fluid is prepared by dissolving 4*44 grms. of arsenious acid, 
and 13 grms. of crystallised carbonate of soda in 1 litre of water. This solution is 
poured by means of a burette into the solution of the chloride of lime intended to 
be tested (10 grms. of the sample to 1 litre), the completion of the reaction being 
known by the paper remaining uncoloured. Mohr, again, has modified this process, 
in not however very essential particulars. 

Dr. Wagner s Method. This test, discovered in 1859, is the so-called iodometrical 
method , and is based upon the fact that a solution of chloride of lime separates the 
iodine from a weak (1 to 10) and slightly acidified iodide of potassium solution, the 
iodine being quantitatively estimated by means of hyposulphite of soda :— 


Iodine, 2I, ( r - n 

Hyposulphite of soda, 2Na 2 S 2 0 3 -|-5H 2 0, j ^ ie 


Iodide of sodium, 2NaI, 
Tetrathionate of sodium, Na 2 S 4 06 , 
Water, sH 2 0 . 


The test is thus executed:—100 c.c. = 1 grm. of• bleaching-powder solution, 
obtained by dissolving 10 grms. of chloride of lime in 1 litre of water, are mixed 
with 25 c.c. of solution of iodide of potassium acidified with dilute hydrochloric 
acid. The ensuing clear, deep brown coloured solution is treated with hypo¬ 
sulphite of soda solution until quite colourless. The hyposulphite of soda solution 
is composed of 24*8 grms. of that salt to 1 litre of water; 1 c.c. of this solution 
neutralises 0*0127 grms. of iodine and 0*00355 grms. of chlorine. 

cworometricai Degrees. The strength of bleaching-powder is indicated in England, 
Russia, America, and Germany by degrees corresponding to the percentage of active 
chlorine; but in Erance the degrees denote the number of litres of chlorine gas at o° 
and 760 millimetre Bar., which 1 kilo, of bleaching-powder can evolve. The 
following table compares the chlorometrical degrees of Erance and England:— 


French. 

63 

65 

70 

75 

80 

«5 

90 

100 

105 

no 

115 

120 

125 

126 


English. 
20*02 
20*65 
22*24 
23*83 
25*42 
27*01 
28*60 
31*80 
33*36 
34-95 
• 36'54 
38*13 

3973 

40*04 


The percentage is calculated by multiplying the French degrees by the coefficient 
0*318, a litre of chlorine gas = 35*5 criths, weighing 3*18 grms. 


CHLORATE OF POTASSA. 


223 


Alkaline Hypochlorites. A solution of hypochlorite of potassa is known in commerce 
under the name of Eau tie Javelle , while the corresponding soda solution is known as 
Eau de Labarraque ; these solutions are prepared by passing chlorine gas into a 
solution of either caustic (1), or carbonated (2) alkali :— 

(1) . 2NaOII+Cl 2 = NaOCl + NaCl-f H 2 0 ; 

(2) . 2Na 2 C0 3 -f- Cl 2 + H 2 0 = NaOCl 4 - NaCl 4- 2 NaHC 0 3 ; 

or by exhausting bleaching-powder with water, and precipitating the solution with 
sulphate or carbonate of soda solution, sulphate or carbonate of lime being thrown 
down, while the hypochlorite and chloride of the alkali remain in solution. 

Hypochlorite of aluniinium, or Wilson’s bleaching powder, is obtained by mixing chloride 
of lime solution with sulphate of alumina; its action is by evolving oxygen, leaving 
chloride of aluminium in solution. Hypochlorite of magnesia (Ramsay’s or G-rouville’s 
bleaching liquor) is obtained by adding sulphate of magnesia to a solution of bleaching- 
powder ; the result is the formation of a very energetic bleaching compound, which, espe¬ 
cially for the purpose of bleaching finely-woven-fabrics, as muslins, &c., is preferable to 
chloride of lime on account of the absence of caustic lime. Varrentrapp’s bleaching salt, 
or hypochlorite of zinc, is another energetic bleaching compound obtained by treating’ a 
solution of chloride of lime with sulphate of zinc, the result being the precipitation 
of sulphate of lime, while hypochlorite of zinc remains in solution; chloride of zinc may 
be employed, but, of course, the solution then retains chloride of calcium. Hypochlorite 
of baryta is sometimes used, hypochlorous acid being obtained by the addition of 
very dilute sulphuric acid. 

chlorate of potassa. This salt (KC 10 3 ) consists in 100 parts of 38 ’5 of potassa and 
61*5 of chloric acid; its crystals are rhombic and tabular in form. It formerly was 
prepared by passing chlorine gas into a concentrated solution of carbonate of 
potassa, the result being the formation of chlorate of potassa and chloride of 
potassium. As the chlorate is the least soluble it crystallises first, while by evapo¬ 
ration the mother-liquor yields chloride of potassium. The chlorate is then washed 
with cold water, and purified by re-crystallisation. 100 kilos, of carbonate of 
potassa yield in this manner 9 to 10 kilos, of the chlorate. At the present day, 
however, chlorate of potassa is prepared by a method, the suggestion of the late 
Dr. Graham. Chlorine is caused to act at a high temperature upon milk of lime, with 
the result of the formation of chlorate of lime and chloride of calcium, the chlorate 
of lime being afterwards decomposed by chloride of potassium. The method by 
which chlorate of potassa is prepared on the large scale according to this plan is the 
following:—1 mol. of chloride of potassium and 6 mols. of hydrate of lime, having 
been mixed with water, are submitted to the action of chlorine gas; the solution yields 
on evaporation crystallised chlorate of potassa, while chloride of calcium remains. 

This operation is carried on by the aid of the apparatus illustrated in Rig. 109. b b are 
earthenware jars, placed in a chloride of calcium bath, and filled with a mixture for 
evolving chlorine gas. This gas is conveyed through the leaden tube, f f, to the vessel, c, 
which is placed in cold water for the purpose of condensing any aqueous vapours. From 
c the gas passes through the leaden tube g into the absorption vessel, a, in which the 
mixture of lime and water has been placed, e is an iron stirrer covered with lead, h, a 
portion of the tube for carrying off the non-absorbed chlorine; d , a tube closed with 
a plug during the operation, and intended for tapping off the contents of the vessel.. The 
milk of lime is poured into the vessel at 50° to 6o° C., while sometimes steam is injected 
for the purpose of keeping up the temperature, which rises as soon as the reaction com¬ 
mences nearly to the boiling-point. A small quantity of hypochlorite of lime is always 
formed. As soon as no more chlorine is absorbed the fluid is tapped off into a lead-lined 
tank, and after the suspended matter has been deposited, is syphoned over into a leaden 
evaporating pan and concentrated to 25 0 to 30° B., any hypochlorite of lime being thus 
converted into chlorate. To the evaporated and concentrated solution there is added 
a hot solution of chloride of potassium, after which the evaporation is continued to crys¬ 
tallisation. According to theory, 2 \ parts of lime require 1 part of chloride of potassium ; 


224 


CHEMICAL TECHNOLOGY. 


in practice, however, to every 3 parts of lime 1 part of chloride of potassium is taken. 
Old chloride of lime which has become unfit for bleaching- purposes may be utilised 
by first preparing 1 chlorate of lime, and boiling a solution of this chlorate, adding to the 
concentrated fluid chlorate of potassium to obtain chlorate of potassa. Chlorate of 
potassa is not altered by exposure to air, is soluble in 16 parts of water at 15-8°, in 8 parts 
of water at 35 0 . and in i-6 parts of water at ioo°. On being heated to fusion, this salt 
yields oxygen; if incautiously rubbed in a mortar with combustible substances, as 
sulphur or phosphorus, violent explosions will ensue. 1 kilo, of the chlorate yields, when 


Fig. 109. 



heated with either 0-5 kilo, of manganese or 1 kilo, of oxide of iron, or, better still, with 
a small quantity of oxide of copper (see “ Chemical News,” vol. xxiv., p. 85), 391-2 grms. 
273-5 litres of oxygen. Chlorate of potassa is chiefly employed in pyrotechny for the pre¬ 
paration of white powder, as an ingredient in the explosive mixture for the cartridge 
of needle-guns, as an oxidising agent in calico-printing, and in the preparation of aniline 
black. Perchlorate of potassa (KC 1 2 0 4 ) is now more frequently used in pyrotechny, 
being less dangerous to manipulate, and owing to the large quantity of oxygen, emitting 
more intense light. 

Alkalimetry. 

Alkalimetry. The potash met with in commerce, no matter from what source it 
is obtained, is always a mixture of carbonate of potassa with other salts of potassa 
and soda; and again the carbonate of soda of commerce is a mixture of the car¬ 
bonate with other soda salts, chiefly sulphate and chloride. The value of either of 
the salts of course depends chiefly upon the quantity of pure carbonate present in a 
given sample. The quantitative determination may be effected by cither of two 
rapid, yet sufficiently accurate, methods:— 

a. The estimation of the quantity of acid required to neutralise the alkaline 

carbonate; 

b. The determination of the quantity of carbonic acid evolved by the addition of 

a strong acid. 

It is clear that these methods can be applied only when no other than the 
alkaline carbonate is present. 

yoiumetricai Method. This method, invented by Descroizilles and improved by Gay- 
Lussac, is based upon the measurement of the quantity of sulphuric acid required to 












































ALKALIMETRY. 


225 


expel the carbonic acid from a certain quantity of carbonate of potassa, this measure¬ 
ment giving the quantity of pure salt. The best sulphuric acid is prepared by 
mixing 100 grms. of pure sulphuric acid, sp. gr. = 1-842, with 1000 grms. = 1000 c.c. 
= 1 litre of distilled water; or, instead of weighing the acid, 54*268 c.c. may be, 
mixed with a litre of water. 50 c.c. of this normal acid solution suffice for converting 
4*807 grms. of potassa into sulphate of potassa. The burette of 50 c.c. capacity and 
graduated to half a c.c., is filled with test-acid; next 4*807 grms. of potassa are 
weighed out and dissolved in boiling water. Some litmus tincture is now added, 
and the test-acid poured from the burette into the potash solution until the colour is 
a wine-red. Supposing 60 demi-c.c. to have been used in saturating the potash, 
and deducting \ c.c. for possible excess, the sample contains potash of 59!°. The 
quantity of potassa per cent, is calculated by multiplying the quantity found by 
1*47. Potash of 50° contains 50 X 1*47 = 75*5 per cent, carbonate of potassa. 

Mohr’s Method. Mohr substitutes for the sulphuric acid crystallised oxalic acid— 

(CaHaCX^HaO = 126 ; | mol. = 63), 

because:—1. It is as strong as, and similar to, sulphuric acid in its action upon 
litmus ; 2. Being neither deliquescent nor efflorescent, it can be readily weighed off 
in a dry state with accuracy; 3. Its aqueous solution is not liable to become mouldy 
by keeping, as are the solutions of citric and tartaric acids; 4. It is not volatile 
when in hot water. To prepare the normal acid liquor, 63 grms. of oxalic acid are 
dissolved in a litre of water; on the other hand, there is prepared a corresponding 
solution of caustic potassa so titrated that, on being mixed with an equal bulk of 
the acid solution, the last drop of the alkaline solution restores the blue colour of 
the previously reddened litmus, provided the liquor does not contain carbonic acid in 
solution. For alkalimetric purposes 6*911 grms. of potash or 5*32 grms. of soda are 
weighed out, these quantities being equal to ^ molecule, and as the test-acid contains 
in 1000 c.c. molecule of oxalic acid, 100 c.c. will exactly neutralise the quantity of 
alkali. Some litmus tincture is mixed with the alkaline solution, to which the 
oxalic acid solution is added in a slight excess (5 to 6 c.c.), the solution being 
boiled to expel all the carbonic acid. There is now added by means of a pipette 
divided into tenths-c.c., just sufficient caustic alkali to turn the litmus blue; 
the number of c.c. of alkali solution employed is deducted from the number of c.c. 
of acid solution employed,'the difference giving the percentage of pure carbonate of 
potassa contained in the sample. For instance, if 3*45 grms. of the potash = mole¬ 
cule, require 36 c.c. of the acid and 3 c.c. of the alkaline liquor, there will be 33 c.c. 
test-acid = 66 per cent, carbonate of potassa, as, instead of mol., ^ mol. having 
been employed, the number of c.c. of test-acid must be doubled. 

These instances of alkalimetric processes will suffice for the purposes of elucidation, 
but the reader will find fuller explanations in works on volumetric analysis. However, it 
is still to be observed that as potash is a very hygroscopic substance, it is necessary to 
estimate the water it contains, or at least to dry the sample. As 6*29 grms. of commercial 
potash and 4*84 grms. of soda contain when pure exactly 2 grms. of carbonic acid, every 
2 centigrms. loss equals 1 per cent, of carbonate. Supposing the loss of weight to amount 
to 164 centigrms. the sample will contain '| 4 =82 per cent, of carbonate of potassa; for 
scientific purposes it would answer to say that such a sample consists in 100 parts of r— 

Carbonate of potassa.82 

Foreign salts . 8 

Water.10 


16 


100 





226 


CHEMICAL TECHNOLOGY. 


For commercial purposes, however, at least abroad, the value (titre) of a sample 
of potash expresses the percentage of anhydrous salt; for instance, by potash at 
is meant potash containing 60 per cent, of real carbonate when in a dry state. But 
if, by having taken up moisture, ioo lbs. have increased in weight to 105 or 109 lbs., the 
expression T 6 3 ° 3 or f 5 ° g is equivalent to saying that the amount of money that would buy of 
dry material will also buy T g° 3 and T 6 s ° g of the moist salt; the purchaser, therefore, does not 
pay for water, and all that he has to do is to ascertain the quantity of water present in the 
sample. In France the quantity of soda contained in a sample is usually expressed in 
degrees indicating the percentage of carbonate of soda, and in England the percentage of 
caustic soda ; thus, as 100 parts of carbonate of soda contain 58*6 of soda and 41*4 of car¬ 
bonic acid, it follows that— 

So 0 French are equal to 46-9° English. 

86° „ „ „ 50-5° 

96 5 > 5 J 5 > 5 2 '8 

Estimating the^aiu^ preceding methods of testing potash no notice is taken of the 

of Potash. soda contained in the samples, nor is the quality of the potassa salts 
considered. It is clear that these determinations require a full analysis, which, by 
Griineberg’s method, is executed in the following mamier:—The carbonate of potassa 
is estimated by Gay-Lussac’s method, the chlorine by the aid of nitrate of silver, the 
sulphuric acid by nitrate of lead, and the quantity of any free caustic potassa is determined 
by means of tartaric acid. All the chlorine is calculated as chloride of potassium, all the 
sulphuric acid as sulphate of potassa, and the rest of the potassa as carbonate; the quantity 
thus found is deducted from that found alkalimetrically, and the remainder is calculated to 
be carbonate of soda in the proportion of 69*1 to 53*0. 


Ammonia and Ammoniacal Salts. 


Ammonia. Ammonia occurs in the atmosphere. Ammoniacal salts are met with in 
a few minerals and in volcanic districts. But the bulk of the ammonia and 
ammoniacal salts industrially used, is obtained from the dry distillation of coals, 
bones, and animal substances, also by the distillation of lant (stale urine), by the 
action of steam on some cyanogen compounds, and as a product of the blast-furnace 


process. 


a. 


Inorganic 

sources. 


The following sources of ammonia are technically available :— 

Y i« Native carbonate of ammonia, 
j 2. Preparation of ammoniacal salts with boracic acid, 

3. Volcanic sal-ammoniac, 

4. Ammonia from nitric acid in the purifying of caustic soda, 

•5. „ „ deutoxide of nitrogen and nitrous acid, 

6. „ „ the nitrogen of the air, 

7. „ „ certain cyanogen compounds. 

8. Coals yield ammonia :—- 

a. By the dry distillation for the purpose of gas manufacture, 

b. By the coking of coals, 

c. By the use of coals as fuel; 

9. Ammonia from lant, 

to. „ „ the dry distillation of bones, 

[i. „ „ beet-root juice. 


A 


Organic 

sources. 


Ammonia, NI 1 3 , consists of 1 volume of nitrogen and 3 volumes of hydrogen, con¬ 
densing to 2 volumes of ammonia gas, a colourless gas of a peculiar and well-known 
odour and sharp biting taste. At 15 0 water absorbs 727, and at o° 1050 times its 
own bulk of this gas, the solution being known as liquid ammonia, or spirit of sal- 
ammoniac, the sp. gr. of which is 0*824 (=31*3 per cent. jSTH 3 ). Usually, however, a 
weaker and more stable liquid ammonia is prepared for pharmaceutical and technical 
purposes, having a sp. gr. = 0*960 (— 9*75 per cent. NH 3 ). The following table 
show’s the specific gravity of liquid ammonia, and the percentage of ammonia 
contained:— 



AMMONIA . 


227 


Sp. gr. 

NH 3 per cent. 

Sp. gr. 

NH 3 per cent. 

0-875 

32*50 

o -959 

10*0 

0-824 

31-30 

0*961 

9*5 

0-900 

26*00 

0*963 

9-0 

0-905 

25*39 

0-965 

8-5 

0-925 

I 9*54 

0*968 

8-o 

0-932 

x 7*52 

0*970 

7'5 

0-947 

13-46 

0-972 

7 *o 

°’ 95 x 

12*00 

0*974 

6-5 

°'953 

II-50 

0-976 

6-o 

°"955 

11 "00 

0-978 

5*5 

0*957 

10-50 




Ammonia gas is very soluble in alcohol. The spiritus ammoniaci caustici Dzondii of 
the Prussian Pharmacopoeia is a solution of ammonia gas in alcohol of o - 820 sp. gr.; the 
ammoniacal solution containing 10 per cent, of real NH 3) and having a sp. gr. of 0-808 to 
0810. The liquor ammonii vinosus is a mixture of I part of liquid ammonia (at 10 per 
cent. NH 3 ) and 2 parts of strong alcohol. Liquid ammonia is industrially employed for 
the extraction of the lichen (orchil) pigments, in the preparation of carmine, the manu¬ 
facture of snuff, the purifying of coal-gas, for the removal of carbonic acid and sulphuretted 
hydrogen, for the saponification of fats, the preparation of ferrocyanide of potassium 
according to Gelis’s plan with the aid of sulphide of carbon, for the extraction of chloride 
of silver from its ores, as antichlor in bleach-works, and in the manufacture of pigments 
and dyes. As regards the use of liquid ammonia for the extraction of copper from 
pyritical ores, Barruel stated (1852) that the copper might be dissolved by simply impreg¬ 
nating finely pulverised ore with liquid ammonia, and forcing air through the mixture, 
the metal being obtained as black oxide of copper after the ammonia is distilled off. 
This process, however, has not been found to answer on the large scale. The researches 
of von Hauer, Schonbein, Tuttle, and others, have proved that the oxidation of the 
ammonia is simultaneous with the oxidation of the copper, and that the nitrous acid thus 
formed is the active agent. Moreover, the experiments of Liebig and Way have proved 
that even if the operation were carried on in air-tight vessels, the ammonia could not be 
entirely recovered, owing to the fact that the ores absorb ammonia, and render it 
insoluble, thereby preventing its action on the copper. But if the copper ore be tolerably 
pure malachite or lazulite, only containing lime or carbonate of that base, liquid ammonia 
may be successfully employed. Liquid ammonia is used in Carre’s ice-making machine. 
The rationale of this machine is that ammoniacal gas being expelled by heat from its 
aqueous solution, is again condensed and liquefied by pressure and cooling; the retort in 
which the ammonia is heated being next cooled by water, a vacuum is created, and as a 
consequence the ammonia contained in the condenser volatilised, returned to the retort, and 
again taken up by the water present. On again resuming the gaseous state, the ammonia 
absorbs a great amount of heat, causing a diminution in temperature sufficient to freeze 
water. Carre’s ice-machine yields 10 kilos, of ice for every kilo, of coal consumed as fuel. 
Although Fournier has suggested that ammoniacal gas might be usefully employed in 
testing the joints of gas-fittings in houses, this is more readily effected by the use of a 
hand air-pump. The application of ammonia as a source of motive power has been tried, 
but it is not at present likely that it will supersede steam. 

Preparation^of Liquid By decomposing with caustic lime either chloride of ammonium 
or sulphate of ammonia, ammoniacal gas is set free, and can be absorbed by water, 
care being taken that the lime is in excess. When carbonate of ammonia is prepared 
on the largo scale by sublimation of a mixture of chalk and sal-ammoniac, a 
large quantity of ammoniacal gas, 14 parts for each 100 parts of carbonate of 
ammonia, is obtained and may be utilised. Wagner has been the first to observe 
that the technical preparation of liquid ammonia might be combined with the 
preparation of baryta-white by precipitating a solution of sulphate of ammonia 
with caustic baryta-water; the clear supernatant liquor will be a solution of 
saustic ammonia. 


CHEMICAL TECHNOLOGY. 


22 6 


The preparation of liquid ammonia on the large scale is effected by means of the 
apparatus shown in Fig. no. a is a cast-iron distilling vessel placed in a brickwork 
furnace. To the neck of the vessel is fitted a lid secured to the flange by means of 
bolts and nuts, and luted with red-lead. The lid carries an iron tube, m, leading to the 
wash vessel, b, of wrought-iron. This vessel is surrounded by cold water contained in a 
wooden tank, and is provided with a wide tube, o, through which rn passes. The wash 
vessel is filled with only so much water as will close the tubes n and o hydraulically, 
a3 during the operation a large quantity of water is distilled over from a. ioo parts of 
slaked lime are mixed with a sufficient quantity of water to form a thin milk of lime, 
which is poured into a; the lime solution having become quite cold, there is added ioo 
parts of pulverised sal-ammoniac or sulphate of ammonia, being thoroughly mixed by 
stirring with an iron rod. The lid being screwed on a, the fire is lighted in c; the 

Fig. iio. 



mercurial gauge, b, shows the course of the operation. The ammoniacal gas proceeds 
from the wash vessel, b, through the tube t into the condensing apparatus, d, invented 
by Brunnquell, and highly useful for this and for similar purposes where it is desired to 
work under a low pressure. This apparatus consists of a large tank or box in which 
four shallow boxes, a', a ", a'", a"", are placed bottom upwards, the sides of the boxes being 
perforated with small slits. The outer tank is filled with water. When ammoniacal 
gas enters through t into a"", it forms a large bubble, similar to an air bubble under 
ice, and reaching one of the small slits rises into a'", and so on, the bubble becoming 
smaller and smaller as the water gradually absorbs the gas. The box or tank, d, is 
placed in a large tank, not represented in the cut, filled with cold water constantly 
renewed. The still, a, is of sufficient capacity to contain 20 kilos, of sulphate of ammonia 
and 80 litres of water. The operation is continued until the bottom of the still becomes 
red-hot. The water contained in B is used at a subsequent operation for mixing with 
the lime. The preparation of liquid ammonia directly from gas liquor, the ammoniacal 
water of gas works, will be mentioned presently. The application of the property of 
chloride of calcium to absorb ammonia and deliver it up on the application of heat 
has been attempted industrially by Ivnab for the storing up of ammonia. Strong liquid 
ammonia only contains 25 per cent. NH 3 , and Knab’s preparation 50 per cent.; as 
reg'ards transport this may not be an uninteresting fact, but chloride of calcium is a very 
deliquescent salt. 

laorgamc^sources of Before proceeding to describe the preparation of ammoniacal 
salts from bones, coals, lant, &c., we must first enumerate the inorganic sources of 
ammonia of industrial importance. 

1. Native carbonate of ammonia, met with in large quantities in the guano deposits of 
South America, was imported into Germany as a commercial article in 1848. On being 
analysed this substance was found to consist of—Ammonia, 20-44; carbonic acid, 54-35°; 






































































































































AMMONIA. 


229 


water, 21-54; and insoluble matter, 21-54 parts. It is, therefore, a bicarbonate of ammonia 
(NH 4 ,HC 0 3 . 

2. The preparation in Tuscany of native sulphate of ammonia as a by-product of the 
preparation of boracic acid has recently become important. The suffioni contain, in 
addition to boracic acid, sulphates of potassa, soda, ammonia, rubidium, &c.; and that 
the quantity of these substances is by no means small may be inferred from Travale’s 
researches, from which it appears that four suffioni yielded within twenty-four hours 
5000 kilos, of saline matter, consisting- of 150 kilos, of boracic acid, 1500 kilos, of sulphate 
of ammonia, 1750 kilos, of sulphate of magnesia, 750 kilos, of the protosulphates of 
iron and manganese, &c. The ammonia is probably due to the decomposition of 
nitrogenous organic matter, occurring largely in the Tuscan mountains, the soil near the 
lagoons being impregnated with sulphate of ammonia. In combination with the sulphates 
of soda, magnesia, and iron, sulphate of ammonia forms the mineral Boussingaultite, 
discovered by Bechi. 

3. The ammoniacal salts due to volcanic action are of no or of little value to industry. 
Mascagnin, sulphate of ammonia, is met with on Vesuvius and Etna; sal-ammoniac is 
sometimes also found on Etna, as in the years 1635 and 1669, in such large quantities as 
to become temporarily an article of commerce at Catania and Messina. 

4. Ammonia is formed during many inorganic chemical operations, but rarely in 
quantities rendering its preparation or recovery commercially available. Ammonia is, 
for instance, set free in the preparation of caustic soda (see page 189), and the purifi¬ 
cation of caustic soda by means of nitrate of soda; the quantity of ammonia set free in 
this case is so large that it would be commercially worth trying to condense the gas in a 
coke scrubber or condenser. When arseniate of soda is prepared by dissolving arsenious 
acid in a caustic soda solution, evaporating this liquid to dryness, and igniting the residue 
with nitrate of soda, ammonia is disengaged in large quantity. 

5. Under the heading “Ammonia as a by-product of the manufacture of sulphuric 
acid,” there is in the original German text a description of a mere suggestion, embodied in 
a provisional specification of an English patent, for the utilisation of the waste nitrous 
vapours of sulphuric acid manufacture in the preparation of ammonia, by passing these 
vapours, with steam, through red-hot tubes or retorts filled with charcoal, the ammonia 
thus formed being absorbed by sulphuric acid. This process could never be available but 
in badly arranged sulphuric acid works, because in well managed works the escape of 
nitrous fumes is so very small that it certainly would not pay to convert them into 
ammonia. 

6. Of the many unsuccessful attempts made to directly convert the nitrogen of the 
atmosphere into ammonia, it will only be necessary to mention Fleck’s suggestion, to 
pass a mixture of nitrogen, oxide of carbon, and steam over red-hot hydrate of lime, 
whereby ammonia and carbonic acid are formed:— 

Nitrogen, 2N 

yield 


Oxide of carbon, 3CO 
Water, 3 H 2 0 


Ammonia, 2NH3, and 
Carbonic acid, 3CO z . 


7. Perhaps the indirect application of atmospheric nitrogen for the preparation of 
ammonia is of more importance. Margueritte suggests that cyanide of barium should be 
prepared, and its nitrogen converted into ammonia by the aid of a current of superheated 
steam at 300°. According to the description of this process in an English patent, not 
however in practice, native carbonate of baryta is calcined with some 30 per cent, of coal- 
tar, for the purpose of rendering- the mass porous as well as more readily converted into 
caustic baryta at a lower temperature. The carbonaceous mass is, after f cooling, 
placed in a retort, and kept at a temperature of 300°, while air and aqueous vapour 
are forced in, the result being the formation of ammonia in considerable quantity, and 
carbonate of baryta, which is again used. Ammonia is evolved from ball soda while 
cooling-, during the formation of cyanogen and cyanide of potassium in blast furnaces, 
and the formation of sal-ammoniac in the process of iron smelting. 


° r g a nic^sources ° f Industrially speaking, the organic sources of ammonia are far 
more important than the inorganic. Among the ammonia-yielding organic sub¬ 
stances coal (8) takes the first place; the average quantity of nitrogen—0-75 per 
cent.—contained in coal is converted into ammonia during three different processes 
employing this valuable mineral, viz.:— 

a. By the dry distillation of coals for the manufacture of illuminating gas, ammonia is 
obtained in the so-called gas-, or ammoniacal gas-water, the liquid mainly consisting of 
an aqueous solution of sesquicarbonate of ammonia. The importance of this source 


230 


CHEMICAL TECHNOLOGY. 


of ammonia production may be inferred from the fact that the one million tons of coals 
yearly carbonized by the London gas-works will yield, supposing all the nitrogen to be 
converted into sal-ammoniac, 9723 tons of that salt. 

/ 3 . Ammonia is also formed when coal is converted into coke in coke ovens. Very 
recently the utilisation of this source of ammonia has been successfully carried on at the 
large coking establishment at Alais, Departement du G-ard, France, and also at the coke 
ovens belonging to the Societe de Carbonisation de la Loire , near St. Etienne, where, in 
ovens constructed according to Knab’s method, large quantities of ammoniacal salts are 
produced. 

7. Ammonia is produced during the combustion of coal as fuel, a portion of the nitrogen 
contained in the coals being eliminated as ammonia; but this, it should be borne in mind, 
is a consequence of imperfect combustion, and consequently of loss of fuel; and although 
a series of experiments have been made, and apparatus devised for collecting and con¬ 
densing the ammonia evolved with the smoke, the industrial production from this source 
has hitherto been very limited. 

A oS-wat f er. m This is the most important source of ammonia production. By 
the dry distillation of coals for the purpose of gas manufacture there are formed, in 
addition to permanent gases, various vapours, some of which on cooling yield tar 
and ammoniacal liquor, consisting chiefly, as before stated, of a solution of sesqui- 
carbonate of ammonia, but containing sulphuret and cyanide of ammonium, sulpho- 
cyanide of ammonium, and sal-ammoniac, and being coloured by tarry matter. 

It is obvious that the quantity of ammonia contained in this liquor is not always 
constant, but depends upon several conditions; for instance, the quantity of nitrogen 
contained in the gas coals, the hygroscopic moisture of the coals, and the degree of 
heat applied to the retorts. The nearer the retorts are kept to a bright orange-red 
heat, and the longer the distillation is continued, the larger the quantity of ammonia 
formed; for at a lower temperature, of course always above red heat, there may be 
formed aniline, chinoline, lepidine, and cyanogen compounds. Taking the average 
quantity of the hygroscopic moisture of coals at 5 per cent., and the nitrogen at an 
average of 075 per cent., 100 kilos, pf coal would yield, under the most favourable 
conditions, 0*91 kilo, of ammonia. According to Dr. A. W. Hofmann’s report (1863), 
coal yields, when distilled, only one-third of its nitrogen, two-thirds being retained in 
the coke ; but no accurate experiments have been made on this subject. It has been 
practically ascertained on the large scale, that 1 cubic metre (=220*096 gallons) of 
gas-water yields at least 50 kilos, of dry sulphate of ammonia. The ammonia of the 
gas-water maybe utilised in various ways. Where fuel is cheap, and crude sulphate 
of ammonia or crude sal-ammoniac marketable article, the gas-water may be at once 
neutralised by an acid, and the liquid thus obtained evaporated. This is done in a 
sal-ammoniac factory at Liverpool, where, during the colder season of the year, 
300 cwts. weekly of this salt are prepared. Generally, however, the gas-water 
is submitted, to a process of distillation, and the ammonia evolved converted into 
sulphate, as in Mallet’s apparatus, or into sal-ammoniac, as in Bose’s apparatus. 

Manet’s Apparatus. This apparatus, in use in many of the large gas-works, is shown in 
vertical section in Fig. hi. The plan of action is to force steam into large vessels 
filled with gas-water, the effect being the volatilisation of the carbonate of ammonia. 
Sometimes lime is added. The volatilised ammonia—of course if lime is added 
caustic ammonia is evolved—is next conveyed into an acid liquor, and thus 
converted into sulphate of ammonia. The apparatus consists of two cylindrical 
boiler-plate vessels, A and B. A is heated directly by the fire, and is provided with 
a leaden tube, c, dipping into the liquid contained in b, this vessel being placed 
to catch the waste heat from the fire, b and e are man-holes ; a and a! stirrers. By 
means of the tube d the fluid from b can be run off into A. Gas-water is poured 


AMMONIA. 



thence through c', into the wash-vessel, c, and thence again through c", into the first 
condenser, D. The partially condensed vapour now passes into the condensing 
vessel, F, the worm of which is surrounded by cold water. The dilute ammonia is 
collected in G, and forced by means of the pump u into C, whence it is occasionally 
syphoned into either A or B. The non-condensed ammoniacal gas is carried from G, 
through a series of Woulf© s bottles, the first bottle, n, containing olive oil for the 


237 

into both vessels and lime added; ammonia is set free, while carbonate of lime and 
sulphuret of calcium are formed, and of course remain in the vessels after the vola¬ 
tilisation of the ammonia. The vessel D is also filled with ammoniacal water, and 
when the operation is in progress this water, already warmed, is run by the aid of 
the tube 7 i from D into B. E is a gas-water tank, from which D is filled by means of g. 
The ammonia set free in A is, with the steam, conveyed by the pipe c into B. 













































232 


CHEMICAL TECHNOLOGY. 


purpose of absorbing any hydrocarbons mixed with the gas; the bottle I contains 
caustic soda ley, in order to purify the ammonia and retain impurities; the bottle K 
is half-filled with distilled water. The ammoniacal gas haying passed through 3v, 
is conveyed to the large lead-lined wooden tank, l, filled with dilute sulphuric acid 
if it is intended to prepare sulphate of ammonia, or with water for making liquid 
ammonia. The vessel L is placed in a tank of water; i is a small pipe for intro¬ 
ducing acid; while the tube leading to M serves to carry off any unabsorbed ammonia, 
M being also filled with acid. 

nose’s Apparatus. In the manufacture of liquid ammonia the apparatus devised by Mr. 
Rose, and shown in Rig. 112, may be advantageously employed. It consists of:— a, a 
boiler; b and c, two vessels in which the gas-water is warmed by the aid of the tubes, 
e and /, through which and g the steam and ammonia gas evolved iu a pass to the 
absorption vessels, n, e, and f, the connection between e and f being formed by the gas- 
filters, o and h. Tlie ammoniacal water can be run into a by means of the tubes, l and m, 


Rig. 112. 



each of which is fitted with a tap or stopcock, a is filled two-thirds with gas-water and 
one-third with slaked lime. The cylindrical sheet-iron gas-filters, G and ir, are filled with 
freshly burnt charcoal to retain any empyreumatical matter which might be carried over 
by the gas. The absorption vessel, d, is filled with hydrochloric acid, while pure water 
is poured into e and f. When a is filled, and the rest of the apparatus put in working 
order, the fire is kindled, the ammoniacal gas evolved in A passes with the steam to b and 
c, where a portion of the steam is condensed and retained as water in e and f. Into the 
boiler, A, is fitted a tube, b, containing a thermometer, surrounded by brass fittings for the 
better conduction of the heat; when this thermometer indicates 92° to 94 0 , the tap h is 
opened, and the tap, i, open up to this time, shut in order to cause the gas to pass into the 
hydrochloric acid contained in d, until the vessels g and h have been filled with fresh 
charcoal, an operation which is required at the beginning of the working as well as when 
the temperature in a has risen to 96°, 98°, and ioo°. This having been done, the tap h is 
again opened. When the temperature has reached 103°, taking the boiling-point of 
the liquid at 100°, all the ammonia is expelled, and the liquid is then run off by opening 
the stopcock, a. Rresh lime having been put into the boiler, the operation is repeated 5 . 
When the temperature in a reaches 103°, the liquid in b becomes heated to 90°, and that 
in c to from 25 0 to 30°. The vessel f contains from 120 to 150 litres of water, which is con¬ 
verted into liquid ammonia of a sp. gr. = 0-910 to 0-920. c and n are glass safety tubes. 

Lunge’s Apparatus. This apparatus, also intended for the utilisation of gas-water, is shown 
in Rig. 113; a is the boiler; h the gas tube connected with the worm, c, which is placed in 
a tank, cl, filled with gas-liquor, run into a by means of the tube e. The tube/ is so fitted 






















































































































































AMMONIA, 


233 



to a as to admit of discharging the waste liquor readily, b represents a stirrer fitted to 
the boiler by a stuffing box, and being intended to rake up the lime and prevent it getting 
caked to the bottom of a ; hi, a tube intended for running gas liquor into d, from a tank 
placed at a higher level; 1, a tube provided with a tap and fitted to the cover of d, to 


convey any gas or vapours from d into the worm, k represents a wash vessel, some¬ 
times "filled simply with water, at others with milk of lime. The gas and vapours having 
passed through k, are conveyed to the absorption vessel, l. The tube, m, through which 
the gas passes, is funnel-shaped, and opposite to the mouth of the funnel, at the bottom of 
the tank, a thick disc of lead is fixed, because at this spot the action of the gas would soon 
wear away the leaden lining of the vessel. 0 is a smaller wooden tank, also lead-lined, 
into which sulphuric acid is poured, and whence it runs into l through the stoneware 
syphon, p. Any vapours given off are caught by the hood, r, and thence conveyed by a 
tube into the chimney. The saline matter deposited in l is removed by a leaden pail, as 
shown in the cut; when this pail is filled it is drawn up by means of the chain and 
pulley aided by the counter weight, t. The salt (sulphate of ammonia) is placed in the 
















































































234 


CHEMICAL TECHNOLOGY . 


basket, u, from which the mother-liquor adhering- to the salt drains again into the tank, l 
Evaporation is therefore unnecessary with this apparatus. 

Ammonia from Lant. g. Lant, or stale urine, is a very important source of ammonia. 
Whenever nitrogenous organic bodies are decaying, ammonia is always formed; 
when the organic substance is a proteine compound, there is formed carbonate of 
ammonia as well as sulphuret of ammonium; but when the organic substance con¬ 
tains no sulphur, only carbonate of ammonia is formed, as is the case with the urea, 
CH4N2O, contained in urine, the urea by taking up the elements of the water being 
converted into carbonate of ammonia. Lant is frequently employed without further 
preparation for various purposes, on account of the carbonate of ammonia it con¬ 
tains, as, for instance, in washing wool and removing the fat from flannel and other 
woollen fabrics. 

The apparatus exhibited in Fig. 114, contrived by Figuera, and until lately in operation 
at a large establishment for the utilisation of the contents of the latrines and cloacse of 
Paris, consists of a steam-boiler, w, the steam generated in which is conveyed to two large 
iron cylinders filled with lant. The carbonate of ammonia expelled is, with the steam, 
condensed in a leaden worm ; the cooled liquid is conveyed to a tank filled with acid, and 


Fig. 114. 



thus converted into carbonate of ammonia. The arrangement of the apparatus is as 
follows:—The wooden vessel, a, contains some 250 hectolitres of lant, and is filled by 
means of the tube /?. c and c' are two cylindrical sheet-iron vessels of 100 hectolitres 
capacity; p and p' are similar vessels, the use of which will be presently explained. At 
the commencement of the operation the boiler, w, is filled with about 130 hectolitres of 
exhausted lant, taken from the vessels c and c\ The lant in a, warn in consequence of 
having served for condensation, is conveyed to c by a tube, and thence by the tube hi’ to 
c', cold lant being poured into a. The boiler, w, is fitted with three tubes, viz., t, 
the steam pipe, m, a safety tube, brought to within a few centimetres from the bottom of 
the boiler, and carried above the roof of the shed, and n a smaller safety tube; v is a tube 
fitted with a stopcock. The steam evolved in w is carried by t into c', evolving from the 
liquid therein the carbonate of ammonia it holds in solution. The carbonate, with the steam 
passes through t into the vessel, p, which serves to retain any liquid carried over from c\ 
The carbonate of ammonia vapour now passes from p through the tube t' to c, and 
taking up in that vessel more carbonate of ammonia, is conveyed through the tube T? into 
p' (which again serves the purpose of p), and thence throughY' into the leaden worm of 
the condensing apparatus. The condensed liquor, a more or less concentrated solution of 
carbonate of. ammonia, is run through t" into s, a wooden vessel, lead lined, and filled 
with a sufficient quantity of sulphuric acid to saturate the carbonate of ammonia. The 
whole operation lasts about twelve hours ; after this time the waste liquid in the boiler is 
run off by opening the stopcock, v, and the operation again repeated. On an average the 
lant operated upon at Bondy, near Paris, yields per cubic metre from 9 to 12 kilos, of 






























































































AMMONIA. 


235 


sulphate of ammonia, and at each operation 200 kilos, of that salt are obtained by the 
working 1 of one of the apparatus just described. It is stated that from the 800,000 cubic 
metres of urine yearly run waste in Paris alone, there could be obtained, by proper treat¬ 
ment, 7 to 800,000 kilos, of sulphate of ammonia. 

Ammonia from Bone. io. By the destructive distillation of animal substances, such as 
bones, hoofs of horses, refuse horn, skins, hides, decayed meat, &c., there is obtained 
a series of products, among which carbonate of ammonia prevails, with cyanogen 
compounds, sulphuret of ammonium, and tarry matter—a very complex liquid con¬ 
taining pyrrol, bases of the ethylamin series, pyridin, C 5 H 5 N, picolin, CeH 7 N, 
lutidin, CyHgN, and collidin, CsH^N. The organic matter of these substances 
contains from 12 to 18 per cent, nitrogen; the organic matter of bones contains 18 
per cent, of nitrogen, and, as the organic matter amounts to about one-third of the 
weight of the bones, these contain about 6 per cent of nitrogen. Buffalo horn con¬ 
tains 17, waste woollen fabrics 10, and old leather 67 per cent, of nitrogen. 

It is evident that the quantity of ammonia in the products of the dry distillation 
of animal substances depends upon the kind and condition of these materials, and 
upon the temperature at which the operation takes place. The carbonate of am¬ 
monia is obtained in the condensers as a solid saline mass, the crude sal cornu cervi, 
or in aqueous solution (so called spiritus cornu cervi), floating on the surface of the 
tar. At the present time the manufacture of ammonia and its salts from the products 
of the dry distillation of animal substances i3 a matter of but limited industrial 
importance, owing to the extended coal-gas manufacture. Indeed, dry distillation 
is now only carried on for the purpose of obtaining animal charcoal, and the occur¬ 
rence of ammoniacal products is rather considered as a necessary but unavoidable 
evil. A large quantity of animal matter is used for the manufacture of phosphorus 
and of prussiates, and in these operations the manufacture of ammoniacal salts is 
either altogether out of the question or effected only on a limited scale. 

The apparatus used for the destructive distillation of animal matter is in some respects 
similar to a coal-gas oven. Big. 115 exhibits the construction in general use for what is 
termed animal charcoal burning*. The retorts intended to contain the bones are set in 

.Big. 115 



furnaces and fitted at the end farthest from the mouth with tubes, c c, communicating 
with leaden chambers, b, c, &c. In these chambers the vapours are condensed, forming 
a solid saline mass, which is purified by sublimation in the iron vessels, d d, fitted with 
leaden covers. If, instead of bones, other animal matters, for instance, horn, woollen 
rags, hair, and leather-cuttings, are operated upon, the result is that, instead of solid 





















CHEMICAL TECHNOLOGY. 


236 

carbonate of ammonia, an ammoniacal fluid of 13 0 to 15 0 B. is obtained, which may be 
utilised in various ways. Where the mother-liquors of salt-works are readily obtainable, 
they may, especially if rich in chloride of magnesium, be employed for the preparation of 
sal-ammoniac by using- the hartshorn spirit (crude carbonate of ammonia solution) for the 
precipitation of the chloride of magnesium solution. 

Ammonia as a ny-Product When the beet-root juice is boiled, ammonia is evolved in 
of 1 iTanuf^ture? ar large quantities, and may be utilised in the preparation o 
sulphate of ammonia. The ammonia yielded by the juice is the product of the 
decomposition of the aspartic acid and betain present in the roots. According to 
Eenard, a beet-root sugar manufactory which yearly consumes 200,000 cwts. of 
beets might thus obtain 887 cwts. of sulphate of ammonia. 

T AmmoniL I ai 1 saits a . nt Sal-ammoniac, chloride of ammonium, NH 4 C 1 , consists in 10c 
parts of— 

Ammonia, 31*83 Ammonium, 3375 

# Hydrochloric acid, 68*22 Chlorine, 66*25 

Prom the thirteenth to the middle of the eighteenth century this salt was imported 
into Europe exclusively from Egypt, where it was obtained by the combustion of 
camel’s dung. The camel feeds almost exclusively upon plants containing salts, and 
the sal-ammoniac is sometimes found ready formed in the animal’s stomach. The 
sal-ammoniac having sublimed with the soot from the combustion of the dung, was 
collected and refined by a second sublimation. 

In localities where dung is used as fuel, it has been tried to obtain sal-ammoniac 
by combustion with common salt. The first sal-amm oniac manufactory in Germany 
was established by Gravenhorst Brothers, at Brunswick, in 1759. We have already 
seen how crude sal-ammoniac may be prepared from gas-water or by other means. 

The salt, no matter whence derived, is purified by sublimation in cast-iron caul¬ 
drons, w, Pig. 116, lined with fire-clay. As soon as the crude sal-ammoniac is put into 

Pig. 116. 



these vessels and tightly rammed, heat is applied, at first gently, so as to drive off 
any moisture. This effected, iron lids, F, G, h, are luted to the cauldrons; the lids 
can be readily moved by means of the pulleys and chains provided with counter¬ 
weights, B, c, D. Instead of iron covers lead hoods sometimes are employed, the 
opening of which is temporarily closed with an iron disc. The hoods or covers are 
always securely fastened to the cauldrons, to prevent them being forced off by the 
pressure of the vapours. The temperature has to be regulated during the process 
with great nicety, for too low a degree of heat yields a loose salt, and with too high 
































AMMONIA . 


237 


a degree of heat the organic matter present in the crude sal-ammoniac is liable to 
give off empyreumatic matter, spoiling the appearance of the sublimed salt and 
interfering with its good quality. Experience has proved that it is expedient to 
have the sublimation vessels of rather large size, 2| to 3 metres interior diameter. 
When the sublimed sal-ammoniac cake has attained a thickness of 6 to 12 centims. 
the operation is discontinued, and the cake removed. The furnace is provided with 
an oven for drying the sal-ammoniac, this oven being shut with a door, E, movable 
by means of a chain running over a pulley, and aided by a counterpoise. At the 
present day sal-ammoniac is often sublimed in earthenware vessels or large glass 
flasks, the crude salt being first mixed with 20 to 30 per cent, of its weight of 
powdered animal charcoal, then dried over a good fire, and next put into the stone¬ 
ware sublimation vessels, B and M, Fig. 117, placed in two rows over the fire-place, G. 


Fig. 117. 



Each of these vessels is 50 centims. in height; the openings arc surrounded by an 
iron plate properly fitted to the neck and provided with a flange upon which rest the 
earthenware vessels wherein the sublimed sal-ammoniac is condensed. When glass 
flasks are used, the height of these vessels is 60 centims. by 30 centims. diameter. 
Sixteen of these flasks, each charged with 9 kilos, of the mixture of sal-ammoniac and 
charcoal, are placed upon a furnace in cast-iron pots, which are filled with sand. 
The cover is in this case a leaden plate. The sublimation is carefully conducted, 
and goes on slowly, lasting about 12 to 16 hours. After this time, the leaden plates 
are removed, bungs or plugs of cotton-wool inserted, and the flasks allowed to cool 
very gradually, for as the salt expands on cooling the glass vessels may be broken. 
The cake of sal-ammoniac when quite cool is scraped clean with a knife, and after¬ 
wards presents a perfectly crystalline appearance. When it is desired to obtain the 
salt free from iron, the crude salt should be mixed, before the sublimation, with 
about 5 per cent, of superphosphate of lime, or with 3 per cent, of phosphate of 
ammonia; by this addition any chloride of iron is decomposed and left in the retort 
as phosphate. The sal-ammoniac of commerce is met with either in crystalline state 
or as a compact fibrous sublimed material; in the latter case the cakes or discs have 
a meniscus shape, weigh abroad from 5 to 10, but in England usually about 50 kilos., 
and exhibit the appearance of having been formed in layers. Crystalline sal- 
ammoniac is obtained by adding to previously re-cystallised sal-ammoniac a boiling 
hot and saturated solution of the same salt, so as to form a thickish magma, which 
is next placed in moulds similar in shape to those in use for making loaf-sugar; after 
draining, the loaf of sal-ammoniac is removed, dried, and packed in paper ready for 
sale. Besides the use made of sal-ammoniac in chemical laboratories, by pharma- 















238 


CHEMICAL TECHNOLOGY. 


ceutists and veterinary surgeons, it is industrially in demand for tinning, zincing, and 
soldering, in calico-printing and dyeing, in the manufacture of paints and pigments, 
in the preparation of platinum, snuff, and very largely in the preparation of a 
mastic—1 part of sal-ammoniac, 2 of sulphur, and 50 of iron-filings—used in joining 
steam-pipes, the sockets and spigots of iron gas- and water-pipes, &c. Sal-ammoniac 
is also employed in the preparation of pure ammonia liqiiida and ammoniacal salts. 

sulphate of Ammonia. It has been already mentioned that sulphate of ammonia— 

(NH 4 ) 2 S 0 4 , 

is met with native in small quantities in the mineral known as mascagnin, in larger 
quantities in the boracic acid of Tuscany, while it is also found in Boussingaultite. 

The inodes of preparing this salt from the ammoniacal water of gas-works, lant, the 
products of the dry distillation of bones, by the aid of sulphuric acid, or by double decom¬ 
position by means of gypsum or sulphate of iron, have been already given. The concen¬ 
tration of the weak solution by evaporation yields the crystalline salt, which, however, 
when obtained from liquors containing* tarry matters is usually of a deep brown colour, 
and has therefore to be purified by being dissolved in hot water, filtered through animal 
charcoal, and then re-crystallised, the best plan being to evaporate the solution rapidly, 
and remove the salt gradually by means of perforated ladles. The salt is then drained by 
being placed in baskets, and next quickly dried on heated fire-clay slabs, in which opera¬ 
tion any particles of tar are decomposed. Sulphite of ammonia obtained by saturating 
carbonate of ammonia solution with sulphurous acid gas is, when exposed to air, gradually 
converted into sulphate. Sulphate of ammonia is, industrially speaking, far the most 
important of the ammonia salts, because besides being very largely used in artificial 
manure mixtures, and by itself for the same purpose, it is extensively employed in alum- 
making, and is the starting-point of the preparation of chloride of ammonium, carbonate 
of ammonia, liquid ammonia, and other similar products. 

carbonate of Ammonia. The salt used in pharmacy and industry under this name is in 
reality sesquicarbonate of ammonia, and composed according to the formula 

> (NH 4 ) 4 C 3 0 8 , or 2 ([NH 4 ] 2 C 0 3 ) + C 0 2 . 

It is obtained either directly from the products of the distillation of bones, or by 
subliming a mixture of chalk and sal-ammoniac. 

Among the products of the dry distillation of bones is found a solid sublimate, essen¬ 
tially impure carbonate of ammonia, purified by sublimation. For pharmaceutical use 
carbonate of ammonia is prepared by submitting a mixture of either chloride of ammo¬ 
nium or sulphate of ammonia with chalk—4 parts of the ammonia salt, 4 of chalk, and 1 
of charcoal powder—to a low red heat. The product is a perfectly pure white salt; during 
the operation a large quantity of ammoniacal gas is evolved, which is either absorbed by 
water or by coke moistened with sulphuric acid. Kunheim decomposes the sal-ammoniac 
by subliming it with carbonate of baryta, chloride of barium being obtained as a by¬ 
product. When freshly prepared, carbonate of ammonia is a transparent crystalline 
mass, which, while absorbing water from the atmosphere, and evolving ammonia, is 
superficially converted into bicarbonate of ammonia (hydrocarbonate of ammonia, 

1 C 0 3 ). Owing to the penetrating odour emitted by this salt, it is known as smell¬ 
ing salts. Impure carbonate of ammonia is also used for cleaning woollen and other 
fabrics, for the removal of grease from cloth, and further, for the extraction of the orchil 
pigments. Pure carbonate of ammonia, besides its use in pharmacy, is an ingredient of 
baking and yeast powders. 

Nitrate of Ammonia. This salt, (jSTH 4 )N0 3 , is prepared by the double decomposition 
of solutions of sulphate of ammonia and nitrate of potassa. The sulphate of potassa 
is first separated, and the solution of ammonia nitrate having been concentrated by 
evaporation is left to crystallise, its crystalline form being similar to that of salt¬ 
petre. When dissolved in water this salt produces cold, and is therefore used in 
freezing mixtures; while the fact that when strongly heated it is converted into 
protoxide of nitrogen and steam (N 2 0 -fi 2ll 2 0) might perhaps render it of use in 
the preparation' of a blasting powder. 


SO AT. 


239 


Soap-making. 

soap. By soap we understand the product of the action of caustic alkalies upon 
neutral fats, and consequently soap may to all purposes be considered to consist of 
stearate, palmitate, and oleate of potassium or sodium. Although soap has been 
manufactured from a very remote antiquity, this industry did not attain its present 
development upon scientific and rational principles until Chevreul published the 
results of his researches on the fats, and before the discovery of Leblanc called the 
soda industry into existence. 

Raw Materials of soap-boiiing. The raw materials used in soap-boiling, as soap manufac¬ 
ture is usually termed in this country, are of two kinds, viz., fatty substances and 
solutions of caustic alkalies. Among the more important fatty substances are the 
following:—Palm-oil, of vegetable origin, met with in the fruit of a palm tree, 
Avoira elais or Elais guianensis ; according to others, however, this oil is derived 
from the Cocos butyracea , C. nucifera, and Areca oleracea , trees growing wild, and 
also cultivated in Guinea and Guiana. The colour of this oil is a red-yellow, its 
consistency that of butter, while it possesses a strong but by no means disagreeable 
odour, similiar somewhat to that of orris root. When fresh, this oil melts at 27 0 , but 
by becoming rancid as it is termed—that is, by its decomposition into glycerine 
and free fatty acids—its melting point rises to 31 0 and even to 36°. It is chiefly 
composed of palmitine mixed with a small quantity of oleine. Palmitine, formerly 
confused with margarin, is saponified by the alkalies and converted into palmitate 
of potassa or soda, while glycerine is set free:— 

Palmitine (tripalmitine), q) 3 } |_( Glycerine, j 0 3 , 

H ^t^P°oW) 3EOk 3 ‘ 3 ruImitateofpctLa.sj^.OJo. 

Palmitic acid is very similar to, and has often been confused with, stearic acid; 
the former is in a pure state a solid white crystalline mass, which fuses at 62°. 
Palm-oil often contains one-third of its weight of this acid in free state, and the 
quantity increases with the age of the oil. The red-yellow pigment of the palm-oil 
not being destroyed by its saponification, the soap made from this oil is of yellow 
colour, but if, previous to saponification, the oil is submitted to a bleaching process, 
that is to say, the pigment destroyed by chemical agents, such as the joint action 
of bichromate of potassa and sulphuric acid, the oil becomes nearly white, and 
yields, on being saponified, a white soap. 

The illipe, or bassia-oil, very similar to palm-oil, is obtained by pressure from the 
seeds of the Bassia latifolia, a tree growing on the slopes of the Himalaya. At first 
the colour of this oil is yellow, but by exposure to sunlight it becomes white. Its 
odour is not very strong, but rather pleasant. At the ordinary temperature of the air 
this oil has the consistency of butter; its sp. gr. is = o‘958; its melting-point 27 0 
to 30°. It is somewhat soluble in alcohol, readily in ether, and easily saponified by 
potassa and soda. In its saponification, oleic acid and two solid acids with a variable 
melting-point are formed. The galam butter produced by the Bassia butyracea , 
a tree met with in the interior of Africa, is sometimes confounded with palm-oil, to 
which it is very similar, but of a deeper red colour. Galam butter fuses at 20° to 21 0 , 
and is in its properties very much like palm-oil. Carapa oil and vateria tallow 
belong to the same class of fatty substances; the first, the product of the kernel of a 
species of Persoonia , a palm tree met with in Bengal and Coromandel, is a bright 


240 


CHEMICAL TECHNOLOGY. 


yellow coloured material, which at i8° separates into an oil and a solid fat; known 
as pine-tallow, Malabar tallow, and obtained from the fruits of the Valeria, indica , 
is a white-yellow waxlike-tallow, melting at 35 0 . Mafurra tallow is obtained by 
boiling in water the seeds or kernels of the mafurra tree found at Mozambique ; 
this seed, very rarely seen in Europe, is of the size of small cacao beans. Mafurra 
seed also occurs in the Islands of Madagascar and Isle de Reunion. The fat obtained 
from this seed has a yellow colour, the smell of cacao butter, and melts more readily 
than tallow. The fat of the seeds of the Brindonia indica , employed at Goa, instead 
of butter, also for medicinal purposes, and for use in lamps, is nearly white; melts 
at 40°, and is insoluble in cold, but somewhat soluble in boiling alcohol. Cocoa-nut 
oil, obtained from the kernels of the cocoa-nut (Cocos nucifera i C. buty raced), is 
largely used in the tropics, where the tree abounds. This oil is imported into 
Europe, and is also obtained here by pressing and by treating the kernels of 
the imported nuts with sulphide of carbon. It is white, has the consistency of 
lard, but possesses a disagreeable odour and a somewhat foliated texture ; its 
melting-point is 22 0 . Chemically considered this fat consists of a peculiar substance 
termed cocinin, with small quantities of oleine; by saponification the former yields 
glycerine-and cocinic acid (cocoa-stearic acid), C I3 H 2 60 2 . W. Wicke obtained in 
i860, 61 # 57 per cent, of fat from the kernels. During the last twenty years cocoa- 
nut oil has been largely used for soap-boiling, because it is an excellent material for 
the preparation of so-called fulling soaps. Tallow is obtained by melting the fatty 
matter deposited in the cellular tissue of the abdominal cavity of cattle and sheep. 
The hardness of the tallow depends partly upon the animals from which it is 
derived, partly upon the food they eat; if the food be fodder, the hardest tallow is 
produced, while if it consists of the refuse from breweries and distilleries the tallow 
is soft. Russian tallow owes its hardness to the fact that the cattle in that country 
are for fully eight months in the year kept on dry fodder. Generally tallow melts at 
37 0 , and contains 75 per cent, of its weight of solid fatty matter, stearin (tristearin) 
and palmitin (tripalmitin), the remainder being olein. If previous to being melted— 
that is, separated by the application of heat from the cellular tissue and membranes 
in which it is enclosed—tallow is preserved for too long a time, it obtains a 
bad odour, removed with difficulty. The operation known as tallow-melting can 
be performed in two ways, either by simply applying heat, which causes the 
cellular tissue to shrink and become dry, the fat being expelled; or the membranes 
and cellular tissue are destroyed by chemical agents, viz., the use of either 
sulphuric or nitric acid, or caustic ley. Among these methods, that of D’Arcet, in 
which sulphuric acid is used, and the operation carried on in closed vessels, is one 
of the best; the sulphuric acid decomposes the vapours which are given off and 
destroys their foetidity, while more tallow and of a better quality is obtained. The 
vapours are carried either into the furnace or into condensing apparatus. D’Arcet 
recommends that to 100 parts of cut-up tallow, 1 part of sulphuric acid and 50 
parts of water should be used. While the loss by the ordinary method of tallow¬ 
melting amounts to 15 per cent., it is only 5 to 8 per cent, when this method is 
employed. 

Lard, owing to its high price, is rarely used in Europe for making soap, but is 
largely employed in the United States, where, especially at Cincinnati, enormous 
quantities of lard are converted into a solid fat (42 to 44 per cent.), and into a fluid 
oil (lard oil, 56 to 58 per cent.) 


SOAK 


241 


Olive-oil is obtained from the fruit of tbe olive tree, Olea Europea , belonging 
to tbe natural order of tbe Jasminece , and largely cultivated in tbe whole of Southern 
Europe and tbe coastlands of North Africa. 

In order to obtain an oil of good quality it is essential that tbe olives should 
bo gathered when they are fully ripe, which happens in the months of November and 
December. Unripe olives yield an oil having a harsh bitter taste, while, again, over¬ 
ripe fruit yields a thick oil, readily becoming rancid. The method of oil extraction 
from olives as carried on in Southern Prance is the following:—The ripe olives are 
first reduced to pulp in a mill; this pulp is put into sacks made of strong canvas, 
or, better, of horsehair, and submitted to pressure. The first portion of oil thus 
obtained is the best, and is known as virgin oil, or kuile vierge. In order to eliminate 
all the oil as much as possible, the cake, after the first pressing, is treated with 
boiling water and again pressed. The oil thus obtained possesses a fine yellow 
colour, but is more liable to become rancid than the virgin oil. Notwithstanding the. 
second pressure the cake retains enough oil to make it worth while to submit it to 
further operation. Some kinds of olive-oil obtained by the second pressing are 
employed, under the name of Gallipoli oil, in dyeing Turkey-red. This oil has an 
acid reaction, consequent upon its containing free fatty acids, is turbid, rancid, and 
possessed of the property of forming with carbonates of alkalies a kind of emulsion, 
which in dyeing is known as the white-bath. The olive-oil used for the purpose of 
greasing wool in spinning is known as lampant-oil. Under the name of Huile d’enfer 
is understood the olive-oil deposited in the tanks, where the water used for adding 
to the olives about to be pressed is kept; it is used in the manufacture of soap. 
During the last few years it has become the custom to exhaust the olives with 
sulphide of carbon instead of pressing them. 

Fish-oil, seal-oil, obtained from the thick skin of several varieties of mammalia 
inhabiting the seas, especially of the colder regions of the globe, and belonging to the 
cetacea and phocena, varies somewhat in its properties, according to the mode 
of preparation and the animal from which it has been derived. The sp. gr. of this oil 
is 0*927 at 20 0 ; when cooled to o° it deposits solid fat; it is readily soluble in 
alcohol, and consists of oleine, stearine, and small quantities of the glycerides 
of valerianic and similar fatty acids. Fish-oil, besides being an important material 
in soap-making, is also used in tanning, tawing, and leather-dressing operations. 
Hemp-oil, obtained from the hemp-seed ( Cannabis sativa ) containing about 25 per 
cent, of oil, is chiefly used for making black, green, or soft soap. When fresh 
pressed, hemp-oil possesses a bright green colour, which in time becomes a brown- 
yellow. Linseed-oil, like the former a so-called drying oil, is obtained from the well- 
known linseed ( Linum usitatissimum ) containing about 22 per cent, of this oil, 
the sp. gr. of which is at 12° = 0*9395. This oil consists chiefly of a peculiar 
glyceride which on being saponified yields a fatty acid different from oleic acid; 
moreover, linseed-oil contains some palmitin. Castor-oil, from Ricinus communis, 
behaves when saponified very much like cocoa-nut oil. As yet, however, this oil is 
not used in soap-making. Eapeseed-oil, as it occurs naturally, does not yield so 
good a soap when saponified as when the oil is first converted into rapselaidin , 
which according to A. Muller, is done in the following manner :—To 1 cwt. of the oil 
is added 1 lb. of nitric acid diluted with to 2 lbs. of water; next some iron nails 
are added, and the acid fluid is well stirred through the oil with a wooden spatula. 
13 y the action of the nitrous acid set free, the oil is gradually converted into a yellow 
17 


242 


CHEMICAL TECHNOLOGY. 


fatty mass, which after having been left standing for some weeks in order to solidity, 
may be directly saponified with soda. The oleic acid largely obtained in the manu¬ 
facture of stearine candles is a very important material in soap-making. This acid 
is a solution of impure stearic and palmitic acids in oleic acid. 

Colophonium, the residue of the distillation of oil of turpentine, a yellow or 
black-brown coloured material, is largely imported from the United States for the 
purpose of preparing resin soaps, for sizing paper, and for the preparation of yellow 
soaps, which are resin and tallow saponified together in certain proportions. 

Ley. The other important material required for soap-making is the ley; that is to 
say, an aqueous solution of caustic potassa or caustic soda. Ley is not so much a 
constituent of soap as the material by which the chemical process termed saponi¬ 
fication is brought about. Usually the soap-boiler prepares the caustic ley, and 
formerly wood-ash or potash was used for this purpose, but at present soda is more 
extensively employed. The conversion of the alkaline carbonates into caustic 
alkalies' is effected by means of quick-lime; but abroad chemical manufacturers 
produce caustic soda, and sell it to the soap-boilers under the name of soap-stone. 


The preparation of soap-boilers’ ley from wood-ash is carried on in the following 
manner :—The sifted ash is placed on a paved floor, and moistened with enough water to 
render it somewhat pasty. This paste is then formed into heaps, constructed with an in¬ 
dentation, into which the caustic lime in quantities of one-tenth to one-twelfth of the weight 
of the ash is placed. Over the lime is next poured sufficient water to cause it to slake, 
care being taken to cover the lime up with ash. The ash and lime having been thoroughly 
mixed, are placed in a tank, shaped like a cone from which one-fourth of the narrow 
part is cut off, and fitted near the bottom with a tap. At a distance of some five inches 
from the bottom a false and perforated bottom is fixed, so that the ley can collect between 
the two bottoms. Under the tap a large iron tank is placed to receive the ley. The mixture 
of ash and lime having been placed upon a layer of straw upon the perforated bottom, 
and care having been taken to squeeze the mass together, water is poured over it for 
the purpose of lixiviating the material until completely exhausted. Usually three different 
lands of ley are prepared and kept, viz.—i. Strong ley, 18 to 20 per cent, of alkali; 
2. Middling strong ley, 8 to 10 per cent, of alkali; and 3. Weak ley, containing only 1 to 4 
per cent, of alkali. This weak liquor is commonly used instead of water for lixiviating 
a new ash and lime mixture. The sodium-aluminate obtained by the decomposition of 
cryolite is used in the United States under the name of “ Natrona refined saponifier,” for 
soap manufacturing purposes. Sulphuret of sodium may also be used instead of caustic 
alkali. 


Theory of saponification. Before Chevreul published his researches, it was supposed 
that fats and oils possessed the property of combining with alkalies. Chevreul 
found, however, that fats separated from their state of combination as soaps 
possessed properties differing from those existing before they were saponified, the 
fact being that the substances we are acquainted with as oil or fats are compounds 
of peculiar acids, stearic, palmitic, margaric, oleic, all non-volatile substances ; 
while certain fats which give off a peculiar odour contain in addition to these acids 
volatile fatty acids, as butyric, capric, capronic, valerianic, Ac. The volatile acids 
in the ordinary oils and fats are combined with a sweet material, discovered by 
Scheele, and known under the name of glycerine. 

According to Berthelot’s researches it is held that all the oils and fats which are 
used in soap-making are ethers of glycerine, C 3 H80 3 , that substance being viewed as a 
C U 1 

trivalent alcohol, 3 j^ 5 j 0 3 . Palmitin, for instance, the main constituent of palm- 
oil, is glycerlyl-tripalmitate, or tripalmitin, that is to say, glycerine in which three 

n tt 

atoms of hydrogen are replaced by the radical of palmitic acid, Jq gll q } 0 3 . 


SOAP. 


243 


Stearine (tristearine) and oleine (trioleine) have an analogous constitution. When 
the fats, take palm-oil for instance, are saponified with caustic alkalies, say caustic 
soda, the fat—that is, in chemical parlance, the ether—is decomposed into alcohol, i.e., 
glycerine, and sodium palmitate, i.e., soap, according to the following equation :— 

Tripalmitin { } °3 | 3 ( Glycerine, } 0 3 

and Caustic soda, 3 NaOH, j -2 | and ^ ^ sodium palm ; tate! ? , C.sH^O J Q 

The glycerine formed during the process of saponification remains, after the 
separation of the soap, dissolved in the mother-liquor from which it is prepared. 
It is clear that such fats as palm- and cocoa-nut oil, which in their ordinary state 
contain fatty acids, are more readily saponified than the perfectly neutral fats, viz., 
olive-oil and tallow ; while the oleic acid derived from the stearine candle manu¬ 
factories is readily saponified by carbonated alkalies. This observation applies to 
colophonium (resin), which consists essentially of a peculiar acid, pinic acid, but 
in these instances no real saponification takes place, inasmuch as no glycerine is 
formed. The decomposition of a fat by an alkali does not take place suddenly and 
throughout the whole of the fat a t once, in the manner of inorganic salts, but passes 
through several stages, the first being the formation of an emulsion of ley and fat; 
next fat acids and fat acid salts are formed, retaining the rest of the fatty matter in 
suspension; gradually the free fatty matter is saponified, and the fat acid salts are 
converted into neutral salts, or in other words, soap. 

When caustic potassa is used, soft soaps are produced, while the hard soaps 
result from the use of caustic soda. We distinguish soaps:— 
a. As hard soaps or soda soaps. 

/ 3 . As soft soaps or potassa soaps. 

According to the fatty substances used in soap-boiling, soaps are distinguished as 
tallow, oil, palm-oil, oleic acid, cocoa-nut, fish-oil, and resin soaps, &c. Technically, hard 
soaps may be divided into :— 

1. Nucleus soaps. 

2. Smooth soaps. 

3. Fulling soaps. 

The term nucleus soap designates the soap that after having been made and separated 
from the ley by the aid of common salt is boiled down to a uniform mass, free from air 
bubbles, and exhibiting after solidification small crystalline particles. The portion of the 
soap which does not separate in that state assumes, by becoming mixed with a large or 
smaller quantity of the impurities of the ley, a mottled appearance. The soap directly 
separating by the addition of salt into globules or nuclei is pure soap, free from any 
adhering ley, water, or glycerine. Smooth soap is obtained by boiling for some time with 
either water or weak ley, the soap taking up a portion of the water, and losing the crys¬ 
talline and mottled appearance. In the preparation of this soap it is first separated by 
means of salt from the mother-liquor (in saline solutions soap is insoluble), but after that 
separation the soap is boiled with weak ley. The only difference existing between the 
two kinds is, that the latter contains more water than the former. The fulling soap, at 
the present that chiefly met with in commerce, is essentially the worst kind of soap, as an 
insufficient quantity of salt is used, the result being that the entire contents of the boiling- 
pan are kept together. The process of boiling is continued until on cooling the mass 
solidifies. The soap is removed, cut into bars, and sold. Soap made from cocoa-nut oil 
possesses especially the property of being hard and dry, notwithstanding that it contains 
a large amount of water; consequently the use of cocoa-nut oil, both alone and with other 
fats to which it imparts its property, is greatly on the increase. Soaps of this kind will 
produce 250 to 300 parts of soap from 100 of oil. 

Chief Varieties The German tallow soap or curd soap is essentially a mixture of stearate 

of Soap. of soda and palmitate of soda, and is commonly prepared indirectly by first 
saponifying tallow with caustic potassa, and next converting, by means of common salt, the 
stearate and palmitate of potassa into the corresponding soda compound. 


244 


CHEMICAL TECHNOLOGY. 


The soap-boiling pan employed is somewhat conical in shape. It is made of cast-iron, and 
provided at the top with a highlintel or bulwark to prevent any fluid boiling over. Supposing 
it to be intended to convert io cwts. of tallow into soap :—Into the cauldron is first poured 
about 500 litres of strong lye at 20 per cent. ( r= 1-226 sp. gr.) ; next the tallow is added, 
and a wooden or iron lid having been fitted to the cauldron, the fire is kindled. When 
ebullition sets in, it is kept up, with occassional stirring of the contents of the cauldron, for 
five consecutive hours. The materials in the cauldron are converted into soap-glue, as it 
is termed, a gelatinous mass, which, if the operation has been well conducted, ought not, 
upon the addition of fresh ley, to become thin, while it also should not flow in drops, but 
similarly to treacle from a spatula. The production of this substance is promoted by adding 
oil of tallow to the ley gradually and in small portions at a time. 

Mege-Mouries recommends either yolks of eggs, bile, or albuminous compounds. As proved 
by the researches of F. Knapp, it is always advantageous to first convert the fat, with the 
requisite quantity of ley, into an emulsion, and to leave the ley either not heated at all, or 
only to 50° in contact with the fat, so as to saponify first slowly in the cold and to finish 
off with ebullition. When caustic soda ley is used it is of a density — io° to 12° B. 
(— 1*072 to 1-088 sp. gr.) When the saponification is complete the operation of fitting or 
parting is proceeded with, and consists in adding 12 to 16 lbs. of salt to 100 of tallow. 
The soap is kept boiling until the soap-glue has become a greyish mass, from which 
the mother-liquor or under-ley readily separates, the latter being let off by a tap ; or, if 
no tap is fitted to the cauldron, the soap is gradually ladled over into the cooling-tank. 
The addition of salt not only aims at the separation of the soap from the ley, but also at 
the partial conversion of the potassa into soda-soap. If the soap-glue has been removed, 
it is again put into the cauldron, and there is added a moderately strong ley and heat again 
applied. The soap again becomes quite fluid, but consists chiefly of soda-soap glue. The 
ebullition is kept up, and during its continuance fresh ley and salt are added alternately. 
By continued boiling the soapy mass becomes more and more concentrated; as soon as 
the foaming ceases, and the whole mass is in a steady ebullition, if is again ladled over into 
the cooling-tank, or the mother-liquor is tapped off. The object to be gained by this 
second boiling is the conversion of the material into a uniform mass free from air-bubbles; 
another is promoted by beating with iron-rods. The hot soap is next placed in a wooden 
box, so constructed that it can be taken to pieces; upon the bottom of this box, which 
is perforated, a piece of cloth is stretched, so as to allow of any adhering ley running 
off. When the soap is cool the box is taken to pieces, the soap cut into bars, and these 
placed in a cool, dry room. The cutting of the soap into bars is now effected by mac hin ery; 
formerly it was performed by hand with a peculiar tool, a copper-wire with suitable 
handles, such as cheesemongers sometimes use. 10 cwts. of tallow yield on an average i6| 
cwts. of soap, which by drying loses some 10 per cent. As it is impossible, even with re¬ 
peated applications of salt, to convert potassa-soap completely into soda-soap, the German 
nucleus, or Kernscifc , is always mixed with a considerable quantity of potassa-soap, to 
which it owes its peculiar softness. According to the researches of Dr. A. C. Oudemans 
(1869) only half the potassa is converted into soda-soap. 

oiive-oii soap. This kind of soap, also known as Marseille, Venetian, or Castilian soap, is 
chiefly prepared in the southern parts of Europe. The olive-oil is frequently mixed with 
other kinds of oil, such as linseed, poppy-seed, cotton-seed oil, &c. Two kinds of ley are 
employed in the prepapation of this soap: the first ley is only a caustic soda solution, 
and used for fitting or preparatory boiling; the other ley is mixed with common salt, 
and intended to effect the separation of the soap. The preparatory boiling aims at the 
formation of an emulsion or the production of an etat globulaire , whereby the contact of 
oil and alkali is greatly promoted, and a real soap-glue ultimately results. In order to 
remove the water from this material as much as possible, a ley containing common salt is 
employed, and lastly by a third boiling the saponification is rendered complete. By the 
use of the ley containing common salt it is possible to keep the soap-glue in such a con¬ 
dition that it can take up alkali without combining with the water. The preparatory boiliim, 
or fitting, is carried on in large copper vessels, capable of containing 250 cwts., the 
caustic soda employed for this purpose having a strength of 6° to 9 0 B. (z= 1-041 to 1-064 
sp. gr.) The ley is brought to ebixllition first, and the oil to be saponified is next 
added, care being taken to stir the mixture in order to promote the reaction. Gradually 
the mass becomes thick, and as soon as black vapours arise, due to the decomposition of 
a small quantity of the soap-glue by coming in contact with the very hot copper, there is 
added the stronger ley of 20° B. (1-157 sp. gr.) If it is intended'' to produce a blue- 
white soap, some sulphate of iron is added. As soon as the mass has become sufficientlv 
thick, the soda-ley mixed with salt is added. After some hours the soap entirely separates 
from the mother-liquor, which is then run off, and fresh ley added also containing common 
salt. The filial boiling is then proceeded with, the ley having a strength of 20”to 28° B. 
The ebullition is continued gently until the alkali is exhausted, when the mother-liquor 


SOAP. 


a +5 


iS again run off, and fresh ley mixed with common salt again added; this operation is 
repeated some fonr or six times, when the soap is at last quite ready. This stage is indi¬ 
cated by the absence of all smell of oil and the peculiar grain of the mass, which is left 
to cool; but if sulphate of iron has been added, it is necessary to stir the soap continuously 
until nearly cold, in order to produce the mottled appearance due to the formation of sul- 
phuret of iron from the sulphate by the action of the sulphuret of sodium of the soda-ley. 
Mottled-soap is produced in England by adding a concentrated solution of crude caustic 
soda containing sulphuret of sodium to the liquid soap, previously impregnated with 
sulphate of iron. When nearly cold the soap is placed in wooden boxes and left to com¬ 
pletely solidify. After ten to twelve days it is ready for being cut into bars. 64 litres of 
oil, — 58 to 60kilos., yield 90 to 95 kilos, of soap. White-oil soap is prepared in a similar 
manner, but purer materials are employed. A good sample of Marseilles mottled soap 
should contain:— 

I. II. 

Fat acids .63 62 

Alkali. 13 n 

Water.24 27 


100 100 

oieic Acid soap. Is obtained from crude oleic acid, a by-product of stearine candle 
manufacture. The oleic acid produced by the distillation process is less suitable for soap¬ 
making purposes. Oleic acid is saponified simply by being mixed with a strong solution 
of carbonate of soda, or by the application of caustic soda. In the use of the carbonate 
of soda, however, there is the disadvantage of the effervescence due to the evolution of 
carbonic acid, and consequent boiling over or spilling of the materials. Pitman uses the 
carbonate of soda in a dry state. Heat is best applied by Morfit’s arrangement, in which 
steam is passed through a system of pipes moved by machinery and acting as stirrers. 
Resin is sometimes added. As soon as the mass has acquired sufficient consistency, and the 
effervescence ceases, the soap is put into moulds to cool and solidify. "When caustic soda 
is used, half the ley (sp. gr. 1*15 to 1-20=20° to 25 0 B.) is first poured into the cauldron 
and brought to ebullition, next the oleic acid is added, and as soon as the soap-glue is 
formed, the other half of the ley is put in, and the ebullition continued until the soap is 
formed. The separation from the mother-liquor is greatly promoted by the addition of 
some salt. The soap is poured into moulds to cool and solidif y. In order to impart greater 
hardness to the soap, some 5 to 8 per cent, of tallow is added to the oleic acid. 100 
kilos, of oleic acid yield from 150 to 160 kilos, of soap, which, when well made, consists in 


100 parts of:— 

Fat acids.66 

Soda.'. 13 

Water .21 


100 

r.csrn-Tai'.ow Soaps. Colophonium and ordinary fir-tree resin combine at boiling heat more 
readily with alkalies than fats and oils; but the compounds obtained by treating resins 
alone with alkalies are not soaps in a chemical sense, nor have they the appearance or 
properties of soap. When tallow is saponified with a portion of resin, a true soap is 
obtained. In England resin-tallow soap is manufactured very largely by first preparing a 
tallow-soap, and when this is ready adding to it about 50 to 60 per cent, of the best resin 
previously broken into small lumps. The mass is thoroughly stirred, and after the resin 
has become incorporated with the tallow, the mother-liquor or under-ley is run off, and 
the soap-making finished by boiling with a quantity of fresh ley at 7 0 to 8° B. The inso¬ 
luble alumina and iron soaps having been removed as scum from the top of the liquid, the 
hot soap is poured into moulds made of wood or sheet-iron ; sometimes palm-oil is added 
in order to improve the colour of the soap. Usually, palm-oil is not saponified alone, hut 
is added to tallow; by treating a mixture of 2 parts of tallow and 3 parts of palm-oil with 
potassa or soda-ley in the ordinary manner, and by mixing this soap with a resin soap 
prepared from 1 part of resin and a proper quantity of potassa-ley, the German palm-oil 
soap is obtained. 

Fuiiing-Soaps. As it is possible to incorporate soda-soaps with a certain quantity of water 
without impairing the appearance, the soap-boilers at the present day only prepare so- 
called fulling-soaps, that is, such as are not completely separated from the under-ley by 
the aid of salt. These soaps contain, in addition to water, glycerine and the salts existing 
in the under-ley. It is owing to the large amount of water contained that the soap-boiler 
is enabled to sell cheap soaps notwithstanding the very greatly increased price of fatty 











CHEMICAL TECHNOLOGY. 


246 

substances. Soap of this kind (in Germany known as Eschweger soap) appears when 
freshly made quite hard and dry, though containing such a large quantity of water. It is 
possible to make from 100 kilos, of fatty matter 300 kilos, of good, bright, hard soap. 

The manufacture of cocoa-nut oil soap resembles that of the other kinds of soap. 
With a weak ley cocoa-nut oil does not form the emulsion common to other soaps, 
but swims on the surface as a clear fat; when, by boiling, the ley has reached a 
proper consistence, the oil suddenly saponifies. A strong soda-ley is used in the 
preparation of this kind of soap. Cocoa-nut oil in saponifying does not separate 
from the under-ley, therefore potash-ley is never employed. To prevent the separa¬ 
tion of the soap from the mixing, the quantity of caustic -ley used must be accurately 
measured. Pure cocoa-nut oil soap hardens quickly. It is white, like alabaster, 
shiny, soft, and easily lathered; it has, however, a peculiarly unpleasant smell, 
which cannot be entirely masked by any perfume. Cocoa-nut oil is seldom used 
alone, but usually as an addition to palm-oil and tallow. This kind of soap can be 
made without boiling, by merely heating to 8o° 0., by means of steam, to melt the 
fats, a strong soda-ley being added, and the mixture quickly stirred. This is known 
as the “ cold method,” and soap can be thus prepared in large quantities in a short 
time, and is generally hard and dry. When exposed to the air for a month or so, 
the soap loses considerably in weight, and becomes effloresced superficially. B. Unger 
(1869) prepares a soap in the following manner :—He saponifies palm-oil with soda- 
ley and salt as usual. The product is palmitate of soda. At the same time cocoa- 
nut oil is saponified by means of carbonated and caustic soda-ley ; this is added to 
the palm-oil soap, and they are boiled. As a rule there are taken 2 parts of palm-oil 
to 1 part of cocoa-nut oil; and to 100 parts of the latter there are added 14*3 parts of 
caustic soda (Na 2 0 ) and 12*8 parts of carbonate of soda. According to Unger’s 
experiments, this soap contains 5 mols. palmitate of soda, 1 mol. carbonate of soda, 
and x mol. water. The “marbling” or “mottling” is effected in the following 
manner:—Colouring matters, oxide of ircn, brown-red, Frankfort-black, are mixed 
with a small portion of soap ; this is poured into the rest of the soap, with which 
it forms layers of unequal thickness. The entire mass is now stirred, and by 
this means a marbled or grained appearance imparted. 

soft-soap. As before mentioned, potash forms with fats and oils only a so/^-soap, 
which does not dry when exposed to the air, but on the contrary absorbs water, 
remaining constantly like a jelly. As .a rule, these so-called soaps are impure 
solutions of oleate of potash in an excess of potash-ley, mixed with the glycerine 
separated in the saponification. Soft-soaps can be prepared only with potash- 
leys, although in practice 1 part of soda-ley is substituted for a part of the potash 
to assist in somewhat hardening the soap. There is no separation of the soap 
from the under-ley, which contains all the impurities; consequently these are disse¬ 
minated in the soap. 

In consequence of the solubility and cleansing properties of soft-soap, its use is 
preferred to that of soda-soap in the manufacture of cloth and woollen articles. It 
will have been seen that the difference in manufacturing hard- and soft-soaps 
consists in employing potash-ley for the latter, and soda for the former. Wood-ash 
is not used in preparing the potash-ley, but always pure potash ; the preparation 
follows the usual method with caustic lime. The fats used are mixtures of the 
vegetable and animal oils, as the fish-oil known as “ Southern,” with rape, hemp, and 
linseed oils. The particular oil used varies according to the time of the year and 


SOAP. 


247 


market price: m winter the soit ons are employed; in summer the firmer oils. 
Soft-soap is generally used for fulling and scouring; but abroad it is sometimes 
used for washing linen, to which it imparts a most disagreeable fishy odour, hardly 
concealed by any amount of perfume. The best soft-soap is made from hem] -seed 
oil, this oil imparting a green tinge, which, however, can be imitated by adding 
indigo to inferior soaps. Summer soap, as it is termed, contains, owing to the fat 
employed, more palmitate of potash in proportion to oleate than the winter soap. 
Sometimes saponification is effected with a mixture of hemp- and palm-oil or 
tallow, of train-oil and tallow, &c. 

The boiling of the soft-soap commences with a strong ley containing 8 to 10 per 
cent, potash, by which an emulsion is formed. The scum is dashed about with a 
stick, the beating-stick, and by this means all the alkali is caused to be taken up. 
A fresh ley is then added, and the boiling continued, until the soap upon cooling 
stiffens into a clear tough mass. When the soap contains too much caustic alkali, 
which can be ascertained by the taste, more oil is added. The clear-boiling now 
commences, during which the excess of water is removed. To avoid lengthy 
evaporation a concentrated ley is employed, and the soap, instead of bubbling up, 
has its surface covered with blisters as large as the hand; these blisters are termed 
leaves. When the boiling is finished—ascertained by placing some of the soap to 
cool on a glass plate, from which, if firm, it can be separated—the soap is cooled, 
and stored in barrels. 

Soft-soap will take up a considerable quantity of water-glass solution without 
alteration. Recently, for fulling, there has been added to the soft-soap a solution of 
sulphate of potash, or a mixture of alum and common salt and also potato-starch. 

various other Soaps. Another soap is prepared from hogs-lard, and when scented with oil 
of almonds or essence of mirbane (nitrobenzol) is sold as almond-soap, and as a cosmetic. 
A soap is made from the grease of sheep’s-wool. The so-called bone-soap is nothing more 
than a mixture of the usual hard or cocoa-nut oil soap with the jelly from bones. The bones 
are first treated with muriatic acid to separate the phosphate of calcium. A variety of 
bone-soap is the Liverpool common soap. Flint-soap is an oil- or tallow-soap with which 
siliceous earth is mixed. When powdered pumice-stone is substituted for the siliceous 
earth, the soap is called pumice- soap. In America as well as in England a water-glass 
solution is substituted for the siliceous earth, although according to Seeber the result is 
not so efficacious. Cocoa-nut oil soap, however, containing 24 per cent, silicate of soda 
and 50 per cent, water, is very firm. In the United States water-glass is added to the soap 
when, still hot from the boiling-pan, it is poured into the moulds. The water-glass solu¬ 
tion is of a density = 35 0 B. (— 1*31 sp. gr.); the proportion of soap is 60 per cent. This 
kind of water-glass soap generally sets hard. Recently cryolite and aluminate of soda 
have been employed. 

Toilet soaps. On account of the reduction in the duty toilet soaps are now very 
largely in demand. They are generally made by re-melting and perfuming 
common soap. English toilet soap is considered the best, as that of France and 
Germany being perfumed while cold is not so equable a product. 

There are three modes of preparing toilet soap, viz.:— 

1. By re-melting raw soap ; 

2. By the cold perfuming of odourless soap; 

3. By direct preparation. 

1. In the method of re-melting, good raw soap is scraped into a boiling pan, and 
after melting and skimming the perfume is added. The soap is then cast in moulds 
of the required form. 2. In the method of perfuming in the cold, odourless soap is 
cut into fine shreds by a machine; the perfume is then added, and the soap is 


248 


CHEMICAL TECHNOLOGY. 


passed between rollers, the sheets or bars thus formed being cut into tablets. 
Struve, of Leipsic, has invented a machine by means of which soap is stamped into 
the shape required. 3. The direct preparation of toilet-soap consists in colouring 
and scenting pure white common soap without an intervening cooling. The colour¬ 
ing materials are—for red, cinnabar, coralline, and fuchsine ; the violet tar colour 
for violet; for blue, ultramarine ; for brown, a solution of raw sugar or caramel. 
Windsor soap is prepared in the following manner:—40 pounds of mutton tallow 
and 15 to 20 pounds of olive- oil are mixed with soda-ley marking 19 0 , making a 
soap of 15 0 ; finally, with ley marking 20°, when the soap is of the consistency of 
marrow. The excess of ley is then neutralised. When the soap is set it is allowed 
to stand six to eight hours, and during this time most of the under-ley separates. 
It is then placed in a flat form, and pressed until no fluid exudes. It is scented 
with cumin oil, bergamot, oil of lavender, oil of thyme, &c. Moist sugar is used 
to impart the brown colour. Rose soap, savon d la rose , is manufactured by melt¬ 
ing the ingredients of three parts of oil-soap with two parts of tallow soap, and 
sometimes water; the perfume is attar of roses, oil of. roses, or gilliflower-water, 
the colouring matter being generally cinnabar. Shaving-soap must not contain 
free alkalies. It is sometimes prepared by boiling fat acids with a mixture of the 
carbonates of soda and potash. Lather-soaps have in equal volume only half the 
substance of the other soaps. Palm- or olive-oil soap is melted with an addition 
of one-third to one-eighth the volume of water, and the mass stirred until it has 
increased to double the volume. It is then placed in a mould. It should be 
remarked that the oil-soaps, and not tallow-soaps, are the true formatives of the 
lather-soaps. 

Transparent Soap. Ordinary dry tallow-soap is cut into splinters and heated with an 
equal weight of alcohol, in which the soap dissolves. The mixture is allowed to 
cool; therewith all impurities are thrown down, and the clear fluid is placed in the 
moulds, where it has to remain three to four weeks to harden. Tincture of cochi¬ 
neal and aniline red are employed for colouring transparent soaps, and also 
Martin’s yellow. The perfume is chiefly oil of cinnamon, sometimes oil of thyme, 
oil of marjoram, and sassafras-oil. Glycerine-soap is prepared from an alcoholic 
solution of ordinary soap, to which glycerine is added. Or 5 cwts. of soap with an 
equal quantity of glycerine are heated by steam in a copper vessel. The mixture 
is placed in moulds, and allowed to set in the usual manner. A solution of soap 
in an excess of glycerine (35 :30) forms fluid glycerine-soap, which is of a clear 
honey consistency. Both varieties are perfumed with essential oils. 

uses of Soap. Soap is used for cleansing purposes in washing, in bleaching cloth and 
woollen materials; for the preparation of lithographic tints, &c. The cleansing proper¬ 
ties of soap are due to the alkalies it contains. The alkali, although combined with the 
fat acids, loses none of these properties, which are in fact included in the combination of 
the alkali with the fatty substances of the dirt to be removed. The explanation of the 
action chemically, according to Chevreul, is the following .—The neutral salts formed by 
the alkalies and the fat acids, stearates, palmitates, and oleates are decomposed by the 
water, whereby insoluble double fat acid salts are separated, while the alkali is set free. By 
means of the free alkali the impurities clinging to the materials are removed, and taken 
up by the fat acid salts, the suspended dirt being thus contained in the lather. 

Soap Tests. The greater the quantity of fat acids combined in the soap, the hio-her is its 
value. A normal soap, besides alkaline fat acids, should only contain free "water the 
quantity of which gives a means of estimating the value of the soap. It is in the power 
of the soap-maker to manufacture 300 parts of a good hard soap out of 100 parts of fat. 
When too small a quantity of water is contained the soap becomes too hard, and 


BORACIC ACID. 


249 


much labour is lost in obtaining- a lather. If, on the other hand, water is hqld in too large 
a quantity there is a great loss of material. The degree of hardness of the soap forms, 
therefore, another means of estimating its value. Many soaps contain 2 to 3 per cent, 
glycerine. But the proportion of water and the hardness of a soap are not the only 
means of estimation, there still remains the estimation of the neutral fat acid alkalies, 
the free alkali, common salt, or unsaponified fat in the residue left after the drying of the 
soap. According to W. Stein, the presence of free alkali may be ascertained by means 
of calomel, or according to Naschold, by nitrate of protoxide of mercury. Uncombined fat 
retards the formation of a lather, and after a time imparts to the soap a rancid odour. 
But the worth of a soap can only be accurately ascertained by means of chemical 
analysis. 

insoluble Soap. All soaps that have not potash or soda for a base are insoluble in water. 
Many of the insoluble soaps are of technical importance. 

Calcium-soap plays an important part in stearine-wax manufacture. It is made either 
directly by saponifying fat with hydrate of lime, or by treating soluble soap with a solu¬ 
tion of a salt of lime; this soap is formed to some extent when ordinary soap is dissolved 
in hard water. Barium- and strontium-soap are similar to calcium-soap. Magnesium- 
soap is made directly with difficulty; it may be obtained indirectly by dissolving ordinary 
soap in sea-water. Aluminium-soap is without doubt an insoluble soap; argillaceous 
earths will not saponify fat unless aluminate of soda or potash is present. Aluminium 
soap is used in waterproofing. According to Jarry, wood impregnated with oleate or 
stearate of aluminium is impervious to moisture. Lately many materials have been ren¬ 
dered waterproof bv being dipped into a solution of acetate of aluminium, and then into 
a soap solution, aluminium soap being thus formed. 

Manganese-soap is prepared by the addition of sulphate of manganese to ordinary soap, 
or by boiling carbonate of manganese with oleic acid. It is usually applied as a siccative. 
Zinc-soap is prepared by the double decomposition of sulphate of zinc and soap, or by the 
saponification of zinc-white with olive-oil or fat, forming a yellow-white mass. Zinc-soap 
is used as an oil-colour, and also as zinc-plaster. Lead-soap or lead-plaster is made ha¬ 
ndbill -white-lead to olive-oil, or acetate of lead to soap solution. Tin-soap is prepared 
by the double decomposition of chloride of tin with soap. Copper-soap, formed by the 
addition of sulphate of copper solution to soap, is soluble in ether and oil, less so in alcohol; 
it is used in preparing water-colours. It may be made by boiling oleic acid with 
carbonate of copper. Mercury or quicksilver-soap is prepared from chloride of mercury 
and soap; it is difficult to dry ; is white, but when exposed to air and light turns grey. 
Mercury-soap was formerly known as quicksilver-soap and quicksilver-plaster. Silver, 
gold, and platinum-soaps, are severally prepared by double decomposition; but they are 
not much used. Gold-soap is employed in gilding porcelain; and silver-soap for dark¬ 
ening the hair. 


Boric or Boracic Acid, axd Borax. 

Boracic acid occurs native as sassolin, H 3 B0 3 ; in 100 parts :— 

Anhydrous boracic acid, B 2 0 3 . 56*45 

Water.43'55 

100*00 

and further in the following minerals 


Boracite, or borate of magnesium with' 
chloride of magnesium .. 

- with 6 

2*5 per cent. 

Boracic acid 

Bhodicite, or borate of calcium .. .. 

• >> 

30 to 45 ,, 

y y 

Hayescine, Tiza, or borate of lime 


30 to 44 ,, 

yy 

Ilydroboracite. • • 

5 > 

47 

y y 

Tincal or borax, borate of soda .. 

y y 

36*53 

y y 

Datholite, or boro-silicate . 

y y 

18 ,, 

yy 

Botryolite. 

y y 

20-35 

y9 

Axinite .. • • . 

y y 

2 to 6*6 ,, 

•> 

Tourmaline . 

y y 

2 to n*S ,, 











250 


CHEMICAL TECHNOLOGY. 


Boracic acid is found also in small quantities in many mineral waters and in. sea¬ 
water. Larderellite, or borate of ammonia, and lagonite, or borate of iron, are both 
found in very small quantities in Tuscany, but are interesting to mineralogists only. 

Boracic acid is found as sassolin in many volcanic regions mixed with sulphur, 
and in the hot springs of Sasso, in Tuscany, and also between Yolterra and Massa 
Maritima in the clefts and rents of the volcanic formation of rock. Hoffer and 
Mascagni (1776), first mentioned the occurrence of boracic acid in the waters sub¬ 
jected, in the clefts of the rock, to the sulphurous exhalations. The little pools 
formed in these clefts are variously known as fumacchi , fumaroles, soffioni , and 
mofetti. The boracic acid deposits in some cases cover an extent of six miles. 
Since 1818 artificial soffioni have been constructed, and the benefit derived by the 
country from the introduction of the industry is immense. The first artificial lake 
was situated near Monte Cerboli, and the product was for some time known as 
Larderellite, from the owner’s name, LardereL The production from these works 
alone amounted in 1839 to 717,333 kilos., and in 1867 to 2,350,000 kilos. The 
increase has been greatest since 1854, owing to the energy with which Grazzeri and 
Durval entered upon the construction of the artificial soffioni. 

The soil of the natural lakes, or beds of the natural soffioni, are of a slimy 
formation, and have a peculiar seething movement due to the escape of the 
sulphurous vapours from the fumaroles or vents. According to Payen, this vapour 
or steam may be considered as condensed and as non-condensed, the former con¬ 
taining besides water, sulphate of lime, sulphate of magnesia, sulphate of ammonia, 
chloride of iron, hydrochloric acid, organic substances, a fishy-smelling oil, clay, 
sand, and a small quantity of boracic acid. The non-condensed vapour consisted of— 


Carbonic acid .0*5730 

Nitrogen .0*3480 

Oxygen .0*0657 

Sulphuretted hydrogen .. .. 0*0133 


Payen is of opinion that the vapours contain no boracic acid, while C. Schmidt 
thinks otherwise, as the vapours, when condensed without contact with the water 
of the soffioni, yield boracic acid. The condensed vapours contain o*i per cent, 
boracic acid. 

Theory of the Formation Dumas and Payen found an explanation of the formation of 
Native Boracic Acid. volcanic boracic acid upon the hypothesis that there exists in 

the interior of the volcano or beneath the under-crust of the earth a layer of sulphide 
of boron (B 2 S 3 ), which under the action of the mineral waters becomes converted 
into boracic acid and sulphuretted hydrogen. P. Bolley gives the action as similar 
to that occurring in the formation of sal-ammoniac, a very common mineral in 
volcanic regions. Professor Becchi, of Florence, found nitride of boron (BN) in 
one of the under-strata, from which he prepared artificially by means of steam 
ammonia and boracic acid. Also Warrington (1854) and Popp (1870) attributed the 
appearance of boracic acid and ammonia in volcanoes to the decomposition of nitride 
of boron by evaporation. Eecently (1862) Becchi has obtained boracic acid by the 
decomposition of borate of calcium in a stream of superheated steam. 

T Boracfc U Add n of Tlie most general method of obtaining boracic acid is by the evapora¬ 
tion of the water of the natural or artificial soffioni. The water is either naturally or 





BORACIC ACID. 


251 


I 

artificially introduced into the natural fumaroles, as these sometimes do not re¬ 
supply themselves with sufficient rapidity. As soon as the water has absorbed a 
considerable quantity of the vapours it is removed and placed in a large mason- 
work cistern; this cistern is imbedded in the soil near the fumaroles, and the 
natural heat is sufficient to cause evaporation. The vapours are condensed in a 
wooden chimney. The separated impurities, gypsum, &c., remain in the cistern. As 
soon as the solution is of a sp. gr. = 1*07—1*08 at 8o°, it is poured into leaden 
crystallising vessels where the boracic acid crystallises out. The mother-liquor is 
evaporated to dryness. It should be remembered that the entire operation is con¬ 
ducted with the assistance of the natural heat of the fumaroles only. Occasionally 
the boracic acid is only present in the natural waters to 0002 of a part; and in 
these cases fuel must be used in the evaporation, which therefore entails the expense 
of carriage, as fuel is very scarce near the soffioni. Charcoal is generally used. 
But by this means an acid is obtained, containing about 70 to 80 per cent, hydrated 
boracic acid, with 10 per cent, impurities. Clouet removes the impurities by treat¬ 
ment with 5 per cent, of ordinary hydrochloric acid. Boracic acid for pharma¬ 
ceutical purposes may be prepared by dissolving 1 part of borax in 4 parts of 
boiling water, and decomposing the solution with one-third part of sulphuric, or 
better with half part of hydrochloric acid of 1*2 sp. gr. The acid separates on 
cooling, and can be purified by crystallisation. 

In 100 parts of commercial boracic acid from Tuscany, H. Yohl (1866) found:— 



1. 

2. 

3 - 

4 - 

5 - 

Boracic acid. 

45*1996 

47*6320 

48*2357 

45*2487 

48*1314 

Water of crystallisation. . 

34*8916 

35*6983 

37*2127 

34*9010 

38*0610 

Water . 

4 ' 5 OI 9 

2*5860 

1*0237 

4*4990 

1*5240 

Sulphuric acid. 

9*6135 

7*9096 

8*4423 

9*5833 

7*8161 

Silicic acid . 

0*8121 

1*2840 

o*6ooo 

0*2134 

0*0861 

Sand. 

0*2991 

0*5000 

0*1000 

07722 

o* 4 i 54 

Oxide of iron. 

0*1266 

0*1631 

0*0920 

0*1030 

0*0431 

Protoxide of manganese.. 

0*0031 

traces 

traces 

traces 

traces 

Alumina. 

0*5786 

0*0802 

0*0504 

0*1359 

0*1736 

Lime. 

0*0109 

0*3055 

0*5178 

traces 

traces 

Magnesia. 

0*6080 

traces 

traces 

traces 

traces 

Potash . 

0*1801 

0*2551 

0*5178 

0*6140 

o* 4 i 34 

Ammonia. 

2*9891 

3 * 5 i 65 

3*5169 

37659 

3*0890 

Soda. 

0*0029 

traces 

traces 

traces 

traces 

Chloride of sodium.. 

0*1012 

0*0595 

0*0401 

0*1671 

0*0321 

Organic substances and loss 0*0918 

0*0101 

0*0101 

— 

0*0449 


100*0000 

100*0000 

100*0000 

100*0000 

100*0000 


Pr o’? e Boracic d Ackt es Pure boracic acid crystallises in mother-of-pearl-like leaves^ 
which at ioo° C. lose half their water of crystallisation without melting, the other 
half being driven off at a red-heat. After cooling the anhydrous acid appears as a 
hard, transparent, brittle glass of 1*83 sp. gr. 1 part boracic acid dissolves in 25*6 
parts water at 15 0 C., and in 2*9 parts at ioo° C. At 8° a saturated solution has a 
sp. gr. of 1’014. It imparts a green colour to the flame of the spirit-lamp. In a 


















252 


CHEMICAL TECHNOLOGY. 


chemical point of view it is similar to silicic acid. Boracic acid is largely used in 
the preparation of borax, for glazing porcelain, and mixed in a weak aqueous solu¬ 
tion with sulphuric acid in the preparation of the wicks of stearine and paraffin 
candles. It is also used for colouring gold, for decorating iron and steel, in the 
preparation of flint-glass, and artificial precious stones. In 1859 boracic acid was 
used in the preparation of hydrated oxide of chromium, known under the name of 
Pannetier’s-green, Vert-Guignet, &c. 

Borax. Borax, or bi-borate of soda, when anhydrous according to the formula 
Na 2 B 4 0 7 , contains in 100 parts:— 


Anhydrous boracic acid (B 2 0 3 ) .. .. : 69*05 

Soda (Na 2 0 ).30*95 


100*00 

It is found native in Alpine lakes, on the snow-capped mountains of India, China, 
Persia, in Ceylon, and Great Thibet. It is found in large quantity at Potosi in 
Bolivia, where the Borax Lake , according to Moore’s analysis (1870) contains in 1 litre 
of its water (sp. g. = 1*027), 3*96 grammes of borax. Pyramid Lake, Humboldt Co., 
Nevada, yields also large quantities. By the heat of the sun the water of the borax 
lakes is evaporated and the borax crystallises out, and is gathered and brought into 
commerce under the name of Tincal. It appears in small six-sided crystals, more or 
less smooth. The Clear Lake in California, to the north of San Prancisco, yields 
daily 2000 kilos, of borax. 

Pormerly tincal was purified by washing in water containing soda to free the 
borax from adhering fatty substances which combine with the soda to form an 
almost insoluble soap. After the borax has been well washed it is dissolved in 
boilin g-water; for each 100 parts of refined salts there are 12 parts of carbonate of 
soda. The solution is next filtered, and then evaporated to 18 0 to 20° B. It is now 
placed in wooden crystallising vessels lined with lead, where it is necessaiy to allow 
the fluid to cool gradually. Another method is to place the tincal in cold water, and 
to stir in 1 per cent, of caustic lime. The fatty substances are thus removed, com¬ 
bining with the lime to form an insoluble calcium soap. 2 per cent, of chloride of 
calcium is added to the fluid, which is next evaporated, and set to crystallise. 
Clouet recommends the powdering of the tincal, which is next mixed with 10 per 
cent, nitrate of soda, and calcined in a cast-iron pan, the fatty substances being thus 
destroyed. The calcined mass is dissolved in water, and the solution evaporated to 
crystallisation. 

Borax from Boracic Acid. In 1818 the manufacture of borax from boracic acid was com¬ 
menced, and since that time borax has sunk to three-fourths its former price. Both 
according to the proportion of water and the crystalline form, there may be consi¬ 
dered two varieties of borax. 1. The ordinary or prismatic borax; 2. Octahedral 
borax. The prismatic borax (Na 2 B 4 0 7 + ioH 2 0 ) contains in 100 parts:_ 

Boracic acid .36*6 

Soda . i6 . 2 

Water of crystallisation. aj - 2 


TOO'O 







BOR AGIO ACID. 


253 


The octahedral borax (Na 2 B 4 0 7 5H 2 0) contains in 100 parts :— 


Boracic acid 

Soda 

Water 


) 


69*36 

30*64 


IOO'OO 

Brismatic borax is .manufactured in the following 1 manner :—There are dissolved in a 
lead-lined vessel, a, Fig. 11S, 26 cwts. of crystallised carbonate of soda in about 1500 litres 
of water, heated by means of steam, to the boiling-point. The boiler, c, is for the 
purpose only of generating steam, which is passed by the pipe, c, and the rose, m, into a. 



By means of the large taps, b and r, the fluid may be removed from a. Through the 
tube a the substances thrown down from the solution can bo removed. Boracic acid is 
added in quantities of 8 to 10 lbs. after the solution has been heated to the boiling-point. 
Besides carbonic acid a small quantity of carbonate of ammonia is developed, and passes 
by 0 into the vessel d, containing dilute sulphuric acid, by which it is absorbed. To 
saturate the solution of 26 cwts. of soda, 24 cwts. of crude boracic acid are necessary. 
The boiling saturated solution marks 21 0 to 22 0 B., and has a temperature of 104°. If 






































































































254 


CHEMICAL TECHNOLOGY . 


the solution is too strong, water is added; if too weak, a small quantity of crude borax, to 
bring it to 21° B. The solution is allowed to stand in a until all insoluble substances are 
deposited. The clear ley is conducted by means of the tap, r, into the crystallising 
vessels, p p, the mud or deposit being received into k. The crystallising vessels are of wood 
lined with lead. The crystallisation is complete in two to three days, and the mother- 
liquor is drawn off into the vessel h. The crystals are placed to drain on the inclined 
plane, M. The mother-liquor is retained for the dilution of a fresh quantity of soda. 
After three or four operations, the mother-liquor contains sufficient sulphate of soda to 
admit of profitable crystallisation; and the ley is allowed to cool at 36°. As the solubility 
of sulphate of soda has reached the maximum at a temperature of 33 0 , it is clear that the 
crystallisation of the sulphate commences at the completion of that of the borax. 
After the crystallisation of the sulphate of soda, the mother-liquor is evaporated to dry¬ 
ness, and the saline residue is sold to the glass-manufacturer. 

Purifying the Borax. The crude borax to be purified is placed in a lead- lined wooden 
cistern, A, Fig. 119, heated by steam. The borax is suspended in a wire sieve 
immediately under the surface of the water with which A is filled. To 100 parts 
of borax, 5 parts of crystallised carbonate of soda are added, and the liquid 


Fig. 119. 



is strengthened from time to time till it marks 22° B. ‘When the solution is settled 
it is removed by the tap to the cooler, B. To prevent loss of ley, the floor under B 
is stippled with waterproof cement, and sloped towards a gutter. The crystallising 
vessel is of thick timbers, H F H, lined stoutly with lead; this vessel is filled with 
ley to within an inch of the edge, the cover being then placed on. The steam con¬ 
denses on the cover, which when removed is found covered with small crystals, the 
larger ciystals falling to the bottom of the vessel. To hasten the cooling, spaces 
are left in timbers, F; but the crystallisation is not effected under 16 to 28 days. 
After this time the ley still has a temperature of 27 0 to 28° C. When quite cool the 
foreign substances separate from the borax. The vessel, B, contains the large 
borax crystals from which the adhering mother-liquor is separated by a sponge. 
If the crystals are not thus carefully treated, they split into thin leaves; for this 
reason also the cooling should be gradual. The crystals are dried on a wooden 
table, finally sorted, and packed. 

In England borax is prepared from boracic acid in the following manner:_The 

crude boracic acid is mixed with half its weight of calcined soda and submitted to 
the action of heat in a muffle-oven. The ammonia, which as sulphate is an im¬ 
portant constituent of crude boracic acid, is, with carbonic acid, given off during 
the process, and passes through a tube to a condensing chamber. The melted 
mass is removed, and lixiviated in an iron pan ; the suspended matter is allowed to 




























BORACIC ACID. 


255 


settle, and the clear liquor is put into smaller vessels to cool, in which beautiful 
crystals form. It has already been mentioned that this manufacture had its origin 
in Prance, where sulphuric vapours were employed. A mixture of calcined 
Glauber salts and boracic acid were placed in a retort and subjected to distillation, 
the residue on lixiviation and crystallisation yielding borax. Kohnke substitutes 
caustic soda for the carbonate of soda, the borax crystallising from a very alkaline 
solution. 

Recently borax has been obtained from native borate of calcium, tiza or borocalcite, 
(formula, according to Wohler, Na 2 B 4 0 7 -f- 2CaB 4 0 7 -J- i 8 H 2 0 ), which occurs in largo 
quantities at Tarapaca in Peru, and in Western Africa. Treatment with sulphuric acid 
gives only unsatisfactory results, and hydrochloric acid is therefore employed. The acid 
is poured upon the mineral to two-thirds of its weight with twice the quantity of water, 
and the whole heated to the boiling-point, and allowed to digest. The heat must be main¬ 
tained to the completion of the digestion, and the water lost by evaporation re-supplied. 
The clear liquor is then decanted, and on cooling the boracic acid crystallises out, the 
mother-liquor retaining chloride of sodium, chloride of calcium, with a slight excess of 
hydrochloric acid. Stassfurt boracite or Stassfurtite, is also becoming largely used in the 
preparation of borax. 

The prismatic borax is colourless and forms transparent crystals of 175 sp. gr., dis¬ 
solved in 12 parts cold and 2 parts boiling water, the solution having a weak alkaline 
reaction upon test-paper, although borax is an acid salt. By exposure to the air it loses 
water. At a moderate heat it separates into a spongy mass known as calcined borax, and 
at a red-heat assumes a glassy appearance; in this condition it is used as a blowpipe 
flux. 

octahediai Borax. Octahedral borax (Na 2 B 4 0 7 + 5II2O), is prepared in the following 
manner:—Prismatic borax is dissolved in boiling water till the solution marks 
30° B. = 1 *260 sp. gr. This solution is then allowed to cool very slowly. When the 
temperature has fallen to 79 0 C., the octahedral crystals begin to form, the forma¬ 
tion continuing till the temperature reaches 56°. After this the mother-ley yields 
only prismatic crystals. Unless great care be taken, a mixed crystallisation results. 
Buran recommends the preparation of octahedral borax by evaporating a borax 
solution to 32 0 B. = 1 ’282 sp. gr., when it is removed to a crystallising vessel. When 
10 cwts. of borax are operated upon, the process will take six days to complete. The 
prismatic and octahedral salt crystallises in distinct layers that can be separated 
mechanically. Indian borax and Chinese half-refined borax sometimes contain 
octahedral crystals. Octahedral borax is known in Prench commerce under the 
names of calcined borax, jeweller’s borax, surface borax, &c. It is distinguished 
from prismatic borax by its crystalline form and the proportion of water contained, 
by its sp. gr. = i'8i, and its greater hardness. While the prismatic borax remains 
unaffected in transparency by exposure to air, the octahedral borax rapidly becomes 
opaque, and absorbing five equivalents of water is converted into the prismatic salt. 

Uses Of Borax. The uses of borax are very numerous. Molten borax has the property, at 

hio-h temperatures, of fluxing metallic oxides, vitrifying with them into coloured trans¬ 
parent glasses; for instance, with protoxide of cobalt a blue glass is formed, and with oxide 
of chromium a green glass. This property is of great utility in chemical analysis, as the 
' various metallic oxides may be thus distinguished in the blowpipe flame. It is also used 
for soldering metals; and is a constituent of Strass, used in glass-manufacture and 
enamelling. ° It is used extensively in glazing the finer kinds of earthenware, and for 
separating metals from their ores. Borax forms with shellac in proportion of 1 part to 5 
parts of a peculiar varnish, soluble in water, and used when mixed with aniline black to 
stiffen felt hats. With casein its gives a fluid resembling a solution of gum-arabic, for 
which it is often substituted. Borax is made into a soap for washing purposes, into a 
solution for cleansing the hair, and it is also used in various cosmetics, &c. It is largely 
employed to fix mineral mordants. According to Clouet, .a mixture of boracic acid and 
nitrate of potash or soda is in many cases a better flux than borax. He recommends 100 
parts boracic acid and 100 parts of the nitrate to be placed in an enamelled iron kettle 


256 


CHEMICAL TECHNOLOGY. 


with, io per cent, water and heated till fluid. When cooled, flat white crystals are formed ; 
those made with nitrate of potash can be used for crystal-glass manufacture, and those 
with nitrate of soda for enamelling. Borate of chromium is known in commerce as Vert- 
Guignet or Pannetier’s green. 

Diamond-Boron, or Wohler and H. Deville in 1857 were the first to notice that boron forms 
Adamantine, similarly to carbon in two allotropic conditions, namely, crystalline* 
and amorphous. Diamond boron is prepared in two ways, either by the reduction of 
calcined borax with aluminium :— 

Boracic acid, B 2 0 3 , t r . 1 , ( Alumina, A 1 2 0 3 , 

Aluminium, 2A, j 5 16 c s | Boron, 2B; 

or by converting amorphous boron into crystalline. The latter method gives the better 
result. 100 grms. of anhydrous boracic acid are mixed with 60 grins, of sodium in a small 
iron crucible heated to a red-heat. To this mixture 40 to 50 grms. of common salt are 
added, and the crucible is luted down. As soon as the reaction is finished, the mass, con¬ 
sisting of amorphous boron with boracic acid, borax, and common salt intermingled, is 
stirred into water acidified with hydrochloric acid. The boron is filtered out, washed with 
a weak solution of hydrochloric acid, and placed upon a porous stone to dry at the ordinary 
temperature. Molton iron, it is well known, converts amorphous carbon into crystalline 
graphitic carbon, and aluminium exercises a similar action upon boron. The crystalline 
boron is prepared in the following manner:—A small crucible is filled with amorphous 
boron, in the centre of which a small bar of aluminium weighing 4 to 6 grms. is placed. 
The crucible is submitted to a temperature sufficient to melt nickel for to 2 hours. 
After cooling the aluminium will be found covered with beautiful crystals of boron. The 
diamond boron is easily separated from the graphitoid. The form is a transparent tetra¬ 
gonal crystal, of a garnet-red or honey-yellow colour, or, if perfectly pure, colourless. It 
is very brittle, hard, and lustrous; it will scratch rubies easily. This discovery may in 
time be of great technical importance. 


Production of Alum, Sulphates of Alumina, and Aluminates. 

Alum. Alum is a saline substance, consisting of sulphate of alumina, sulphate of 
potash or ammonia, and water of crystallisation. It occurs native as potash-alum 
and as ammonia-alum, being, in fact, a double salt, consisting of either suljihate 01 
alumina and sulphate of potash, or sulphate of alumina and sulphate of ammonia. 

A1 f * 

The alum known as potash-alum, jA j- 4S0 4 -f- 24 H 2 0 , is found in alum-shale. But 

all natural alums are of more mineralogical than technical interest, the alums 
of commerce being always artificially prepared. We shall, therefore, pass on to the 
consideration of the latter. 

Manufacture. The manufacture of alum grounds itself on the formation of sulphate 
of alumina and aluminate of soda from the various alum-ores. These ores or 
earths necessitating different methods of treatment, may be divided into four 
groups, viz.:— 

1. Those which contain alumina, potassa, and sulphuric acid in such proportions that 
the addition of an alkaline salt is not requisite. To tins group belongs alum-stone, and 
several varieties of alum-shale. 

2. Those in which the sulphate of aluminia is alone present, necessitating the addition 
of alkali salts in large quantities. To this group belong the alum-shale and alum-earths 
found in the brown-coal formation. 

3. Those in which alumina only is contained, and to which both sulphuric acid and 
alkali salts must be added. To this group belong— a. Clay; jB. Cryolite; 7. Bauxite: 
5 . Refuse slack. 

4. To the fourth group belong those materials, such as felspar, containing alumina and 
potash in sufficient quantity, but needing the addition of sulphuric acid. 


* Graphitic boron is by a later discovery of Wohler’s (1S67) resolved into boracic- 
aluminium; formula, A 1 B ? . 




ALUM. 


257 


Pr fron? Alum-stone? 1S ^ ^ r0U P' —Alum-stone or alunite occurs only in volcanic 
regions, and is tlie product of the action of the sulphurous vapours upon sub¬ 
stances rich in felspar. It is found at Talfa, near Civita-Veccliia, and in large 
quantities at Muszag, in Hungaiy. The crystallised alum-stone consists of sulphates 
of potash and alumina with hydroxide of aluminium, according to Al. Mitscherlich— 
K a S0 4 +Al a (S0 4 ) 3 +a(Al a 0 3 ,3H a 0). 


Alum-stone loses its water at a red-heat, the product of the calcination being influenced 
by water, while unburnt alum-stone is not. At a strong red-heat the sulphate of alumina 
separates into alumina, sulphurous acid, and oxygen, and the sulphate of potash is also 
decomposed. The mineral is calcined in lime-kilns in the ordinary manner. The calcined 
alum-stone is lixiviated with boiling water, the supernatant liquor decanted, and the alum 
crystallised out. Roman rock, or roche alum is prepared in a similar manner, the red 
colour being due to peroxide of iron. 

Preparation of Alum from 2 nd Group. — This mode of preparation yields the greatest 
and'Aiuin-eaiUis. amount of alum with as much facility as from alum-stone. 

Aium-shaie. Alum-shale or schist is a sulphurous iron pyrites, found under beds cf 
clay in Upper Bavaria, in Prussia, near Dusseldorf, Saxony, Bohemia, Belgium, &c. 
Only very inferior kinds require an addition of alkali salts. 

Alum Earths. Alum-eartli is more or less a mixture of sulphurous iron pyrites with 
various bitumnious matters. The sulphur is present partly in free state, partly as 
iron and vitriol pyrites ; the iron is present partly as sulphuret, partly as iron 
humate. 

preparation of Alum. The preparation of the alum may be considered in the following 
six operations :—• 

Roasting the Alum-Earth, i. The roasting of the alum earths is the easiest of the opera¬ 
tions. The greater part of the alum manufactured is produced by precipitating sulphate 
of alumina with a solution of alkali salts. It is not always necessary the schist should 
be burnt to concentrate the sulphate of alumina, a lengthy weathering being sufficient. 
The action may be explained as follows:—By the weathering the bisulphide of iron ab¬ 
sorbs oxygen, to form sulphate of iron, which separates into protoxide of iron and sulphuric 
acid, the latter acting upon the alumina forming- an equivalent quantity of sulphate of 
alumina. Or by roasting, the bisulphide is decomposed to monosulphide and sulphur, 
which, with the sulphur of the alum-earth, gives rise to sulphurous acid, and this acting 
upon the alumina produces sulphite of alumina and also the sulphate. The roasting or 
calcination, however, should not take place with earths that have been subjected to less 
than a year’s weathering, as there is found to be in practice a loss of one-sixth of the sul¬ 
phate of alumina. 

Lixiviation. 2. The lixiviation of the calcined alum earths is effected in a lixiviation 
cistern in which the earth is placed. These tanks stand in row's of five, the best arrange¬ 
ment being to build them on a slope near the calcination heaps. Each vessel has a length 
of 6 to 7 metres, is 5 metres broad, and about 1-3 metres in height. They are three-parts 
filled with the burnt earth, and completely with water ; the lixivium flows from the highest 
tank to the lowest. If the ley is not of 1 -16 sp. gr. fresh shale is added. _ 

Evaporation of the Ley. 3. The concentration of the raw ley by evaporation is accomplished in 
leaden pans. These, however, deteriorate, crack, are easily melted, and their place is now 
generally supplied by cisterns of masonry. But most to be preferred is Bleibtreu’s method 
of heating with gas, introduced in the alum-works on the banks of the Rhine. The treat¬ 
ment of the raw ley while being concentrated depends upon its condition and upon the 
sulphate of iron it contains. As sulphate of iron is commonly present in large quantities 
in the raw ley or liquor, many of the German alum-works are also vitriol-works. When, 
however, the quantity of sulphate of iron is too small to admit of being advantageously 
treated for the preparation of sulphate of iron, the liquor is at once evaporated until it has 
attained a sp. gr. of 1-40. During the ebullition basic sulphate of iron is deposited, the 
liquor becomes of yellow-red colour, assumes a somewhat slimy condition, and has to he 
rendered clear before alum is obtained from it. This clearing is effected by pouring the 
liquor into large wooden water-tight tanks; the liquor having deposited, the suspended 
matter is tapped or syphoned off from the sediment, and transferred to the precipitation 
tanks. 1 Q 


258 


CHEMICAL TECHNOLOGY. 


Alum-Flour. 4. The precipitation of flour of alum is effected in case it is desired to 
make potash-alum by the addition to the liquor of a potash salt, or of an ammonia salt 
if it is desired to make ammonia-alum. The solution of the alkaline salt is called the 
precipitant; by the combination of the sulphate of alumina contained in the liquor with 
the precipitant alum is formed, and deposited as a solid salt, care being- taken to prevent 
the formation of large ciystals by keeping the liquid stirred. By this means the alum is 
deposited as a crystalline powder or so-called flour of alum, which by being washed with 
cold water can be freed from any adhering mother-liquor. The precipitation was formerly 
effected by the addition of wood-ash ley or lant; at the present day chloride of potassium 
obtained either from kelp, carnallite, or beet-root molasses, and sulphate of potassa derived 
from the decomposition of kainite, are employed for tliis purpose. Chloride of potassium 
is useful only when the solution contains large quantities of sulphate of iron, which being 
converted into chloride of iron forms sulphate of potassa. Potash can only be used when 
the ley contains enough free sulphuric acid. to combine with the salt, for otherwise a 
portion of the sulphate of alumina would become precipitated as insoluble alumina. The 
ammonia salt made use of is generally sulphate of ammonia; 100 parts of sulphate of 


alumina require for precipitation— 

Chloride of potassium ... . 43-5 parts- 

Sulphate of potassa .50-9 „ 

Sulphate of ammonia. .. 47-8 „ 


The liquor covering the alum-flour is somewhat of a green colour, and contains little 
alum, but chiefly proto-perchloride of iron, sulphates of iron, sulphate of magnesia, or 
chloride of magnesium, dependent upon whether the precipitation was effected by sulphates 
or by chlorides. This liquor is used for making impure alum, sulphate of iron, or is em¬ 
ployed in the preparation of sulphate of ammonia. 

Washing and 5- The floury alum is generally washed in the hydro-extractor or cen- 

Re-crystaiiisation. trifugal machine and the liquor obtained again used for preparing alum. 
The washed floury alum is (6) converted into large crystals by re-crystallisation, the alum 
at the same time being purified. For this purpose the alum flour is dissolved in 40 per cent, 
of its weight of boiling water, the operation being carried on in wooden lead-lined tanks. 
The hot solution is run into crystallising vessels, where the crystallisation is finished 
according to the temperature of the air in eight to ten days. From this operation hardly 
any mother-liquor remains, the vessel being almost entirely filled with alum crystals. 

Piepa fromciay AIum 3rd Group .—The manufacture of alum and of sulphate of alumina 
from such materials as contain only alumina, to which consequently sulphuric acid 
and alkaline salts have to be added, has come largely into practice in England. The 
materials employed are:—a. Clay; ( 3 . Cryolite ; y. Bauxite ; 8. Blast-furnace slag. 

a. Preparation of Alum from Clay .—The clay to be employed for this purpose should 
be as free as possible from carbonates of lime and iron. It is first gently heated in 
contact with air, partly with the view of dehydratation, partly for the purpose of converting 
any iron into oxide, and lastly to render the clay more readily soluble in acids. By 
dehyadratation the clay becomes porous and fit to take up sulphuric acid by capil¬ 
larity. The gently ignited and powdered clay is gradually put into sulphuric acid of 50° B. 
(~ 1'52 sp. gr.) contained in a leaden pan, and heated nearly to the boiling-point. The 
mass effervesces and becomes thick, and is next transferred to iron tanks, where it 
solidifies. It is afterwards lixiviated with water, or better, with the liquor obtained by 
washing the alum-flour. The lixivium having become clear by standing is syphoned off 
from the sediment, and boiled with a sufficient quantity of bisulphate of potash or 
sulphate of ammonia from gas-liquor. The hot solution is transferred to a shallow 
leaden pan, and kept stirred for the purpose of converting the alum on solidifying into 
flour. The flour is washed, dried, and is then converted into large crystals as described 
above. The product known in the trade as alum-cake is the result of the action of 
sulphuric acid upon clay; it is met with in a pulverised state, is used more especially 
in the manufacture of inferior kinds of paper, and contains from 13 to 17 per cent, of 
alumina. 

Pre Fro r mcryo°iite. lum 13 ■ Since the year 1S57 alum and sulphate ol alumina have been 
prepared along with soda, from the mineral known as cryolite or Greenland spar, 
Al 2 Fl6-}-6NaFl, and consisting in 100 parts of— • 

Fluorine .54*5 

Aluminium. *o 

Sodium .32*5 








ALUM. 


259 


"The following are the methods employed for this purpose :— 

a. Decomposition of Cryolite by Ignition with Carbonate of Lime according to Thomsen's 
Method. —1 molecule of cryolite is ignited with 6 molecules of carbonate of lime, carbonic 
acid escapes, and soluble aluininate of soda, and insoluble fluoride of calcium are formed 
(Al 2 Fl 6 , 6 braFl)-b 6 CaCo 3 ==Al 2 0 3 , 3 N'a 2 0 -f-6CaFl-{-6C0 2 . From the ignited mass the 
aluminate of soda is obtained by lixiviation with water, and into the solution carbonic 
acid gas is passed. The result is the precipitation of hydrated gelatinous alumina 
and carbonate of soda, which remains in solution. If it be deshed to obtain the alumina 
as an earthy compact precipitate, bicarbonate of soda is used as a precipitant instead of 
carbonic acid. While the clear liquor is boiled down for the purpose of obtaining car¬ 
bonate of soda., the precipitated alumina is dissolved in dilute sulphuric acid; this solution¬ 
is evaporated for the purpose of obtaining sulphate of alumina (so-called concentrated 
alum), or the solution after having been treated with a potassa or ammonia salt is converted 
into alum. 100 lbs. of cryolite yield 33 lbs. of alumina, which require 90 lbs. of sulphuric 
acid to yield a neutral solution ; 100 lbs. of cryolite will therefore yield 305 lbs. of alum, 
and may give in addition :— 


Calcined soda.75-0 lbs., or 

Crystallised carbonate of soda .. .. 203*0 „ or 

Caustic soda .44-0 „ or 

Bicarbonate of soda.119-5 „ 


b. Decomposition of Cryolite with Caustic Lime by the Wet Way (Sauermein's Method ).— 
Very finely ground cryolite is boiled with water and lime, the purer the better, and as free 
from iron as possible, in a leaden pan. The result is the formation of a solution of alumi¬ 
nate of soda and insoluble fluoride of calcium. 

(Al 2 Fl 6 ,6NaFl) + 6CaO=Al 2 0 3 , 3 Na 2 0 -f 6CaFl 2 . 

"When the fluoride of calcium has been deposited, the clear liquid is decanted, and the 
sediment washed, the first wash-water being added to the decanted liquor, and the second 
and third wash-waters being used instead of pure water at a subsequent operation. In 
order to separate the alumina from the solution of aluminate of soda, there is added to the 
liquid while being continuously stirred, very finely pulverised cryolite in excess, the result 
of the decomposition being exhibited by the following formula :— 

(Al 2 0 3 ,3Na 2 0) -f (Al 2 Fl 6 ,6NaFl) =2Al 2 0 3 -f i 2 NaFl. 

When no more caustic soda can be detected hi the liquid—a small quantity of which 
should, after filtration, yield, upon the addition of a solution of sal-ammoniac and applica¬ 
tion of heat, a precipitate of alumina—it is left to stand for the purpose of becoming clear. 
The clarified solution of fluoride of sodium is then drawn off, and the alumina treated as 
above described. The solution of fluoride of sodium having been boiled with caustic lime 
yields a caustic soda solution which, having been decanted from the sediment of fluoride 
of calcium, is evaporated to dryness. Recently the fluoride of calcium obtained as a by¬ 
product of the cryolite industry is used in glass-making. 

c. The decomposition of cryolite by sulphuric acid yields sulphate of soda, convertible 
into carbonate by Leblanc’s process, and sulphate of alumina free from iron. 238 parts of 
cryolite require for decomposition 240 parts of anhydrous or 321 parts of ordinary sulphuric 
acid. The resulting compounds are sulphate of alumina, sulphate of soda, and hydrofluoric 
acid :— 


Al„Fl 6 6NaFl, ) 
6 H 2 S 0 4 , ) 


yield 


A 1 2 (S 0 4 ) 3 . 
3Na S0 4 . 
12HFI. 


This method of decomposing cryolite is, however, by no means to be recommended, as 
owing to the liberation of hydrofluoric acid, peculiarly constructed apparatus are required; 
while the sulphate of soda has to be converted into carbonate of soda. Persoz suggests that 
cryolite should be treated in platinum vessels with three times its weight of strong sulphu¬ 
ric acid, to be recovered with the hydrofluoric acid by distillation. The solid residue 
should be treated with cold water in order to dissolve the larger part of the bisulphate of 
soda contained in the saline mass, from which the anhydrous sulphate of alumina is ex¬ 
tracted with boiling water, and converted by the addition of stdphate of potassa or ammonia 
into alum free from iron. The solution of bisulphate of soda having been evaporated to 
dryness, is employed for the preparation of fuming sulphuric acid, Glauber's salt remain¬ 
ing as a residue. 

Pre ?rom t Bauxite lum 7- s 01110 parts of Southern France, in Calabria, near Belfast, Ire¬ 
land, and other parts of Europe, a mineral occurs, consisting essentially (60 per cent.) 
of hydrated alumina of greater or less purity, termed bauxite, from the fact of 





2 bo 


CHEMICAL TECHNOLOGY. 


haying been first found in the commune of Baux, in France. In order to prepare 
alum and sulphate of alumina from this mineral it is first disintegrated by being 
ignited with carbonate of soda, or with a mixture of sulphate of soda and charcoal; 
in each instance the lixiviation of the ignited mass yields aluminate of soda, from 
which, by processes already described under Cryolite, alum, or sulphate of alumina, 
and soda are prepared. 

from BiIst-Furna^sSg. J * Furmann recommends that the slag be decomposed by 
means of hydrochloric acid. From the resulting solution of chloride of aluminium 
the alumina is precipitated by carbonate of lime, any dissolved silica being preci¬ 
pitated at the same time. The alumina is dissolved in sulphuric acid, leaving the 
silica, ioo kilos, of slag containing 25 per cent, of alumina yield 180 kilos, of alum 
and 31 kilos, of silica. 

Alum from Felspar. 4 th Group .—The manufacture of alum from minerals, (for instance, 
felspar) containing alumina and potassa, is not of any'industrial importance ; we 
therefore refer the reader to what has been said (see page 132) on the Preparation of 
Potassa Salts from Felspar. 


A 1 ) 

Properties of Alum. Potash-alum, j^ 2 j 4SO4+24II2O, Or F 2 S 0 4 + A 1 2 (S 0 4 ) 3 -f- 24H a O, 
consists in ioo parts of:— 

Potassa . . .3 . 9'95 


Alumina.10*83 

Sulphuric acid. 33 * 7 1 

Water .45 *51 


100*00 

crystallises readily in regular octhahedra, loses at 6o° 18 mols. of water, and fuses 
at 92 0 in its water of crystallisation, yielding a colourless fluid which retains its state 
of aggregation for some time after cooling before solidifying into a crystalline mass. 
At a temperature a little below red heat alum loses all its water, becoming converted 
into burnt-alum, alumen ustum, a white, porous, readily friable mass. When ignited 
with carbonaceous matter, air being excluded, potash-alum forms a pyrophoric 
compound:—■ 

100 parts of water at o° dissolve 3*9 parts of potash-alum. 

>> 20° ,, 15*8 ,, ,, 

*» >> 40 ° „ 3 i *2 

»> 5> IOO° ,, 3^0*0 ,, ,, 

The solution of alum in water (the salt is insoluble in alcohol) has an astringent sweet 
taste, and possesses an acid reaction so strong that when alum is heated with common salt 
hydrochloric acid is evolved; while a concentrated solution of alum destroys the blue colour 
of many—not of all—artificial ultramarines. 


Ammonia-Alum. This salt, J 4S0 4 -f 24IPP, or (NH 4 ) 2 S0 4 -f A 1 2 (S 0 4 ) 3 -f 24HO, 

consists in 100 parts of:— 

Ammonia . 3-89 

Alumina. 11-90 

Sulphuric acid .35‘io 

Water .48-11 


ioo-oo 

Ammonia-alum is now far more extensively manufactured than potash-alum. When 
ammonia-alum is strongly heated, sulphate of ammonia, water, and sulnhuric acid are 
driven off, and alumina remains. 










ALUM. 


261 


100 parts of water at o° dissolve 5-22 parts of ammonia-alum. 
»» » 20 ,, 13*66 ,, ,, 

» » 4 ° ,, 27*27 ff ft 

tt » 100 „ 421-90 „ „ 

soda-Aium. The formula of this salt is— 

Na'" } 4S0 * + 24H2 °’ or Na 2 S0 4 +A1 2 (S0 4 ) 3 + 2 4 H 2 0 


containing in 100 parts:— 

Soda. 6*8 

Alumina .11 *2 

Sulphuric acid.34*9 

Water.47*1 


IOO'O 

j*t is as readily prepared from sulphate of alumina and sulphate of soda as the alums 
already mentioned, but its solubility prevents the separation from the mother-liquor, 
while its solution when boiled loses the property of crystallising. As iron cannot be 
removed from this salt by re-crystallisation, the materials it is obtained from should be free 
from that metal. The solutions should be mixed cold, and gently evaporated at a 
temperature not exceeding 6o°. 

Neutral or cubical alum (K 2 S 0 4 -f- A 1 2 0 3 , 2 S 0 3 ) is obtained either by adding to an alum 
solution so much carbonate of potassa or soda as will begin to separate the alumina, or 0 
solution of alum is treated with gelatinous alumina. By boiling 12 parts of alum and 1 part 
of slaked lime in water, the same salt is obtained. This neutral salt is often preferred 
in dyeing and calico printing, as it does not affect certain colours. When ammonia-alum 
is similarly treated, it also yields a neutral alum. Blesser (a) and Schmidt ( b) found the 
following to be the composition of cubical alum in 100 parts:— 

a. b. 

Sulphuric acid .34-52 33’95 

Alumina. ii-86 11.48 

Potassa. 9-44 9-04 

Water.45*27 45-61 


101*09 100*08 

A 1 ) 

Insoluble, or basic alum, k! 2S0 4 , is obtained by boiling a solution of alum with 

hydrate of alumina; it is a white, insoluble powder, and as regards its composition 
similar to alum-stone. Basic alum is soluble in acetic acid. 

sufiphate of Alumina. The active principle of alum is evidently the sulphate of 
alumina, not the sulphates of potassa and ammonia, the object of the preparation of 
the double salt being simply the obtaining of a definite compound, which, while it 
readily crystallises, can be obtained in a pure state, especially free from iron, a very 
injurious ingredent in alum used in dyeing and calico-printing. However, at the 
present day, with improved methods of manufacture, sulphate of alumina is largely 
prepared, and of excellent quality. It is often sold under the name of concentrated 
alum; and occurs in the trade as square cakes. It is white, somewhat transparent, 
and may be cut with a knife; is readily soluble in water, contains always free 
sulphuric acid, and also to some extent potassa, and soda-alum. 

In the pure state this salt has the formula, A 1 2 (S 0 4 ) 3 + i 8 H 2 0 , and contains in 
100 parts—alumina, 18*78 ; sulphuric acid, 38*27 ; water, 42*95; total, 100. That 
the composition of this salt as met with in commerce varies greatly may be inferred 
from the following results of Yarrentrapp’s analyses of different samples of this 
salt:— 

1. 2. 3. 4 * 

Alumina. 15*3 12*5 I 5' 1 I 3 ‘° 

Sulphuric acid .. .. 38*0 30*6 38*0 34*0 













262 


CHEMICAL TECHNOLOGY. 


According to the formula, the quantity of sulphuric acid in these samples should 
have been— 

i. 2. 3. 4 - 

35*8 29*2 43 *3 30*5 

The quantity of water even varies between 56 and 48 per cent, for different 
parts of the same cake. Weygand found a sample of this salt prepared at Schwemsal 
to contain—alumina, 15*57; sulphuric acid, 38*13; oxide of iron, 1*15; potassa, 
0*62; water, 45*79 parts. The sulphate of alumina prepared from cryolite at 
Harburg contains about 5 per cent, of sulphate of soda. The results obtained in 
the analyses by H. Fleck of various samples of sulphate of alumina are :— 


Sulphate of alumina .. 

• • 47*35 

50-80 

51*63 

Sulphate of soda 

•• 4*35 

1*24 

0*77 

Free sulphuric acid 

• • 0*73 

0-27 

— 

Water . 

• • 47*37 

47*47 

46-94 


99*80 

9978 

99*34 


Sulphate of alumina is prepared either from clay, cryolite, or bauxite by methods 
already described. When clay is employed, the iron has to be removed from the dilute 
Solution of the sulphate of alumina by precipitation as Berlin blue by means of ferro- 
cyanide of potassium. When cryolite is used, the alumina, separated from the solution 
of aluminate of soda by carbonic acid, or powdered cryolite, is put into sulphuric acid, 
contained in a wooden lead-lined tank, and heated to 8o° to 90°, the addition of the alumina 
to the acid being continued until solution ceases to t ake place. The solution having been 
clarified by standing for some time is next evaporated in a copper vessel until the salt 
fuses; it is then cast into moulds. With due care sulphate of alumina may be used in 
dyeing and calico-printing, but it cannot be altogether substituted for alum, owing to its 
variable composition. 

Aluminate of Soda. Aluminate of soda is now prepared on the large scale, as it has 
been found to be a useful form of soluble alumina, especially in dyeing and calico- 
printing. The preparation of this compound is based upon the solubility of hy¬ 
drate of alumina in caustic potassa or soda-ley, and the ready decomposition of 
the solution by carbonic and acetic acids, bicarbonate and acetate of soda, sal- 
ammoniac, &c. 

Aluminate of soda was first brought under the notice of dyers by Macquer and 
Haussmann in 1819, but owing to the preparation being too expensive it did not come 
into industrial application until comparatively recently. We have already described 
the mode of manufacturing aluminate of soda from cryolite; but in Germany—the 
chief seat of cryolite industry—this salt is not made on the large scale ; in France 
it is manufactured by Merle and Co., at Alais, and in England at the Washington 
Chemical Works. In France bauxite, containing 60 to 75 per cent, of alumina, and 
from 12 to 20 per cent, of oxide of iron, is the raw material, and is treated with 
caustic or carbonate of soda. If caustic soda is used the pulverised mineral is 
boiled with a solution of the alkali; while if the carbonate is employed the mixture 
is ignited in a reverberatory furnace. In either case aluminate of soda is produced, 
dissolved—in the case of ignition the semi-fused mass is lixiviated with water—and 
evaporated to dryness. The salt met with in commerce is a white powder with a 
green-yellow hue, dry to the touch, and consisting of— 

Alumina .48 

Soda .44 

Chloride of sodium and Glauber’s salt .. 8 


100 








ALUM. 


n &3 


The formula, Nag} 06 would require :— 

Alumina '.. .. 5279 

Soda .47*21 

IOO'OO 

Aluminate of soda is equally soluble in cold and hot water. Exposed to air it absorbs 
moisture and carbonic acid, and consequently on being dissolved in water the salt so 
changed yields a turbid solution, owing’ to alumina being suspended. The aqueous solution 
of this salt is not stronger than io° to 12 0 B., — i’07 to i’c>9 sp. gr. According to Le 
Chatellier, Deville, and Jacquemart, sulphate of alumina is the starting-point of the 
preparation of the aluminate of soda by precipitating from the sulphate the alumina, 
and re-dissolving the latter in caustic soda ley. Aluminate of soda is used in dyeing 
and calico-printing; further, for the preparation of lake colours, induration of stone, 
and the manufacture of artificial stone, and for the saponification of fats in stearine 
candle manufacture, an alumina soap being first formed, which is decomposed by 
acetic acid into acetate of alumina and free fatty acid. Aluminate of soda is largely 
used in the preparation of an opaque, milky-looking- glass, or semi-porcelain. Aluminate of 
soda is a by-product of Balard’s method of soda manufacture from bauxite, Glauber’s 
salt, and coal; this by-product, or rather product of the second stage of the process, is 
decomposed by carbonic acid into carbonate of soda and alumina, which is thrown down. 
The Pennsylvania Salt Manufacturing Company at Natrona, near Pittsburg, manufacture 
large quantities of aluminate of soda, which is used in soap-boiling* under the name of 
natroha refined saponifier. 

Uses of Alum and of Owing to the great affinity of the alumina contained in alum for 

Sulphate of Aiuuuna. textile fibres, especially wool and cotton, alum is largely used as a 
mordant in dyeing, except when the tar colours are employed. Again, owing to the 
affinity of alumina for many pigments, alum is employed in the preparation of the lake 
colours, combinations of active colouring- principles with alumina. It is also used in the 
melting of tallow; for hardening gypsum; is found in the preparation used for sizing- 
hand-made paper, the alum in this case forming with the glue or size an insoluble com¬ 
pound. Alum with resin is employed for the same purpose in machine-made paper, an 
alumina-pinate being formed. It is very largely used for the preparation of acetate of 
alumina, and with common salt in the tawing of leather. Alum is employed in clarifying- 
turbid fluids, more especially water ; in this case the alum takes up the alumina suspended 
in the water, and forming an insoluble (basic) alum carries down organic and other 
suspended impurities. A boiling solution of alum, common salt, and nitrate of potassa 
is used by jewellers for the purpose of colouring gold, that is to say, to produce a film of 
pure gold on the alloy, the copper of which is dissolved by the boiling solution. 

Acetate of Alumina. This salt is prepared by double decomposition ; generally sulphate of 
alumina and acetate of lead are used, and occasionally the acetates of barjda and lime. 
The liquor, separated by filtration from sulphate of lead, is gently evaporated to dryness ; 
the dry salt is gelatinous, and does not crystallise, is very hyg-roscopic, and possesses a 
strongly astringent taste. When a solution of acetate of alumina is evaporated in con¬ 
tact with air, acetic acid is driven off, and a basic acetate, insoluble in water, formed. 
Commercially pure acetate of alumina is rarely used, as the so-called red-liquor, mordant 
rouge, consists of a mixture of alum, acetate of potassa, and sulphate of potassa. When 
it is desired to prepare neutral acetate of alumina from alum, to 100 parts of acetate of 
lead 62-6 parts of alum are required for complete mutual decomposition; but it is more 
advantageous to convert a solution of alum into insoluble alumina by means of 
carbonate of soda, and to treat with acetic acid. Acetate of alumina is not an ordinary 
article of commerce, as the salt is usually prepared by the consumers. Besides being 
lai-gely used in dyeing and calico-printing, acetate of alumina is employed for water¬ 
proofing woollen fabrics. Among the salts of alumina employed industrially are—hypo¬ 
sulphite of alumina, suggested by E. Kopp as a mordant for cotton; hypochlorite of 
alumina, known as Wilson’s bleaching-liquor, and used in bleaching-works; sulphite of 
alumina, for the purpose of purifying beet-root juice ; oxalate of alumina, suggested by 
Dent and Brown for the preservation of stone, marble, dolomite, &c. 



264 


CHEMICAL TECHNOLOGY. 


Ultramarine . 

ultramarine. Under this name is now understood an artificial blue pigment, 
formerly and still obtained in small quantities from the lapis lazuli. The quantity 
of artificial ultramarine manufactured in Europe amounts to 180,000 cwts. annually- 
Lapis lazuli is a scarce mineral, possessing a beautiful blue colour. The sp. gr. 
varies from 275 to 2*95. The coarser pieces of this mineral are pulverised, heated 
to redness, and immediately dipped into water, then very finely ground, and the 

Native ultramarine, powder treated with dilute acetic acid to eliminate carbonate of 
lime. The powder is next well incorporated with a mixture of equal parts of resin, 
wax, linseed-oil, and Burgundy-pitch; this paste is kneaded under water until no 
more blue pigment remains suspended. The quantity of ultramarine obtained 
amounts to 2 to 3 per cent. This natural ultramarine is highly prized for its extreme 
beauty, softness of colour, and durability, not being affected by light, oil, and lime. 
Chemical analysis of the lapis lazuli first gave the clue to the true composition of 
this material, and led, after many unsuccessful attempts, to the preparation of artificial 
ultramarine, not, however, by any means equal to the native pigment, although it 
has driven smalt and other blue pigments nearly out of the market. Lapis lazuli 
consists in 100 parts of—silica, 45*40 ; alumina, 31*67 ; soda, 9*09; sulphuric acid, 
5*89; sulphur, 0*95; lime, 3*52; iron, o-86; chlorine, 0*42; and water, 0*12. 

Artificial ultramarine. Gmelin first made artificial ultramarine on a very small scale in 
1822; but not before 1828 was ultramarine industrially obtained by Guimet, at 
Lyons. In Germany the first manufactories of ultramarine were established at 
Wermelskirchen, in 1836, by Dr. Leverkuss, and at Nuremberg, in 1838, by MM. 
Zeltner and Leykauf: the manufacture of artificial ultramarine in England is of 
very recent date, and is still on a very limited scale. France and Germany are the 
countries where this industry is most developed. Of late years the process of 
manufacture has been improved by K. Hoffmann, the manager of a factory at 
Marienberg, in Hessen; Wilkins, at Kaiserslautern; Fiirstenau, at Coburg; and 
Gentele, at Stockholm. 

naw Materials. These are—1. Silicate of alumina as free as possible from iron, a 
good china clay, the kaolin of Cornwall being esteemed the best; 2. Calcined sul¬ 
phate of soda; 3. Calined soda; 4. Sulphuret of sodium, as a by-product of the 
manufacture; 5. Sulphur; 6. Pulverised charcoal, or pit-coal. 

Porcelain, or china-clay, is generally used, or a white clay, the composition of 
which is nearly the same. Small quantities of lime and magnesia have no injurious 
effect, but the oxide of iron should not exceed 1 per cent. The composition of the 
clay should approach as nearly as possible to the formula Si 2 0 7 Al 2 ; the silica may 
be combined or partly free. The clay is washed with water and treated in the same 
manner as for the making of porcelain; it is next dried, ignited, and ground to a 
very fine powder. The sulphate of soda should not contain any free acid, lead, or 
iron. If the sulphate does not possess the requisite qualities it is dissolved in 
water, milk of lime being added to neutralise th e acid and to precipitate oxide of 
iron. The clear solution is left to crystallise; and the crystals are ignited in a 
reverberatory furnace and then pulverised by millwork. The clear solution is in 
some cases evaporated to dryness and ignited in iron vessels. Barium, but not 
potassium salts, form ultramarine (see “Chemical News,” vol. xxiii., pp. 119,142,204). 
The calcined soda is obtained from the alkali works, and should contain at least 90 per 


ULTRAMARINE. 


2G5 

cent, of ■carbonate of soda; it is also finely pulverised. Very recently caustic soda 
Has been substituted in some ultramarine works. Sulphuret of sodium (Na 2 S) is 
usually a by-product of tbe process of making ultramarine, and is obtained either 
in solution or as a dry powder. Tbe sulphur is used very finely pulverised. The 
carbonaceous matter employed is also in a very fine powder. Its use was introduced 
by Laykauf for the purpose of deoxidation. In order to have the carbon in as 
finely divided state as possible it is ground to a pulp with water under granite stones; 
the pulp is lixiviated, and the fine powder obtained dried and passed through a sieve: 
in some cases resin and pitch is employed. For those ultramarines not to have their 
colour discharged by alum, pure silica, either as fine glass, sand, or pulverised 
quartz is used. Several substances are used to reduce the depth of colour of 
ultramarine, viz.—gypsum, sulphate of baryta, baryta-white, and flour; the last is 
employed in making up washing-blue. 

Manufacture of ultramarine. The methods of ultramarine preparation may be classified, 
according to the crude materials employed, as the three following:— 

a. Preparation of Sulphate, or Glauber’s salt ultramarine. 
j8. , ,, Soda-ultramarine, 

y. ,, ,, Silica-ultramarine. 

a. Preparation of Sulphate-Ultramarine. —This ultramarine is prepared according 
to the Nuremberg process from kaolin, sulphate of soda, and charcoal; the pre¬ 
paration consisting in two distinct stages, viz. :— 

a. Preparation of green ultramarine. 
h. Conversion of green into blue ultramarine. 

a. Preparation of Green Ultramarine. —In order to obtain a most intimate mixture of 
the dry and finely pulverised materials, small quantities are weighed off, mixed in wooden 
troughs by means of shovels, and several times passed through sieves. If solutions of 
Glauber’s salt, soda, and sulphide of sodium are used instead of powders, the kaolin is 
mixed with these solutions, and the whole evaporated to dryness, gently ignited in a 
reverberatory furnace, and then pulverised and sifted. The quantities of the crude 
materials vary, but the following conditions have to be complied with :—1. Soda, whether 
sulphate or caustic, must be present in such quantity that it can saturate half of the silica 
of the clay (kaolin). 2. There must be sufficient soda remaining to form with the sulphur 
a certain quantity of polysulphuret of sodium. 3. There ought to remain enough sulphur 
and sodium to form another sodium sulphuret (NajS), after deducting from the whole 
mixture as much green ultramarine as, according to its composition as proved by recent 
analysis, the silica and alumina present are capable of forming. The following figures will 
give an idea of the proportions :—- 


Kaolin (dried) . 100 100 

Calcined Glauber’s salt .. 83—100 41 

Calcined soda . — 41 

Carbon (char- or pit-coal).. 17 17 

Sulphur . — 13 


For 100 parts of calcined soda 80 parts of calcined Glauber s salt, and for 100 parts of 
the latter 60 of dry sulphuret of sodium are taken. 

It is usual to have a large quantity of this mixture prepared for use. If this mixture is 
ignited without access of air, a white mass is obtained, which, having been treated with 
water, is a light, somewhat flocoulent, white substance, to which Ritter has given the 
name of white ultramarine. It becomes green by exposure to air, and blue by being cal¬ 
cined in contact with air. The mixture is well rammed into fire-clay crucibles, placed 
in furnaces similar in construction to those used for burning porcelain, being raised and 
maintained at a high temperature with a very limited supply of air. This operation lasts 
seven to ten hours, and is completed at a bright white heat. The furnace is closed and 
slowly cooled; on removing the crucibles, the contents appear as a semi-fused grey- or 
yellow-green mass, which is repeatedly treated with water. The ultramarine thus obtained 





266 


CHEMICAL TECHNOLOGY. 


is in porous lumps, which are pulverised to an impalpable powder ; this is washed, dried, 
and again ground, then sifted, and finally packed in boxes or casks, and sent into the 
market as green ultramarine, consisting, acccording to Stolzel’s analysis (1855)1 i n 100 
parts, of— 


Alumina. 3 °' 11 

Iron. 0*49 

Calcium . 045 

Sodium . 19*09 

Silica.3 7'46 

Sulphuric acid. 0*76 

Sulphur . 6*o8 

Chlorine . 0*37 

Magnesia, potassa, phosphoric acid .. traces 


94-Si 

Oxygen . 5*19 


100*00 


(peroxide of iron, 0*7) 
(soda, 25*73) 


Green ultramarine is a pigment of comparatively inferior value, owing to its being less 
brilliant than the green copper pigments. 

b. Conversion of Green into Blue Ultramarine .—This operation may be variously effected, 
generally by roasting the green ultramarine and sulphur at a low temperature with access 
of air, so as to form sulphurous acid, while a portion of the sodium is oxidised into 
soluble sulphate and afterwards washed out; but the sulphur originally present in the 
green ultramarine remains combined with a smaller quantity of sodium. The roasting 
may be variously carried out, but very frequently the apparatus consists of a fixed iron 
cylinder similar to a gas-retort, provided with a stirring apparatus, by means of which 
the mixture of green ultramarine and sulphur (25 to 30 lbs. of the former to I lb. of 
sulphur) is submitted equally to the source of heat. The addition of sulphur is repeated 
until the desired blue colour is produced; but in some works this calcination is interrupted 
by repeated lixiviation, the object being to produce a superior article. Muffle-ovens 
and a kind of reverberatory oven are also used for this operation. The sulphurous acid, 
which is evolved in large quantities, is now generally employed in making sulphuric 
acid, sometimes a co-product of ultramarine manufacture, and used for the preparation 
of the sulphate of soda required. The ultramarine, when quite blue, is pulverised, lixi¬ 
viated, dried, and finally separated into various qualities known in the trade as No. 00, 1, 
2, 3, &c. 

I>re ui r tiamarine S . 0da * As manufactured in France, Belgium, and some parts of 
Germany, this ultramarine is either pure soda-ultramarine or a mixture of soda- 
and sulphate-ultramarine. The materials and proportions are— 



I. 

II. 

in. 

Kaolin . 


100 

100 

Sulphate..' 

— 

4 i 

— 

Soda. 


4 i 

90 

Carbon (charcoal or pit-coal) 

.. 12 

17 

6 

Sulphur. 

60 

13 

100 

Bosin . 

— 

— 

• 6 


The ignition takes place either in crucibles, or, better, in a reverberatory furnace; 
the result is the formation of a brittle and porous green substance, *which absorbs 
oxygen very rapidly, so that during the cooling of the mass in the oven, the greater 
part is converted into blue ultramarine. The complete conversion, after the addition 
of sulphur, is obtained by heating in a large muffle to redness, the product being 
distinguished from the foregoing by a greater depth and beauty of colour. By 
increasing, within certain limits, the quantities of soda and sulphur, the formation 
of blue ultramarine may be at once obtained, the product containing 10 to 12 pei 
cent, of sulphur. 



















ULTRAMARINE. 


267 

lrcp uuraSfcrine l . llca * Silica-ultramarine is really soda-ultramarine in the prepara¬ 
tion of which silica to the amount of 5 to 10 per cent, of the weight of the kaolin is 
added. The calcination at once yields blue ultramarine, and further treatment with 
sulphur is therefore unnecessary. 

This ultramarine is not acted upon by a solution of alum, and may be recognised 
by its peculiar red hue, the intensity of which is increased by an increase of silica. 
Notwithstanding the superiority of the ultramarine obtained by this process, its 
preparation is disadvantageous owing to the tendency of the mixture of crude 
materials to fuse during ignition. 

Constitution of ultramarine. Since 1758 the chemical constitution of ultramarine has 
been the object of a series of researches. The latest experiments are those of 
W. Stein, who comes to the conclusion that ultramarine consists chiefly of a white 
mass, with which black sulphide of aluminium is most intimately and molecularly 
incorporated, the blue colour being due, not to chemical composition, but to the 
optical relation of its component substance. Green ultramarine contains less soda 
than the blue pigment, and that again less than the white (so-called) ultramarine. 
The quantity of sulphur contained in blue ultramarine is less than that in green. 

Properties of ultramarine. Artificial ultramarine is an impalpable powder of a fine blue 
colour, entirely insoluble in water, and when washed with distilled water leaving no 
residue on evaporation of the filtrate. It is not acted upon by alkalies, but is highly 
sensitive to the action of even very dilute acids and acid salts, sulphuretted hydrogen being 
evolved and the colour discharged. Native ultramarine obtained from lapis lazuli is not 
thus decomposed by weak acid solution. There sometimes accidentally occurs in soda 
furnaces a more or less blue ultramarine which exhibits the same resistance to acids. That 
kind of ultramarine commercially termed acid proof is manufactured with the addition 
of silica, as described, but it really only resists the action of alum-salts. Ultramarine is 
now largely used for the purposes to which smalt, litmus, and Berlin-blue were applied ; 
that is to say, ultramarine is employed as a paint, as a pigment in stereochroiny, for 
paper-hangings, calico-printing with albumen as fixing material, for colouring printing- 
ink, for the bluing of linen and cotton fabrics, paper, stearine, and paraffine-candles, and 
lump-sugar. Tor 1000 cwts. of sugar 2b lbs. of the pigment are employed, a quantity so 
small as to be perfectly innocuous ; further, ultramarine does not contain anything 
injurious to health. Green ultramarine is a dull-coloured powder used by wall-paper 
stainers, and is sometimes mixed with indigo-carmine and a yellow pigment to improve the 
colour. 

Adulterations of ultramarine with Berlin-blue, smalt, and other blue pigments do not 
now occur, as ultramarine is a cheaper material; but to obtain lighter tints ultramarine 
is sometimes mixed with chalk, kaolin, alabaster, and chiefly with sulphate of baryta. 


division nr. 


TECHNOLOGY OF GLASS, CERAMIC WARE, GYPSUM, LIME, AND MORTAR 




Glass Manufacture. 




D ^ropertie8 n of < Giassf I Glass is an amorplious composition of various silicates obtained 
by a process of smelting, alkaline and calcium silicates being tbe chief constituents. 
That which is termed glass-water—viz., a silicate of potassa or soda—of course con¬ 
tains no other silicates; but real glass contains other bases in addition to soda 
and potassa, either alkaline earths, as lime, baryta, strontia, or other more or less 
basic bodies, as magnesia, alumina, or metallic oxides,—those of lead, bismuth, zinc, 
thallium, protoxides of iron and manganese, while in the case of optical or fine 
crystal glass boracic acid or borax is substituted for a portion of the silica. 

Glass is generally transparent; when opaque it is either white or coloured. Glass 
is not acted upon, in the common acceptance of the term, by either water, acids, or 
alkalies. It is, as has been said, amorphous, for as scon as it becomes crystalline it 
ceases to be glass. The amorphism of glass is due to its composition; simple sili¬ 
cates have a tendency to crystallise, and are hence unfit for glass manufacture. 
Owing to its amorphism glass exhibits a conchoidal fracture. When blown to very 
thin laminse or drawn into thread, glass possesses a remakable degree of elasticity. 
As regards the chemical and physical qualities of glass, much depends upon the 
constituent silicates; the alkaline silicates render glass soft and contribute to its 
ready fusibility. Silicate of potassa glass is less bright and glossy than glass in 
which silicate of soda prevails, but the latter silicate imparts a blue-green colour. 
Silicate of calcium renders glass harder, brighter, but less readily fusible. Silicates 
of lead and bismuth render glass very fusible, impart to it a high degree of lustre, 
and greatly increase the refrangih,ility ; they are therefore used in making glass for 
optical purposes. Silicates of zinc and baryta impart similar properties ; the former 
has the property of reducing the blue-green colour due to silicate of soda. Silicates 
of iron and manganese render glass readily fusible, and impart colour to it. Silicates 
of other metallic oxides are only of secondary importance in imparting colour to 
glass. 

ciassiflcationof^various According to its chemical composition glass may be classified 

as follows:— 

I. Potassium-calcium glass, or Bohemian crystal glass, is quite colourless, very 
difficultly fusible, hard, and very difficultly acted upon by chemicals. Abroad, 
mirrors are often made of this glass, mixed with any of the following kinds. 

II. Sodium-calcium glass, French glass, window glass, somewhat harder than the 



GLASS. 269 

preceding but more readily fusible, exhibiting, as does all soda-containing glass, 
a peculiar blue-green hue. Crown-glass is of similar composition. 

III. Potassium-lead glass, crystal glass, very readily fusible, soft to cut, has a 
higher sp. gr. than other glass, and is more refractive. Among the varieties of this 
glass are:—1. Plint-glass, optical glass, in addition to lead often containing bis¬ 
muth and boracic acid. 2. Strass used for preparing imitation gems. 

IY. Aluminium-calcium-alkali glass, or bottle-glass, always contains oxides of 
iron and manganese; and sometimes magnesium instead of calcium. The colour 
varies from a red-yellow to a deep black-green. 

The sp. gr. of glass depends upon its composition. The alkali-calcium glass is 
the lightest, next follows aluminium-calcium-alkali glass, while thallium glass is 
the heaviest, as may be seen in the following table :— 


Bohemian crystal glass.2*396 Sp. gr. 

Crown-glass . 2*487 ,, 

Mirror-glass .2*488 ,, 

Window-glass.2*642 ,, 

Bottle-glass.2*732 ,, 

Lead glass .. .. ..2*9 to 3*255 ,, 

Flint-glass (Frauenhofer’s recipe). 3*77 ,, 

,, (Faraday’s ,, ). 5*44 

Thallium glass. ... 5*62 ,, 


Slowly cooled glass possesses single, rapidly cooled doubly refractive powers; the 
refractive index of glass differs considerably, but is never so high as that of the diamond. 
Taking the index of refraction of the vacuum of Torricelli as unity, that of quartz is 
= 1-547; diamond, 2-506; optical glass (2-52 sp. gr.)= 1-534 to 1-544; flint-glass of 
3-7 sp. gr., 1-639 ; thallium glass = 171 to 1*965. 

Kaw Materials used in These are:-I. Silica, viz. quartz, for very pure glass, for other 
Glass-making. kinds sand of varying quality or pulverised flint stones. For very 
pure glass the silica ought to be free, or very nearly so, from iron; in some cases the 
peroxide of iron adhering to the quartz or mixed with the sand is removed by hydro¬ 
chloric acid, while the sand is always first ignited and in some instances previously 
washed to remove clay, marl, humus, &c. Ordinary glass is made with coarser materials, 
the sand is not required to be so pure, as when it contains lime, chalk, or clay, it renders 
the mass more fusible. 

2. Boracic acid is sometimes used as a substitute for a portion of the silica. It 
increases the fusibility of the glass, imparts to it a high polish, and prevents devitrifica¬ 
tion. It is employed as borax or as a boro-calcite, a native boracic acid. 

3. Potassa and soda are used in a variety of forms, the former chiefly as potash 
(carbonate of potassa), or partly lixiviated wood-ash. 

Not so large a quantity of soda is required as of potash; 10 parts of carbonate of soda 
correspond to 13 parts of carbonate of potash. Recently the soda has been used in the form 
of Glauber’s salt; in this case, so much carbon is added to the siliceous earth and Glauber’s 
salt as will reduce the sulphuric acid of the sulphate of soda to sulphurous acid, and the 
carbon to carbonic oxide. The silicic acid then easily decomposes the sulphurous acid of the 
sulphite. To 100 parts of Glauber’s salt (anhydrous) 8 to 9 parts of coal are measured. 
An excess of carbon is detrimental, as a large quantity of sulphide of sodium is formed, 
which imparts a brown tint to the glass. 

4. The lime used in glass-manufacture must be free from iron. It is generally 
employed as marble or chalk, either raw or burnt. To 100 parts by weight of sand, 20 
parts by weight of lime are added. In the Bohemian manufacture the lime is employed 
as neutral silicate of calcium, Wollastonite, Si 0 3 Ca. Instead of lime, strontia, and 
baryta can be used, the former as strontianite (SrC 0 3 ), the latter as witherite (BaC 0 3 ). 
Fluor-spar (CaFl 2 ), and aluminate of soda were at one time used in making milky or 
semi-opaque glass. 

5. Oxide of lead is employed in most cases in the form of minium or peroxide,_ giving 
up some of its oxygen to form a lower oxide, and purifying the glass. The lead gives the 
glass a higher specific gravity, greater brittleness, transparency, and polish. It must be 










270 


CHEMICAL TECHNOLOGY . 


free from oxide of copper and tin, the former imparting a green colour, and the latter an 
opacity to the glass. White-lead is as efficacious as red-lead, provided no heavy spar be 
present. 

6 . Oxide of zinc is always added as zinc-white. When the colour is not of importance, 
zinc-blende with sand and Glauber’s salts may be used. 

7. Oxide of bismuth is only added in small quantities in the preparation of glass for 
optical instruments. Bismuth may be employed either as oxide or nitrate of the oxide. 

The natural silicates are only employed alone in the manufacture of bottle-glass ; some 
of the preceding additions are requisite in clear glass manufacture. 

Bleaching. Coloured glass as it occurs in the first process of manufacture may have the 
.colour disguised by mechanical mixture with white glass, or the colour may be discharged 
by chemical agents. Such agents are usually—braunite, arsenious acid, saltpetre, and 
minium or red-lead. 

1. Braunite, Mn 0 2 , has long been used as a material for glass-clearing. This oxide of 
manganese is, however, used only in small quantities; too much imparts a violet or 
amethyst-red colour to the glass; while an excessive amount renders the glass dark 
coloured and opaque. The violet-coloured glass is generally prepared with silicate of 
manganese by the addition of braunite to colourless glass. The action of braunite 
in clearing glass or rendering it colourless has been variously explained. It may be con¬ 
sidered that there arises in the molten glass the colours complementary to white, that is, 
the green from silicate of iron and the violet from silicate of oxide of manganese; this view 
is supported by the experiments of Korner, who obtained a colourless glass from a mix¬ 
ture of red and violet glasses ; and further by those of Luckow who obtained a colourless 
glass by the melting together of a glass strongly tinted red by protoxide of manganese 
with oxide of copper. The glass-blowers of the Bavarian Waldenses assert that a rose-red 
quartz there found is equalled by no other quartz in the production of the best crystal or 
clear glass. Von Fuchs says that this quartz contains 1 to 1-5 per cent, of oxide of 
titanium, which similarly to braunite, effects the chromatic neutralisation. Ivohn 
employs for this purpose protoxide of nickel or oxide of antimony. Oxide of zinc has 
lately been employed to remove or mask the green colour of Glauber’s salt glass, also 
imparting a higher polish. 2. Arsenious acid effects the removal of colour by chemical 
means only from glass containing carbon or silicate of iron : in glass containing carbon— 
Arsenious acid, As 2 0 3 | . ( Arsenic, As„, 

Carbon, 3C ) ^ ne \ Carbonic oxide. 3CO ; 

« in glass containing protoxide of iron :— 

Protoxide of iron, 6FeO, | o .. . f Oxide of iron, 3Fe 2 0 3 , 

Arsenious acid, As 2 0 3 , ) e \ Arsenic, As 2 . 

The arsenious acid is reduced by the carbon and protoxide of iron at a dull red heat, 
while the arsenic is volatilised. 

3. Saltpetre is added chiefly as Chili-saltpetre or nitrate of soda. In the manufacture 
of lead-glass (flint-glass) nitrate of lead is substituted for the nitrate of soda. Nitrate 
of barium has recently been employed to discharge the colour of glass; its action is similar 
to that of arsenious acid. 

4. That minium serves to render glass colourless has already been noted. Chambland 
states that glass may be whitened by forcing through it while molten a stream of air. 

utilisation of Kefuse The materials of glass manufacture are never melted alone, but 

mass. always with nearly the third part of prepared or finished glass. For 
this purpose, pieces of broken glass, flaw glass, the hearth droppings, and the glass 
remaining adherent to the blowers’ pipes may be utilised,—serving a purpose in the 
manufacture of glass similar to the rags in paper-making. Thus there is only a very 
small loss of materials. At each re-melting, however, a portion of the alkali of the frag¬ 
mentary glass is volatilised, and must be replaced by the addition of an alkaline salt. 

The Melting Vessel. The vessels in which the glass is melted are placed immediately 
upon the hearth, and are made of difficulty-fusible clay and powdered chamotte- 
stone. They are usually o-6 metre in height, the walls being 9 to 12 centimetres 
thick. They are dried in a temperature of 12 0 to 15 0 , and then placed in a chamber 
heated to 30° to 40°. After remaining about a month, the vessel is put into the 
tempering or annealing oven, heated to 50° ; it is next removed to the ordinary 
melting-oven, and gradually heated to the melting-point of glass, at which it remains 
for three to four hours. When a new pot is first used for glass-melting, the alkaline 
constituents of the glass act upon the clay, forming a rich clay glaze or glass, which, 
if allowed to mix with the ordinary glass, would be highly detrimental. Conse- 


GLASS. 


271 

quently broken glass and refuse are first melted in the vessel, and the glaze 
imparted, termed technically the lining, is a sufficient protection to the glass in 
after practice. The shape of the melting vessels varies. For melting with wood 01- 
gas the conical form, Fig. 120, is employed. When coal is used as fuel, the vessel 
takes the covered form, Fig. 121. Fig. 122 represents a rather peculiar form ; the 

Fig. 121. 



glass constituents are melted in A, the clear molten glass passing by the aperture in 
the central wall into B. The glass in b is thus always free from glass-gall or impu¬ 
rities, which remain behind in A. In the manufacture of looking-glasses, large 
quadrangular vessels, Fig. 123, are employed for refining purposes. 

The Giass-oven. The glass-ovens are respectively—1. The melting-oven ; 2. The 
tempering- or annealing-ovens, used in the after-manufacture. The melting-oven 
can only be made of fire-proof clay. It is built of a mixture of white clay and burnt 
clay of the same kind. Ordinary mortar and cements are useless for this purpose 
on account of their fusibility, therefore the same clay as is used for building is also 
used for binding. The oven must be built on dry ground ; if built on damp ground 
it is difficult to maintain the lower parts at a constant heat, requiring a larger supply 
of fuel. The arch is closed with a single piece of fire-proof clay weighing 800 to 
1000 cwts. After building the oven is dried for four to six months at a temperature 
of 12 0 to 15 0 ; a low fire is then lighted, and the temperature gradually increased foi 
about a month until the oven is fit for actual work. The arch is further covered 
with massive backstones, and these again are covered to a thickness of 5 to 6 inches 
with a lime-mortar. When much in use, and if not built of very good clay, an oven will 
not remain in working order for longer than if to if years; but if fire-clay is used, and 
only easily-fusible lead-glass is manufactured, the oven may last for four to five years. 
The oven contains six or eight to ten melting-pots, which must all be raised to the 














































































































272 


CHEMICAL TECHNOLOGY. 


same temperature. Further, the melting-oven is placed over half the fire-room. 
The annexed woodcut, Fig. 124, is a ground plan of a complete oven. Fig. 125 is a 
section showing the melting-oven and work-holes; Fig. 126 a vertical section 


Fig. 124. 



through the length of the oven; Fig. 127 a vertical section of the breadth. In the 
ground plan, Fig. 124, 0 0 is the flue; ccc are the melting-pots; n n, pots containing 
glass in another stage of preparation; ddd, the work-holes ; b b, the banks; i i, warm¬ 
ing and cooling ovens ; h h , tempering ovens; e e, the breast walls ; //, the splint 
walls; l l are small hearths to increase the heat in the tempering oven when 

Fig. 125 



required. In Fig. 125 l is the flue; y y are blocks of stone, bearing the wooden 
frame-work, z z, on which the wood used as fuel is placed to dry. Fig. 126 shows 
the bank, //, on which the melting-pots, h li h, stand ; over these pots are the work- 
holes ; n n are the side chambers. In Fig. 127, & b is the key-stone ; c d are the 
banks; g the flue, although in most glass-ovens there are no flues. The flame from 











































































GLASS. 


the fuel burning in both grates, m m, Fig. 126, after heating the melting oven, 
passes by the tempering rooms, and finally to the chimney-stalk. 

Siemen’s gas-oven has lately found extensive use. At the Paris International 
Exhibition of 1867 this oven obtained the gold medal. It consists of two parts, the 


Fig. 126. 



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yyyyyyyyyM*^ 


generator, Fig. 128, and the melting oven, Fig. 129. These parts are separate, and 
can be 30 or more metres from each other, being connected by a large gas-pipe. The 
fuel, brown coal, turf, stone coal, or wood, is placed in the generator at A, Fig. 128, 


Fig. 127 . 



and falls on the sloping grid, 0. The gas, a mixture of. carbonic oxide and nitrogen, 
ascends at a temperature of 150° to 200°, and flows out of the generator by a large 
pipe, V, 4 to 5 metres in height, and is conveyed thence by a horizontal pipe to the 







































































































































































































: 74 


CHEMICAL TECHNOLOGY. 


melting oven. Tlie upper chambers of the melting oven are similar to those of the 
usual ovens, r P are the melting-pots. The gas first passes into the first system of 
regenerators, the stones of which are raised to a red-heat, and passes thence to the 
melting room, where it meets with air heated in like manner. The products of com¬ 
bustion then pass to the second regenerating system, the stones of which are cold 
until heated by the passing gases. The waste gas is finally conducted to the 
chimney-stalk. When stone-coal is used in the generator, lead-glass may be melted 
in the oven in open vessels without reduction. The saving of fuel in comparison 
with the old system is about 30 to 50 per cent. 

Preparation of the Material, Formerly manufactured glass was only an imitation of crystalline 
and Melting. siliceous earths, the chemical action being but little known. The 
“Ikaline constituents were added as fluxes, and to this day retain that name. However, 

most of the results attending the variations 



Fig. 128. of temperature were known, and, in fact, the 

chief practical detail. 

Of especial importance in glass manufacture 
is the knowledge of the behaviour of glass 
in the fire. At the maximum temperature of 
glass-melting ovens, 1200° to 1250° C., the 
glass forms a thin fluid of the consistency of 
syrup. This condition is essential to the 
refining of the glass, as the thinness of the 
fluid admits of the settlement of foreign 
substances to the bottom, or of their floating 
to the surface of the glass contained in the 
melting-pot. In this condition also the clear 
molten glass can be run off. At a red-heat 
glass is exceedingly ductile and flexible; upon 
this quality depends its application in manu¬ 
facture. Two pieces of glass raised to a red 
heat can be welded into one piece by mere 
pressure. Glass as a fine thread is generally 
flexible, and may be spun. Undoubtedly glass 
will be used as a spinning-fibre at some 
future time; even now, in the International 
Exhibition of 1871, there are several articles 
of habiliment made of spun glass, exhibited by 
an Austrian firm. Brunfaut, of Vienna, in 1 869, 
prepared glass-wadding, feathers, bows, favours, 
nets, &c. Glass fibre, according to the mea¬ 
surement of Fr. Kick, of Prague, can be spun to 
a diameter of o - oo6 and o'oi2 millimetres. 
When glass is allowed to cool extremely slowly it loses its transparency, and is transformed 
into an opaque mass known as Reaumur’s porcelain. The chemical action taking place when 
glass is rendered opaque is, in spite of numerous researches, still unexplained. On the other 
hand, glass cooled too suddenly acquires peculiar properties. Detonating bulbs are small 
glass flasks which have been cooled immediately after being made. If a sharp grain of 
sand be dropped into the interior of one of these flasks it will fly to pieces with excessive 
violence, while the exterior will bear hard usage without result. Another peculiarity of 
glass manufacture are glass-tears, or Prince Rupert's drops, long pear-shaped drops 
of glass, tapering to a very slender tail, which are formed by dropping molten <dass 
into cold water. The bulb of these drops may be struck with a hammer; but if 
only a small portion of the tail be snapped off, the entire drop will break up with a loud 
report. This brittleness is more or less the characteristic of all unannealed glass, 
and is probably due to unequally cooled layers, which are consequently at different degrees 
of tension. 


Drying the Materials. Before tlie materials are placed in the melting oven, they are first 
subjected to a tolerably strong heat, not sufficient, however, to effect fusion in the 
drying oven. The benefit of this operation is the removal of the carbonic acid and 
water which would otherwise be disseminated in the melting oven. Some manufae- 

























GLASS . 


-75 


hirers dispense with this portion of the process, running a risk of turning out 
imperfect glass that can be avoided at a very small expense. 

Melting the Glass Material. When the temperature of the melting oven has reached the 
required degree, the material first frits together and is then melted. The oven 
must be heated equably throughout. At the melting-point the siliceous earth 
combines with the potash, soda, lime, alumina, oxide of lead, &c., to form 


Fig. 129. 



glass. The substances not taken up form a scum, known as glass-gall, upon 
the molten glass, which is removed by the aid of iron shovels. This scum is 
generally composed of sulphate of soda and chlorides of the alkalies. The progress 
of the melting process is from time to time ascertained by removing a sample of the 
glass by the help of an iron rod terminating in a flat disc, in fact a large fiat spoon. 

clear-melting. When the mass is well molten it is “ cleared,” that is, maintained for 
some time at such a temperature that the glass remains in a thinly fluid condition. 
During this period the uncombined substances settle to the bottom of the melting 
vessel, the air-bubbles disappear, and the glass-gall still remaining is volatilised or 
separated. At the commencement of the melting the disengagement of the gases 
from the molten mass causes an advantageous agitation, by which the several con¬ 
stituents of unequal specific weight and different composition become well mixed. 
After the disengagement of the gases the lower part of the melting vessel is at a 
lower temperature than the upper part, consequently the molten glass is well stirred 
with the iron ladles or “poles.” Lastly, a piece of either arsenious acid, damp 
wood, raw turnip, or any other water-containing substance, is introduced to the 
bottom of the vessel on an iron rod, the end in view being the violent agitation of 
the molten glass by the steam ovolved. 

Coid-stoking. After the completion of the clearing follows the cold-stoking, that is, 
the lowering the temperature of the oven till the glass attains a tough fluid consis¬ 
tency requisite before it can be blown. The glass remains at this temperature, 
700° to 8oo° C., during the rest of the manufacture. 






















276 


CHEMICAL TECHNOLOGY. 


The length of the several processes is as follows :— 


Melting. io to 12 hours. 

Clearing. 4 to 6 ,, 

Blowing. 10 to 12 ,, 


so that five to six meltings can he effected in a week. 

Defects in Glass. It is extremely difficult to prepare glass perfectly free from blenush. 
The principal defects are—streaking, threading, running unequally, or dropping, stoning, 
blistering, and knotting. Streaking follows from heating the glass unequally,, another 
consequence of which is the threading or the formation of the striae, by glazing, into 
coloured threads, generally green. By dropping is understood the lumps or globules 
formed in the glass by the glazing of the clay cover of the melting vessel, and its combi¬ 
nation with the volatilized alkalies, the crude glass thus formed on the cover dropping 
into the molten glass contained in the vessel. Blistering is a common result of the imper¬ 
fect clearing of the glass from air bubbles. Lastly, knotting, another common defect, 
results from uncombined grains of sand taken up in the glass; the small particles of the 
oven and melting vessel detached during the melting similarly giving rise to stoning. 
Other defects., such as the imperfect combination of the materials, arising from careless¬ 
ness or inability of the workman, need not here be noticed. 

various Kinds of Glass. Glass is separated according to its composition or method of 
manufacture into 

I. Glass free from Lead. 

A. Plate-glass, a. Window-glass :— 

a. Boiled glass. 

/ 3 . Crown glass. 

b. Plate-glass :— 

a. Blown plate-glass. 

/ 3 . Cast plate-glass. 

B. Bottle glass:— 

a. Ordinary bottle glass. 

b. Medicine and perfumery glass. 

c. Glass for goblets, drinking glasses, &c. 

d. Water pipes and gas tubes. 

e. Betort glass. 

C. Pressed or stamped glass. 

D. Water glass. 

II. Glass containing Lead ( Flint-Glass ). 

A. Crystal glass. 

B. Glass for optical purposes. 

C. Enamel. 

D. Strass. 

III. Coloured Glass and Glass Staining. 

IY. Glass Decorations. 

riate or window-Giass. The glass melted in muffles or vessels is manufactured as plate- 
glass or as crown-glass. Plate-glass, as its name implies, is formed in large or small 
plates; window glass is generally either ordinary bottle glass, or a finer glass of 
a whiter colour. Becently, thick has taken the place of thin glass for windows, but 
the colour is hereby considerably increased. That window glass should be prepared 
cheaply is an essential point, consequently crude materials are employed—crude 
potash and soda, wood-ash, Glauber’s salt, ordinary sand, and broken glass from the 





GLASS . 


277 

warehouses, &c. Plate- or window-glass is generally composed of 100 i>arts sand, 
30 to 40 parts of crude calcined soda, 30 to 40 parts of carbonate of calcium. 
Instead of the soda may be substituted an equivalent quantity of Glauber’s salt. 
Benrath (1869) found in several kinds of plate-glass the following constituents :— 


Silicic acid . 

Soda . 

Lime . 

Alumina and oxide of iron.. 

.. .. 1*92 

7 i '56 

12- 97 

13- 27 

1*29 

73 *ii 

13-00 

13-24 

0-83 


99-46 

99-09 

100-18 


Tools. The tools ordinarily used by the glassblower in the preparation of plate- and 
crown-glass are the following:— 

a. The pipe or blow-tube, Pig. 130? is an iron pipe 1*5 to i*8 metres in length, 3 to 4 
centimetres thick, and 1 centimetre interior diameter, a is the mouthpiece, made so as 

Fig. 130. 


c 



to turn easily between the lips, c is a hollow handle from 0-3 to 0*5 metre in length, b is 
the part attached to the glass. 

b. The handle or hand irons are rods 1 to 1-3 metres in length, used to transport the 
hot vessels, &c. c. The marbel, Pigs. 131 and 132, is a piece of wood with semi-globular 
indentations, which serve as matrices for the glass to be taken up on the blower’s pipe. 
d. The whip, a block of wood, hollowed so as to form a long neck to the soft semi-molten 



Pig. y 3 . 



Pig. 134- 



glass ; it is also used to remove the glass from the pipe. e. Fig. 134 are the shears used 
for trimming the molten glass, and to cut openings during the blowing of various 
articles. 

Plate-glass is manufactured as crown-glass or as rolled glass. 

Crown-glass. Crown-glass is the oldest kind of window glass. It is formed in the manufac¬ 
ture as a disc of glass, generally of about six inches in radius from the periphery to the 
centre knot left by the glassblower’s pipe, technically termed the bull’s-eye. The 
largest discs are scarcely 64 to 66 inches, from which a square plate of 22 inches only can be 
cut, the bull’s-eye interfering with the cutting of a larger size. In. the preparation of this 
glass three workmen are employed; the first takes so much molten glass on the end of a 
pipe as will serve for a single disc, and passes pipe and glass to the second workman, the 
blower. He blows the glass into a large globe or ball, which, when finished, he hands to a 
third workman, the finisher, who opens the globe and forms the sheet or pane. The 
labour is divided in detail in the following manner:—The first workman receives the 
warm pipe, thrusts it into the vessel of molten glass, and turns it steadily round until he 
has collected upon the end a knob of glass of sufficient size. The weight of this knob is 
generally 10 to 14 lbs. The first workman imparts somewhat of a spherical form by 
means of the marbel to the solid glass ball, which is now taken in hand by the blower. 





































CHEMICAL TECHNOLOGY. 


27b 

who by turning and shifting the glass about, at the same time blowing through the tube, 
perfects the hollow spheroid. The glass has by this time cooled considerably, and with 
the pipe is therefore returned to the oven, the tube of the pipe being fastened in a fork or 
hook in the ceiling of the oven. As the globe of glass is gradually heated the weight ol 
the rod causes it to flatten out, and it is removed by the finisher as a disc of nearly 
molten glass. He places the tube in the cavity of the whip, and by a series of dexterous 
movements perfects the shape, enlarges the disc if required, or in some cases makes 
a larger disc by removing the partially flattened sphere from the oven, opening the bottom 
with a maul or iron rod, and causing the glass to take the form of a disc by means of the 
centrifugal force resulting from a rapid rotary motion of the rod. Finally the discs are 
separated from the pipe by the help of a drop of cold water, and are next placed in an 


Fig. 135. 



annealing oven to the number of 150 to 200 to cool. The finished plates are cut to the 
required size ; the centre's or bull’s eyes serve for the making of strass and for other pur¬ 
poses. 

Su e nd?rGia 8 °s r < Rolled or sheet glass is made by cutting a glass cylinder or roll 
throughout its length, and beating or rolling it out flat on a table. It is for this 
reason termed sheet glass. Usually this sheet glass is used for ground glass, and is 
further separated into ordinary sheet or roll-glass and fine sheet glass, the latter 
haying larger dimensions. 







































































































































































GLASS. 


279 


The preparation of sheet glass is one of the most difficult processes of glass manu¬ 
facture ; it may be considered as consisting of two operations— 

1. The blowing of the roll, or cylinder; and 

2. The flattening. 

After the molten glass has cleared, and attained the barely fluid consistency 
before mentioned, the workman inserts his pipe into the mass, and by turning 
manages to accumulate on it a globe of glass, during the time blowing into the tube 
to keep it clear of the molten glass. The glass now takes the form a, Fig. 135. By 
continued manipulation in the marbel, and by blowing, the enlarged forms, b and c, 
and finally d, are obtained. The glass has by this time cooled, and is taken to the 
oven to be re-heated. When this is effected, the workman by means of his tools, by 
a continued rotation of glass, and by blowing, brings the globe to the shape repre¬ 
sented by /. He then opens out the bottom of this form with a maul-stick, and 
obtains the cylinder e, which is separated from the pipe by dropping a little cold 


Fig. 137. 


water upon the neck, 0, joining the two. The removal of this neck is next effected 
by means of a red-hot iron rod, which also serves to open the cylinder throughout 
its length as shown by h. 

After a great number of these cylinders have been blown, the operation being generally 
continued for three days, the opening into plates is commenced. _ The cylinders are placed 
in an oven termed the plate-oven, shown in ground plan in Fig. 136, consistmg of two 
chambers, one the heating room, c, and the other the tempering or annealing room, d. In 
the passage b, the heated glass rolls or cylinders, a a a, are suspended upon two iron rods, 
where they are maintained at a certain heat. The most important part of the plate-oven 
is the platten, c, made of a well-rammed fire-clay. . A similar plate, d, is placed in the 
annealing room. When sufficiently heated, the cylinders are brought to the flattening 
table, c, Fig. 137, where they are speedily opened out in the manner shown in the woodcut. 
A workman stationed at cl, Fig. 136, receives the flat panes of glass, and leans them 
against the iron bars, s s, in the annealing room, whence, having gradually cooled during 
four to five days, they are removed to be sorted and packed. 

piate-Giass. Plate-glass is either blown or cast. The manufacture is very similar 
to that of table-glass just described. The materials are in great part the same as 
those employed in the manufacture of fine white glass. This branch of glass manu¬ 
facture is most strikingly illustrative of the rapid growth of the industry during the 
last ten or twenty years. Formerly plate-glass was esteemed an article of luxury, 
whereas now' it is that most generally used for workshop windows, carriages, show¬ 
rooms, &c., and for windows of private residences. It far surpasses in transparency 



Fig. 136. 














28 o 


CHEMICAL TECHNOLOGY. 


and elegance the small panes formerly used. By the Glass Jury of the Interna¬ 
tional Exhibition of Paris of 1867, it was surmised that before ten years had elapsed 
plate-glass would be that most generally in the market. The blowing of plate-glass 
is effected with the same tools as the blowing of table-glass; and the cylinder is 
obtained in a similar manner. The lump of glass taken by the blower on his pipe 
from the melting vessel weighs about 45 lbs., from which a plate of 1*5 metres in 
length and 1 to i*i metres breath by 1 to i-i centimetres thickness is obtained. 
But the chief method of making plate-glass is by casting. Cast plate-glass is 
always made from pure materials, and may be considered as a soda-calcium glass 
free from lead. Potash-calcium glass is far more expensive, being almost a colour¬ 
less glass. In England, Belgium, and Germany the raw materials used in manfac- 
turing cast plate-glass are—sand, limestone, and soda, or Glauber’s salts. 

Benrath (1869) found in English (a) and in German (/ 3 ) plate-glass :— 



a. 

0 . 

Silica . 

.. 76-300 

78750 

Soda . 


13-000 

Lime . 

6-500 

6-500 

Alumina and oxide of iron .. 

0-650 

1750 


100*000 

IOO'OOO 

Sp-gr . 


2-456 


The following description of casting the plates is mainly founded upon the method 
pursued at St. Gobin and Bavenhead. The manufacture is included in— 

1. The melting and clearing, 

2. The casting and cooling, 

S- The polishing: including 

a. The rough-polishing, 

/ 3 . The fine-polishing, 
y. Einishing. 

rbe Melting and Clearing. The melting and clearing vessels are of very different form and 
size. The first is a conical vessel surmounted by a cupola having three apertures, making 

Fig. 138. 



an angle of 120 0 with each other. The clearing pans are small, wide, and low vessels. 
These vessels are never in the same oven. After the materials are melted, which is 
effected in sixteen to eighteen hours, the molten mass is poured into the clearing vessels. 















GLASS. 


2S1 


The impurities are then removed with a large copper ladle, this process occupying about 
six hours. During the clearing the excess of soda is volatilised. When the glass is 

Casting and Cooling, sufficiently cleared the casting commences. The vessel containing the 
molten glass is taken up by a crane and swung to the casting table, this table or mould 
being on a level with the cooling or annealing oven. The casting table consists of a 
large polished metal plate, Fig. 138, in the French work of copper or bronze, 4 metres 
long, 2*25 metres wide, and 12 to 18 centimetres thick. The plate at St. Gobin weighs 
55,000 lbs., and cost 100,000 francs (£4000). In England the plates are of cast-iron, 25 
centims. thick, 5 metres in length, and 2-8 metres wide. In order that the glass plate shall 
be of equal thickness, a bronze or cast-ii'on roller passes over the surface on guides of the 
thickness required. The metal plate is first warmed to prevent the sudden cooling of the 
glass. The operation of casting includes— 

a. The conveyance of the pan to the table; 

b. The cleansing of the plate and the pan; 

c. The casting and conveyance of the plate to the annealing' room. 

The cooling room has two fire-places and three glass tables. The temperature is at first 
that of the glass plate introduced. So soon as three plates are placed in the oven, all the 
openings are closed, and the glass left for a day to cool. The cooled glass plate is taken 
out of the annealing oven to the cutting room, laid on a cloth-covered table, and cut to 
size with a diamond. 

Polishing. The glass plate is cut into tablets. The under side of the plate, where it has 
been in contact with the table, is smooth, while the upper surface is wavy, and requires to 
be polished. This is effected by fastening the plate or tablet to a bench with plaster-of- 
Paris, and grinding the upper surface smooth with some sharp powder; or another plate 
is caused by machinery to move above the former in such a manner that the surfaces of 
both are ground smooth. The ground plates are then removed to the polishing table, 
where a similar process is gone through, but with a finer powder. Finally, when placed 
upon the finishing table only the finest powder and leathern pads are employed. By grind¬ 
ing and polishing the glass sometimes loses half its weight and thickness. Suppose a plate- 
glass manufactory to produce 400,000 square feet of glass annually, there will be with this 
amount of glass weighing about 16,000 cwts., a loss of 8000 cwts., corresponding to 2700 
cwts. of calcined soda, and a money value of more than £1000. 

silvering. After polishing, each glass tablet intended to make a looking-glass is silvered, 
or more correctly coated on one side with an amalgam of tin. In the preparation of this 
amalgam tin-foil is used, but it must be beaten from the finest tin, and possess a surface 
similar to that of polished silver. The art of silvering is simple, and merely requires 
dexterity. The glass plate having been thoroughly cleansed from all grease and dirt with 
putty-powder and wood-ash, the workman proceeds to lay a sheet of tinfoil smoothly 
upon the table, carefully pressing out with a cloth dabber all wrinkles and places likely to 
form air bubbles. He spreads over it a quantity of mercury, taking care that all parts are 
equally covered, and then the glass plate is pushed gently on to the surface, commencing 
at one edge. A glass plate of 30 to 40 square feet requires 150 to 200 pounds of mercury, 
although the amalgam is not so thick as a sheet of the finest paper. The glass is allowed 
to remain for twenty-four hours. It is then removed to a wooden incline similar to a 
reading desk, to allow of the excess of mercury draining off. As the amalgam gradually 
sets, the incline is increased till finally the plate reaches the perpendicular, when the pro¬ 
cess is finished, and the mirror removed to the store-room. 

silvering by The former method of coating the glass with tin-amalgam obtains its 
Precipitation, name of silvering by analogy only: the true process of silvering* is the fol¬ 
lowing, patented in 1844 by Mr. Drayton :—32 grms. of nitrate of silver are dissolved in 
64 grms. of water and 16 grms. of liquid ammonia, adding to the filtered solution 108 
grms. of spirits of wine of 0 842 sp. gr., and 20 to 30 drops of oil of cassia. Call this fluid 
No. r. Another fluid (No. 2) is prepared by mixing 1 volume of oil of cloves with 3 
volumes of spirits of wine. The workman places the glass plate upon a table, carefully 
levels it, and floods it to a depth of 0'5 to 1 centimetre with fluid No. 1. He then preci¬ 
pitates the silver by adding 6 to 12 drops at a time of fluid No. 2 until the whole of the ' 
surface is covered. For every square foot of glass 9 decigrammes of nitrate of silver aro 
required. Liebig recommends an ammoniacal solution of fused nitrate of silver, to which 
450 c.c. of soda-ley of ro35 sp. gr. are added. The precipitate thrown down is dissolved 
by means of ammonia, the volume being increased to 1450 c.c., and by water to 1500 c. c. 
This fluid is mixed shortly before application with one-sixth to one-eighth of its volume of 
solution of sugar of milk, containing 10 parts by weight to 1 of sugar of milk. The glass 
is flooded with this fluid to about half-an-inch in depth; reduction soon sets in, and the 
glass becomes thickly coated. 1 square metre of glass plate requires 2'210 grms. of silrer. 


282 


CHEMICAL TECHNOLOGY. 


The plate is then dried, cleaned, and polished. Lowe employs nitrate of silver, starch- 
sugar, and potash; A. Martin, nitrate of silver, ammonia, and tartaric acid. 

Platinising. According to the researches of Dode, platinum may be used for coating plate- 
glass. In Trance, Creswell and Tavernier have already brought platinised mirrors before 
the public. Hitherto platinum has been used in ornamenting porcelain, and the glass 
plates are prepared in a similar manner, the metal being burnt in, as it is termed. The 
platinum is precipitated from its chloride by oil of lavender, the chloride being spread 
equally over the glass with a fine-haired paint-brush. The plate is then placed in a 
muffle. Cheapness is a prominent feature of this process ; while all faulty glasses can be 
very easily repaired, these by the old methods being thrown aside as useless. In Paris the 
lids of boxes and fancy articles are largely manufactured from platinised glass. 

pottle Glass. Bottle glass includes all kinds of glass made into vessels for holding 
fluids. It is made from common green glass, from fine white glass, and from crystal 
glass. Medicine bottles, &e., are made from common green glass ; tumblers, or 
drinking glasses, from fine white glass; and crystal glass is employed for the same 
articles, but selling at a higher price. 

The materials for ordinary bottle glass are sand, potash or soda, basalt, &c. Tor 


medicine glass the materials must be free from iron, and still purer for the articles 
of white glass. In the manufacture of bottle glass no considerable amount of care 
is required, the desiderata being strength and sufficient resistance to the action of 


ordinary acids. 

The processes of melting and 

annealing 

are conducted in tl 

ordinary manner. 

The analyses 

of several glasses gave the following 

results:— 

Silicic acid .. 

.. .. 747 1 

74*66 

75'94 

74*37 

74*26 

Potash .. 

.. . . — 

4*32 

— 

12'48 

— 

Soda 

.. .. 1574 

11*01 

I 5 'i 5 

3*42 

14*06 

Lime 

.. .. 877 

9* I 3 

8*oi 

9‘02 

8*6o 

Alumina 

.. .. 0*43 

\ 



( 2*52 

Oxide of iron 

0*14 

o-88 

0*90 

071 

0*38 

Oxide of manganese .. 0*21 

' 



l 0*18 


100‘00 

100*00 

100*00 

100*00 

100*00 

Sp. gr. .. 

.. .. 2-47 

2*48 

2*47 

2*30 

2*40 


J-axc UCtCUIO LllC/ QCVOXCXJ. piUCCCCCO 5AU-00 AiiclXXL4.J.«^LU..Lt; CLLVy CilLtM. tilt; 

of the rough shape out of tough fluid glass, so various that only single examples can be 

given. We will select the ordinary wine-bottle. 
The glassblower, taking some molten glass on 
his pipe, turns and moulds it into the shape 
of a, Tig. 139. By continued blowing the 
enlarged form, b, is obtained; this form still 
more enlarged, as at c, is placed in the mould, 
d. The workman now blows sharply into the 
incipient bottle, the glass filling out the 
mould and producing the sharp curve of the 
shoulder of the wine-bottle. The rod or pun- 
til, c, is now introduced, and a firm footing 
given by pressing in the bottom of the bottle. 
While the blower prepares a new bottle, the 
assistant places that already formed in the 


annealing oven. In the making of flasks 
and retorts the flask-tongs, Tig. 140, are em¬ 
ployed, the neck being allowed to remain 
straight, as at a, Tig. 141, to form a flask, or 
bent, as at b , to make a retort. The manu¬ 
facture of a beaker will be readily understood 
from Tigs. 142 and 143, a, b, c, being the 

t method of producing a globular body, and 

1 cl Afl I 1 I fl An 4-,, K, A. Z __ i 1 1 



# t i O XX.ACXA X. JV-lJ y CL XI 

a, b, c, a beaker with nearly perpendicular sides. Glass-tubing is drawn out as shown at 
" 144. Glass rods are similarly made, but without blowing. 


Fig. 








































GLASS. 


283 


pressed and cast Glass. Pressed or cast glass comprises the many cheap glass orna¬ 
ments, and, indeed, ornamental glass work of all kinds, now so general. The tall, 
narrow-mouthed chimney ornaments are thus made hy being blown into engraved 
brass moulds, instead of into plain moulds as in the case of the bottle. Cup-shaped • 
articles are made with molten glass pressed between a concave and convex surface, 
the surplus glass escaping at some point purposely arranged. As a rule the objects 
taken from the moulds require but little polishing. 


Fig. 140. Fig. 141. 



water-Giass. By water-glass is understood a soluble alkaline silicate. Its prepara¬ 
tion is effected by melting sand with much alkali, the result being a fluid substance, 
first observed by Yon Helmont, in 1640. 


Fig. 142. 




Fig. 144. 


Fig. 143. 





It was made by Glauber in 1648 from potash and silica, and by him termed fluid 
silica. Yon Fuchs, in 1825, obtained what is now known as water-glass by treating 
silicic acid with an alkali, the result 'being soluble in water, but not affected by 
atmospheric changes. 

The various kinds of water-glass are known as— 

Potash water-glass. 

Soda ,, 

Double ,, 

Fixing ,, 

Potash water-glass is obtained by the melting together of pulverised quartz or 
purified quartz sand 45 parts, potash 30 parts, powdered wood charcoal 3 parts, the 
molten mass being dissolved by means of boiling in water. The solution contains 









































284 


CHEMICAL TECHNOLOGY. 


much sulphuret of potassium, which is removed by boiling with oxide of copper. 
The addition of carbon assists in reducing part of the carbonic acid to carbonic 
oxide, which disappears during the melting. Soda water-glass is prepared with pul¬ 
verised quartz 45 parts, calcined soda 23 parts, carbon 3 parts; or, according to 
Buchner, with pulverised quartz 100 parts, calcined Glauber’s salt 60 parts, and 
carbon 15 to 20 parts. Double water-glass (potash and soda water-glass), is 
prepared, according to Dobereiner, by melting together quartz powder 152 parts, cal¬ 
cined soda 54 parts, potash 70 parts; according to Yon Fuchs, from pulverised 
quartz 100 parts, purified potash 28 parts, calcined soda 22 parts, powdered wood 
charcoal 6 parts. It is further obtained by melting tartrate of potash and soda, 

| C 4 1I 4 06 + 4H2O, with quartz ; from equal molecules of nitrate of potash and 

soda and quartz; from purified tartar and nitrate of soda and quartz. It is more 
fusible than the foregoing. For technical purposes a mixture of— 

3 volumes of concentrated potash water-glass solution. 

2 ,, ,, soda ,, ,, 

is employed. By the name of fixing water-glass, Yon Fuchs designates a mixture 
of silica well saturated with potash water-glass and a silicate of soda, obtained by 
melting together 3 parts of calcined soda with 2 parts of pulverised quartz. It is 
used to fix or render the colours permanent in stereochromy. 

That known commercially as prepared water-glass is obtained by boiling the pow¬ 
dered water-glass with water; and the solution, as found in the market, is known 
as of 33 0 and 66°, the difference being that the first 100 parts by weight contain 33 
parts by weight of solid water-glass and 67 parts by weight of water. It therefore 
follows that in solutions of 40° and 66°, the water is proportioned as 60 and 34 parts 
respectively. Acids, with the exception of carbonic acid, decompose water-glass 
solutions, separating the silica as a gelatinous substance; it should, therefore, be 
kept in vessels well set apart from volatile acids. 

Water-glass is an important product in industry. It is used to render wood, linen, 
and paper non-inflammable. The water-glass of 33 0 is first mixed with double its 
amount by weight of rain-water, and is then treated with some fire-proof colouring 
matter, as clay, chalk, fluor-spar, felspar, &c. The material to be rendered unin¬ 
flammable is painted with the solution, and again with another coat after the first 
has remained twenty-four hours to dry. Wood is thus preserved from being worm- 
eaten, from encrustation of fungi, &c. Another industrial application of water- 
glass is as a cement; in this it is equal to lime, and, indeed, is known as “ mineral 
lime.” Chalk mixed with water-glass forms a veiy compact mass, drying as hard as 
marble; no chemical change is hereby effected; there is no conversion to silicate of 
calcium or carbonate of potash; the hardening is entirely the result of adhesion. 
Phosphate of calcium treated with water-glass acts similarly. Zinc-white and 
magnesia lose none of their useful properties when mixed with water-glass. 
Another important application of water-glass is in the painting of stone and concrete 
walls, and in the preparation of artificial stone. The latter, first made by Bansome, 
is daily meeting with more extended application in England, India, and America. It 
is prepared by mixing sand with silicate of soda to a plastic mass, which is pressed 
into the required shape, and then placed in a solution of chloride of calcium. By 
this means siliciatc of calcium is formed, and cements the grains of sand to "ether, 
while the chloride of sodium is removed by repeated washings. As cement for stone, 


GLASS. 


285 

glass, and porcelain, water-glass is especially useful. It is also employed in the 
preparation of xyloplasfic casts, made of wood rendered pulpy by treatment with 
hydrochloric acid, and aftewards impregnated with water-glass. 

stereochromy. An interesting and important application of water-glass is in the new 
art of mural and monumental painting, termed by von Fuchs Stereochromy (arepeos, 
solid , and xp^pu, colour). In this method of painting the water-glass forms the 
foundation or binding material of the colour. There is first to be considered the 
mortar or cement ground upon which the painting is to be executed. This ground 
has to receive an under- and an over-ground. It is essential, of course, that the 
fundamental groundwork should be of a stone or cement possessing every requisite 
for durability. The next, or under-ground, is made with lime-water, and is allowed 
to remain for some time to harden. When well dried the water-glass solution is 
applied, and allowed to soak well into the interstices of the mortar. After the under¬ 
ground has been thus prepared, the over-ground, or that to receive the painting, is 
laid on. This consists of similar constituents to the under-ground, with the exception 
* that a good sharp sand is used, and the mixture treated with a thin ley of carbonate 
of lime. This over-ground of fine cement being nicely levelled, and having dried, it 
is thoroughly impregnated with water-glass. When this is dry, the painting is 
executed in water-colours. Nothing further is necessary than to fix these colours, 
which is effected by a treatment with a fixing water-glass. The colours employed 
are:—zinc-white, chrome-green, chrome-oxide, cobalt-green, chrome-red (basic 
chromate of lead), zinc yellow, oxide of iron, sulphuret of cadmium, ultramarine, 
ochre, &c. Yermillion is not employed, as it changes colour in fixing, turning to 
a brown. Cobalt-ultramarine, on the contrary, brightens on the application of the 
fixing solution, and is, therefore, a very effective colour. As a decorative art 
stereochromy will doubtless attain great importance, the paintings being unaffected 
by rain, smoke, or change of temperature. 

crystal Glass. Crystal glass includes all lead-containing potash glass. Crystal glass 
was first prepared in England. There are a few difficulties in manufacturing this 
glass. The smoke from an anthracite coal fire is injurious to the pure colour of 
the glass, so that the melting-pot is provided with a cover ; but this addition has the 
disadvantage that the temperature necessary to melt the glass cannot easily be 
obtained. A larger proportion of alkali must therefore be added, which deteriorates 
from the quality of the glass, rendering it liable to after-change. To prevent this 
as much as possible oxide of lead is used to make the glass more easily fusible, 
and by this means a beautifully clear, transparent glass results. The following 
table will give some idea of the proportions of the materials :— 

Sand .300 

Potash.100 

Broken glass . .. 300 

Minium . 200 

Sesquioxide of manganese .. o'45 
Arsenious acid.o*6o 

The following mixture is used in the glass houses of Edinburgh and Leith:— 

Sand .300 

Potash.100 

Minium.150 

Lead-glaze. 50 

And a small quantity of sesquioxide of manganese (braunite) or arsenious acid. 











486 


CHEMICAL TECHNOLOGY . 


To render the glass fluid, saltpetre is sometimes added, but in moderate quantities. 
Dumas recommends sand 300, minium 200, dry potash 95 to 100. On the suppo¬ 
sition that there is no loss during melting, the mixtures contain:— 

Silica .... 57-4 57 

Oxide of lead .. 36*3 36 

Potash .... 6*3 7 

100*0 100 

The wnoie melting process is included in 12 to 16 hours. The glass is treated in 
a manner similar to that already described, but is more easily worked. Benrath (a) 
and Faraday (/ 3 ), found crystal glass by analysis to consist of:— 



a. 

/ 3 «» 

Silicic acid 


5 1 '93 

Oxide of lead .. 


33*28 

Potash . 


13*67 

Alumina, &c. 

0*04 

— 


99’95 

98*88 


According to Benrath normal crystal glass has the formula K IO Pb 7 Si 3 608 4 (*.€., 
5 K 2 0 , 7 Pb 0 , 3 6 Si 0 2 ). 

Polishing. Crystal glass is either cast in brass moulds or is ground. Its hardness 
admits of its taking a better polish than other glasses. The grinding wheel is of cast- 
iron ; above the periphery is fixed a vessel containing water and fine washed sand, which 
constantly drops upon the wheel, assisting in the cutting. The polishing wheel is of wood, 
well served with pumice-powder and water. 

optical Glass. The preparation of good optical glass, especially in large dimensions, 
is a matter of much difficulty. Transparency, hardness, a high refractive power 
with perfect achromatism are all required, and must be obtained at the outlay of any 
amount of labour. The glass must also be entirely homogeneous, else the light 
is not refracted regularly; threads and streaks (striae) are the results of inequality, 
and it naturally follows that if these appear to the unassisted eye, they will 
seriously affect delicate observations when high magnifying powers are used, as 
in telescopes and microscopes. It is an error, however, to suppose that these irre¬ 
gularities arise from impurities; they are rather due to interruptions in heating 
and cooling, or to unequally heating and cooling during manufacture. This must 
especially be evident in the case of waviness or an undulating structure of the glass. 
Crown-glass, free from lead, is not so liable to faults as flint-glass; both these 
are employed for optical purposes. 

The Rev. Mr. Harcourt’s experimental researches as to the best optical glass, communi- 
oated to the British Association at the recent meeting at Edinburgh, by Professor Stokes, 
show fully what has been accomplished in preparing glass of this order. Mr. Harcourt’s 
researches were chiefly carried on with phosphates, combined in many cases with fluorides, 
and sometimes with tungstates, molybdates, and titanates, owing to the difficult fusibility 
and pasty consistency of silicate glasses. The experiments included glasses containing 
potassium, sodium, lithium, barium, strontium, calcium, aluminium, manganese, magne¬ 
sium, zinc, cadmium, lead, tin, nickel, chromium, lead, thallium, bismuth, antimony, 
tungsten, molybdenum, titanium, vanadium, phosphorus, fluorine, boron, and sulphur. 
The molybdic glasses first prepared were of a somewhat deep colour, deteriorating with 
age ; but at length molybdic glass was obtained free from colour and permanent. 
Titanic acid gave results much superior to those obtained -with molybdic. Glass made 
with terborate of lead agreed in dispersive power with flint-glass; while a prism of this 
glass extends the red and blue ends of the spectrum equally with a prism of one part by 







GLASS. 


287 


volume of flint-glass with two of crown-glass. Notwithstanding the great difficulties 
arising from strice, Mr. Harcourt finally succeeded in preparing discs of terborate of lead 
and of a titanic glass, 3 inches in diameter, almost homogeneous. 

It is well known that flint- and crown-glass form an achromatic combination. Flint- 
glass is very easily rendered fluid, conducing to the formation of strife. A variation of 
the proportions of the constituent materials, though not producing effects visible to the 
eye alone, will strongly striate the glass, rendering it unfit for optical purposes. The con¬ 
stituents must be equally distributed throughout, and this is a great difficulty. The 
oxide of lead being of so much greater weight sinks to the bottom, while the lighter con¬ 
stituents float at the upper part of the melting vessel. Usually this is so much the case 
that glasses of different specific gravities are obtained from the upper and lower parts of 
the melting-pot. Lamy has lately employed thallium flint-glass in the preparation of 
optical glass, thallium taking the place of potash. Cl. Winkler substitutes bismuth for the 
lead. 

Bontemps manufactures flint glass in the following manner :—A glass mass is 
prepared of— 

White sand . 100 kilos. 

Minium . 106 ,, 

Carbonate of potassa . 43 ,, 

and placed over an anthracite or stone-coal fire in a small melting oven, shown in 
Fig. 145 in vertical, and in Fig. 146 in horizontal section. The oven contains 01.ly 
one covered melting vessel, B, standing on the bank, A. a a are the grate bars; c 
an iron rake, enclosed in a fire-clay cylinder, d, and resting upon the roller, /. 
After about fourteen hour’s the mass becomes equally fluid; and a red-hot rake is 
introduced into the vessel by which the several layers of material are intimately 


Fig. 145. 



Fig. 146. 


a. 



mixed In about five minutes the mass is sufficiently stirred; the iron rod is then 
removed, the clay cylinder remaining. This stirring is effected several times with¬ 
out removing the clay cylinder ; and the glass is then ready for blowing or casting. 
But for optical purposes it is, after the removal of the clay cylinder, allowed to cool 
gradually during eight days in an annealing oven. The most perfect pieces of glass 










































288 


CHEMICAL TECHNOLOGY. 


are then cut from the interior of the mass. According to Dumas’s analysis of a 
sample obtained from Gruinand, flint-glass consists of— 

Silica.42*5 

Oxide of lead .43*5 

Lime. 0*5 

Potash. 11 *7 

Alumina, oxide of iron, and) ^ 
protoxide of manganese ) 


100*0 

The second kind of optical glass, crown-glass free from lead, contains, according 
to Bontemps Sand, 120; potash, 35; soda, 20; chalk, 15; and arsenious acid, 
1 part. 

strass. The imitation of precious stones is an interesting feature of glass manu¬ 
facture, and in Egypt and Greece it is an art that has attained to great perfection. 
All precious stones, with the solitary exception of the opal, can be imitated arti¬ 
ficially. The chief constituent of these artificial gems is strass, or as it is termed 
by Eontanier, Mayence base ; and in Erance artificial gems are mostly known as 
Pierres de Strass. This base, then, is colourless, and may be considered as a boro- 
silicate of the alkalies containing oxide of lead, this being in larger proportion than 
in flint-glass. 

Donault-Wieland found colourless strass by analysis to consist of:— 


Silica.38*1 

Alumina . i*o 

Oxide of lead .. .. 53*0 

Potash., 7*9 


Borax ) , 

Arsenious acid j * * ^ races 


100*0 

This analysis gives the formula— 

( 3 E 2 0 , 6 Si 0 2 ) + 3 ( 3 Pb 0 , 6 Si 0 2 ). 

The various gems are imitated by the addition of colouring oxides, the whole ot 
the materials being ground to a fine powder, intimately mixed, and melted at a 
strong heat. The imitation of the topaz is obtained by taking—strass, 1000; anti¬ 
mony, 40; and Cassius’s purple, 1 part. The topaz can also be imitated with— 
strass, 1000 ; oxide of iron, 1 part. The imitation ruby is obtained with 1 part of 
the topaz paste, and 8 parts of strass, the whole being melted together for thirty 
hours. A ruby of less beauty is obtained with—strass, 1000; peroxide of man¬ 
ganese, 5 parts. A good emerald can be prepared from—strass, 1000; oxide of 
copper, 8; oxide of chnomium, 0*2 parts. The sapphire is obtained from strass, 
1000; pure oxide of cobalt, 15 parts. The amethyst from—strass, 1000 ; peroxide 
of manganese, 8 , oxide of cobalt, 5 j Cassius’s purple, 0*2. The beryl or a<pxa 
marina is imitated by—strass, 1000; glass of antimony, 7 ; oxide of cobalt, 0*4. 
The carbuncle by—strass, 1000 ; glass of antimony, 500; purple of Cassius, 4; 
peroxide of manganese, 4 parts. Much attention has not been paid to the mode 
in which the colouring is effected by the metallic oxides; nor have experi- 










GLASS. 289 

merits been tried with any definite result as to the application of tungstic acid, 
inolybdic acid, titanic acid, chromic acid, and protoxide of chromium, &c. 

C °GiaItsuLinTng? d Coloured glass may be considered in two classes—that coloured as 
a whole, and that only partially coloured. The latter is prepared with such 
metallic oxides as will impart to the glass very intense colour; for instance, prot¬ 
oxide of copper, protoxide of cobalt, oxide of gold, and oxide of manganese.’ This 
kind of glass is termed superfine, and is prepared in the following manner :—Two 
melting vessels are placed in the oven; one contains a lead-glass, the other the 
coloured glass. We will take as an example glass coloured red with protoxide of 
copper, which if further oxidised imparts a green colour to the glass. The glass- 
blower dips his pipe first into the red glass, and collects a sufficient quantity to blow; 
then he dips this into the white glass, and proceeds to form a cylinder or roll, as in 
the making of table glass. Superfine glass is known as “ outside” and “ double,” 
or “ double layer.” In the first case the workman takes a lump of white glass upon 
his pipe and covers it with the coloured glass; or, in the second case, he takes up 
only a small quantity of white glass, then sufficient of the coloured glass, and again 
more white glass. Red glass may be obtained with either Cassius’s purple, protoxide 
of copper, or oxide of iron as the colouring ingredient. Cassius’s purple is used 
chiefly for ruby-red glass. It was long thought that ruby-coloured glass could not 
be obtained with any other preparation than Cassius’s purple, but twenty-five years 
ago Fuss showed that chloride of gold was effectual. If glass containing salts of 
gold or protoxide of copper is cooled suddenly, the colour disappears; then if again 
gently warmed, not quite to softness, the colour suddenly reappears in full splendour. 
This phenomenon occurs equally in atmospheres of oxygen, hydrogen, and carbonic 
acid. In the preparation of protoxide of copper glass, lead-glass is taken as a basis, 
to which 3 per cent, of the protoxide is proportioned. The drawback to the employ¬ 
ment of the protoxide is the readiness with which it becomes oxide, this imparting 
a green colour to the glass. To prevent this change iron filings, rust, or tartar is 
added, or the glass is stirred with green wood. Copper-glass, as has just been said, 
is colourless on cooling, regaining its colour during the process of annealing. Oxide 
of iron, known commercially as blood-stone, ochre, or red chalk, is also used to 
impart a red colour. Yellow and topaz-yellow are obtained by means of antimoniate 
of potash or glass of antimony, chloride of silver, borate of oxide of silver, and by 
sulphuret of silver. Oxide of uranium imparts a green-yellow. Blue is obtained 
from oxide of cobalt, more seldom by means of oxide of copper. Green results 
from the addition of chrome-oxide, oxide of copper, and protoxide of iron. Violet 
is obtained from oxide of manganese (braunite) and saltpetre; black, from a mixture 
of protoxide of iron, oxide of copper, braunite, and protoxide of cobalt. A beautiful 
black results from sesquioxide of iridium. 

Glass Tainting. The delineation of figures and scriptural events in coloured glass 
dates from a very remote period. At first the work was merely mosaic, pieces of 
coloured glass being inserted in leaden framework. Glass painting was known in 
Germany in the middle ages, and soon extended throughout Europe. In the 13th 
century, when Gothic architecture became prevalent, glass painting also became 
more general, as until then the heavy, round-arched windows were too small to 
admit of ornament. But it was not until the 15th century that the heavy outlined 
figures were discarded for the more mingled colours of heraldic device, as seen in 


290 


CHEMICAL TECHNOLOGY. 


the churches of Sebaldus and Lorenz, of Nuremburg, in the productions of tne 
celebrated Hirschyogel family. This style lasted till the 16th century, when the 
glass-maker tried the effect of pigments upon glass. Since that time the art has 
gradually improved, the improvement at first being most manifest in France and 
the Netherlands. 

The nature of glass-painting or staining is in principle the following:—When 
coloured glass, rendered easily fusible by the metallic oxide it contains, is finely pul¬ 
verised, and laid upon a plain glass surface and heated, it forms a skin, or ■“ flash,” 
as it is termed, this skin or layer of glass being said to be “ flashed on.” It is evident 
that very brilliant effects may thus be attained. The near surface of the glass 
receives the strong shades and colours, the other or distant surface the lighter tints. 
White was not employed in the older glass paintings, but is now used in the flesh- 
tints, pure white effects, &c. Oxide of tin and antimoniate of potash yield a good 
white. For yellow, Naples-yellow, or antimony-yellow, or a mixture of the oxides 
of iron, tin, and antimony, or of antimonic acid and oxide of iron, of sulphuret of 
silver and sulphuret of antimony, or chloride of silver is used; for red, oxide of iron, 
purple of Cassius, and a mixture of oxide of gold, oxide of tin, and chloride of 
silver; for brown, oxide of manganese, yellow ochre, umber, and chromate of iron; 
for black, oxide of iridium, oxide of platinum, oxide of cobalt, and oxide of man¬ 
ganese ; for blue, oxide of cobalt, or potassium-cobalt nitrate; for green, the oxides 
of chromium and copper. Two kinds of colours are distinguished, the hard and the 
soft. The soft are called varnish colours, are not very easily fluid, forming a kind of 
glaze upon the glass. These colours are placed upon the outer surface. The hard or 
decided tints are semi-opaque, and are placed upon the inner surface of the glass. 
The binding fluid or vehicle is a mixture of silica, minium, and borax, with which 
the colour, being previously ground to a fine powder, is intimately mixed. This 
mixture is painted on the glass with a pencil, and the glass plate is afterwards fired 
in a muffle. Eecently volatile oils have been employed as a vehicle, viz., oil of 
turpentine, lavender, bergamot, and cloves. The burning-in, or firing, the colours 
was formerly effected by placing the glass tablet with dried and pulverised lime in 
an iron pan raised to a red heat. But recently the muffle oven has been employed. 
The bottom of the muffle is covered to a depth of one inch with dry powdered lime, 
upon which the plate of glass is laid, and again a layer of lime. The oven is then 
raised equally to a dark red heat. After six to seven hours the fire is gradually 
withdrawn, and the oven allowed to cool. The glass is taken out, cleansed with 
warm water, and dried. 

En Sast?r 0 Gi e as^ la8s ‘ By enamel is understood in glass manufacture a coloured or 
colourless glass mass rendered opaque by the addition of oxide of tin. It formerly was 
prepared in the following manner:—An alloy of 15 to 18 parts tin and 100 parts lead 
was oxidised by heat in a stream of air, the oxide pulverised and washed. The 
mixture of the oxides was then fritted with the glass. An enamel-like appearance 
is imparted to glass by arsenious acid, chloride of silver, phosphate of calcium, 
cryolite, fluor-spar, aluminate of soda, and precipitated sulphate of barium. Bone 
glass, so-called, is a milk-white, semi-opaque glass, containing phosphate of calcium 
in the shape of white bone-ash, sombrerite, or phosphorite. It is employed for lamp- 
globes and shades, thermometer scales, &c. It is made by adding to white glass 
about 10 to 20 per cent, of white bone-ash, or a corresponding quantity of mineral 
phosphate. After melting the glass is generally clear and transparent, becoming 


GLASS. 


291 


milk-white and opaque during the process of blowing. The colour is finally 
developed during annealing. A similar glass to the preceding is alabaster glass, but 
the latter is more opaque. It is also termed opal glass, rice glass, or rice-stone 
glass, and Reaumur's porcelain. The materials are the same as in the preparation of 
crystal glass, of which it may be considered the scum or underlayer of impurities, 
though it is really imperfectly prepared crystal glass. 

cryolite Glass. Cryolite glass, or hot-cast porcelain, has recently been manufactured 
in Pittsburg. It is a milk-white glass, obtained by melting together 

Silica.67’ 19 per cent. 

Cryolite.23 ’84 ,, 

Oxide of zinc. 8*97 ,, 

Fluor-spar or aluminate of sodium may be substituted for cryolite. Benrath 
found (1869) i n such a milk glass— 

Silica .70*01 per cent. 

Alumina. 10*78 ,, 

Soda . 19*21 ,, 


IOO’OO 

ice Glass. Ice glass is made by plunging the mass of glass attached to the end of the 
blower’s pipe, still at a glowing red-heat, into hot water, in which the glass is opened 
and blown out. It then resembles a mass of thawed ice, with a beautifully pellucid 
appearance. It is also known as crackle-glass; in France, as verve craquette. Agate glass 
is obtained by melting together the waste pieces of coloured glass. 

Hsematinon. Astraiite. This is a glass resembling that found in the Pompeiian excavations, 
and mentioned by Pliny. It possesses a beautiful red colour, between that of ve rm ill i nn 
and of minium, is opaque, harder than ordinary glass, bears a high polish, and has a 
sp. gr. r= 3-5. The colour is lost by melting, and by no addition can be recovered. The 
glass contains no tin or protoxide of copper as a colouring matter. Yon Pettenkofer 
assimilated to this glass by melting together silica, lime, burnt magnesia, litharge, 
soda, copper hammerings, and smithy scales. A part of the silica in the mixture is decom¬ 
posed by means of boracic acid, and a mass is obtained which, when ground and polished, 
exhibits a dark red colour of great beauty. Pettenkofer gave to this glass the term 
astraiite, from the beautiful shotte-colour of blue or dichromatic tint shimmering through¬ 
out the mass. 

AYenturin Glass. Aventurin or avanturin glass was formerly made only in the Island of 
Murano, near Venice, but is now prepared throughout Germany, Italy, Austria, and 
France. It is a brown glass mass in which crystalline spangles of metallic copper 
according to "Wohler (of protoxide of copper according to von Pettenkofer) appear 
dispersed. Fremy and Clemandot have produced a glass similar to aventurin glass, and 
which consisted of 300 parts glass, 40 parts protoxide of copper, and 80 parts copper-scale. 
The Bavarian and Bohemian glass-houses produce an aventurin glass rivalling the 
original. Von Pettenkofer has prepared aventurin glass direct from hsematinon by mixing 
sufficient iron-filings with the molten mass to reduce about half the copper contained. 
Pettenkofer surmises, and with good reason, that aventurin glass is a mixture of green 
protoxide of copper glass with red crystals of silicate of protoxide of copper, these comple¬ 
mentary colours giving the brown tint. This glass is also well imitated by melting a 
mixture of equal parts of the protoxides of iron and copper with a glass mass. The protoxide 
of copper appears after a long annealing as a separate, crystalline, red combination, 
while the protoxide of iron is lost in the green colour it imparts to the glass. Pelouze 
found that by freely adding chromate of potash to the glass materials spangles of oxide of 
chromium were separated. He termed this glass chrome-aventurin; it has been 
employed by A. Wachter in the glazing of porcelain. 

Glass Relief. Glass relief is obtained by enclosing a body of well-burnt unglazed white 
clay, moulded to the required form between layers of lead-glass, the result being similar 
in appearance to an article in matted silver. Gold matte is imitated by employing a yellow 
glass. This branch of their art has been known to *he Bohemian glass manufacturers for 
upwards of eighty years. 









292 


CHEMICAL TECHNOLOGY. 


ruigree, or ■Reticulated By fibre or filagree glass is understood that kind of glass wort 
Glass. formed of variously coloured or white opaque glass threads, these 

threads being sometimes as fine as a single hair. They are generally drawn out from 
tubes or sticks of glass of various colours, heated to redness, and formed into sticks, tubes, 
or spirals. Two of these tubes are taken, placed together, and blown out into a vessel of 
the required form, which is characterised by the conformation of the glass threads in the 
stick. From the spiral network thus formed this kind of glass is sometimes termed 
reticulated. 

Miiiifiore Work. Millifiore work is a peculiar form of mosaic glass work, in preparation 
similar to that of Petinet glass. Small filagree canes of different coloured glass are placed 
side by side to form a thick cord or column, the cross section of which appears of a parti¬ 
coloured grain. These cords or columns can be twisted to almost any required form, or 
when heated and drawn out the glass threads of various colours of which it is composed 
form a single thread of very varied hue and great beauty. These threads again can be 
worked into ornaments, or formed into lumps or balls. The best kind of millifiore work 
are the paper-weights, often sold at fancy bazaars as Bohemian glass weights—these are 
merely lumps or rolls of the many-coloured glass thread placed together, heated, and 
finally coated with a film of clear white glass by being’ for a few moments held in the 
white glass melting-pot. 

Glass Pearls. There are two kinds of artificial or glass pearls, namely, solid or massive 
pearls and blown pearls. The first are known as Venetian pearls, and those made in 
Venice are preferred, the export from this city in 1868 representing a money value of 
7,755,000 francs. The manufacture is chiefly carried on in the Island of Murano. The 
pearls are made from small glass tubes, either white or coloured. Oxide of tin is employed 
in the preparation as well as the various metallic oxides for imparting the desired colours. 

solid Pearls. The glass tubes are cut into small pieces or cylinders. The sharp edges of 
these cylinders are removed by placing them in an iron vessel brought to a red heat, 
the beads being constantly stirred with an iron spoon. Previous to this operation the 
interior or hollows of the beads are filled with powdered charcoal. They are then 
well washed, dried, and packed. By another mode of preparation the pieces of glass 
tubing are placed in a revolving vessel similar to a coffee-roaster. The finished pearls 
are generally strung-, the charcoal being placed in the interior or tube of the bead to 
prevent its closing. 

Blown Pearls. The preparation of blown pearls is quite a distinct manufacture. They 
resemble the real pearl in form, colour, and surface. Jaquin, a French paternoster or 
rosary maker, in the year 1656, remarked that when whitings (Cyprimis alburnas , ablettes) 
were washed with water, a residue remained consisting of a beautiful pearly substance. 
This was the foundation of the manufacture of the artificial pearl. Jaquin scaled the 
fish, mixed the scales with water, and obtained the celebrated “ Oriented pearl-essence ,” or 
“ Essence d' Orient ,” a substance identical with Guanin. A small bead of gypsum or 
other hardening paste is coated with this mixture, dried, and dipped into molten glass, a 
thin film of which adheres. 

The pearl is sometimes round, sometimes pear-shaped, or flat. Another method of 
preparing the pearls is by means of beads blown from glass tubes of various thicknesses. 
These beads or small bulbs are then filled with pearl-essence. To prepare this essence, 
say a quantity of 120 grms., 4000 fish are necessary; thus a pound of pearl-essence 
requires 18,000 to 20,000 fish for its preparation. The scales are allowed to stand about 
an hour in water to permit the slimy matter adhering to them to settle ; they are rubbed 
down in a mortar with fresh water, and strained through a linen cloth. Thus prepared 
the paste is ready for insertion in the glass beads, a littie ammonia being added to prevent 
decay. 

Hyaiography. Hyalography, or the art of etching on glass, is due to one Heinrich 
Schwankhardt or Scliwandard, an artist living at Nuremburg in 1670. It consists of the 
following operations :—Powdered fluor-spar is treated with concentrated sulphuric acid in 
a leaden vessel; gentle heat is applied, the vessel being covered with the glass plate to be 
etched coated with wax, through which the design is traced with a steel etching-needle. 
Vapours of hydrofluoric acid (F 1 H) are evolved, which combine with the silica of the 
glass, forming fluoride of silicon, SiFl 2 , and volatilising. The plate is afterwards washed 
with warm oil of turpentine. The first practical application is due to Hann of Warsaw 
in 1829. More recently, Bottger and Bromeis, with Auer, of Vienna, have improved the 
processes. The etching-ground used for engraving on metallic surfaces would not in this 
case give favourable results. Pul recommends a molten mixture of 1 part asphalt and 
. part colophonium, with so much oil of turpentine as will bring the mass to the con¬ 
sistency of a syrup. Etched glass plates have been used by Buttger and Bromeis to print 
from instead of steel and copper. In the press the glass plate is backed by a cast-iron 


EARTHENWARE. 


m 


plate. The process, however, has not been practically successful; it is better suited to 
the production of bank notes, &c., than engraving's, the resulting 1 etchings being hard in 
tone. But for purposes of decoration, etched glass is largely used. By the method of 
Tessie du Motay and Marechal of Metz, a bath is made of 250 grms. of hydrofluoride or 
fluoride of potassium, 1 litre of water, and 250 grms. of ordinary hydrochloric acid. Kessler 
employs a solution of fluoride of ammonium. 


Ceramic or Earthenware Manufacture. 

ciays an ^ e {^ Application - To the most important alumina combinations found native 
belongs felspar. This mineral is one of the chief members of the class containing 

gneiss, granite, and porpyhry. Potash-felspar, J Os, with 6-54 parts of silica, 

18 alumina, and i6‘6 potash, is also known as orthoclase or adularia ; when sodium 
takes the place of potassium, the felspar albite is formed. According to Mitscher- 
lich some felspars contain o'4 to 2*25 per cent, of barium. When felspar is under 
the influence of water and carbonic acid with changes of temperature, it loses its 
silicate of pfotash, which being washed out, the potash is taken up by plants, and will 
perhaps account for some portion of the potash always present in their ash; some 
of the silicate is acted upon by carbonic acid, by which the silicic acid is separated 
and soluble carbonate of potash formed. In following this decomposition to a con¬ 
clusion, we may surmise that the silicic acid thus set free becomes a constituent of 
the opal and chalcedony spar. All clays are essentially silicate of alumina ; and in 
many instances, as in Devonshire and Cornwall, the change from felspar of the fine 
white granite to clay by disintegration is very perceptible. By washing this clay 
to free it from quartz and mica a fine white clay is obtained, known as kaolin or 
Kaolin, or Porcelain clay, porcelain clay. Again, by washing with potash ley, whereby the 
free silica is taken up, there is obtained, in most cases, a fine plastic mass, consisting 
of 1 molecule of alumina, 1 molecule of silica, and 2 molecules of water. The 
quantity of free silicic acid varies between 1 to 14 per cent. 

The weathering of the felspar may be formulated thus— 

1 mol. felspar, Si 3 0 8 KAl, or ^^ j 0 £ 

gives, under the influence of water, 

1 mol. porcelain clay, 2 Si 0 4 HAl, and 
1 „ acid silicate of potash, 

the latter forming a soluble combination similar to water-glass. Porclain clay occurs in 
the following localities:—1. Bavaria: Aschaffenburg, Stollberg, Diendorf, Oberedsdorf. 
2. Prussia: Mori and Trotha, near Halle (material for Berlin porcelain manufacture— 
decomposed or disintegrated porphyry). 3. Saxony : near Schneeberg and Mionia. 
The first is a weathered granite; the latter, porphyry. 4. Eastern Hungary: 
Brenditz in Moravia; near Carlsbad, Bohemia; Prinzdorf in Hungary. 5. Prance: 
St. Yrieux, near Limoges. 6. England: St. Austell, in Cornwall. Weathered granite ; 
a mixture of orthoclase and quartz. It is found chiefly on Tregoning Hill, near Helstone. 
7. China. It naturally follows that the clay should contain foreign substances; and it is 
from the quality and quantity of these substances that the several varieties of clay are 
obtained, of course with due reference to the chief constituents—silicic acid and alumina. 
The purer clays contain generally the following foreign substances:—Sand, partly as 
quartz sand, as silicate of potash, and partly as particles or fragments of undecomposed 
minerals ; baryta combinations ; carbonate of magnesium; carbonate of calcium; oxide of 
iron; sulphur pyrites; and organic matter. 

Th Quauues C ofth T e n ciay t ^ nt Eor the technical application of the clays the important 
qualities are colour, plasticity, and well hardening under heat. 


294 


CHEMICAL TECHNOLOGY. 


colour. Naturally clays are white, yellow, blue, or green. Pure clay is white ; 
coloured clays are the result of several admixtures. "White clay contains but a small 
quantity of protoxide of iron, and becomes after burning yellow or red; these colours 
originatingfrom the organic substances disappear on their being volatilised after many 
firings. The coloured clays change their colour during firing, becoming red or red- 
yellow. Fine clays are prepared only from those becoming white by continued 
burning. 

plasticity. The clay should absorb water readily, forming a tenacious mass, capable 
of taking sharp and clear impressions. It is clear that the plasticity of the clays 
depends in a great measure on their composition. Sand is the constituent most 
prejudicial to plasticity, lime less so, and oxide of iron least of all. Clay pos¬ 
sessing a high degree of plasticity is said to be fat or Iona , and when in the opposite 
condition lean , thin , or short. All shrunk clays, that is, all clays decreased in volume 
by burning, are said to be either drawn or hurst. The amount of shrinkage depends 
of course upon the quantity of water the clay contains; the same kind of clay does 
not always exhibit the same shrinkage. Fat clays shrink more than short clays. 
The diminution in surface by shrinkage varies between 14 and 31 per cent., the 
capacity or solid contents between 20 and 43 per cent. Clay may be burnt so hard 
as to give sparks when struck with steel; but its property to form a plastic mass 
with water is then wholly lost. Pure clay (silicate of alumina) is by itself infusible, 
but by mixture with lime, oxide of iron, and other bases becomes more or less easily 
fusible. According to the experiments of E. Eichters (1868) the refractory qualities 
of clay are least influenced by magnesia, more so by lime, still more by oxide of iron, 
and most by potash. Fusible clay obviously is not adapted to the manufacture of 
porcelain or such ware as is likely to be exposed to a high temperature. A fusible 
and a refractory clay, when heated together, enter into a mass that does not cleave 
to the tongue. By the manufacture of clay ware, then is understood the binding of 
certain clays together by means of a suitable flux. 

Kinds of clay. The clays employed in ceramic manufacture are— 

1. Befractory clays : as porcelain and plastic clays. 

2. Fusible clays; as potter’s clay. 

3. Limey clays; as marl, loam. 

4. Ochre clays; as ruddle, ochre. 

Of these porcelain clay is the most important ; it is of various colours, very 
tenacious, plastic to a high degree, burns white, and is not fusible in a porcelain- 
oven fire. It is ordinarily found in the tertiary formation, almost always accom¬ 
panied by other kinds of clay, by quartz-sand, and by brown coal. For practical 
purposes it is important to know that clays of the same strata and of the same pit 
often differ largely in their refractory property. This is not only the result of 
experience, but of a lengthy series of experiments made by C. Bischof, Otto, and 
Th. Eichters. The strata near Klingenberg-on-the-Maine, at Coblenz, Cologne, 
Lautersheim, and Yallendar-on-the-Bhine, Weisboch in Baden, Bunzlau in Silesia, 
Schwarzenfeld near Schwandorf, and Kemnath in Bavaria, in the province of 
Hessen, in Saxony, in Belgium, near Dreux in France, and Devonshire and Stour¬ 
bridge in this country, are all celebrated for this clay. The following analyses 
give the composition of various refractory clays :— 


EARTHENWARE. 


29* 



I. 

2 - 3 - 

4- 

5 * 

Silica 

47 ‘ 5 ° 

45*79 53 *oo 

63*30 

55-50 

Alumina 

34*37 

28'IO 27*00 

23*30 

27*75 

Lime . 

0*50 

2*00 1*25 

o *73 

0*67 

Magnesia 

I'OO 

— — 

— 

o *75 

Oxide of iron 

1-24 

6*55 i *75 

i*8o 

2*01 

Water .. .. 

1*00 

16*50 — 

10*30 

io *53 

1. Almerode in Kurhessen (crucible). 2. Schildorf near 

Passau (graphite crucible). 

3. Einberg near Coburg 

(porcelain 

capsule). 4. Stourbridge. 

5. Newcastle (fire-brick). 


The composition of the Stourbridge fire-clay will be seen from the following 
analyses by Professor P. A. Abel, P.B.S., Chemist to the War Department:— 


Sample. 

Silica. 

Alumina. 

Peroxide of Iron. 

Alkalies, Waste, &o» 

1 

66*47 

26*26 

6*63 

0*64 

2 

65*65 

26*59 

5*71 

2*05 

3 

65*50 

27*35 

5*40 

i -75 

4 

67*00 

25*80 

4*90 

2*30 

5 

63*42 

31*20 

4 * 7 ° 

o*68 

6 

65*08 

27*39 

3*98 

3*55 

7 

65*21 

27*82 

3 * 4 I 

3*56 

8 

58*48 

35*78 

3*02 

2*72 

9 

63*40 

3170 

3*oo 

i*9d 


The sample No. 9, containing only such a small quantity of iron, is much 
superior to No. 1, whose refractory properties maybe doubted. The clay is dug 
from pits varying from 120 to 570 feet in depth. It is generally found below three 
workable coal measures, between marl or rock and an inferior clay. The seam 
averages 3 feet in thickness, never exceeding 5 feet, and the middle of the seam 
contains the clay selected for crucibles, &c. Pot-clay or crucible-clay only occurs 
in small quantities, and costs at the pit-mouth 55s. a ton, ordinary fire-clay only 
realising 10s. a ton, 

potter’s ciay. Ordinary potter’s clay also possesses most of the properties of plastic 
clay; many varieties form with water a similarly tenacious mass. But potter’s clay 
is highly coloured, retaining the colour after burning. It effervesces on the applica¬ 
tion of hydrochloric acid, and changes to marl. It follows from its containing large 
proportions of lime and oxide of iron that it is fusible, and melts according to 
the quantity of these constituents at a higher or lower temperature into a dark 
coloured, slag-like mass. It is found in the last formation, or entirely on the 
surface of the earth, and sometimes in the tertiary formation. It contains among 
other foreign substances organic matter, iron and other pyrites, gypsum, &c. 

waikerite. Walkerite, or Walker’s clay, is a soft, friable mass, occurring from the 
weathering of Diorite and Diorite slate. In water it separates to a powder, not 
forming a plastic pulp. In its powdered condition it is of use as an absorbent of 
fat, &c., whence its application to the removal of grease spots in books, &c. It is 
found at Beigate in Surrey, Maidstone in Kent, further at Aix-la-Chapelle, in 
Saxony, Bohemia, Silesia, and Moravia. It is employed in paper-making, and as 
an addition to ultramarine. 

Mari. Marl is a mechanical mixture of clay and carbonate of calcium, containing 
sand (sand-marl), and other constituents; that containing lime is called lime-marl; 


296 


CHEMICAL TECHNOLOGY. 


that clay, clay-marl. In water it falls to powder, and forms a non-adhesive, pasty 
mass. With acids it effervesces, whereby more than half the weight is lost. It melts 
easily. It is found in the lias and chalk formation. Its chief application is to the 
improvement of land. 

Loam. Loam may be considered as the result of the mixture of clay with sand. It 
is a clay more or less mixed with quartz-sand and iron-ochre, also with lime, when 
it assumes a yellow or brown colour, changing on burning to a red. It forms with 
water a slightly plastic mass, and is not very refractory. It is found always on the 
surface of the earth, and known as common clay, employed in the manufacture of 
bricks, coarse pottery, &c. 

There is sometimes, but very seldom, used in earthenware manufacture, a mixture 
of clay and iron-ochre or hydrated oxide of iron (2Fe 2 0 3 ,3lI0). 

composition of xaoiin. Kaolin in pure condition, and only by means of washing, freed 
from coarse substances, quartz, sand, &c., is a mixture of porcelain clay with rocky 
residue. Porcelain clay, i.e. the plastic part of kaolin, is always of equal composi¬ 
tion. The composition of kaolin is given in the following analyses:— 

Silica. 


From. 

Pocky residue. 

Free. 

Combined 
with Alumina. 

Alumina. 

Water. 

St. Yrieux 

.. .. 97 

io’9 

31*0 

34*6 

I2'2 

Cornwall 

19*6 

1*2 

45*3 

24 # o 

87 

Devonshire 

• • • • 4'3 

IO’I 

34 *o 

36-8 

127 

Passau .. 

.. .. 4’5 

97 

367 

37 *o 

12*8 

Aue 


17 

34*2 

34 ’ 1 

11*0 

Mori, near Halle . 43*8 

4*4 

21*6 

22-5 

7*5 

Kinds of Clay Ware. 

Clay ware is generally separated into dense and.porous 

ware. The 


dense ware is so strongly heated that half its mass is lost; its fracture is glazed and 
conchoidal; it is translucent and compact, being impenetrable to water; and it gives 
a spark when struck with steel. Porous clay ware is, in the mass, not glazed, its 
fracture open and earthy; and, when not superficially glazed, water freely per¬ 
colates through it. It also clings to the tongue. The burnt mass, whether dense or 
porous ware, either remains rough or is glazed. 

The following are the essential varieties of clay ware :— 

I. Dense Clay Ware. A. Hard porcelain. The mass equal throughout; not indented 
with a knife; fine-grained, translucent, sonorous, and white. Fracture, fine-grained, and 
eonehoidal. Sp. gr. — 2-07 to 2-49. It may be considered as composed of two substances— 
namely, as a natural clay or true kaolin, infusible, and preserving its whiteness under a 
strong heat; and as a flux consisting of silica and lime, or felspar, with or without 
gypsum, chalk, and quartz. The glazing is essentially due to this flux, and not to oxide of 
lead or tin. It is characteristic of the manufacture of hard porcelain that the burnings 
are included in one operation. 

B. Soft or tender porcelain. The mass more easily fluid than hard porcelain. Two kinds 
are known :—- 

a. Prench porcelain, a glass-like mass, essentially a potash-alumina silicate, prepared 
with the addition of clay, therefore erroneously termed a clay ware, and containing lead 
similarly to crystal glass. 

fi. English soft porcelain. The mass similar to kaolin, plastic, remaining white when 
burnt (pipe-clay). It is made with a vitreous grit, consisting of gypsum, Cornish stone 
(weathered pegmatite), bone-ash (essentially phosphate of calcium), in very varied pro¬ 
portions. The glaze is obtained by pulverised Cornish stone, chalk, powdered fire-clay, 
and borax, mostly with, seldom without, the addition of oxide of lead. The glazing is a 
second process. 




EARTHENWARE. 


297 


C. Statue porcelain, or biscuit ware :— 

a. Genuine and unglazed porcelain. 

; 3 . Parisian porcelain, or parian. Unglazed statue porcelain is similar to English 
porcelain. 

7. Carrard, less translucent than parian, and sometimes of a whiter colour. 

D. Stoneware. Dense, sonorous, fine-grained, homogeneous, only in the least, if at all, 
translucent, white or coloured. 

a. Glazed porcelain stoneware. Plastic, remaining white after burning, slightly refrac¬ 
tory with the addition of kaolin and fire-clay; a felspar as flux; the glaze contains borax 
and oxide of lead. 

fi. White or coloured unglazed stoneware. Wedgwood ware. 

7. Co mm on stone-ware (salt-glazed). No fluxing material is employed, but the firing 
is increased. Glazed with siliceous soda-alum. 

II. Porous Clay Ware . A. Fine Fayence with transparent glaze. The body earthy, 
clinging to the tongue, non-transparent, sometimes sonorous; the glaze containing lead, 
borax, felspar, &c. 

B. Fayence, with non-transparent glaze. The body of a yellow burnt potter’s clay or 
clay-marl, with non-transparent white or coloured glaze or enamel, containing tin. To this 
class belongs majolica, delf ware, &c. 

C. Ordinary potter’s ware. The body of ordinary potter’s clay or clay-marl, red- 
coloured, soft, and porous. Mostly glazed with lead, the glaze being always non-trans¬ 
parent. According to the colour of the glaze, the ware is distinguished as white and 

brown. 

D. Plate, terra-cotta, fire-clay ware, tubes, ornaments, vases, &c. The body earthy; 
mostly more or less unequal; always coloured, porous, easily fluid, and slightly sonorous. 
Is not usually glazed. 


I. Hard Porcelain. 

Gri th'e n Mate d rki ixing Hard porcelain is composed of a mixture of colourless porcelain 
clays with felspars as a flux, which sometimes is composed of quartz, chalk, or 
gypsum. The porcelain clay, in itself infusible, and becoming in the fire only an 
earthy, opaque mass, when intimately mixed with the flux material, melts easily at 
a higher temperature than that of the glass oven. The materials of porcelain 
manufacture are not found native in such a condition that they may at once be 
employed; they must be ground to a fine powder, and this washed to separate the 
foreign substances. Pure kaolin, however, is not utilisable in porcelain manufacture, 
as it becomes much decreased in volume on the application of heat. It is therefore 
mixed with fine washed quartz sand, although this addition somewhat impairs the 
plasticity. This mass on treatment with fire would be porous, and it is for the 
closing of the pores and to form a binding glass that felspar is added. The propor¬ 
tions in Berlin porcelain, according to G. Kolbe (1863), are 66 6 parts silica, 28 4 o 
parts clay, 070 part protoxide of iron, o’6 part magnesia, and 07 part lime. 

Proportions of the materials as employed at—a. Nymphenburg; / 3 . Vienna; 7. Meissen:-— 


Kaolin from Passau 

.. .. 65 

Sand therewith . 

.. .. 4 

Quartz. 


Gypsum. 

.. .. 5 

Broken biscuit ware 

.. •• 5 

Kaolin from Zedlitz 


Kaolin from Passau 

.. .. 25 

Kaolin from Unghvar .. 


Quartz. 

.. .. 14 

Felspar. 

.... 6 

Broken ware. 

.. .. 3 

Kaolin from Aue. 

.. .. 18 

Kaolin from Sosa. 

.. .. 18 

Kaolin from Seilitz 

.. • • 3 6 

Felspar. 


Broken ware. 

.. .. 2 
















CHEMICAL TECHNOLOGY. 


29S 

Tlie mixture of the materials in the required proportion takes place in large vat», 
whence the thin pulp is pumped and forced through sieves into another vessel. 

Drying the Mass. After the water is removed from the sediment at the bottom of the 
vat or tank, the clay appears as a slime, which has to be dried to the required con¬ 
sistency. The drying or evaporation of the water is effected in wide wooden tanks 
exposed to a strong current of air. This is a very general method of drying the 
mass, but can only be employed during the summer months on account of the 
dampness of our climate. It is not, therefore, sufficiently extensive for large 
manufacturers, and consequently other means of drying are resorted to—usually 
by means of absorption, the mass being laid on a porous layer of burnt lime, 
gypsum, &c. Drying by means of gypsum is expensive, as it soon becomes 
hardened, and has to be removed. The mass can also be dried by means of air- 
pressure, being in this case placed in flat porous boxes, under which a vacuum 
chamber is situated. Talbot’s apparatus is formed on this principle. In 
Grouvelle and Honore’s system of drying, the water is first partially removed, 
by means of draining over gypsum, and the mass is then put into firm 
hempen sacks, which are subjected to pressure in a screw or lever press. Pressed 
clay has greater plasticity than that dried by artificial heat; but the method is 
expensive, as the sacks soon require replenishing, being speedily worn out by the 
constant pressure. When the mass is dried by pressure or by absorption, the water 

KneadingOie Dried j n a ]q cases j s no t equally expelled, and there are also air-bubles, 
which must be removed. This is done by kneading and treading the mass with the 
feet and hands, and by this means also the plasticity of the mass is improved. 
Another method of improving the plasticity is by allowing the moist clay to stand 
till it becomes putrid. Stagnant water is often employed. Brongniart explained 
the action of this rotting, as it is termed, to be that gases were formed in the body 
of the clay, and that by the continuous movement caused in their endeavour to 
escape, the finest particles of the material were intimately mixed. Salvetat gives 
the following hypothesis:—By the rotting there is formed in the mass a large 
quantity of sulphuretted hydrogen gas. This gas effects the reduction of the 
alkaline sulphurets to sulphuret of calcium under the influence of the organic sub¬ 
stances, the sulphuret of calcium being set free, a similar action taking place with 
the carbonic acid in contact with the air. The bleaching of the mass on exposure to 
the air is due to the oxidation of the black sulphuret of iron to sulphate of iron, 
which is removed by washing. The decomposition of the felspar constituents may 
also ensue from the long-continued action of the water. According to E. von 
Sommaruga, of Vienna, the existing sulphates are decomposed by the air into 
sulphuretted hydrogen and carbonated salts, and these being removed with the 
water, the refractory nature of the clay is improved. 

The Moulding. The kneading and rotting accomplished, the porcelain mass is taken 
to another room to be moulded. This is effected either on a potter’s wheel or in a 
mould. 

The Potter’s wheel. The potter’s wheel consists of a vertical iron axis, on which a 
horizontal solid wheel is fixed, and caused to revolve by the feet or by steam-power, 
the motion in the latter case being regulated by the feet. A lump of clay is placed 
upon the wheel, the thumb being placed in the centre of the lump and pressed down¬ 
wards; a hollow is thus formed, which is widened, or the walls continued vertically 
according to the shape of the vessel to be made. The constant revolution of the 
wheel easily allows of the moulder obtaining a perfectly cylindrical form. By thus 


EARTHENWARE. 


299 


humouring the clay, elongating the vessel, again depressing it, widening it, and by 
continued manipulation in this manner, the most exquisite shapes are produced. 
To form the ridges or sharp edges of the vessel a small piece of iron, a strip of horn 
or wood, termed a bridge, is used. The perfectly formed vessel is cut away from 
the wheel by a piece of brass wire. 

Moul p!im Forms ter ° f A m ould is first taken from the pattern or original object, which 
may be of clay, wax, gypsum, or metal. The moulding is performed with dry 
material, with clay of the consistency of dough, or with fluid clay. The moulds 
must possess a certain amount of elasticity, and be porous in order to absorb the 
moisture expressed. For these reasons plaster-of-Paris is generally used. The 
mould is taken from the original article in parts, which, are trimmed to fit together 
accurately; into each, part is then pressed sufficient clay to fill the indentations of 
the pattern, more clay being added till a proper thickness is obtained. The parts are 
then fitted together, and the moulds left for some time. This method of moulding 
is sometiTn.es called press work, and is adapted to all kinds of pottery not of circular 
form. Plates, cups, and dislies are also made in a similar manner. A leaf of clay 
is rolled out and pressed between flat moulds. Sometimes, instead of rolling, the 
clay is beaten out with, a wooden liammer covered with leather. 

casting. Moulding porcelain articles out of thin pulpy clay is one of the most 
ingenious arts of the potter. The fluid clay is poured into porous moulds, which 
absorb a portion of the water, thereby reducing the pulp to a certain consistency. 
The interior pulp remaining fluid is now poured out, and the cast or coating of clay 
adhering to the mould allowed to harden. "When sufficiently hard the vessel is 
taken to the lathe to be finished, or if not of circular form, to the finishing room, 
where with sharp tools any required pattern is cut, or handles, spouts, &c., which 
have been made in separate moulds, attached. 

Articles 'without* Moillds. The finest porcelain is finished by hand, as machinery or 
moulds could not give sufficient sharpness to the beautiful flowers and figures sculp¬ 
tured on vases, &c. The flowers, &c., are first prepared in moulds, are then 
attached to the body of the article, and finally are finished off with edged tools. 
The stalks of the flowers are sometimes formed on wire; and the leaf is first roughly 
constructed in the palm of the hand, the furrowing and veining being done after¬ 
wards. The texture of drapery is imitated by means of a piece of tulle, which is 
laid on the clay, and allowed to dry. During the burning the tulle is consumed, 
leaving the pattern on the porcelain. 

Drying the Porcelain. After the porcelain ware is formed, it is dried for some time at 
the ordinary temperature. This is continued till the clay contains no moisture, 
that is, until its weight is tolerably constant. During this drying the clay is said 
to be in the green state, and possesses a greater tenacity than it has in any of the 
former processes. 

Glazing. Only very few articles of porcelain ware, generally statues or figures, remain 
unglazed; these are termed biscuit ware. All other articles are glazed. The glazings 
employed are of four kinds:—1. Earth or clay glazings are transparent, and formed by 
melted silica, alumina, and alkalies; they easily become fluid, and melt about the 
temperature at which the vessels are baked. This kind of glazing is used for hard 
porcelain. 2. Lead glazes are transparent glazes containing lead; most of these melt 
at the temperature at which the articles are burnt. 3. Enamel glazes are partly white, 
partly coloured opaque glasses containing oxide of tin besides oxide of lead. This kind 
of glaze is easily melted, and serves to cover the unequal colour of the under mass. 4. 
Lustres are mostly earth and alkali glazes. This class includes the ordinary salt-glazed 
ware, as well as glazes containing metallic oxides used to imitate gold and silver surfaces 
for ornament merely. 


3 oo 


CHEMICAL TECHNOLOGY. 


porcelain Glaze. We will here, however, concern ourselves only with porcelain 
glaze. It is necessary that this glaze should melt readily at the temperature at 
which the article is fired; that it should be colourless and opaque; that it should 
fire sufficiently hard to withstand pressure, grinding, and ordinary cutting. The 
glaze is added to the porcelain mass with a flux, so that the melting may be readily 
effected. At Meissen the glaze used contains :— 


Quartz .37 *o 

Kaolin from Seilitz .37*0 

Lime from Pirna. 17*5 

Broken porcelain. 8*5 


100*0 

In the Berlin porcelain manufacture the following glaze is employed:— 


Kaolin, from Morle, near Halle.31 

Quartz-sand . .. 43 

Gypsum . 14 

Broken porcelain 12 


100 

Applying the Glaze. The glaze can be put on in four ways :—1. By immersion. 2. By 
dusting. 3. By watering. 4. By volatilisation. The glaze is either mixed with 
the ingredients, or applied superficially by one of the preceding methods. Glazing 
immersion, by immersion is employed in the case of porcelain, the finer Fayence ware, 
and sometimes for stoneware. It requires some degree of porosity in order that the 
glazing pap may be absorbed. The glazing materials are mixed with water to form 
a thin pulp. The articles previous to their immersion are slightly baked to prevent 
the clay being softened and running fluid in contact with the water of the glaze. 
The articles are dipped into the glaze, which they readily absorb, a coating or thin 
layer of glaze remaining on their surface when they are removed from the bath. 
The glaze is removed from the bottom of the article immediately in contact with 
the substance on which it stands to prevent its sticking. Glazing by dusting is a 
Dusting, surface method, and only used for costly ware. The freshly formed and 
still damp ware is dusted with lead glaze or minium, a layer being left on the 
surface. The powders employed chiefly contain oxide of lead, which combines with 
the silica and alumina of the clay mass during the firing to form a glaze. Ke- 
watering. cently finely-pulverised zinc blende and Glauber salt have been em¬ 
ployed. Watering is a method of glazing employed for non-porous articles, 
such as English porcelain, ordinary pottery ware, and some kinds of Fayence 
ware. Glaze of the proper consistence is poured over the articles, the in¬ 
terior sometimes being left coated with a white glaze, while the outside is 
again coated with a coloured glaze, as is seen in common brown-ware. 

By volatilisation or smearing. Glazing by volatilisation is effected by conveying into 
the oven a salt or metallic vapour which shall form with the silica of the mass an 
efficient glaze. The most general method is applied to ware not requiring to be 
baked in fire-clay vessels. Common salt is placed in the oven with green wood for 
fuel to form an irriguous smoke. This, the salt, heated to redness, receives, and is 
decomposed into hydrochloric acid and soda, the vapours of which fill the oven. 
The inside and the outside of the vessel submitted to this process are thus simulta¬ 
neously glazed. Fine stoneware baked in fire-clay vessels may be glazed bv the 
ignition of a mixture of potash, plumbago, and common salt. During the baking 









EARTHENWARE. 


301 


or firing chloride of lead is formed, which, combines with the silica of the clay to 
form a thin glass. This method of glazing is in England termed smearing , boracic 
acid being employed. 

Lustrcs^and Flowing A method of glazing by volatilisation, known as glazing with 
flowing colours, is employed for porcelain. It essentially consists in the ignition 
of a mixture of chloride of calcium, chloride of lead, and clay, placed in a small 
vessel in the firing capsule or firing chamber, and to which some metallic oxide is 
added, as cobalt oxide. The oxide is converted into chloride, and combines with 
the constituents of the article. 

The capsule, or sagger. Porcelain ware and superfine earthenware are not exposed, 
when burnt, to the free action of the flame, as various impurities, such as ashes 
and smoke, would deteriorate the beauty. They are therefore enclosed in fire-clay 
vessels, termed in Prance gazettes , in Germany Jcapseln, and in England saggers. 
These saggers are manufactured of the best fire-clay, with which is mixed a 
cement made from broken saggers. Pirst, into each sagger is put a perfectly true, 
disc of the same material, and upon this the porcelain ware is placed, three knobs 


Fig. 147. Pig. 148. 



or small props projecting from the disc, and keeping the article from contact with 
a large surface to which the glaze would cause it to adhere. 

The porcelain oven. Pig. 147 is a vertical section of the porcelain oven, and Pig. 148 
the elevation. The oven is essentially a reverberatory furnace with three stages 












































































$02 


CHEMICAL TECHNOLOGY. 


and five fire-rooms supplied with, wood fires. The oven may be considered as a tall 
cylinder, surmounted by a cone, in tbe apex of which, is the chimney opening, the 
fiat vaults by which it is divided being pierced to allow of communication. Both 
the stages, L and i/, serve for the “strong firing” of the porcelain. The upper 
stage, l", termed variously the howell , crown , or cowl , serves for the “ raw burn¬ 
ing.” At the bottom of both the lower stages are built the fire-places, /, leading 
by g into the oven. G is the ash-pit, T the opening to the ash-pit closed during the 
burning; o is an opening through which fuel is introduced ; c c are the openings 
admitting of the circulation of the hot gases, p is the door by which the oven is 
entered. The ovens are gradually heated first to glowing heat and then to a strong 
red heat. At this stage the openings are closed and the oven raised to a stronger 
heat, at which it is allowed to remain for a short time.* This intense burning lasts 
about seventeen to eighteen hours; the oven is then opened, and allowed to cool 
gradually for three to four days. 

Emptying the Oven and After the oven is cooled, the saggers containing the ware are re¬ 
sorting the Ware, moved, and the ware taken out. It is then separated into four kinds:— 
a. Superfine, containing no blemished ware. b. Medium, the ware slightly inferior in 
glaze, &c. c. The chipped and imperfectly glazed ware. d. Waste, or ware so dis¬ 
torted or cracked as to be useless. 

Faulty Ware. The chief faults are :—Cracking, from the porcelain not being sufficiently 
plastic, from drying unequally, and from unequal heating. Part fusing from a too strong 
heat. Air-bubbles causing lumps to appear on the surface of the ware through the 
expansion of the air by heat. Spotting, from fragments of the sagger fusing and falling 
in upon the ware. Yellow-colouring, from smoke having entered the sagger. The chief 
faults in the glaze are :—Blowing, the result of the development of gas by the reaction of 
the constituents of the glaze upon each other; also resulting from too strong a firing. 
Shelling, or the exfoliating of the glaze. 

Porcelain Painting. Porcelain painting is really a branch of glass painting, the colours 
being glass-colours, which when burnt in become durable and bright. The 
colours employed, technically termed muffle colours, are:— 

Oxide of iron, for red, brown, violet, yellow, and sepia. 

,, chromium, for green. 

,, cobalt and potassium-cobalt-nitre, for blue and black. 

,, uranium, for orange and black. 

,, manganese, for violet, brown, and black. 

,, iridium, for black. 

,, titanium, for yellow. 

,, antimony, for yellow. 

,, copper (and protoxide), for green and red. 

Chromate of iron, for brown. 

,, lead, for yellow. 

,, barium, for yellow. 

Chloride of silver, for red. 

Chloride of platinum, for platinising. 

Purple of Cassius, for purple and rose-red. 

These colours are mixed with a fluxing material, so that by the melting a silicate 
or borate may be formed, yielding a good glaze. Therefore the oxide of cobalt and 
the oxide of copper must first be mixed with silicic acid and boracic acid, oxide of 
antimony with oxide of lead, &c., to form a blue, green, or yellow colour, becaus > 
there are few metallic oxides yielding these colours that are not affected inj uriouslj 
by heat, or are by themselves sufficiently easily fluid. The burning-in of the 


EARTHENWARE. 


3 C 3 

colours is effected in a muffle, Fig. 149, the opening 0, serving as a communication 
with, the interior, by which the degree of heat may be ascertained ; the opening, m, 
serves for the escape of the vapours of the essential oils (oil of turpentine, oil of 
lavender, &c.), with which the enamel colours are sometimes ground up. Fig. iv> 


Fig. 150. 



shows the method of heating the muffle. The heating is commenced at a low tem¬ 
perature and is gradually increased to a red heat. From time to time the muffle is 
opened till the colours begin to disappear; then the muffle is carefully closed, raised 
to a bright red heat, and finally allowed to cool as slowly as possible. 

Ornamenting the Porcelain. The gold employed for decorating the porcelain is dissolved in 
aqua regia, and precipitated with either sulphate of iron, nitrate of protoxide of mercury, 
or by means of oxalic acid. In its application the gold must be intimately mixed with a 
flux, generally nitrate of oxide of bismuth. Shell gold is employed, also gold-beaters’ 
refuse. The article to be gilt must be thoroughly freed from grease, else the gold will not 
adhere. The gold powder, finely ground up with sugar or honey, or some such soluble 
substance, is applied with a pencil brush. The buming-in is effected in a muffle. The 
gold is not melted during the burning, but becomes firmly set upon the article by means 
of the flux. After burning the gold does not at once appear bright, but requires 
burnishing with an agate tool. 

Bright Gilding. Bright gilding differs from the foregoing in requiring no after polishing 
or burnishing. It is effected by burning-in a solution of sulphuret of gold or fulminating 
gold in balsam of sulphur. When an article is gilded with precipitated metallic gold or a 
bright gold preparation, the gilding is secure from injury by handling or scratching with 
the finger-nail, &c. 

silvering and Platinising. Silvering and platinising are usually only in slight requisition. 
Metallic silver is thrown down from its solution by means of copper or zinc; the 
platinum is precipitated from its neutral chloride by means of boiling with potash 
and sugar. The tarnishing of silver on porcelain by sulphuretted hydrogen may. 
according to Rousseau, be prevented by placing, before burning, a thin layer of gold upon 
the part silvered; the result then is a white layer of gold-silver. Much care is not neces¬ 
sary in this process. The silver and platinum are mixed with basic nitrate of oxide of 
bismuth, painted on and burnt in, and afterwards burnished. 

Lithophanie. Transparent porcelain is used in the art of lithophanie, or making transpa¬ 
rencies. A thin and unglazed porcelain plate is pressed into a flat gypsum mould 
bearing the pattern in high relief. The figures by transmitted light appear in delicately 
rounded tones of light and shade. The applications of this art to the manufacture of 
lamp-shades, window ornaments, &c., are too well known to need remark here. 



























































304 


CHEMICAL TECHNOLOGY. 


II. Tender Porcelain. 

French Fritte Porcelain. Tender or fritte porcelain, is distinguished in commerce as of 
two manufactures—French and English. The French manufacture, in 1695, was 
first carried on at St. Cloud, near Paris, by Morin, who employed a glassy mass 
without the addition of kaolin, but containing lead, somewhat similar to crystal 
glass. It can, therefore, hardly be considered a porcelain, strictly so called, until 
melted with lime and alumina. Thus fritte porcelain is composed of:—1. A glass 
mass or fritte , obtained from silica and alkalies. 2. Marl, as a clay constituent. 
Chalk, as a lime constituent. The proportions of these constituents are:— 


Fritte 

•• • 75 

75 

Marl .. .. 

.. .. 17 

8 

Chalk 

.. .. 8 

W 


The fritte is mixed with the chalk and marl to form a thin pulp, which is allowed 
to remain for a month to dry, and then again pulverised. When required quickly 
plasticity is obtained by adding soap- or lime-water. Fritte porcelain is burnt 
in saggers, generally before glazing. During the burning this kind of porcelain 
softens more than the hard, and requires supporting on every side. It is for this 
reason generally baked in fire-clay moulds. The ordinary oven is employed. The 
glaze for tender porcelain is a kind of crystal glass containing lead. This glaze 
is poured over the articles, as they are non-absorbent on immersion. French porce¬ 
lain is similar to cryolite glass or hot-cast porcelain. (See p. 291.) 

English Fritte Porcelain. English tender porcelain consists of a plastic clay, so-called 
China clay or Cornish stone , a weathered pegmatite, with fire-clay and bone-ash. The 
addition of the latter is due to Mr. Spade, in 1802; recently phosphate of calcium, 
as apatite, phosphorite, staffelite, or sombrerite, has been substituted. The glaze is 
composed of Cornish stone, chalk, fire-brick, borax, and oxide of lead. The article 
must be baked before glazing, as the glaze is so much more easily meltible than the 
body of the article; and in this second firing lies the difference between the manu¬ 
facture of tender and of hard porcelain. In hard porcelain the melting-point of the 
glaze and the body are the same. English porcelain is far less solid and more liable 
to crack than the hard; upon the other hand, English porcelain is the more plastic, 
and can be produced at a lower temperature in saggers of inferior fire-resisting 
qualities, consequently at a less expense. The burning takes place in a stage oven 
with anthracite coals, the articles being placed in saggers. The glaze is applied by 
immersion. Recently boracic acid has been largely employed in glazing English 
porcelain. 

Parian and Carrara. Parian is an unglazed statue-porcelain, similar to English porcelain, 
but more difficultly fusible, containing less flux and more silica. The colour is a very 
slight yellowy the surface is wax-like. Parian was first prepared by Copeland, in 1848, 
although the idea was not new, as before this time Kuhn, of Meissen, had prepared 
statues and medallions of porcelain in imitation of marble. The composition of parian 
is very variable ; some on being tested yield phosphate of calcium, others silicate of barium, 
and again some contain only kaolin and felspar. 

Carrara, so named in its imitation of the marble produced from Carrara in Tuscany, is 
intermediate to parian and stoneware, is less transparent than parian, and sometimes 
whiter in colour. 



EARTHENWARE . 


305 


III. Stoneware. 

stoneware. Stoneware differs entirely from porcelain; it is dense, sonorous, fine¬ 
grained ; does not cling to the tongue. It is semi-fused and opaque. Even fine 
white stoneware is different from porcelain in transparency, being entirely opaque, 
although in some other respects similar. Stoneware is distinguished— 

1. As porcelain glazed. 

2. As white or coloured unglazed. 

3. As common stoneware, salt-glazed. 

The fine white stoneware is made from a plastic clay, burning white, and not very 
refractory. To the clay is added kaolin and fire-clay with a felspar mineral, 
generally Cornish stone, as a flux. The glaze contains oxide of lead and borax, and 

Fig. 151. 




is transparent. The flux is used in the making of stoneware much more freely than 
in porcelain, in the proportion of more than half the weight of the mass. It follows 
that stoneware can be burnt at a lower temperature than porcelain. The articles 
21 



















































































































CHEMICAL TECHNOLOGY. 


306 

are fashioned out of the plastic clay in the same manner as porcelain. Fine stone¬ 
ware is used as a cheap substitute for porcelain, it being much more easily burnt. 

White or coloured unglazed stoneware, or Wedgewood ware, is made from a 
plastic, slightly refractory clay, kaolin, fire-clay, and Cornish stone, the latter in 
the proportion of half the weight of the whole. It is more easily fusible than porce¬ 
lain, requiring a lower temperature in burning. The coloured stoneware is of the 
same composition as the white, the colouring being only superficial. Frequently 
other coloured clays are used for ornaments in relief. Coloured Wedgewood-ware 
is known as Egyptian, bamboo, fine salt ware, fine biscuit, &c. 

Common stoneware differs from the preceding in containing no flux, the clay 
being semi-fused by the continued action of the fire. To the clay is added fine 
sand, or pulverised fragments of stoneware. Chemical and pharmaceutical utensils, 
acid tanks, &c., are made of this ware, it being strong and durable. The colour is 
generally grey. 

stoneware ovens. The ovens for burning stoneware are so constructed that the articles 
can either lie down or be placed vertically. Fig. 151 is the vertical section of such 
an oven through the line a b in Fig. 152. Fig. 153 is a section through the line 
CD, seen from B. Fig. 154 is a section through CD, seen from A. Fig. 152 is the 
plan on the line EF, Fig. 151. a a is the arch or vault of the oven, built of clay ; 
b, the vessel chamber ; c, the fire-room; d, the fire-bars ; e, the stok3-hole; /, the 
ash-pit; g. an air-draught; i i, a pierced wall; k, a pierced back-wall, through 
which the flame and hot gases escape into 0, serving as a flue. Stone-coal is used as 
fuel. Another form of oven in which mineral water bottles are burnt is shown in 


Fig. 153. Fig. 154. 



Fig. 155. It is constructed on an easy slope ; at the lowest part is the fire-room, A. 
In the middle of the burning-room is the pierced wall, C, technically termed the 
window, through -which the hot gases and flame escape into D. The vault and walls, 
b and E, are of broken earthenware bound with mortar. A chimney is unnecessary, 
the gases escaping through the pierced wall, E, into the air. The burning usually takes 
about eight days. The high temperature at which common stoneware is burnt, and 
the nature of its components, render glazing unnecessary; but generally a glaze is 
obtained -with the help of common salt placed in the oven during burning. After the 







































































EARTHENWARE. 


3°7 


placing of the salt the openings of the oven are closed for some time, and then a 
second quantity of salt is introduced. The silica, with the assistance of the steam, 
decomposes the salt into hydrochloric acid and soda, with which it combines. Thus 
there is formed on the surface of the ware a glaze of silicate of soda and alumina. 
The salt will take up more than 50 per cent, silica, according to Leykauf’s experi¬ 
ments ; therefore, the more silica the better glaze. An oven of moderate size will 


Fig. 155. 



require 80to 100 pounds of salt; the purity of the salt is not a subject of much 
consideration. The glaze is colourless, and the vesse lappears the colour of the clay. 
Stoneware that is unequally coloured, one part brown, the other grey, has been 
brought to that state by the escape of hydrocarbons into the burning-room. 

Lacquered Ware. Lacquered ware, known as Terralite and Siderolite ware in northern 
Bohemia, and manufactured by the firms of Yilleroy and Boch, of Dresden, is an inter¬ 
mediate ware to fine and common stoneware ; it has no glaze, but a strong surface colour 
of varnish or lacquer. Candlesticks, bowls, flower-vases, jugs, flower-pots, baskets, 
butter-dishes, fruit-dishes, &c., are formed from this ware, and baked in saggers in the 
usual manner. Great care and attention are required in burning the ware. The colour 
or bronze is mixed with varnish thinned with turpentine or linseed-oil, and applied with 
a pencil. The ware is then placed in a slow oven; the etherial oils volatilise, and the 
bronze colour becomes fixed to the surface of the ware. 

IY. Fayence Ware. 

Fayenceware. Fayence ware (English fine stoneware) derives its name from the 
town of Faenza, in the Italian States, where the ware was skilfully made. In the 
9th century the Spanish Moors manufactured fayence in the Island of Majorca, 
whence the present Majolica, the slight alteration in the manner of spelling being 
accounted for by Dante in his “ Tra isola di Capri e Majolica ,” on the ground that 
the older Tuscan writers spell the name of the Island “ Majolica.” The industry 
developed from the 13th to the 15th century; from that to the 17th it culminated, 
and then commenced to decline. In the middle of the 16th century Bernard Palissy 
introduced the ware known as Palissy-fayence into France. Palissy’s celebrated 
Pieces rustiques consist of ware ornamented with fish, fruit, vegetables, &c., 
naturally coloured in enamel. The body of porous fayence ware is earthy, and 
clings to the tongue. It is opaque, with more or less plasticity, and little or no 
sonorosity. It consists generally of plastic clay, or a mixture of this with common 
potter’s clay. It differs from clay ware in the employment of finer materials, mani¬ 
pulated with greater care. Fine white fayence is distinct from common enamelled 
fayence. Fine fayence (semi-porcelain) consists of a plastic clay with pulverised 
quartz or fire-bricks, with kaolin or pegmatite and felspar minerals. It remains 
white after burning, and is coated with a transparent glaze. The fayence 
ware of different countries differ greatly ; some are easily fusible, others again are 





. CHEMICAL TECHNOLOGY. 


Jos 

burnt to a high temperature. The composition of the glaze is therefore very varied. 
Common lime fayence is a mixture of potter’s or plastic clay, marl (clay with 
carbonate of lime), or quartz and quartz-sand. It is characterized by containing 
15 to 25 per cent, of lime, that, at the low temperature at which common fayence is 
burnt, only loses a portion of its carbonic acid. The common fayence ware is thus 
easily distinguished from other wares by its property of effervescing when an acid 
is poured into a vessel made of this ware. Its fracture is earthy; the colour, con¬ 
sequent upon its containing 2 to 4 per cent, of oxide of iron, a decided yellow, so that 
an opaque glaze is employed. The glaze or enamel contains usually oxide of tin, 
oxide of lead, alkalies, and quartz. The more oxide of iron and lime contained in the 
mass, the lower the temperature required for burning. Fayence, like porcelain, is 
twice burnt, first without, and finally with, the glaze. It is burnt in saggers ; the 
ware is placed in the saggers, and these are piled one upon the other in the furnace, 
with a layer of fat clay between each pair. The articles stand in the saggers upon 
small tripods in order to expose as small a contact surface as possible. The hard- 
burnt ware has next to be glazed. A thin pulp with water is made of "the materials 
of the glaze placed in a cistern into which the articles are dipped. The glaze usually 
consists of felspar (Cornish stone), fire-clay, heavy spar, sand, borax, and boracic 
acid, crystal-glass, soda and nitrate of soda, white-lead, minium, and smalt. The 
composition of this glaze is ordinarily very complicated, but the essential consti¬ 
tuents are silica, boracic acid, alumina, oxide of lead, and alkali. Recently the 
Peruvian mineral, so-called tiza (borate of soda and lime), has been employed. The 
addition of lead serves to render the glaze easily fusible, while the felspar imparts 
the softness characteristic of a lead-alkali glaze. 

0l ra™ence ns Fayence is ornamented by—1. Painting; 2. Casting; 3. Printing; 
4. Lustring. Painting is usually done with the brush, partly under, and partly 
upon the glaze. The glazing oven not attaining so high a temperature as the porce¬ 
lain oven, the colours are not affected by the heat. The colours used are oxide of 
chromium, oxide of cobalt, oxide of iron, oxide of antimony, &c. The rose- and 
purple-red colours are obtained from gold preparations. The pink colour, carna¬ 
tion pink, was discovered in this county, and is essentially a protoxide of chro¬ 
mium. To make this colour— 

Stannic acid. 100 

Chalk . 34 

Chromate of potash . . . . 3 —4 

Silica . 5 

Alumina. 1 

are well mixed and allowed to stand for some hours in a strong heat. The mass 
appears as a dirty rose-red colour, attaining its full brilliancy when washed with 
water acidulated with hydrochloric acid. The casting consists in the fayence vessel 
receiving a surface layer of coloured clay in any required part, independently of the 
•colours of the mass. These coloured clays or clay-washes are made of the ordi¬ 
nary fat clays and metallic oxides. The printing is accomplished with the aid of a 
thin tissue paper, upon which the pattern is first printed from a copper plate, and 
afterwards transferred to the ware. For black, a mixture of forge-scale, manga¬ 
nese, oxide of cobalt, or chrome-black is employed; for blue, oxide of cobalt mixed 
with, for bright blue, fire-brick, and for less intense colours, heavy-spar, both of 
course being pulverised. This mixture is burnt, the frit ground, and mixed with a 






EARTHENWARE. 


309 


flux of equal parts of flint-glass and fire-clay. Copper plates, in which the pattern 
is deeply cut, are charged with colour mixed with linseed-oil; a transfer is then 
taken on the fine “pottery tissue” paper, and laid on the ware. By means of a 
rubber the colour is caused to leave the paper, which has been previously moistened 
with water, and adhere to the ware. The paper is then washed off, and the article 
taken to the kiln. 

Flowing colours. Flowing colours are much employed in ornamenting fayence. The 
common fayence or delf ware is coloured blue in this manner by means of prot¬ 
oxide of cobalt mixed with the glaze. When the vessels are taken to the burning- 
kiln, a mixture of chloride of calcium, chloride of lead, and clay is also introduced 
on a small plate. The protoxide of cobalt is converted into a chloride by combin¬ 
ing with the volatilised materials, and in turn combines with components of the 
material of the vessel. By this means the articles obtain an apparent transparency 
somewhat similar to the characteristic of porcelain. 

Lustres. Some kinds of ware have a second coating—a metallic lustre or glaze—given 
to them after burning. Gold Lustre : The different kinds of gold lustre are very similar 
and need not be detailed. They are essentially composed of fulminating gold and balsam 
of sulphur, the latter prepared by heating linseed oil and sulphur together. Platinum 
Lustre : This is obtained by mixing anhydrous chloride of platinum with lavender oil or 
balsam of sulphur; also by the well-known precipitation of platinum by sal-ammoniac. 
Silver Lustre is either a yellow lustre or a cantharidine lustre, so-called fi'om its simi¬ 
larity in appearance to the wing-case of the Spanish fly (Gantharis vesicatoria). Salvetat 
believes that chloride of silver may be employed as a yellow lustre, similarly to gold 
preparations. The canthai'idine lustre is generally a yellow lustre, the difference being 
that it is only used for white grounds, while the former is employed for blue grounds, on 
which it appears slightly tinged with green. Copper Lustre is both red and yellow; it is 
used for Spanish fayence and Maj olica wares. It is chiefly formed by a silicate of copper. 
Oxide of lead, or lead-lustre, is merely a lead-glaze. Chloride of silver mixed with lead- 
lustre is reduced, the result being a deposit of a gold-yellow or a silver-white colour accord¬ 
ing to the proportion of silver. 

Etruscan Vases. The vases of the old Romans were a kind of fayence ware, containing 
iron, and formed of a clay decomposed by quartz, only slightly burnt, sometimes unglazed, 
sometimes coated with an easily fusible glaze. These vases and articles are celebrated 
more for their beauty of form than for any peculiarity in composition, which is very 
analogous to the well-known delf-ware of which our table services are made. 

clay Pipes. In the manufacture of clay pipes there is employed the beautifully white 
pipe-clay, containing neither iron, sand, nor carbonate of lime. The clay, if pure, 
always burns white; but occasionally, when a yellow colour appears, the clay is burned 
for a longer time, whereby the oxide of iron colouring the clay is removed. The pipes 
are formed in a moidd similar in shape to the pipe. A roll of clay is taken, and care¬ 
fully spread out to the length of the pipe. The mould is constructed in two halves, 
hinged together like a meerschaum pipe-case, and is generally of iron. The roll of clay 
is placed on the lower half of the mould, and the other half is then pressed or screwed 
down. A wire is then pushed up the entire length of the stem. The pipe is then taken 
out of the mould, and set aside to dry. It is afterwards taken to the oven, where about 
a gross of pipes are introduced into each sagger. The saggers are long clay tubes. 
Sometimes the pipes are burnt without saggers. To prevent the pipe adhering to the lips 
on account of the porosity of the clay, the end put to the mouth is rubbed with a mixture 
of soap, wax, and lime-water. 

Watercoolers. The Spanish water-cooling vessels, or alcarrazas , are made of a porous, 
unglazed earthenware. The constant evaporation-of the water exuding to the outer 
surface of the vessel causes the water to be kept cool in the hottest climates. The vessels 
are only slightly burnt. According to Sallior, water can be cooled 15° in an alcarraza, 
while Sevres ware only permits of the cooling of its contents in a similar manner some 
2° or 3 0 . These vessels are known in France as hydrccerames. In this country Egyptian 
wine- and butter-coolers are very common, while in Egypt, Spain, Turkey, the Indies, and 
Americas, they are really necessaries. In Bengal these coolers are made from the mud of 
the Ganges. In the Levant they are termed baldaques ; in Syria and Egypt collies or 
auRics, while in many places they are also known as yargoulettes. 


3*o 


CHEMICAL TECHNOLOGY. 


Y. Common Pottery. 

common Pottery. To distinguish between the different kinds of this ware is extremely 
difficult. The manufacture is entirely distinct from the preceding. For the so- 
called white pottery, used for culinary purposes, ordinary potter’s clay is employed, 
and for brown-ware a moderately refractory clay. The natural clays are, as a rule, 
too fat to be used without the addition of some other material, generally sand; 
besides sand, fire-brick, chalk, charmotte, and anthracite coal-ash. The vessels 
are formed upon a potter’s wheel, air dried, and then glazed. The employment of 
a lead-glaze was but a short time ago unknown in the glazing of this kind of ware. 
Ordinarily the mass is white or yellow, sometimes brown-red; the glaze being 
transparent, the colour of the body or mass is always apparent. Partly because 
the ware is very easily fusible, and partly because a low heat is used in the burn¬ 
ing, the glaze must also be very easily fusible. For this reason a lead-glaze, forming 
an aluminium and lead glass is very applicable, and is employed mixed with loam 
(clay and sand). The materials are ground and very intimately mixed in a hand- 
mill. The lead used is generally a lead-glance. During the burning the lead- 
glance is roasted, and the sulphur is driven off as sulphurous acid. The oxide of 
lead combines with the silica and alumina of the loam, or mixture of sand and 
clay, to form aluminium lead and silicate. 

The glazing of the air-dried ware can be performed in three ways; either by immersion, 
by sprinkling, or by dusting. By immersion the workman’s hands come into contact 
with the lead-containing glaze, with detriment both to his health and the adhering of the 
glaze if his hands should be greasy. This method is not therefore often employed. 
Sprinkling is generally adopted. In dusting, the ware is first immersed in a pulp of fat clay, 
and then, while still damp, dusted with the finely pulverised glaze. The danger of this 
process is the inhaling of the fine particles of glaze floating in the air of the workroom. 
When the oxide of lead is properly proportioned to the silica of the clay or loam, the 
resulting lead-glass is not affected by ordinary organic acids. But if the oxide of lead is 
not well combined with the silica, it will be dissolved by boiling vinegar. The experiments 
of Buchner, A. Yogel, Erlenmeyer, and others, have shown that the insolubility of lead- 
glaze is not so great as has been supposed, very dilute vinegar in some cases being suffi¬ 
cient to effect a solution. The use of vessels thus glazed may therefore have no little 
influence upon the health of a family, and it becomes necessary to consider if there is not 
some substitute. All injury likely to accrue from the use of this glaze would be removed 
if the potter would but re-burn imperfect ware, or employ ovens of the best construction; 
but this is not always the case. Decently the preparation of a glaze free from lead has 
been attempted, by employing water-glass, or a mixture therewith of borate of lime. 

Burning. The glazed vessels are next taken to the oven. This is generally a reverbera¬ 
tory furnace, 2 \ to 2f metres in height, and 7 to 10 metres in length. At one end is the 
fire-grate, and at the other the chimney. The vessels are burnt Without saggers, and are 
exposed to the full influence of the flame. The fire is at first kept low for eleven to twelve 
hours, and then maintained strongly for four to five hours. The vessels can be removed 
from the oven about eighteen to twenty-four hours after being burnt. 

YI. Brick- and Tile-Making, &c. 

Bricks. This manufacture may be said to include brick-making, tile-making, and 
the manufacture of terra-cotta goods, and must not be confounded with the ancient 
Egyptian method of making air-dried bricks, still pursued for some minor purposes. 
In order to the better comprehension of the methods of brick-making, we will first 
consider the preparation of the material. This may be divided into— 

The preparation of the clays ; 

The moulding of the brick ; 
a. By hand. 
iS. By machinery; 

The burning of the dried brick. 


EARTHEN WARE. 


3 11 


ierra-cotta. The term terra-cotta ware generally includes tlie burnt, unglazed 
yellow or red clay ware, and also tiles, employed in building and architectural 
ornamentation. The preparation of this ware is almost entirely mechanical, and 
does not call for any further elucidation in this work than will be found in the 
following pages descriptive of the class of manufacture to which it belongs. 

Brick Material. Various clays are used in brick-making. Usually those only are 
selected that will form a brick capable of bearing a considerable strain. In the 
burning a test-brick is employed, which is removed from time to time to see the 
progress of the fire, to prevent the over-burning of the bricks, or the lowering of the 
fire till the bricks are sufficiently burnt; but this brick must not bo confounded 
with another test-brick for the following purpose. A brick is made of any new clay 
to be tested, and is set apart in an active kiln, being burnt at the same temperature 
as the bricks of this kiln afterwards sent into the trade. By the qualities of this 
test-brick the nature and worth of the new clay is judged. A batch of bricks should 
be composed of clays that may all be burnt at the same temperature, else very 
unequal results will follow; some bricks will be under-burnt and some over-burnt, 
while only those bricks to the clay of which the temperature is adapted will be of use 
commercially. A brick-clay containing much carbonate of lime can be burnt at a 
very low temperature, and indeed bricks so composed are very solid, and have great 
durability. Brick-clays often contain felspar, mica, hydrate of oxide of iron, phos¬ 
phate of iron, besides organic matter. When these are not in large quantities their 
presence is not detrimental. Mica and felspar with oxide of iron act as fluxes, and 
in known quantities are useful rather than pernicious. Plint stones, large pieces of 
carbonate of lime and gypsum interfere with the easy applicability of brick-clays. 
Sulphur pyrites render clays unsuited to the manufacture of bricks,, as the sulphuret 
of iron remaining in the brick after burning oxidises in the air to sulphate, which in 
a short time weathers out and renders the brick brittle. In the Netherlands, in the 
Thames near London, on the banks of the Ganges and Nile, in the mouths of rivers, 
and in nearly all clays exposed to the ebb and flow of water, is found an admirable 
material for brick-making. Since 1852 a mixture of lime, river sand, and water has 
been extensively used as a brick material, and for other building purposes. 

Preparation of the Clays. The excavating of the clay for making bricks is carried on in the 
summer or spring. The clay is placed in not too high a layer, and allowed to weather. 
It is very advantageous if, during the weathering, a frost sets in. The clay is allowed to 
remain thus exposed to atmospheric influence until it becomes boggy or marshy. In this 
condition it is brought to a tank dug in the ground, 4 metres long, 2 metres broad, 
and 1 *3 metres in depth, where it is mixed with about as much water as will stand to a 
height of 6 centimetres in the tank. So soon as the clay is thoroughly saturated it is 
treadled, that is, the brick-maker fastens boards or wooden shoes to his feet, and care¬ 
fully treads over the clay, picking out all the flints, &c., which resist the passage of his 
foot to the bottom of the layer. This process is repeated two. or three times. Sand is 
then added to the clay. If the clay is fat the mixture is proceeded with; but if it is a 
poor clay it is advantageous to wash out a portion of the sand. This may be effected in 
two ways. The ground-tank just described may be inundated with water, and the sand 
allowed to settle to the bottom; or the mixed sand and clay is placed in a large wooden 
tub with a hole in the side near the bottom stopped with a plug. When the water has 
thoroughly impregnated the clay it is let off, carrying part of the sand with it. Or the clay 
is stirred with the water to a thin pulp, and allowed to run out of the wooden cistern 
into a ground tank, where, with the water, the sand settles to the bottom. London clay, 
being mostly alluvial, has to be very carefully treated to free it from flint stones, &c.: 
it is afterwards mixed with ash or sand. 

The “treading” of the clay is at the present time performed in mills, termed “pug” 
mills and “ washers.” At the late International Exhibition (1871) several machines were 


312 


CHEMICAL TECHNOLOGY. 


exhibited for performing the whole process of brick-making continuously. Among these 
was the three-process brick-making machine of Messrs. Clayton, Son, and Howlett, of 
the Atlas Works, and combining at one operation crushing, pugging, and brick-making. 
The rough clay is thrown into the hopper of the machine; in this hopper revolves a 
shaft, upon which are keyed several small knives to cut up the clay previously to its 
being crushed. It next passes through a pair of crushing rollers, and these effectually 
reduce any stones or hard lumps of clay which may enter. The clay, thus partially 
prepared, next passes into a horizontal pugging or mixing cylinder situated beneath, 
where it is mixed by the pug-knives fixed upon the central shaft. The knives force the clay 
towards the further end of the cylinder, where it is received by rollers and forced through 
the dies, forming a smooth bar of clay of the width and depth of a brick. This bar is 
cut into the required lengths by wires. The machine is capable of producing 20,000 to 
30,000 bricks per diem, and is, perhaps, the best of its class. Mr. Bawden has constructed 
a machine in which no rollers or crushers are employed, the clay being turned out as 
wet and as soft as in hand-moulding. One horse will pug the clay and mould from 12,000 to 
15,000 bricks per day. It consists of a square pug-mill, through which runs a vertical shaft 
bearing pug-knives. On the top of this shaft, above its bearing, is attached the horse-pole, 
which gives motion to the whole machine. Upon the lower end of the shaft, which 
passes through the bottom of the pug-mill, is a wheel having two cams, on which two 
rocking arms work. One arm presses the soft clay through a grating into a six-brick 
sanded mould, and the other arm is connected to a slide for pushing the empty sanded 
moulds under the grate, the empty mould at the same time pushing the full one out. 
Among the best Continental machines are those of Henschel of Cassel, and of Karrens. 

Moulding the Brick. The moulding of the brick by hand is a very simple matter. A 
mould of wood or cast-iron sufficiently large to allow for the shrinkage of the 
material during burning is usually employed. Pig. 156 shows the plan (b), and the 
section (a), of the mould. Sometimes it is made so that two bricks can be 
moulded at the same time, Pig. 157. The moulder takes a ball of clay and places it 
in a sand-strewn mould, pressing it well in. Then with the striker, A, Pig. 158, 
he removes the superfluous clay. The mould is then emptied, and the brick placed 


Pig. 156. 


Pig. 157. 


Pig. 158. 


C 


A 


D 



by a child on a barrow, to be taken to some other part of the brick-field, to be sun- 
and air-dried. The air-dried bricks are then taken to a kiln to be burnt. In many 
cases the bricks are dried by artificial heat in sheds, the floors of which are heated 
by fires. A gang of labourers, numbering five to ten persons, can at the maximum 
produce only 1000 bricks per day. 

Brick Moulding by Machinery. The moulding of bricks by machinery is daily becoming 
more general. A moulder, no matter how experienced, has never been known to pro¬ 
duce more than 6000 bricks in a day, and a continuity of this labour would be most 
improbable. "Where there is a large demand, it becomes necessary to produce 
30,000 bricks per day regularly, and this can be done by machinery, without 
employing a large number of hands. Purther, the consumption of fuel in the 
machine can at once be stopped, or regulated to meet the demand, while a large 
number of workpeople cannot always be dealt with so satisfactorily to the well- 
meaning employer. But the machine engrosses a large capital that is not always to 
tie invested, whereas a number of hands may be paid from the result of their labour, 
if the demand is good. It therefore does not always happen that machinery can 
compete with hand labour in this particular, as there are, in this trade especially, 





















EAR THEN WARE. 313 

many makers who pay as they receive, sending out the bricks as soon as they 
are burnt. The machines constructed may be classed as follows:— 

1. Those in which the brick is moulded or finished as by hand. 

2. The machines in which the moulding proceeds uninterruptedly. 

3. Those in which the brick is cut out of a cake of clay. 

4. Those in which a band or stream of clay of the length and breadth of the 

brick is cut by means of knives or wires to the requisite depth. 

I. The machines of the first class, imitating the motion of the moulder’s hands, 
are constructed of an iron mould, with machinery or arms having a to-and-fro 
motion, somewhat similar to a shuttle in a loom. Such a machine is that of Carville 
of Issy, near Paris (Pig. 159). The brick material flows from the pug-mill, A, under 
the press roller, B, which is supplied with water from the reservoir, c, to prevent the 
clay adhering. Sand is next spread over the clay from D. The clay now arrives 



Fig. 159. 


W 


under the pressing apparatus worked by the arm, F, and counterpoise, G. The bricks 
then pass away on the endless band of moulds, 1, to which motion is imparted by 
means of the revolving arms, J J. The bricks in the passage of the moulds over 
these arms are shot out, the chain of moulds passing through the tank of water, Ts T , 
and thus being cleansed. M is a box to receive the waste clay, which is taken to the 


Pig. 160. 



pug-mill. Pig. 160 is an enlarged view of the chain of moulds; M M being the plan, 
and the lower figure the side view. 

II. The second class of machines are very similar to the foregoing. Instead 
of the pressing apparatus, a roller is substituted, which presses the clay into the 














































































314 


CHEMICAL TECHNOLOGY. 


moulds as they pass under it. The moulds sometimes form the periphery of a largo 
circle in the horizontal plane,- as by this means the operation can be going on undor 
several rollers at the same time. 

III. The machines of the third class differ from the preceding in that the mould 
descends upon a cake of clay of the required thickness. This kind of machine 
is generally used in the manufacture of ornamental bricks, as by substituting other 
moulds any desired pattern may be produced. 

IV. The machines of the fourth class, in which a band of clay is divided in cross 
section, may be best considered under two subdivisions, the one containing those 
machines in which the clay is forced through an- opening of the proper size, the other 
those in which the clay is pressed by rollers into a band of the required dimensions. 
The separation is effected either by a knife or. by cutting wires. By a method similar 
to the first process, drain pipes are manufactured. The machine of Terrasson- 
Fougeres is a very fair example of the older system of rolling the clay. An endless 
band, B, conveys the clay under the press-roller, A, Fig. 161, the motion being 

Fig. 161. 



continued by the rollers, D, and the clay kept to the required breadth by the guides, 
C. Fig. 162 shows the cutting apparatus mounted on a strong timber framework, G, 
and also on wheels for the removal to any part of the shed or field. It will be 
readily seen from the woodcut how the copper or iron wires kept taut by the weight, 
F, sever the band of clay. 



Bricks from Dried Clay. Pressed bricks are bricks pressed from dried clay in which the 
natural moisture of the clay is all that is employed to render the brick coherent. The 
pressure must, therefore, be considerably more than that used in the making of moist 
clay into bricks; but pressed bricks are much more solid and firm than moist clay bricks, 
a smaller number making a more secure wall. One of the most general machines 
for making this kind of brick is that of Nasmyth and Minton, in which a peculiar form of 





































































EAIl then ware. 


315 


eccentric sets the moulds in action. The same movement of the primary axis pul¬ 
verises the clay, and causes it to be forcibly compressed into the mould. With this 
machine and with that of Julienne, who has recently made some improvements, 4000 
bricks can be made daily with the labour of a man and boy. 

The Burning of the Bricks. The burning of the air-dried bricks or tiles is carried on in 
ovens or in kilns. The ovens are either open ovens, similar to a blast furnace, 
or vaulted, or ovens in which the burning is continuous. The fuel is partly wood, 


Fig. 163. 


Fig. 164. 




partly turf, brown coal, and anthracite or stone-coal. From the many forms of 
brick-kilns and ovens, the following are selected as best conveying a clear idea of the 
process. Fig. 163 is a stage-oven, fuelled with wood, and consisting of three 


Fig. 16 6. 



chambers lying one above the other, A, B, and c. These floors can be heated in rota¬ 
tion. The furnace D, fed through the door, F, gives a great length of flame, which 
passes through the pierced wall, I, into the chamber, A, and thence through the 














































































































3 i6 


CHEMICAL TECHNOLOGY. 


furnace, n, fed through the door, G. The flame from this hearth passes to the upper 
chamber, c, passing through J and the pierced wall, K, and eventually by L to the 
chimney, n. Fig. 164 is another section of this furnace. Fig. 165 is a plan of the 
middle stage. This kind of oven effects a considerable saving in fuel, as bricks can be 
burnt in all the stages. One of the most economical ovens burning wood fuel is shown 
in section in Fig. 166, and in plan in Fig. 167. There are three fire-places, of which p 


Fig. 167. 



is the middle one. The fire-place has no grating, but is vaulted in by a series of iron 
bars, 000, through the interstices of which the flame passes into the chamber, b b, 
open at the top. The bricks to be burnt are placed upon the bars 000 transversely, 
spaces being left for the passage of the flame and hot gases. It will be seen that this 
method of burning is much more expensive than the foregoing, owing to the 
amount of heat wasted; while wood as a fuel is naturally more expensive than 


Fig. 16S. 



Fig. 169. 



stone-coal, to produce the same amount of heat. With the form of oven designed ly 
Carville, and shown in Figs. 168 and 169, 80,000 bricks can be burnt with 160 hecto¬ 
litres of stone-coal. Thus, as 1 hectolitre of stone-coal weighs 80 kilos., and 
as 100 kilos, of coal cost 3 francs 12 cents., the burning of the 80,000 bricks can be 
effected at a cost of 400 francs (£16). Stone-coal may be burnt in the oven shown 
in Fig. 170. The capacity of this oven is limited only by the enclosing walls, b b, of 
thick masonry. The bricks to be burnt are placed upon the sole of the oven, c. 






















































































EARTHENWARE. 


317 


which is constructed to admit of the free circulation of the products of combustion. 
Fig. 171 shows the method of placing the bricks in the oven; and Fig. 172, a plan, 
the two hearths, D d. 


Fig. 170. 


Fig. 171. 


Fig. 172. 



Many experiments have been made with the view of combining the burning oi 
lime with the burning or baking of the bricks. Figs. 173 and 174 show an oven 
built for this purpose. The sole of the chamber, A, is covered with limestone, which 
is burnt equally with the bricks placed above it. The draught is regulated by 
the dampers in the chimney, B, and by the openings, c. The six fire-rooms are sepa¬ 
rated from each other by the blocks of strong masonry, D and G. The fuel is placed 
in the furnace, E, under which is the ash-pit, F. 


Fig. 173. Fig. 174. 



Annular Kilns. The circular or annular kilns of Hoffmann and Licht, are much used. 
These ovens are in plan in the form of a ring, capped by a chimney. In each oven 
there are a number of chambers in which the bricks are stacked. One of these 
chambers is filled with what are termed green bricks, that is bricks fresh from the 
field. The fire being applied, the steam passes off to the chimney. The second 
chamber is then filled with bricks; and when the steam has passed off from the firs;' 
chamber, the products of combustion there are admitted to the second chambe. 
through flues in the partition wall. This process is repeated with each chamber in 
succession. As soon as the bricks are burnt the door and flues of the chamber are 
opened to admit the cold air; when cold the bricks are removed, and green ones 
supplied in their place. It is clear that by this means there need be no interruption 
in the burning; and also that— 


/ 









































































318 CHEMICAL TECHNOLOGY. 

a. As the doors and flues are oj)ened in the chamber in which the bricks have 

been finally burnt, the air entering is highly heated. 

b. The effect being to augment the heat of the next chamber ; while 

c. This heat can be so proportioned out to the unburnt bricks as to render only 

a very short actual firing necessary. 

The saving of fuel by the use of these kilns must be evident. Also from the con¬ 
tinuity of the firing, which in practice is never allowed to go out, the ovens or 
chambers never get perfectly cold, and are consequently soon re-heated. 

Field Burning. In contrast to the permanent kiln is the field-kiln, in which bricks or 
tiles are burnt at the same place that building is going on, or where a sufficiency of 
brick-clay is likely to yield a good return. Bricks burnt in these temporary kilns 
are termed field-bricks. The fuel employed is either turf, wood, or stone-coal. When 
turf or wood is used, the bricks are stacked similarly to the method employed in 
ovens in which these fuels are the firing materials. Flues are constructed in these 
kilns of the bricks themselves set in a thin layer of lime; while the wind-side of the 
stack is covered with hurdles thatched with straw. 50,000 bricks can thus be burnt 
at one firing. The flames and hot gases find their way hither and thither in the 
stack, and finally escape at the top. By the time that the outer bricks are hot, the 
interior of the stack or kiln has reached a very high temperature. When coal is 
employed the bricks are laid alternately with a layer of coal, a layer of lime serving 
as an outside cover, in which draught holes are made to regulate the burning. 
When the kiln is built the firing is commenced, and gradually extends to the 
several layers of coal until all is burnt. The kiln, consequently upon the con¬ 
sumption of the coal, falls or sinks together, a matter of no inrportance. 

Dutch clinkers. Hollanders, or Dutch clinkers, are a very hard, semi-glazed brick, of a 
green or dark brown colour, and possessing the property of not absorbing water. 

Roofing and Dutch Tiles. For the manufacture of tiles abetter and more carefully selected 
clay than that for ordinary bricks is employed. While “treading” is much used 
in the making of bricks, a mill is always considered necessary for tiles. As a rule they 
are burnt at the same time as bricks; the upper part of the oven being sufficiently heated 
for the purpose, owing to their thinness. When it is desired that the tiles should be of a 
grey colour, there is added to the fire, while the tiles are at a red heat, a quantity of leaves 
and damp twigs. By this means large volumes of smoke are disengaged, and pass into 
the interior of the kiln, where the pores of the tiles absorb the carbon, which imparts the 
grey colour remaining on cooling. Similarly the dark green colour results from the 
reduction of the peroxide of iron to black oxide and protoxide. Flat tiles are mostly used 
for paving purposes. Hoofing tiles are made in many shapes ; some with a nose or pro¬ 
jecting piece, with a hole through which a nail passes to fasten the tile to the rafters; 
others without this protection, and with a couple of holes simply. Ridge tiles form the 
capping of pointed roofs and dormer windows, &c. 

Drain and Gutter Tiles. The use of hollow tiles and bricks dates from a very remote 
period. Vaulting tiles are no more than hollow bricks or tiles, employed to reduce the 
weight of upper parts of large arches or masses of brickwork; they are 21 to 24 centi 
metres in height, and 9 to 13 centimetres in diameter, with the middle hollow and hard- 
burnt. A similar form of pipe is used for draining land, &c. For some purposes, bricks 
are constructed hollow through their width and not through the length. The advan¬ 
tages of hollow bricks where they are applicable are:—1. That 60 to 70 per cent, of 
materials are saved. 2. That they materially reduce the pressure by decreasin the 
weight of superincumbent masonry. 3. They dry more equally, and admit of good ven¬ 
tilation. 4. They can be baked at a lower temperature, with a saving of 20 to 30 per 
cent, of fuel. 5. The cost of transport is less consequent upon the reduced weight. 
Figs. 175 and 176 show two kinds of hollow tiling. 

Floating Bricks. Floating bricks, or bricks sufficiently light to float upon water, are of 
very ancient date. Posidonius, and after him Strabo, state that a peculiarly argillaceous 
earth was brought from Spain, which was used to polish silver, and from which bricks 
could be made that would float upon water. Further, that these bricks were made in 
several parts of Asia, and on an island of the Tyrian Sea. Vitruvius Pollio thought 


EARTHENWARE. 


319 


these bricks to be made of a very light unknown stone; and Pliny likens it to pumice 
stone. But the secret remained hidden for a thousand years, until Giovanne Fabroni, in 
1791, after many experiments, succeeded in producing a brick that would remain on the 
surface of water. The material employed was fossil meal, found near Santafiora in Tus¬ 
cany. It was capable of combining with lime mortar, resisted Avater, and Avas unaltered 
by variation in temperature. The strength of these bricks was scarcely inferior to that 
of ordinary bricks, and greatly more in the proportion of their Aveight. Fabroni, as an 
experiment, constructed the poAvder magazine of a wooden ship of these bricks ; and the 
vessel, being set on fire, sank before the explosion of the powder. About the same time, 


Fig. 175. Fig. 176. 



Faujes, of Coiron, France, found a fossil meal possessing* the properties of that found in 
Tuscany; and in 1832, the labours of the Count de Nantes, and of Fournet, a mining- 
engineer of Lyons, found an application for these bricks. The powder magazines, 
the cooking-galleys, the hearth of the steam-engine, the flues, the spirit-room on board 
ship can all be made of these bricks, and the chances of fire reduced. This kind 
of brick is also useful for the vaults of ovens, &c., in which a high temperature is main¬ 
tained, as they are infusible. Kiitzing found that these bricks contained immense 
numbers of the microscopic siliceous shells of infusoria. While an ordinary brick 
weighs 2*70 kilos., the weight of an equal bulk of this infusoria clay is only 0*45 kilos. 
Coated -with wax it swam like a cork. The strongest porcelain-oven-fire Avas Avithout 
effect upon it. By the addition of clay or lime the firmness and tenacity of an ordinary 
brick was obtained. 

Ordinary porous bricks are made by adding to the clay, coal-dust, saw-dust, turf, tan, 
&c. Light bricks were used for building purposes in Nuremburg in the 14th and 15th 
centuries. Chimneys were built of them. In Southern Bavaria, a light brick made from 
a mixture of turf and sand lime has been in use for many years. 

rire-Bricks. Fire-bricks, or bricks made with fire-clay, are employed instead of 
ordinary bricks in the construction of furnaces, and all places exposed to an 
exceedingly high temperature, which would melt the common brick. These bricks 
contain silica and alumina, but little or no lime, protoxide of iron, or alkalies; 
while the clay, to prevent contraction in burning*, is mixed with already burnt 
clay, sand, carbon (coal, coke), &c. 

The process of manufacturing fire bricks at Stourbridge is so admirably described 
in Lieutenant Grover’s “ Report on Fire-clay Goods’ 5 in the International Exhibi¬ 
tion of 1871, that the particulars maybe quoted in extenso. “The clay,” he says, 
“is firstly exposed in spoil heaps over as large an area as can he secured, for from 
3 to 18 months, according to the state of the weather. The action of frost, as with 
ordinary brick earth, is of great service in disintegrating the compact tough lumps of 
clay, and in dry weather the clay is frequently watered. In veiy wet weather, a 
3 months’ exposure will suffice for its proper ‘mellowing’ or ‘ ripening,’ and it ulti¬ 
mately slacks and falls to pieces. When new, it is termed, in the local phraseology, 
‘ short and rough; ’ after due exposure it becomes ‘ mild and tough.’ On some of 
the w T orks the spoil heaps of clay contain over 10,000 tons, and it is estimated that 
7 tons measure about 6 cubic yards. After sufficient weathering, the clay is ground 








































320 


CHEMICAL TECHNOLOGY. 


in a circular pan by two rollers or cylindrical stones, shod with iron rims 2| inches 
thick, and weighing from to 3* tons a-piece. After being ground, the clay is car¬ 
ried on an endless band to a ‘ riddle ’ of about 4 or 6 mesh to the inch for fire-bricks, 
6 or 10 for fine cement clay, and 12 or 14 mesh to the inch for glass-house pot-clay, 
the larger sized mesh being used for the sifting of the clay in wet weather. The 
large particles which will not pass through the ‘ riddle ’ are carried back on an end¬ 
less band to the pan, and there re-ground. As a general rule, it is only for very 
large fire-brick lumps, that re-ground pots, crucibles, or bricks—locally termed 
‘ grogg ’—are added to the clay before grinding; and. fire-cement clay is always 
ground pure. After passing through the ‘ riddle ’ the clay is tempered, or brought to 
a proper degree of plasticity by the addition of water. It is then thoroughly stirred 
and kneaded in a circular cast-iron pug-mill, by revolving knives projecting from a 
vertical shaft driven by steam-power. The clay is forced down by the obliquity of 
the rotating knives, and streams slowly from a hole near the bottom, whence after 
being cut by wires into the proper forms, it travels on in an endless band to the 
moulding sheds. The bricks are then moulded by hand in the usual manner, 
and dried at a temperature of 60 or 70 degrees, in sheds about 120 feet long and 30 
feet wide, beneath whose floors run longitudinally two flues. In fine weather, how¬ 
ever, the sun’s heat is made to economise fuel. The bricks are burnt in circular- 
domed kilns or cupolas, locally termed ‘ ovens,’ where they remain for from eight to 
fourteen days, being fired with the real intensity of flame or white heat, for about 
four days and three nights. They usually require seven days to cool down. The fire 
s slowly increased and gradually lowered, the time of burning being regulated 
by the kilnman in charge, who inspects the baking bricks from time to time through 
holes in the domed roof of the ‘ oven.’ The chimney stack is on the outside of the 
kiln, and the flame burns with a down draught, descending through holes in 
the floor, the fire-holes being merely openings left in the thickness of the wall of the 
kiln, and protected from the wind by buttresses long enough to allow room for 
the firemen to attend the fires. The coal is of course obtained from the pits which 
provide the clay. Most of the kilns hold each 12,000 bricks, but some are large 
enough to contain each 30,000 or 35,000 bricks, the capacity cf a kiln being roughly 
calculated upon the assumption that ten bricks require one cubic foot of space in 
the kiln.” 

Some analyses of fire-clay were given when treating of the different kinds of clay. 
Several analyses of fire-bricks are as follows :— 


Silica . 

1. 

Alumina . . . . 


Lime. 


Magnesia . . . . 

. . 0*66 

Oxide of iron 

. . 2*88 

Potash. 


Soda . 


Titanic acid . . . . 



100*00 

1. Clay from Dowlais. 2. Brick from c 
broke. 4. Brick from a blast-furnace. 5. 


2. 

3 - 

4 - 

5 - 

88*i 

88*43 

69*3 

77-6 

4*5 

6*90 

29*5 

19*0 

1*2 

3*40 

— 

2*8 

0*3 

6*i 

1*50 

2*0 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

100*0 

100*00 

100*0 

100*0 


)er-smelting furnace in Wales. 3. In Pem- 
•ick from a reverberatory furnace. 










EARTHENWARE. 


321 

Dinas bricks are made from material obtained from tbe Vale of Neath, in Glamorgan¬ 
shire ; but they have been imitated in Germany by a mixture of pure quartz-sand with 
1 per cent lime. Dr. Siemens, F.R.S., says of these bricks—“ Welsh Dinas brick, con¬ 
sisting of nearly pure silica, is the only material of those practically available on a large 
scale that I have found to resist the intense heat (4000° E.) at which steel-smelting furnaces 
aie worked. Messrs. Martin Brothers, of Lee Moor, Plympton, have made some bricks 
j e jL efuse kaolin, or china-clay, mixed with quartz-sand, carefully selected and 
washed. The kaolin is found in Cornwall and Devonshire, and is produced by the disin¬ 
tegration of pegmatite or felspathic granite, under the action of the atmosphere ; it then 
becomes a basic silicate of alumina. The following are some analyses of these kaolinitic 
bricks; they possess remarkably high refractory power from the small quantity of iron 
contained: J 


Silica . 


75-36 

73-50 

76-70 

Alumina. 


21-47 

22-70 

20*10 

Peroxide of iron .. 

.. 1-96 

1-79 

170 

1*70 

Alkalies, waste, &c. 

.. 0-50 

1-38 

2*10 

1-50 


ioo-oo 

100-00 

100-00 

100-00 


Sanitary Ware. Sanitary ware is one of the largest branches of stoneware manufacture. 
Stoneware is admirably adapted for employment where an impermeable and water-tight 
body is desired, as in drains, sewers, subways, &c. Pormerly, when about thirty years ago 
the manufacture of stoneware drains was commenced, the processes were all manual, and 
consisted in building up the large pipes or tubes section by section on a strong potter’s 
wheel. But machinery now effects the formation of this ware with a great economy of time 
and labour. The clay is placed in a strong cylinder of iron, in the bottom of which is a 
circular opening corresponding with the solid section of the pipe; an iron piston, driven 
by steam, descends, forcing the clay through this opening. By this means the pipe is 
formed: the socket or joint is generally added on a wheel. Bends, for the turning of the 
corners of streets, &c., are made by simply bending the pipe by hand as it is squeezed out 
of the machine. Messrs. Clayton, Williams, Whitehead, and Ainslie are among the most 
celebrated manufacturers of these machines. Messrs. Clayton recently exhibited, at the 
International Exhibition, a small machine working on the principle just described, that 
can be manipulated by a man and a boy. 

Crucibles. Eor crucibles it is necessary that materials shall be used that will with¬ 
stand the highest temperature. Good crucibles do not crack on being rapidly cooled, 
and they must also withstand the action of the fluxes that may result from the 
smelting of metals. The most common crucibles are the Hessian, the graphite or 
plumbago, and the English. The Hessian crucible is made of 1 part clay (of 71 parts 
silica, 25 parts alumina, and 4 oxide of iron) and one-half to one-third the weight of 
quartz-sand. They are refractory, remain unaltered by variations in temperature, 
but are unsuited to some chemical operations on account of coarseness of grain and 
porosity. If containing too large a proportion of silica, they become perforated by 
oxide of lead, alkalies, &c. Graphite or plumbago crucibles are made from 1 part 
of refractory clay and 3 to 4 parts graphite. The Patent Plumbago Crucible Company 
of Battersea, as well as the Nuremberg manufacturers, employ Ceylon graphite and 
fire-clay. Graphite crucibles will bear the highest temperature, and they can be 
made to almost any required size. English crucibles are made from 2 parts of 
Stourbridge clay and 1 part of coke. Crucibles containing coal become reduced 
when heated in contact with metallic oxides, and are therefore unfitted to the 
smelting of metals. Eecently lime and chalk crucibles have been employed for this 
purpose. Caron has used magnesia crucibles in the smelting of iron and steel. 
Gaudin employs an equal mixture of bauxite or cryolite and magnesia. Very 
similar are the bauxite crucibles of Audouin. 


22 








322 


CHEMICAL TECHNOLOGY. 


Lime and Lime-Bukning. 

Lime. Lime, protoxide of calcium (CaOrz 56), in its combination with carbonic acid 
as carbonate of lime (CaC 0 3 ) is a substance of the most frequent occurrence. It is 
a constituent of bone, of the shells of the mollusca, and is found most extensively 
in the minerable kingdom as marble, lime-stone, coral, Iceland spar, arragonite> 
chalk, &c. Its technical applications are as marble in building, in the manufacture 
of artificial mineral waters, as Iceland spar for optical purposes, as chalk in colours 
and drawing materials, in the manufacture of soda, in the preparation of hydraulic 
mortars, building and plastering materials, &c. Limestone, Alpen lime, lias lime, 
Jura lime, &c., is, when mixed with clay, iron, and other metallic oxides, used as a 
colour. Lithographic stone is a yellow-white limestone, employed as its name im¬ 
plies, in lithography. Chalk or earthy carbonate of lime occurs in strata in North 
1 . Germany, Denmark, France, and England. To this class belongs marl-limestone, 
distinguished by containing clay. With carbonate of soda, carbonate of lime 
forms Gay-Lussite (CaC 0 3 -j- Na 2 C 0 3 ); with carbonate of baryta, baryto-calcite 
(CaC 0 3 BaC 0 3 ) ; .and with carbonate of magnesia, bitter-spar or dolomite 
(CaC 0 3 -f- MgC 0 3 ), the latter occurring with 3 molecules of carbonate of magnesia 
to 1 molecule of carbonate of lime. 

properties. Carbonate of lime is not soluble in pure water; but if the water should 
hold carbonic acid in solution, bicarbonate of lime is formed. When this solution 
by means of evaporation loses half its carbonic acid, an insoluble carbonate is formed. 
In this manner are naturally formed stalactites and stalagmites. The deposit of calc- 
sinter upon objects deposited in caverns, in limestone-rock, &c., is thus explained. 
When carbonate of lime is ignited to whiteness in a porcelain crucible, the car¬ 
bonic acid is disengaged, and there remains protoxide of calcium (CaO) or caustic 
lime. 100 parts of carbonate of lime yield 56 parts of burnt lime. The volume 
of the lime undergoes no diminution by burning. Burnt lime is the form under 
which lime most commonly appears in the market. Carbonate of lime, heated in 
a closed porcelain tube, melts, and forms a crystalline mass, a carbonate, afterwards 
unalterable. 

Lame-Burning. The burning of the lime is effected— 

In kilns, 

In field-ovens, and 
In lime-ovens. 

Lime-burning in kilns is accomplished in the following manner -The limestone, 
unless it has previously been broken into small pieces, is heaped up into cairns similar 
to the heaps of wood to be converted into charcoal. The kiln is then covered with 
earth or turf, and the fire so placed that the larger pieces of lime in the interior of 
the heap are burnt. The regulating of the draught, the kindling, the covering, and 
the cooling, are on the same principle as that followed by the charcoal burner in the 
conversion of wood into charcoal by combustion. According to' P. Loss, a kiln of 
this kind, 4-5 metres in height, contains 35*5 cubic metres of lime as well as 2*6 cubic 
metres of lime-dust. In the field-ovens the burning is similarly conducted, but 
sometimes on a larger scale, the kilns being always temporary. It is easy to see 
that the burning in this manner is only of slight technical importance; besides the 


LIME. 


323 


great waste, only a small quantity could be produced at an operation. Therefore 
permanently constructed ovens are employed. These are divided into— 

a. Those kilns in which the burning is interrupted, or occasionally employed 

(the periodical kiln). 

b. Those kilns in which the burning is continuous (the continuous kiln). 

In the occasional kiln, after the burning is finished, the kiln is cooled, and the lime 
then removed. In the continual kiln, on the contrary, the calcination is continuous, 
the kiln never being allowed to cool. It is so constructed that the burnt lime can be 
removed and fresh limestone introduced, without in the least interrupting the process. 
The continual kiln has many recommendations—among them that of effecting a 
saving in fuel, as use can be made of the refuse lime for this purpose. In a small 
way, where, as a rule, burning cannot be constantly carried on, the small occasional 
kiln is, of course, to be preferred. 

periodK^imns. The occasional or periodic kiln with interrupted burnings have, or 
sometimes have not, a grated furnace. Pigs. 177 and 178 show two lime-kilns of the 
ordinary construction without grated furnaces. They are built either on the slope of 
a hill or on the slope of the limestone quarry itself. As a rule the kilns are built 
near one another, so that one wall serves for two kilns. The height of the vault 
varies from 1*3 to 1 *6 metres, and it is generally built of the largest limestones, while 


Fia. 178. 



the smaller stones and lime-dust are placed in the interior of the kiln. Through the 
furnace doors, easily combustible fuel, such as brushwood, light timber, shavings, &c., 
is introduced. The mass-becom.es gradually heated, the larger stones crack and break 
up, and the whole mass sinks together. As the firing is increased the lime becomes of 
a brighter colour and the flames free from smoke. As soon as the lime immediately 
under the stones on the top of the kiln is at a white heat the burning is complete. 
The mass by this time will have sunken one-sixth. A burning generally occupies 
thirty-six to forty-eight hours. An occasional kiln with a grated furnace effects a 
quicker and more complete, combustion of the fuel; but they are open to the objec¬ 
tion that the consumption is greater. On the other hand, the kilns without a grated 
furnace are less perfectly heated. A kiln much used in Hanover is shown in 
Fig. 179, and in plan in Fig. 180; Fig. 181 shows the under part of the kiln in 
vertical section. The lower room serves for the calcination of the lime ; over this is 
a vaulted chamber 3 , i2 metres in diameter and 11 feet in height, e e e e, Figs. 180 













324 


CHEMICAL TECHNOLOGY. 


and 181, are four stoke-holes for the introduction of fuel, stone-coal, brown-coal, 
breeze, &c. B is the approach by which the limestone is introduced into the furnace; 
d the door by which entrance is obtained to remove the burnt lime. Both these 
openings are closed during the actual burning, a is an approach to the “upper 
jacket,” as the upper chamber is termed. This opening is necessary as a draught to 
assist the flame and hot gases in their escape from the top of the kiln; it also causes a 
more intense flame in other parts of the kiln. Figs. 180 and 181 show how the lime- 


Fig. 179. 



stone is kept clear of the hearths. A piece of wood is placed vertically in the centre 
of the oven to direct the flames upwards when the fire is lighted. During the first 
six hours the fire is weak; then a stronger fire is obtained until the yellow lime- 
flames spring from the openings in the vault, and the oven is in a clear glow. 

The continuous Kilns. The construction of the kilns for continuous burning is somewhat 
different to that of the preceding. They are of two kinds. In one the fuel and the 
limestone are placed in alternate layers; in the other kind, the fuel and the limestone 


Fig. 180. 



Fig. 



are not in contact, there being furnaces for the former and separate chambers for 
the latter. In either, fresh limestone is added in proportion as the burnt stone is 
removed from the bottom of the kiln. 





































LIME, 


325 


At Riidersdorf, near Berlin, a very efficient kiln is employed, shown in section in 
kig. 182. The lining wall of the shaft, d, is built of fire-brick, the counter wall, 
e, is separated from the lining wall by a chamber filled with ashes, building refuse, 
&c. The outer wall, B B, is not an essential portion of the kiln; it serves merely 
as a jacket for the retention of the heat, while the galleries, H and F, can be used 
as drying rooms for wood, fuel, &c. During the process, the under part, B, of the 
shaft is filled with prepared lime, 
which is removed by the draught 
hole, a, in the sole of the shaft. 

For the purpose of hastening the 
descent of the burnt lime, the 
sides of the lower part of the shaft 
are sloped towards the draught- 
holes. The shaft is usually 14*123 
metres in height. About 4 metres 
above the sole of the shaft is situated 
the fire-room, h. Three to five fire 
rooms are in action in a single shaft. 

The fuel is wood or turf, i is the 
ash-pit, whence the ashes fall into 
E. The flame enters the shaft 
through the opening, 5 , at the end 
of the fire room. The freshly-burnt 
lime is received in F. K K is a draught 
gallery communicating with n. 

The kilns are locally known as three-, four-, or five-fired kilns according to the 
number of fire rooms. Should the kiln not have been in Use for some time, the 
firing is commenced by adding fuel, such as wood, turf, &c., to the limestone in 
the shaft. When the shaft is thoroughly warmed and a good draught obtained, 
lime only is introduced into the shaft. The shaft is entirely filled with limestone, 
and sometimes the limestone accumulates upon the mouth or top of the kiln to a 
height of 1*3 metres. 

Kilns for Burning When the locality is favourable the kilns are arranged to bum both lime 

Lime and Bricks” and bricks at the same time. The annular kiln of Hoffmann and Licht, 
described under Brick-making, is the most suitable for this double purpose. 

properties of Lime. The quality of the burnt lime is greatly influenced by the consti¬ 
tution of the limestone burnt. When the limestone consists chiefly of pure car¬ 
bonate of lime, the resulting lime is what is termed a “fat” lime. On the other 
hand, if the limestone is of similar composition to dolomite (CaC 0 3 -f- MgC 0 3 ), 
containing magnesia, the resulting lime forms a short, thin pulp with water, and is 
termed “poor.” With 10 per cent, of magnesia the lime is noticeably poor, and 
with 25 to 30 per cent, almost useless. The lime on being taken from the kiln is 
by no means found to be burnt equally. Some pieces that have almost escaped 
the fire are merely superficially burnt, and contain a kernel of unburnt limestone. 
Other pieces exposed to the full heat of the kiln are “over-burnt.” The “over¬ 
burning” of the lime is either due to the forming of “half-burnt” lime 
(CaC 0 3 + CaH 2 0 2 ) by a strong and sudden ignition; or by means of the high tem¬ 
perature the small quantity of silica and alumina contained in the limestone 


Fig. 182. 













$26 


CHEMICAL TECHNOLOGY. 


hecome sintered over the surface, and the lime is thus prevented by a coating of 
silicate from combining with the water to form a pulp. 

slating Lime. Burnt lime moistened with water slakes with great violence, ioo 
parts by weight of lime requiring only 32 parts water, or 3 vols. of lime to 1 vol. 
water, to obtain by the combination a temperature of 150°. The result of the 
slaking is a soft, white powder, lime-meal or powdered lime, hydrate of protoxide 
of calcium (CaH 2 0 2 ), which in volume exceeds three times that of the lime slaked. 
If less water is added than is requisite for the formation of the hydrate, a sandy 
powder is obtained of little value technically. It is therefore very disadvantageous 
to place lime in baskets in damp situations. For technical application to building 
purposes, after the lime has been slaked with one-third of its weight of water, an 
equal quantity of water is added to the mass to form a thin pulp. Slaked lime retains 
its water of formation with such obstinacy that at a temperature of 250° to 300° no 
loss of weight occurs. The hydrate forms a thin pulp wi,th water, and from this 
pulp by further dilution lime-water or milk of lime is obtained. If the lime-water 
be filtered, there results a saturated solution of hydrate of lime, containing 1 part 
hydrate to 778 parts water. When exposed to the atmosphere, lime-water rapidly 
absorbs carbonic acid, and is soon covered with a thin film of carbonate. Lime- 
water has a strong alkaline reaction, due partly to the lime itself, and partly to the 
fact that most limestones contain common salt and alkaline silicates, which, under 
the influence of the caustic lime, are converted into caustic alkali. 

Uses of Lime. The technical applications of lime are very many. Its great affinity for 
carbonic acid fits it especially for the preparation of the caustic alkalies. Slaked lime is 
employed in the preparation of ammonia from sal-ammoniac, of hypochlorite of calcium 
(chloride of lime), in the precipitation of magnesia from the mother-ley of salines; in the 
purification- of illuminating gas from carbonic acid and partly from sulphuretted 
hydrogen; in the refining of sugar and the separation of the sugar from beet-root juice ; 
in the manufacture of soda; in tanning, to remove the hair and prepare the hide ; in 
bleaching; in the manufacture of stearine candles; in the preparation of alum and sul¬ 
phate of alumina from cryolite ; for neutralising the sulphuric acid in the preparation of 
starch-sugar, &c. One of the latest applications of lime is to the oxy-hydrogen or 
oxy-calcium light, which is of so much importance in signalling, and such a valuable aid 
to the lecturer. The most important application of lime is doubtless in the making of 
mortar. 


Mortar. 

Mortar. Mortar is a mixture of sand with cream of lime, used in building as a 
binding material. The ordinary mortar sets or hardens only in the air; hydraulic 
mortar sets under water. 

a. Common or Air-setting Mortar. 

When slaked lime is exposed to the atmosphere it absorbs carbonic acid, and the 
mass becomes much shrunken and cracked. The hydrate of lime thus formed on 
becoming perfectly dry attains the hardness of marble. Such a material, with 
certain modifications, is consequently admirably adapted as a cement to bind 
together bricks, blocks of stone, &c., in building. But as the contraction or 
shrinkage would give rise to great unevenness in the construction of walls, it 
becomes necessary to add sand or some similar substance to the lime-cream. This 
addition gives a body to the mortar, which with the bricks combines into one 
coherent mass. Common mortar is ordinarily made with slaked lime, an intimate 
mixture with sand and water being formed. Angular or sharp sand is preferred to 
smooth, round sand, as making a more tenacious mortar. Bound-grained sand 
yields a very brittle mortar. The proportion of sand to the lime is a matter imme- 


LIME. 


327 

diately affecting the quality and hardness of the mortar. In practice, 1 cubic 
metre of stiff lime-cream requires 3 to 4 cubic metres of sand; but poor, magnesia- 
containing lime will only admit of 1 to 2§- cubic metres of sand. When mortar is 
employed in brick-laying, the surface of the brick is moistened, the mortar laid 
between each brick, and left to dry. When dry it is often harder than the brick 
itself. 

Hardening the Mortar. Mortar sets or hardens very quickly; after a day it will attain a 
firmness that will last for centuries. The drying out of the water from the mortar is not 
the sole cause of its hardening, as may be very easily ascertained by drying the mortar in 
a water-bath or over the spirit-lamp; the result is not a stone-like, but a friable, non¬ 
coherent mass. Fuchs accounts for the hardening of mortar by supposing the formation 
of the so-called neutral carbonate of lime (CaC 0 3 fl- CaH 2 0 2 ), a combination which has not 
been known to suffer conversion into ordinary carbonate of lime (CaC 0 3 ). Recent 
researches have shown this supposition to be erroneous, as it does not agree with the 
results of analyses, which have yielded a quantity of carbonic acid incompatible with the 
existence of a neutral carbonate ; 20 and even 70 per cent, of carbonic acid have been found. 
The experiments of Alexander Petzholdt, A. Yon'Schrotter, and others, have proved there 
to be an increase of soluble silica. The conversion of quartz-sand into soluble silica under 
the influence of hydrate of lime, is not, however, a reaction at all explanatory of the 
hardening of mortar, as washed chalk instead of silica forms an equally hard mass. 
W. Wolters gives the formation of silicate of lime as accounting for the hardening of 
mortar. It is not seldom in the analysis of old mortar from the interior of walls that 
caustic alkalies are found. 

b. Hydraulic Mortar , 

Hydraulic Mortar. Limestone containing more than 10 per cent, silica possesses, when 
burnt and made into a mortar, the peculiar property of hardening under water. 
Lime burnt from such limestone is termed hydraulic lime, and the mortar hydraulic 
mortar. 

When unburnt, hydraulic lime is a mixture of carbonate of lime with silica or a 
silicate, generally silicate of alumina, the latter being insoluble in hydrochloric 
acid. During the burning, the hydraulic lime suffers a change similar to that 
taking place when a silicate insoluble in acid is precipitated, during the application 
of heat, with an alkaline carbonate. After burning, the lime is to a great extent 
soluble in hydrochloric acid, and has lost some of its carbonic acid. Yon Fuchs, 
Feichtinger, Harms, Heldt, W. Michaelis, and A. von Kripp’s experiments have 
proved that the silica of hydraulic lime is precipitated in a gelatinous condition, 
and that constituents such as alumina and oxide of iron are of influence only when, 
under ignition, they have formed a chemical combination with the silica. 

Hydraulic mortars are made :— 

1. With a thin cream of lime and water to which sand is added; or with 

2. A mixture of ordinary air-mortar with water and cement. 

During the slaking of the hydraulic lime water is absorbed, but without any con¬ 
siderable evolution of heat or increase in volume. Hydraulic mortar is applied in 
the same manner as ordinary mortar—the lime-cream must be freshly made, and 
the brick or masonry work moistened. The mortar should be placed thickly 
between each layer of bricks, in order to afford a good firm bed, and allow for 
shrinkage. 

cements. It follows from what has been said that an artificial hydraulic mortar 
can be prepared from ordinary lime by the addition of silica. Such a preparation 
is termed a cement. A few natural cements are found, and may be considered as 
chiefly of volcanic formation.. To this class belong tuff-stone, tarras, or trass, a 
tertiary earth, the basis of which appears to be pumice-stone with small quantities 
of basalt and calcined slate, the pozzolano of Italy, and santorin. 


328 


CHEMICAL TECHNOLOGY. 


Tarras, or trass, also contains magnetic iron in small quantities, as ■well as titanic iron. 
The following are the constituents according to analysis :— 


Soluble in Insoluble in 

hydrochloric acid. hydrochloric acid. 

Silica . 11 *50 37 * 4 A 

Lime. 316 2*25 

Magnesia. 2-15 0-27 

Potash . 029 0-08 

Soda. 2-44 1*12 

Alumina. 1770 1*25 

Oxide of iron. 11-17 075 

Water . 7*65 — 


56-86 42*98 

This cement has been employed for 300 years as a hydraulic mortar, and is one of the 
most important of its class. 

Pozzolano is another tertiary earth, occurring chiefly at Puzzuoli, near Naples, as a 
loose, grey, or yellow-brown mass, of partly a fine-grained and partly an earthy 
fracture. It contains in 100 parts :— 


Silicic acid . 

Alumina 

Lime 

Magnesia 

Oxide of iron 

Potash .. 

Soda 

Water .. . 


44'5 

150 

8-8 


47 

120 


5‘5 


9-2 


100-0 

The oxide of iron contains small quantities of titanium. More lime must be added to 
form a hydraulic mortar. The masonry of the light-room of the Eddystone Lighthouse 
is cemented with a hydraulic mortar formed from equal parts of pulverised pozzolano and 
slaked lime. 

Santorin derives its name from the Greek Island of Santorin, where it was first found. 
It is, similarly to trass, a volcanic formation, and, according to G. Feichtinger (1870) con¬ 
sists of a mixture of cement and sand, the latter containing large quantities of pumice- 
stone. It is not largely employed as a cement, on account of the difficulty of separating 
the true cement from the accompanying sand. 

Artificial cements. The high, price of natural cements consequent upon the smallness 
of the quantity found, and the difficulty of working them, has given much en¬ 
couragement to the manufacture of artificial cements. Indeed, the use of natural 
cements is the exception and not the rule. Parker, Wyatt, and Co., were the first 
artificial cement manufacturers, and took out their English patent in 1796 ; they 
may therefore be considered as the founders of the extensive industry of the pre¬ 
sent day. The cement prepared by them, and now in use, is known as English 
or Roman cement. It is manufactured by burning a peculiar clay-shale found 
above the chalk formation in the Isle of Sheppey and the Isle of Wight. The burn¬ 
ing is effected in an ordinary lime kiln, and the burnt shale is afterwards pul¬ 
verised. The resulting red-brown powder eagerly absorbs carbonic acid and water 
from the air. It is packed in casks and stored ready for use. When prepared as a 
mortar, it hardens or sets in fifteen to twenty minutes. 

Michaelis found by the analysis of various Roman cements:— 



1. 

2. 

3 - 

4 * 

Lime . 

58-38 

55*50 

47*83 

58-88 

Magnesia . . . . 

5*00 

i *73 

24*26 

2*25 

Silicic acid . . . 

28*83 

25*00 

5*8o 

23*66 

Alumina . . . . 

6*40 

6*96 

1*50 

7*24 

Oxide of iron. . . . 

4' 80 

9*63 

20*80 

7*97 






















LIME. 


329 


The analyses are from cements free from water and carbonic acid. No. 1 is 
Koman cement from Eiidersdorf limestone; 2. Prom limestone from the Isle of 
Sheppey, yellow-brown in colour, coarse and hard; 3. Prom limestone forming 
the under bed of the lead ores at Tarnowitz, of a blue-grey colour, firm, and of a 
crystalline appearance; 4. From Hausbergen limestone. 

Portland cement, so named from the resemblance it bears when set to Portland 
stone, is a scaly crystalline powder of grey colour, and was first prepared by Mr. 
Joseph Aspdin of Leeds, in 1824. According to his Letters Patent, he prepared 
the cement in the following manner:—A large quantity of limestone was taken 
and pulverised; or the dust or pulverised limestone used to mend the roads was 
employed. This material was dried and burnt in a lime-kiln. An equal quantity 
by weight of clay w T as added to the burnt lime, and thoroughly kneaded with water 
to a plastic mass. This was afterwards dried, broken in pieces, and burnt in a 
lime-kiln to remove all the carbonic acid. The mass, thus transformed to a fine 
powder, is ready for the market. It is known in commerce as a grey, or green- 
grey, sandy, palpable powder. But Pasley must be considered the true founder of 
artificial cement manufacture in England; he, in 1826, obtained a cement by the burn¬ 
ing of river-mud from the Medway, impregnated with the salts from the sea-water, 
with limestone or chalk. The mud from the Medway is probably best adapted for the 
manufacture of Portland cement on account of the sodium salts it contains, and 
from this supposition there seems good ground for Pettenkofer’s recommendation 
that various marls, burnt after lixiviation with a solution of common salt, should 
be tried. At the present time the mud from the mouths and delta formations of 
several large rivers is employed in the preparation of this cement. 

The manufacture of Portland cements usually follows this mode. The raw mate¬ 
rials, limestone and clay or mud in equal quantities, are intimately mixed, the 
mixture dried in the air, and then burnt in a shaft-oven. The shaft-oven is gene¬ 
rally 14 to 30 metres in height, with a width of 2*3 to 4 metres. At a height 
of 1 to 1 *3 metres from the ground is a strong grating, through which the lumps of 
limestone mostly fall, those remaining being afterwards broken by the heat. The 
oven is so arranged that a layer of fuel and a layer of cement stone alternate. 
Coke is generally chosen as fuel, being found by experience best adapted for the 
purpose. After the mass has been submitted to a red heat for one hour, it assumes 
a yellow-brown colour, and at a higher temperature becomes a dark brown. Gra¬ 
dually the lime becomes causticised, and enters more and more into chemical com¬ 
bination with the silicates. At a white heat the mass becomes grey in colour, with 
a streak here and there of green. If during the operation these* colours are shown 
at the several stages, the resulting cement will be good and set hard. If the heat¬ 
ing is continued, the cement will assume a blue-grey colour and become quite use¬ 
less. If removed at the first stage the mass yields a yellow-brown, light powder; 
at the second, a grey, sharp powder tinged with green. Beyond this stage the 
powder is blue-grey, or grey-white, clear and sharp, and very similar to glass- 
powder. The more lime the mixture contains, or, it might be said, the more basic 
the mixture, the more durable is the cement, and the less it falls to pieces in burn¬ 
ing. A mixture in which clay predominates is always more or less a weaker 
cement, falling to pieces readily, or, technically, not binding well. According to 
Michaelis, tho addition of lime or alkalies prevents the cement separating, and 
renders it more binding; but in practice this addition would not be sufficiently 


53° 


CHEMICAL TECHNOLOGY. 


economical. Tlie more intimately the clay and lime are mixed, the larger the 
amount of lime that may be incorporated. Prom the moment of stiffening till the 
final hardening, the cement, if set in the air, experiences no change; but if in water, 
there is at first a small loss of the more soluble constituents—the alkalies. 

Portland cement mixed with water to a pulp stiffens in a few minutes, and after 
the elapse of a day sets tolerably hard. After a month the cement sets into a sub¬ 
stance so hard and firm that it emits a sound when struck by a hard body. It is 
admirably adapted, when mixed with sand or gypsum, for being cast into the 
various architectural ornaments, and, indeed, has from this property been termed 
artificial stone. Lately Gruneberg has made crystallizing-vessels of this cement, 
and Posch employs it in constructing reservoirs for hot fluids. 


Manufacture of Artificial The process of manufacturing true Portland cement being confined 
Cement in Germany, to England by letters patent, the cements of this kind made in Ger¬ 
many may be considered as artificial cements. They result but from a slight variation in 
method only, chalk and clay or mud being mixed, and the mixture formed into bricks or 
tiles, then burnt and ground to powder. This cement answers in every respect the 
purposes of the original cement. In the preparation of hydraulic mortar a mixture 
of chalk and lime is also used, together with marl, the ashes of pit-coal and turf, the 
alum-shale and alum-earth resulting from alum manufacture, burnt potter’s earth, broken 
porcelain, pulverised flint, &c. Chalcedony cement is a mixture, invented by H. Friihling 
(1870b of 1 volume of burnt chalcedony with 1 volume of lime and 2 volumes of white 
sand. This cement has a glaze much resembling polished marble. Although the prin¬ 
ciples of the hydraulic nature of various cements and mortars are known, not many 
experiments have been made in verification. The elements of success seem to he in 
a due regulation of the heat during burning*, in the intimate mixing of the ingredients; 
the chief principle, the chemical combination of the several substances, is but very little 
known. Of the various uses of hydraulic mortars, we have nothing to do ; the conditions 
of applicability are :—1. That the proportion of 25 per cent, of clay be preserved ; 2. That 
the clay be of the requisite quality, rich in silica, finely divided, and form an intimate 
mixture with carbonate of lime. These conditions are very seldom entirely fulfilled. 
Portland cement was first introduced into Germany in 1850, by M. Gierow, of Stettin; 
and in 1S52 M. H. Bleibtreu, of Stettin, erected a building at Bonn in which this cement 
was largely employed. Since that time there has hardly bepn a building in the erection 
of which Portland cement was not used. 

M. W. Michaelis gives the following analyses of Portland cements, the samples being 
free from water and carbonic acid:— 



1. 

2. 

3* 

Lime 

59-o6 

62*81 

61*91 

Silicic acid .. 

24*07 

23*22 

24*19 

Alumina 

6*92 

5-27 

7*66 

Oxide of iron 

3AI 

2*00 

2’54 

Magnesia .. 

0*82 

I-I4 

i*i5 

Potash .. ^ 

Soda 

073 \ 
0*87 J 

1*27 

f0*77 
(0*46 

Sulphate of lime 

2*85 

1*30 

— 

Clay | 

Sand j 

1*47 

2‘54 

1*32 


4- 

5* 

6. 

7- 

8. 

60*33 

61*64 

6 i -74 

55-o6 

57-83 

25*98 

23*00 

25-63 

22*92 

23*81 

7*04 

6*17 

6*17 

8*oo 

9-38 

2*46 

2*13 

o ‘45 

5-46 

5*22 

0*23 

— 

2*24 

0*77 

r 35 

0*94 

— 

o*6o 

113 

o-59 

0*30 

— 

0.40 

1*70 

0*71 

1*52 

i-53 

1*64 

i-75 

in 

1*04 

1*28 

i-i3 

2*27 

— 


9* 

55-28 

22*86 

9*03 

6*14 

1*64 

0*77 

3*20 

1*08 


No. 1 is Portland cement from White and Brothers, analysed by Michaelis. No. 2 is 
Stettin cement, analysed by Michaelis. Nos. 3 and 4 are Wildauer cements. No. 5, known 
as Star cement; and No. 6, another Stettin cement, by the same analyst. No. 7 is 
English cement. No. 8 cement from works near Bonn, both analysed by Hopfpartner. 
No. 9 is a strong and porous cement, analysed by Feichtinger. 

An analytic comparison of German and English cements will be interesting. German 
Portland cement has the same colour as English cement, and similarly hardens under 
water to the same degree of durability. Under the microscope both possess the same 
foliated and slaty appearance. The specific weight is in both cases the same. A peculiar 
marl, Kufstein marl, is found in the Tyrol, near Kuf stein, yielding an excellent cement of 
which Feichtinger gives the following notice :—“ Kuf stein Portland cement is a natural 


LIME. 


33i 


hydraulic lime, unlike English Portland cement, which is an artificial hydraulic lime. It 
is the product of burning a marl found largely in most Alpine districts, and in every 
applicable condition similar to English Portland cement. The following is an analysis 
of this marl:— 


, Carbonate of lime . 70-64 

Constituents f Carbonate of magnesia. 1-02 

soluble in f Oxide of iron . 2-58 

hydrochloric \ Alumina ... .. 2'86 

acid | Gypsum . 0-34 

V Water and organic substances .. .. 079 


Total constituents soluble in hydrochloric acid .. 


Constituents 
insoluble in 
hydrochloric 
acid 


! Silica 
Alumina 
Oxide of iron 
Potash 
Soda .. 


78-23 

15-92 

3 '°S 

1-40 


Total constituents insoluble in hydrochloric acid 21-77 
The quantity of the insoluble constituents amounts only to 2177 per cent., while most 
marls contain much more clay; in practice, however, the clay is increased to 25 to 30 per 
cent. The Kufstein marl, differs, too, in the chemical composition of the clay, and as 
is known, the constitution of the clay greatly affects the qualities of the cements. A 
comparison of the two clays will therefore possess interest. In 100 parts of silica:— 

Clay from Clay from 

Kufstein marl. Medway mud. 

Alumina . 19-34 17-0 

Oxide of iron . 8*79 21*6 

Potash. 3-45 2*8 

fcoda e • •• .. •• •• •• .. «• •• .. 515 30 


3 6 73 44'4 

These analyses show, that with the clay of the Kufstein marl, a large quantity of 
important bases enter into combination, more than possessed by the clay of the Medway 
mud. Therefore the clay of this marl may be more readily smelted in a small fire. The 
small quantity of magnesia contained in the Kufstein Portland cement probably is 
productive of good effect; all good hydraulic cements contain but little magnesia.” 

The mention of concrete, so largely used in England where a good weathering mortar is 
required, must be included in that of cements. Concrete is a mixture of ordinary mortar 
with stones, grit, broken brick, tiles, &c. To the concrete is generally added lime, and 
then the whole mixed with two to three times the quantity of fine sand. Pasley tells us that 
a better product may be obtained with 1 part of freshly burnt lime, in pieces not larger than 
the fist, 3^ parts of sharp river-sand, and 1-5 parts of water, the whole being well 
mixed. The bricklayer prefers to mix the dry materials and then add water, the concrete 
in this manner taking a longer time to harden, and admitting of greater care being taken 
to fill all interstices. The several uses of concrete are too well known to need mention. 
The employment of unslaked lime in the preparation of concrete was first introduced by 
Mr. Smirke, of London, to whom also it3 employment as a foundation to brickwork is 
mainly due. 

HydrSfiic'Monore. The hardening of hydraulic mortars has often been the subject of 
investigation. Two views may be taken : first, the mere setting, the congealing of 
the mass from a fluid state to a moderate degree of hardness ; and then the harden¬ 
ing to a stony state. The knowledge we possess of the setting of these mortars is 
chiefly due to the experiments of Yon Fuchs, Yon Pettenkofer, Winkler, Feich- 
tinger, Heldt, Lieven, Schulat-Schenko, Ad. Eemete, Heereen, W. Michaelis, and 
Yon Schcenaich-Carolath. The cements when thus considered are best divided in 
two classes:—The first class, of which Eoman cement is the type, embraces the 
mixture of caustic lime with pozzuolane, pulverised tile, and brick, and such 
hydraulic mortar as is obtained by burning hydraulic lime and marl. All the 
cements contain caustic lime unacted upon. The second class comprehends Port- 


















CHEMICAL TECHNOLOGY. 


33 * 

land cements, containing no fresh caustic lime. M. Yon Fuchs has explained the 
chemical actions taking place during the hardening of Eoman cements as being 
principally the combination of the lime with silicic acid, the combination giving 
rise to the peculiar property of hydraulic mortars. He draws this conclusion partly 
from the fact that from all hydraulic mortars the silica can be thrown down as an 
insoluble gelatinous mass by the action of carbonic acid. 

A similar gelatinous mass results from the combination of silicic acid and lime. 
Silicates do not yield when treated with hydrochloric acid alone, gelatinous silica, 
but attain this property when subjected for a length of time to the influence of 
lime under water; the water also dissolves out the alkalies. Kuhlmann, who has 
long been employed in the study of the chemistry of hydraulic cements and arti¬ 
ficial stones, states that lime can be rendered hydraulic by the intimate mixture of 
io to 12 per cent, of an alkaline silicate, or by treating with a water-glass solution. 
Collecting the results of these experiments, the setting of Eoman cement appears 
due to the combination of acid silicates or silica with burnt lime, forming a hydrated 
silicate of lime intermixed with the alumina and oxide of iron. 

The hardening of Portland' cements has been investigated by Winkler and 
Feichtinger. According to the former, the chemical action, which is effected under 
the co-operation of the water, consists of the separation of the silicates into free 
lime and combinations between the silica and the calcium, the alumina and the 
calcium. The separated lime combines with the carbonic acid in the air to form 
carbonate of lime. The hardened Portland cement contains the same combinations 
as hardened Eoman cement; these combinations are formed, however, under the 
influence of water on opposed conditions. From the results of Winkler’s experi¬ 
ments it would appear that the silicic acid in the Portland cements can be repre¬ 
sented by alumina and oxide of iron. Alumina does not affect the hardness, but 
may lessen the capability of the cement to withstand the action of carbonic acid. 
During the hardening the influence of the water separates the lime, till finally the 
combinations Ca 3 Si 3 0 9 and CaA.l 2 0 4 remain, the latter being gradually decomposed 
by carbonic acid, remaining, however, so long as there is any hydrate of lime in 
the cement. H. Feichtinger maintains a theory differing from that of Winkler. 
His experiments lead him to the opinion that in all hydraulic mortars the harden¬ 
ing depends upon the chemical combination between lime and the silica, and 
between lime and the silicates contained in the cement. In all hydraulic cements 
free lime is contained; and upon this fact we may base the following experi¬ 
ments. When Portland cement is brought to a pulp with a concentrated solution 
of carbonate of ammonia, and stirred for a long time, no hardening is traced, the 
greater part of the lime forming carbonate of lime. Then let the excess of car¬ 
bonate of ammonia be washed away, the cement dried, and made into a mortar 
with pure water. This mortar will not harden unless some hydroxide of liine be 
added, when it hardens similarly to fresh mortar. The same result may be obtained 
by substituting a stream of carbonic acid gas for the carbonate of ammonia; by 
this means 27 per cent, of carbonate of lime may be obtained. Consequently the 
views of Winkler must be regarded as the most correct. These experiments also 
show that in Portland cements silicates or free silica are contained; that, further, 
free lime does and must exist. Portland cement will not take a glaze, and can 
only be so far affected by burning as to cause the sintering of the clay contained in 
the cement. 


GYPSUM. 


333 


Gypsum and its Preparation 


occurrence. Gypsuta is a hydrated sulphate of calcium according to the formula 
0 aS 0 4 -|- 2H 2 0. 100 parts contain :— 


Sulphur 

Oxygen 


Lime. 

27.Q1 I Sulphuric acid . . . . 

7 y ' Water. 


32-56 

46*51 

20-93 


100*00 

It belongs to the commonly occurring class of minerals, and is found alone or with 
anhydrite (karstenite, CaS 0 4 ) in strata chiefly of the tertiary formation. The 
following kinds are distinguished:—1. Gypsum spar, foliated gypsum, glass-stone, 
isinglass-stone, or selenite, possessing a very perfect cleavage, and allowing fine 
laminae to be separated. 2. Fibrous gypsum, or satin spar. 3. Froth-stone, a scaly 
crystalline gypsum. 4. Granular gypsum, or alabaster, of coarse or fine-grained 
texture. 5. Gypsum stone, plaster stone, or heavy stone, a laminated gypsum. 
6. Earthy gypsum, or plaster earth. 

Nature of Gypsum. Gypsum is soluble in 445 parts of water at 14 0 C., and in 420 parts 
at 20*5° 0 .; the solubility is increased by the addition of sal-ammoniac. Its 
behaviour under the influence of heat is important. Graham states that gypsum 
placed in a vacuum over sulphuric acid and heated to ioo° 0., loses half its water, 
forming the combination CaS 0 4 -f- II 2 0 , with 12*8 per cent, water. According to 
Zeidler, the statement that this combination does not harden with water is incorrect. 
By heating to 90° for some time 15 per cent, of the water may be expelled; at 170°, 
according to the experiments of Zeidler, all the water will be given off. But of 
more importance are the experiments not carried on in vacuo. In the air gypsum 
begins to lose its water at ioo°, and the loss is not complete under 132 0 . Gypsum 
from which all the water has been removed is termed burnt gypsum, or spar-lime ; 
it has the property of re-forming with water the same hydrate, then becoming 
hardened. Advantage is taken of this property in the application of gypsum a s a 
mortar. According to Zeidler, gypsum as technically employed in stucco-work, &c., 
is not anhydrous, but contains 5*27 per cent, water. If gypsum is “ over-burnt,” that 
is, heated above 204°, it loses the property cf hardening with water, probably owing 
to the fact of its being converted into anhydrite, which does not re-form with water. 

The water of crystallisation of the gypsum is saline, and consequently can be 
removed by the addition of salts; this probably accounts for the hardening of unburnt 
gypsum when treated with a dilute solution of sulphate or carbonate of potash, &c. 
The hardening in this follows more quickly than with burnt gypsum and pure 
water. With sulphate of potash a double salt is formed according to the formula 
K 2 S 0 4 -f- CaS 0 4 + H 2 0 ) ; gypsum and bitartrato of potash gives rise to tartar and 
crystalline gypsum. Chlorate and nitrate of potash, as well as sodium salts, do not 
effect the hardening of powdered gypsum. Gypsum thus hardened, if re-powdered 
and again treated with sulphate or carbonate of potash solution, hardens once more. 
Technical use is made of this property in re-hardening old or in hardening gypsum 
not sufficiently burnt, by employing instead of water a solution of carbonate of potash. 

The Buvning of Gypsum- Gypsum is burnt to effect the removal of the water. Lately 
many improvements have been made in the methods of burning, it having been found 





334 


CHEMICAL TECHNOLOGY. 


that the good qualities of the gypsum mainly depend upon the preparation. There 
is, however, a choice in the stone to be burnt, the heavier and denser varieties of 
gypsum yielding the best commercial article. 

Payen, by experimenting with large quantities of gypsum, obtained the following 
results:—(a.) The lowest temperature at which the gypsum can be burnt with 
advantage is 8o° C., a long time even then being required. (&.) A temperature of 
no?—120° yields the best technical preparation, (e.) In order that the burning may 
take place equally, the gypsum should be first reduced to powder or small pieces. 
The aim, of course, is in all cases to obtain a small homogeneous product rather than 
a large quantity unequally burnt. Small quantities of gypsum may be burnt in an 
iron vessel over a coal fire : the operation should be continued till no aqueous vapour 
is condensed on a cold glass plate. 

Kims, or Burning ovens. In large quantities gypsum is burnt in an oven or kiln, the one 
necessary precaution being to avoid arranging the layers of gypsum with such fuel 
as will reduce the gypsum to sulphuret of lime (CaS 0 4 -f- 4C = OaS 4 - 4CO). 


Fig. 1 S3. 



A very simple and very general 
construction of kiln is shown in 
Fig. 183. It consists of walls of 
strong masonry, A, spanned by a flat 
arch, ventilated at a a a. In this 
room is placed the gypsum only, the 
fire being lighted in a series of small 
chambers in the lower part of the 
room : brushwood is the best fuel. 
& is a door through which the ma¬ 
terial is introduced. The oven 
(Fig. 184) used by M. Scanegattyis 
very similar. The inner room is 
divided unequally by an arch, p. 


Fig. 184 























GYPSUM. 


335 


about i foot from the floor; into the upper part the gypsum is introduced through the 
door G. The under part or fire-room is in connection with a flue, E, of a furnace, 
A a, the flames from which, driven by the draught from the gallery c, are carried 
through X to play upon the arch p, the hot air and gases passing through c cc into 
the upper room. The aqueous vapour escapes through n. 




185. 

•\v 


Lately Dumesnil’s oven, shown in p 

plan at Fig. 185, and in section 
Fig. 186, has been much employed. 

It somewhat resembles Scanegatty’s 
oven in construction, and consists of 
an under fire-room and an upper 
room or oven in which the gypsum 
is burnt. The fire-room contains an 
ash-pit, a, with a door, b, a grate or 
grid, c, and the hearth, d. A draught, 
h, assists the combustion. The hot 
air and gases pass by the flues, e, to 
the chamber, r. The walls of the 
oven, j, K, L, are of solid masonry. 

1 is a depth, furnished with a stair¬ 
case, g h, to facilitate access to the 
furnace, p, the chimney, is of iron 
plate, with a clack, q, which can be 

regulated by the chain tr u. 00 are p IG 

ventilating pipes. In the wall of the 
burning-room are two openings; one, 

M, through which admittance to the 
interior is gained to place the lower 
layers of gypsum ; the other, n, for 
the upper layers of gypsum : both are 
closed by doors of iron plate. An 
equal heat is necessary in the burning- 
room, and is maintained by the pe¬ 
culiar arrangement of the chamber r. 

This chamber, closed at the top by the 
cap, G, is provided with twelve open¬ 
ings, each 07 metre high, the chamber 
itself being 1 metre in diameter. The 
channels thus commenced by the 
openings in f are continued to the 
walls of the room by the arrangement 
of large blocks of gypsum. The layers 
of gypsum, e, s, T, are placed cross¬ 
wise alternately with intermediate 
layers, so as to facilitate the draught 
in every possible way. The firing is 
continued gently for four hours, then strengthened for eight hours, when all the openings 
are closed, and five to six cubic metres of coarse gypsum powder spread equally over tiie 
top of the burning gypsum. By this means the quantity of burnt gypsum is increased 
without a further expenditure of fuel. After standing twelve hours in the oven to cool 
the whole contents are removed. 


Grinding the Gypsum. After the burning the gypsum is to a certain extent in powder, 
but if not sufficiently even it has to be ground. The usual modes of grinding are in 
a stamp or roller mill. After grinding the gypsum is sifted, and placed in some 
position wdiere damp cannot affect it. Sometimes the grinding and sifting are con¬ 
ducted in one apparatus; generally the mill and sieves are separate. 

uses of Gypsum. Gypsum is employed industrially in very many ways. It is some¬ 
times used unburnt in building; it is then difficult to manipulate w r ith water, but 
becomes soluble by continued moistening. The heavy and fast fine-grained gypsum, 
especially the white powdered gypsum, is used in building for architectural purposes. 











































336 


CHEMICAL TECHNOLOGY. 


From the alabaster of Yoltena, Florence vases were fabricated of great beauty: the 
same material is used for making Eoman pearls. The clear varieties of gypsum are 
used in the manufacture of cheap jewellery, being ground and polished. The fibrous 
gypsum is sometimes used for writing sand, as a substitute for pounce, &c. Fine 
gypsum powder is an ingredient of porcelain manufacture. Unburnt gypsum finds 
further application in the conversion of carbonate of ammonia into sulphate. 
Gypsum contains 46’5 per cent, sulphuric acid and i8*6 per cent, sulphur. It is 
largely employed in agriculture as a manure, both burnt and unburnt. It is 
generally received that the favourable action of the gypsum upon vegetation is due 
to the absorbed ammonia which is again yielded up. 

Putridity gives rise to the formation of carbonic acid, which combines with the 
lime of the gypsum, leaving carbonate of lime and sulphate of ammonia. This 
explanation of the efficacy of gypsum-dunging, as it is termed, is, however, insufficient. 
The investigations of Mayer have shown that in clayey soils the oxide of iron, &c., affords 
larger and better combinations with ammonia than the gypsum. The quantity of gypsum 
used is generally about 5 cwts. to the acre, containing and realising at the most 2-fe cwts. 
of carbonate of ammonia. Mayer’s researches, however, show that in an acre of 
Field land .. .. 227 cwts., 

Chalky soil .. .. 158 cwts., 

of a mm onia were contained. According to Liebig’s late researches (1863) it appears that 
the gypsum gives up to the earth a portion of its lime in exchange for magnesia and 
potash. But it must be borne in mind that pulverised gypsum, as well as unbumt gypsum, 
when brought into contact -with a solution of potash, sets into a difficultly soluble mass. 
We must, then, wait for an adequate theory until the several reactions have been more 
closely studied. 

Gypsum Casts. The employment of gypsum in casting, and in all cases where im¬ 
pressions are required, is very extensive. A thin pulp of 1 part gypsum and 2% parts 
water is made: this pulp hardens by standing, forming (CaS 0 4 -}- 2H 2 0). The 
hardening of good, well-burnt gypsum is effected in one to two minutes, and more 
quickly in a moderate heat. Models are made in this substance for galvano-plastic 
purposes, for metallic castings, and for ground works in porcelain manufacture. The 
object from which the cast is to be taken is first well oiled, to prevent the adhesion 
of the gypsum. Where greater hardness is required a small quantity of lime is 
added: this addition gives a very marble-like appearance, and the mixture is much 
employed in architecture, being then known as gypsum-marble or stucco. The gyp¬ 
sum is generally mixed with lime water, to which sometimes a solution of sulphate 
of zinc is added. After drying, the surface is rubbed down with pumice-stone, 
coloured to represent marble, and polished with Tripoli and olive-oil. Artificial 
scaliogla work is largely composed of gypsum. Gypsum is also largely employed 
in the manufacture of paper. 

Hardening of Gjpsum. There are several methods of hardening gypsum. One of the 
oldest consists in mixing the burnt gypsum with lime-water or a solution of gum- 
arabic. Another, yielding very good results, is to mix the gypsum with a solution 
of 20 ounces of alum in 6 pounds of water: this plaster hardens completely in 15 to 
30 minutes, and is largely used under the name of marble cement. Parian cement 
is gypsum hardened by means of borax, 1 part of borax being dissolved in 9 parts 
of water, and the gypsum treated with the solution. Still better results are ob¬ 
tained by the addition to this solution of 1 part of cream of tartar. 

The hardening of gypsum with a water-glass solution is found difficult, and no 
better results are obtained than with ordinary gypsum. Fissot obtains artificial 
stone from gypsum by burning and immersions in water, first for half a minute, after 


GYPSUM. 


337 


■which it is exposed to the air, and again for two to three mintftes, when the block 
appears as a hardened stone. It would seem from this method that the augmenta¬ 
tion in hardness is due to a new crystallisation. Hardened gypsum, treated with 
stearic acid or with paraffine, and polished, much resembles meerschaum : the re¬ 
semblance may be increased by a colouring solution of gamboge and dragon’s blood, 
to impart a faint red-yellow tint. The cheap artificial meerschaum pipes are 
manufactured by this method. 


23 




DIVISION IV. 


VEGETABLE FIBRES AND THEIR TECHNICAL APPLICATION. 


The Technology of Vegetable Fibre. 

Vegetable fibre or cellulose, C 6 H lo 0 5 , is the fundamental constituent of the struc¬ 
ture of plants, forming a large proportion of the solid of every vegetable. Tbe 
fibres of tbe bemp-plant, tbe nettle, and tbe cotton-plant are long and fluffy, and 
are technically termed spinning fibres. These and similar fibres are employed in 
fabricating woven tissues, paper, &c. Treated with sulphuric acid, cellulose is 
converted into dextrose or glucose. Tbe pure cellulose constituents of wood, 
cotton, flax, and paper are nearly equal, as shown by tbe following analyses:— 


Material of Cells. 

Wood. 

Cotton. 

Flax. 

Paper. 

Carbon .. 

• • 43-87 

43*30 

43*63 

43-87 

Hydrogen 

6*23 

6*40 

6*21 

6*12 

Oxygen .. .. 

.. 49-90 

50-30 

50*16 

50-01 


100*00 

100*00 

100*00 

100*00 


Tbe vegetable fibre for use in spinning must be firm, pliable, easily divided, and 
capable of withstanding bleaching operations, if required. 

Flax. 

riax. The flax used in spinning is tbe fibre of tbe flax-plant, Linum usitatissimum , 
a plant of tbe class Pentandrise, order Pentagynise, in tbe system of Linnaeus, and 
tbe type of tbe order Linaceae in tbe natural system of Botany. Tbe flax is gathered, 
tied in bunches, and dried in tbe fields. After drying tbe plant is combed with an 
iron or flax comb, to separate tbe seeds, and is then bound in thick bunches. Tbe 
flax fibre used in linen fabrication lies under tbe bark of tbe plant, and is surrounded 
by a gummy substance, or pectose according to J. Kolb, which must be removed by 
mechanical means to fit tbe fibre for industrial purposes. This is done by ‘ ‘ softening” 
or “ rottening,” by which, according to Kolb, pectin-fermentation is setup, and tbe 
pectin converted into pectic acid. Tbe flax is kept under water until tbe impurities 
float on tbe surface, leaving tbe fibre intact; this is tbe soaking method. Another 
method, dew-softening, as it is termed, consists in spreading out tbe flax in layers 
to tbe influence of tbe atmosphere, water being occasionally thrown over tbe flax. 
Both these methods are unsound, as tbe flax is liable to become rotten, while tbe 
impurities are not thoroughly removed. 









VEGETABLE FIBRE. 


339 


Hot water cieaiuinj. After many experiments with different chemical substances, an 
alkaline bath and dilute sulphuric acid have been found the best agents to effect the 
separation. The flax is placed in large vessels of water heated to 25 °—30° by steam: 
after standing 60 or 90 hours the operation is complete. This mode of treatment, 
aided by an alkaline or acid solution, yields the best results, the value of the process 
being—1. That the construction of the fibre is equally affected, rendering the article 
better suited for manufacture. 2. That the fibre does not lose weight as in the other 
methods, where 10 per cent, is sometimes lost. 3. That there is a considerable saving 
in expense. 

The retted flax, as it is techni- Fig. 187. 

cally termed, consists of cellulose 
and pectic acid. The next process 
is termed scutching , and includes 
the separating of the fibre from the 
woody structure of the stem. The 
machine for this purpose is shown 
in Fig. 187. It consists of two 
parts; the upper, b, is of wood, in 
the form of two splints, working on 
hinges. Wooden knives are placed 
under the splints, and are arranged to act upon the fibre placed in A by pressure 
upon the handle c. 

Keating or Batting the Flax. Scutching consists in two operations—bruising Fig. 188. 

the flax and beating away the woody part from the fibre. For the 
latter operation the Belgian batting-hammer, Figs. 188 and 189, is 
generally used. It is a deeply grooved wooden block, furnished with a 
long curved handle. The sheaf of flax is laid on the ground, untied, 
and spread out, and is beaten with the hammer by the workman. If the flax is not suffi¬ 
ciently loosened by batting, it is submitted to the swinging block, Fig. 190, having a cut 




Fig. 189. Fig. 190. 



at three-fourths of its height serving to hold about a handful of flax. This flax is then 
beaten with the scutch-blade, Fig. 191, a piece of hard, tough wood, generally walnut- 
wood. Instead of the swinging-block a grinding knife, Fig. 192, is sometimes used on an 



























340 


CHEMICAL TECHNOLOGY. 


iron block. This knife is formed of a thin blade, o, and a heavy wooden handle, p. A 
bunch of flax is held in the left hand, at an angle for the easy use of knife with which 
the flax is beaten. Notwithstanding these clarifying processes the bark still adheres to 
the flax, which has to undergo a further operation, that of combing. 

Combing the Flax. The combing or hackling of the flax removes all the material detrimental 
to the ultimate spinning of the fibres, and also equalises their length, rendering them 
smooth and parallel. The combs are made of zinc or steel, and are of varying degrees 
of fineness, the process commencing with a coarse comb and finishing with a fine one. 

Tow, or Tangled Fibre. However carefully the operation of scutching may be performed, 
there is always a certain amount of waste resulting from the entanglement of the fibre, 
and this waste is termed scutching-tow or codilla. It is used in the manufacture of ropes, 
and for similar inferior purposes. The flax fibre, before it i3 fitted for spinning, has to 
be boiled in an alkaline ley, to remove the dirt and grease. 

100 kilos, of cleansed flax weigh after 

Bruising . 45—48 kilos. 

Scutching . 15—25 „ 

Combing . 10 „ 

Fiax spinning. The spinning of the combed flax into yarn is effected by hand and 
by machinery. The combed flax is first placed in bands of equal thickness, and 
then stretched. The hand-spinning wheel is universally known. The mechanical 
spinning consists in—1. Placing the fibres in a parallel series of equal thickness 
and length throughout. 2. These bands are stretched, the finer the fabric to be 
woven the greater being the stretching required. 3. By further stretching and 
twisting cord is spun. 4. The fine cord is still further stretched and twisted. Tow, 
or codilla, is spun similarly to the flax, being previously combed and placed in bands 
of equal length. Plax yarn is either used unbleached or is bleached before 
spinning. Linen thread is obtained by twisting several cords together. 

weaving the Linen Threads, By weaving the cords parallel to one another, chain cords 
are spun. Webbing, wrappers, and thick fabrics are made in this way. 

Linen. Linen is produced by weaving the twisted cord. The selvage is made by 
the return of the shuttle on each side of the fabric. Por coloured fabrics 
coloured threads are used instead of white, only more shuttles are required, one 
shuttle to each colour. Linen damask is woven in various patterns, as-well as drill, 
the difference being that the woof forms the pattern on drill, while chain-cord is 
used for that of damask. Batiste is a fine linen cloth, slightly thinner than 
cambric. 


Hemp. 

Hemp. Hemp [Cannabis sativa ), is chiefly cultivated for the fibre of its inner bark. 
This fibre, although rough, is very hard and firm, and better adapted for the manufacture 
of sail-cloth, canvas, rigging, &c., than any other. Its uses for inferior domestic pur¬ 
poses are manifold. The working of the hemp stalk accords essentially with that of 
flax, being steeped in water, dried and crushed in a hemp mill. By the old method 
the husk is crushed under a large stone cone, Fig. 193, moving in a circular course around 
a vertical axis. The construction of the new hemp mill, Fig. 194, is more advantageous. 
The hemp is purified by winnowing and afterwards combing. It is difficult to spin 
on account of its length, and is woven in two or three parts. Of late various foreign fibres 
have been used as substitutes, principally the following:— 

its Substitutes. a. Stalk Fibre. 

I. Chinese grass ( Chinagras Tschuma), a fibre from TJrtica s. Boehmcria nivca and lictcro - 
phylla, which is cultivated in China and the East Indies, Mexico, the Valley of the Mis¬ 
sissippi, Cuba, the Waldenses in Russia, the South of France, and in Algiers. The 
Chinese method of treating the fibre is remarkable. The fibre is not spun, but cut into 
appropriately small pieces, these being placed end to end, and rolled by the hand until joined 
together. The fibre is thus rolled quite smooth and does not require pressing. It forms 




VEGETABLE FIBRE. 


341 


a beautiful texture of singular brightness, called grass linen, or China grass cloth. The 
raw material is of a green or brown colour, but when bleached can, be dyed any colour. 

2. The Great Nettle, Urtica s. dioica. The interior fibrous pith supplies the material 
for' nettle cloth and muslin. 

3. Ramie hemp, from Urtica s. Bochmcria ntilis, is of the nettle species, and a native 
of Borneo, Java, Sumatra, and other islands of the Indian Archipelago. Of late various 
experiments as to its mode of manufacture have been tried in Germany. It is from 
one to two metres in length, of a delicate golden white, and not so bright and stiff as 

flax. 

4. Rhea Grass, Urtica s. Rhea tenacissima , is a native of the East Indies, of little 
value for manufacture. 


Fig. 193. Fig. 194. 



5. Jute (7 mut hemp), is obtained from a lime tree, a native of the East Indies and 
China, Corchorus capsularis, C. iextilis, C. olitorius, C. siliquous. The fibre for spinning is 
brown, and in England is used for sackcloth and coarse packing thread. It is not a 
material adapted for purposes of nautical application, as it has not sufficient firmness to 
withstand water. 

6. Bombay Hemp, from Hibiscus cannabinus. The woody fibre of this plant is roasted 
and separated by means of beating. In England it is used for cordage, rigging, &c. 

7. Sun Hemp, Japan, or East Indian Hemp, from Crotolaria juncea , resembles other 
hemp in the length and firmness of its fibres. 1 

J3. Leaf Fibre. 

8. New Zealand Flaxes ( Phormium tcnax ) are used in their native country for articles 
of domestic use. The leaf is straight, the fibre tough, and of a shining white. The pre¬ 
pared material is similar to ordinary hemp in roughness and stiffness. 

9. Aloe Hemp is a native of Peru, the East and West Indies, and Mexico. A. 
Americana, A. Vivipara, A. Foetida, &c., where the leaf is cultivated for its fibre, which is 
generally a yellow-white, and used for rope-making. 

10. Manilla Hemp (Feather Fibre) comes from Musa textilis, M. troglodytarum, and 
M. paradisiaca, a native of the East Indies and many islands of the Indian Archipelago. 
It is commercially known as a yellow-wliite or brown-yellow fibre, from 1-3 to 2'2 metres 
long. The inside bark is stripped off from the bottom upwards, refined, and combed. The 
white kind is silky and bright, and is used in the manufacture of damask furniture and 
various fancy articles. 

11. Ananas Hemp comes from the West Indies, Central and South America, where the 
common Ananas is cultivated, Ananassa sativa s. Bromelia ananas , as well as other species. 
It is rather inferior to some for spinning. 

12. Pikaba Hemp is from the leaf of the Attalia funifera, a Brazilian palm. It is 
used in rope-making. 

13. Cocoa-nut Fibre is a reddish-brown fibrous material, in which the cocoa-nut shell 
(Cocos nucifera) is enveloped. It is very strong and elastic, and is used for matting, ropes, 
hurdles, &c 






























































CHEMICAL TECHNO LOG Y. 


342 


Cotton. 

Cotton. Cotton is the fruit of a shrubby plant of the species Gossypiuvi, cultivated 
in the tropics and the Southern States of America for manufacturing purposes. The 
fruit consists of a cup-shaped calyx, enclosed in a tliree-cleft exterior calyx, bearing 
a soft white down.. Another species, Gossypium religiosum , bears a yellow down, 
used by the Chinese in manufacture. The down is kept separate from the seed when 
packed for travelling, to prevent its becoming oily and unfit for use. While in a raw 
state, it is subjected to an operation termed ginning in a saw-gin, to separate the 
wool from the seed. Whitney’s saw-gin consists of 18 to 20 circular saw-blades, 
revolving on a horizontal axis about 100 times a minute. The teeth of these saws 
project through a grating, seize the wool and pull it through, the bars of the grating 
being too narrow to admit the seed. Twenty saw-blades will clean 400 lbs., and 80 
saw-blades worked by 2-horse power, 500 lbs., raw cotton per day. Of late the 
carding cylinder is sometimes used instead of the saw-gin. In America oil is largely 
extracted from the seed, 30 lbs. yielding about one pound of oil. The seed is also 
used for manure. 

Species of Cotton. The quality of cotton is decided by its smoothness, and distinguished by 
the country from which it is imported. The various kinds are :—North American : Sea 
Island, or Long Georgia, Orleans, Upland, Louisiana, Alabama, Tennessee, Georgia, 
Virginia. South American: Fernambac, Bahia. Columbian and Peru via. West Indian: 
Domingo, Bahama, Barthelemy. East Indian: Dhollerah, Surate, Manilla, Madras, 
Bengal. Levant: Macedonian, Smyrna. Egyptian: Mako or Jiimel. Australian: 
Queensland. European : Spanish and Sicilian. 

cotton spinning. Before being spun into yarn, the cotton has to be subjected to the 
following processes:— 

1. The loosening and purifying of the raw cotton from the various impurities, such as 
sand, grit, &c., is accomplished by beating with the hand, or by the Wolf machine, by 
means of a cylinder, the surface of which is covered with sharp iron teeth. The Willow is 
similar to the Wolf, but it is not furnished with such sharp teeth. The fulling or ro ll in o- 
machine ( batleur etaleur), and the beating machine ( batteur Gpluchcur ), are both employee?. 
The beating machine loosens the cotton that was not quite opened, and allows it to fall 
through a grid beneath. 

The Fulling or Rolling Machine ( batteur ttaleur). —The mechanism of this machine is 
smoother, and pulls in the cotton more quickly, working it into fibres of the consistence 
of flax, which are drawn over the roller and afterwards carded. A new machine has been 
constructed under the name of VEpurateur, a step between the beating and cleaning 
machine, which supplies advantages not met with before. The Epurateur is preferable 
for the manufacture of wadding. 

2. The Combing or Carding.—Before the cotton is placed in the carding machine, it is 

passed under a wooden roller to remove the surface thread and other small impurities 
which fall off. After the rolling the fibre appears like a delicate flax. The next operation 
is the true carding, in which two machines are used, the coarse comb, a revolving wooden 
drum covered with steel teeth, and the fine comb, which finishes the separation of the 
filaments of the fleece. The combed fleece, when it leaves the carding machine is in the 
form of a loose ribbon band. It is now submitted to the doubling or lapping machine 
to equalise the length of the bands, the carding process making the fleece loose and of 
unequal substance. Of late the fibres are separated before carding, the chief distinction 
being between the long fibre of Georgia (Sea Island), and the finer or silkv fibres of 
Elorett silk. J 

3. The Streching or Drawing.—The machine effecting this consists of sometimes two to 
six rollers, but usually two pairs of small rollers, over which the ribbons are drawn until 
they are of equal substance. 

4. Roving, or unwinding the ribbon into yarn, which may be considered as the first 
process of spinning. The fleece is stretched 100 times finer than it was before drawing 
and the more it is stretched the finer becomes the yam for spinning. The yam is strained 
loosely at first, in proportion to its length, and drawn more tightly as required. By this 
process yams of various degree of fineness are easily obtained. The first drawing vields 


VEGETABLE FIBJRE. 


343 


coarse yam, the subsequent drawings furnish the finest and most delicate yarn for spi nnin g. 
If the yam be too fine for the purpose required, as in the manufacture of coarse fabrics, 
several card ends, as they are technically termed, are placed together from the first drawing 
and formed into one ribbon; this process can be continued until the required texture is 
obtained. 

Fine Spinning. The yam (twist) is now rendered firmer by means of the throstle and the 
self-acting mule machine, which has quite superseded the Jenny. To the mule machine 
Yam. we owe the yam termed water-twist, which is very strong and indispensable in the 
manufacture of corded materials. 

cotton Fabrics. Of the different textures in which cotton is employed, we have those 
with parallel cords:— 

a. Linen, glazed:—i. Calico, cotton and linen prints. 2. Nankeen. 3. Shirting. 

4. Towelling cambric. 5. Scotch cambric. 6. Jaconet, 7. Printed 
calicoes. 8. Coloured textures, such as gingham, cotton barege. 9. Various 
transparent muslins, such as Zephyr, organdi, vapour, corded mull muslin, 
tulle, and gauze. 

b. Cotton materials with cross cords:—1. Huckaback. 2. Cotton merino. 

3. Drill. 4. Bast. 5. Satin. 6. Pustian. 

c. A rough woollen stuff called beaverteen, resembling fustian, a finer moleskin. 

d. Other cotton fabrics are:—1. Dimity. 2. Drill and fustian. 3. Cotton 

damask. 4. Pique. 

e. Erom the same manufacture we get cotton velvet (Manchester). 

Substitutes for Cotton. Substitutes for cotton are found in the black poplar (Populus nigra) 
and the aspen (P. tremula) ; the fibres of the latter are not so elastic as some of the sub¬ 
stitutes discovered. The rush {Juncus cffusus ), the German tamarisk, and the thistle 
( Agrostis ), the Salix pentandra, the Zostcra marina , and the flax tree, supply material for 
manufacture. Some twenty years ago Chevalier Claussen endeavoured to open the filaments 
of flax by chemical action by steeping the fibres in a bath of 1 part sulphuric acid to 200 
parts water, and then dipping it into a weak solution of carbonate of soda. By this pro¬ 
cess the flax is changed into a downy mass resembling cotton in lightness ; but the method 
was not successful, as the firmness of the fibre was injured, and its value deteriorated in 
other ways. 

De ifin t eu g Fab t rics . il1 There is a great difficulty in detecting cotton in linen fabrics when 
the fibres are closely interwoven. The old method of testing the presence of cotton in 
linen was by placing it under a powerful microscope, but chemical analysis presents 
more reliable methods. The following tests, recommended by Kindt and Lehnert, 
proves the existence of cotton in linen by absorption. The linen containing cotton 
fibre is placed in a bath of sulphuric acid of 1*83 sp. gr. for 1 to if minutes. The 
cotton fibre is immediately absorbed, the sulphuric acid acting upon it more quickly 
than upon the linen ; the fabric upon being dried has a curled or shrivelled 
appearance. Other fibres, sheep’s wool, silk, and flax, are now treated chemically, 
and their smoothness and glossiness are attributable to chemical agency, which is 
found to be the greatest preservative against decay. The colour test of Eisner is 
useful, but not always successful, on account of the transition of the delicate colours 
being so instantaneous as to make it difficult to form a decision. As a colour-test 
there may be taken half an ounce of the root rubia tinctorum, macerated in 6 ounces 
of alcohol at 94 per cent, for twenty-four hours. When filtered, the tincture appears 
a clear brown-yellow. Pure linen fabrics immersed in it become a dull orange-red, 
and pure cotton yellow; the flax fibre will assume a yellow-red, and the cotton a 
bright yellow, the fabric appearing not uniform in colour, but streaky. When the 
fabric becomes so unequally streaked as to make it difficult to discern whether it be 
linen or cotton, the following test will prove decisive:—Place the streaky fabric in a 
solution of spirits of wine, and then in a weak solution of aniline red, by which it 


344 


CHEMICAL TECHNOLOGY. 


becomes coloured, and finally let it remain one to three minutes in a weak solution 
of sal-ammoniac; the colour of the cotton fibre will be dissipated and the linen will 
become a beautiful rose-red. From Eisner’s first test for change of colour the 
method of previously colouring the linen fabric was established. Cochineal was 
selected for this purpose, and the linen placed in a weak solution, chloride of lime 
being used to prevent the colour in the linen running, while the cotton contained in 
the fabric changes colour immediately. Frankenstein’s oil test for uncoloured fabrics 
can be recommended for its simplicity and excellence. The fabric is dipped in olive 
or rape-seed oil; it quickly becomes soaked through, and the surplus oil is removed 
by blotting-paper, the linen fibre becoming transparent, leaving the cotton opaque. 
When an unbleached fabric is tested in this manner it appears shining at first, but 
becomes dimmer in the parts where the cotton is present. A truer method of testing, 
however, is given by the magnifying glass. Bottger gives a test with potash. The 
linen fabric is immersed in a concentrated solution of potash; in about two minutes 
it becomes a deep yellow, the cotton fibre assuming a light yellow. 

Stockhardt gives a spirit test. Linen fabrics are placed in layers with lighted 
brandy; the linen fibre extinguishes the flame, while the cotton acts as a wick, 
absorbing the spirit. This experiment can be successfully used with coloured 
materials, with the exception of those coloured with chrome-yellow, chromate of 
oxide of lead. The singeing test requires the most delicate treatment. The fibre is 
placed in a glass vessel over the flame of the spirit-lamp until it becomes a light 
yellow; then by microscopic examination the cotton fibres will be found curled up, 
while the flax fibres are distended and clearly separated from each other. Hemp and 
flax act in the same manner, but do not separate so much. Nitric acid can be so 


Fia. 196. 



applied as to leave the flax fibre unchanged in colour, while the hemp immediately 
becomes a pale yellow, and the New Zealand flaxes, Phormium tenax , a blood-red. 
The admixture of cotton in linen fabrics became known through 0 . Zimmermann, 
who tried the following test:—Place the fabric in a mixture of 2 parts saltpetre and 
3 parts sulphuric acid for eight to ten minutes, then wash, dry, and treat with alcohol 
containing ether. The cotton so treated is soluble as collodion, the linen fibre is not. 

Separation of Animal and Vegetable Fibres by Means of Singeing.—The mixture 
is placed near a bright flame to singe until the hair is consumed, leaving a black 
ashy mass in the same proportion as the fibre, if it be mixed with sheep’s wool. 







TAPER. 


345 


Animal and flaxen fibres are separated by boiling in potasb, ■which loosens the 
filaments of wool or silk, leaving the cotton and linen fibres unaltered. Pohl gives 
us the following test:—Place the fibres in a solution of picric acid for one minute; 
then carefully wash; the wool or silk filaments will have turned yellow, the cotton 
or flax fibre remaining white. This can be applied to mixed fabrics ; but the most 
certain method is under the microscope, where the linen fibre appears in a cylindrical 
form, Pig. 195, and never flat. It is not stiff nor twisted, and is chiefly characterised 
by the narrowness of its inner tube. Hemp is similar to flax fibre, being easily 
broken ; its ends branch out stiffly, and its tube is open. The fibres in cotton fabrics 
are long, of a close, thin texture, like a twisted band, as in Pig. 196. Sheep’s wool 
under the microscope appears thicker than the other filaments, having a perfectly 
circular stalk with tile-shaped scales, as seen in Pig. 197. The silken fibre, Pig. 198, 


Pig. 199. 



is a slender column, smooth on the exterior and easily distinguishable from wool, 
Pig. 200, representing a mixed silken and woollen fabric, as it appears under a low 
power. Wool and cotton, Pig. 199, are also easily distinguished from one another. 

Paper Making. 

History of Paper. Paper is in reality a thin felt of vegetable fibres mechanically and 
chemically clarified, crushed and tom into a pulp suspended in water. This pulp is 
spread equally in thin layers, drained, pressed, and dried into the compact substance 
we call paper. 

Of the history of paper we have the followingIn very ancient times men engraved 
si° r ns upon stone, iron, lead, ivory, wood, &c., and by this means handed down their 
thoughts to posterity. Later, palm and other leaves were used for this purpose, also 
various barks of trees, especially the smooth inner bark. The old Germans wrote upon 
birch bark, and there is still an old Pagan poem in existence written on this bark. Other 
nations painted with a brash on cotton or taffeta. Indeed, about 600 years before 
Christ the Egyptians prepared the Cyprus grass, Cyperus Papyrus or Papyrus antiquorum , 
for writing purposes'. This grass grew from 2 to 3 metres high; specimens are very rare. 
In the time of the Koman Empire it was the customary means of conveying intelligence, 
and was considered a luxury until 1100 or 1200, when its use was discontinued. A cotton 
cloth was then substituted under the name of parchment, and was held in great favour on 
account of its strength. Spanish paper was much esteemed until 1200. About that time 
an attempt was made to mix cotton with linen rags. This was accomplished in 1318. It 
was not well known in Germany until 1400, although the first account of its manufacture 



CHEMICAL TECHNOLOGY. 


346 


is in 1390, when Murr opened a large paper mill in Nuremburg. Later still we have 
mention of a paper mill by Shakspeare in the Second Part of Henry VI., the plot of the 
play being laid about a century before the time it was written. History records that 
Sir John Spielman owned a paper mill near Dartfordin 1588, for the erection of which he 
was knighted by Queen Elizabeth. Since this time the manufacture has steadily 
progressed. 

raperManufacture. The chief materials of paper manufacture are the waste rags from 
flax, hemp, silk, wool, and cotton. The linen rags are mostly in request for making 
the best and most durable white writing and printing paper. Silk and woollen rags 
are unfit for this purpose, as the bleaching material will not act upon animal sub¬ 
stances. Cotton in a raw state requires less preparation than hemp. Hags are 
classed under different denominations,—fines, seconds, and thirds, the latter com¬ 
prising fustians, corduroys, stamps, or prints as they are technically termed. The 
waste refuse from the wadding machine used in cotton spinning is employed for 
scribbling paper. Bibulous papers, such as blotting and filter papers, are made from 
woollen rags, on account of their open texture ; cotton rags, also, make a spongier, 
looser paper when unmixed with linen. 

Substitute for Rags. The consumption of paper in Europe has more than doubled within the 
last fifty years, and, owing to the inefficient supply of rags, substitutes had to be found 
in straw and wood. The Chinese first used vegetable pulp for paper manufacture. The 
inner bark of the bamboo is particularly celebrated as affording a paper yielding the most 
delicate impressions from copper-plate, and this paper was originally called India-proof. 
The Chinese also use the bark of the mulberry and elm trees, hemp, rice-straw, and wheat. 
Among the straw species appears the maize (Indian corn), from the fibre of which a paper is 
made that for purity and whiteness cannot be equalled. Also the Andropogon glycichylum , 
ox Sorghum saccharatim , a native of North America, is used; in fact nearly every species 
of tough fibrous vegetable, and even animal, substance has been tried, but of these straw 
has been most successfully applied, in combination with linen and cotton rags, when the 
silica contained in the straw is destroyed by means of a strong alkali. If the straw is 
not properly prepared the paper will be brittle, and unfit for use. The use of straw is 
not very extensive, owing to the extra expense of preparation, and its waste under the 
process. It is used for making common brown paper, but it is chiefly used for giving a 
stiffness to cheap newspapers. All soft woods are fit for paper-making, such as the 
trembling poplar, linden, aspen, fir, &c.; the pine is of too resinous a nature to be of 
much value. The preparation from wood is made in the following manner:—The bark is 
sawn and split into suitably-sized pieces, and the fibres separated by pressure between 
horizontal rollers copiously supplied with a stream of water. The water, which forms 
two-thirds of the mass, is then removed by further pressure, generally hydraulic. In 
1867, Basket and Machard treated the woody material with hydrochloric acid. Later, 
waste wood has been treated chemically, in the large manufactory of Manayunk, of 
Philadelphia. The finest wood is set apart into lots. No. 1 is used for making writing 
and printing paper; No. 2, wall paper, packing paper, and inferior kinds of printing 
paper; Nos. 3 and 4 for label and pasting paper. Spanish woods are largely used, on 
account of their smoothness. 

Mineral Additions We find minerals used in the present manufacture. A moderate addition 

to the Rags. 0 f a m i ne ral body to the paper material whitens the whole, and for inferior 
or ordinary paper is successfully employed. It is unfit for very thin paper, making it 
shiny and brittle. A profitable addition of mineral matter is from 5 to 10 per cent, of the 
weight of paper, a greater addition making the paper dull, brittle, and hairy to write upon. 
The usual mineral mixtures in frequent use at the present day are—clay free from sand, 
China clay, and kaolin. Aniline pearl-hardening, dissolved into a pulp resembling clay, 
is most preferred, being not so expensive. . In 1850 it was favourably received, under the 
names of fixed white, raw white, patent white, or permanent white. With 100 kilos, of 
paper pulp 15 kilos, of the paste is generally employed. 

Manufacture^of Paper The old method of making paper by hand was from the pulp of 
waste paper placed in a mould of the required size ; but this method, although still 
used for writing paper, was found to restrict the size of the sheets, and different 
methods were tried with varied success, until a machine was invented which, without 
the aid of moulds, manufactured the paper in any length. 


TAPER. 


347 


Cutti "tho n Rag6 Canins The Cutting and Sorting of the Rags. The first operation is per¬ 
formed by two machines, called the half-hollander and the whole-hollander. The 
rags are next treated chemically with potash to rot them. By the old method, rags 
were cut into pieces about 4 inches square, by being drawn across a sharp knife fixed 
upon a table. Machinery has superseded this arrangement, and various cutting 
machines have been invented, among which we may mention that of Mr. Davey, in 
which a horizontal knife revolves around a fixed cylinder cutting the rags into strips. 
Bennet’s cutting machine consists of two knives radiating from awheel, and bearing 
against another knife. Some machines are constructed with a quantity of circular 
sharp-edged steel plates, like the machine of Uffenheimer, of Vienna. After cutting, 
the rasrs are cleansed from dust and other impurities by the Willow machine. The 
best kind of sifting machine is in the form of a drum with the upper part covered 
with a wire grating. The rags are put in by a side door, which acts, as the drum 
revolves, as a refuse door, casting off the sand and impn#ities, leaving the rags win¬ 
nowed. They are next boiled in an alkaline ley, or solution of 4 to 10 pounds of 
carbonate of soda, with one-third of quick-lime to 100 of the material. The rags 
are placed in large cylinders slowly revolving, and causing them to be constantly 
turned over. Into these cylinders a jet of chlorine water, with a pressure of 30 lbs. 
to the square inch, is directed. H. Volter patented in 1859 a horizontal steam 
cylinder, which receives the steam from a tubular guide-cock provided to the boiler, 
an inner cylinder revolving to move the rags. The distant end of the boiler and the 
tubular cylinder draws up, and the mass is easily poured into the washing machine 
when in a fluid state (Silberman’s Washing Hollander). Although partly cleansed 
by the above method the rags still require further boiling. 

The separation of the Ra^ The machine used in separating and rending the rags 

for Half-stuff iuid the Whole-stuff. 1 & fob 


1. The German stamping machine. 

2. The rag mill (rolling hollander). 
a. The half-hollander. 

| 3 . The whole-hollander. 

formerly the rags were rotted before crushing, being placed in a stone trough, where in 
two or three days they became heated, and developed a strong ammoniacal odour. 
When the surface was covered with a mould, the rags were sufficiently decayed for the 
nose 0 f manufacture. They were then taken out in a brown mass, those remaining 
behind as sediment being used for coarse paper. The present method of boiling the rags 

with alkalies is preferable, giving the paper greater firmness. • - 

•tam Machine. The German stamp machme is at the present time only to be found in 
smaller manufactories. It is of the nature of a hammer. Six or eight stamp rods are 
fixed into a strong oak beam, and work intermittently with a set below. Through an 
rvnenin 0- provided with a fine sieve the water is conveyed away. As the hammers rise 
, » ■2 gtamp holes serve for a water conduit. Three to five hammers work in each 
hole The ra gs are mixed with sufficient water to form a pulp, and remain in the 
machine 12 to 1 2 * * * & 20 hours and more. 

The Hollander. Thehollandermill is fast becoming a universal favourite. It is somewhat 
similar in principle to the stamping machine, but in strength and speed greatly excels 
every other machine. Fig. 201 is a half-hollander; Fig. 202 the vertical section 
through the line AB. The chief characteristics of the hollander are:—1. Speed of 
revolution of the trimming knife. 2. The box of knife edges under the revolving 
cylinder. 3. The trough and revolving cylinder. 4. The cap or partition above the 
trough to prevent the mass being cast out when in motion. The trough, c c, is a long 
oblcn" cistern of cast-iron, stone, or wood lined with lead. The cover rests upon a 


34 8 


CHEMICAL TECHNOLOGY . 


partition, x jc, of equal height with the outside wall. The machine is divided into two 
parts, the working side in which the rags are tom or shredded between the knife- 
edges on the cylinder and those in the box, and the running side into which the 
shredded rags are thrown by the revolving cylinder. Under the cylinder is a 
massive oak block, t, the craw, its concave surface comprising the fourth part of the 
circumference of the cylinder. The side y is a little, and 2 much inclined. Half- 


Fig. 201. 



way between h i are two strong beams, l, m, supporting the metal bearings, in which 
works the axle, 0 0, of the cylinder. From the roller, q, a numbers of cutters run 
parallel to the axis. The knives are of soft steel, and in the whole-hollander some¬ 
times bronze. Beneath these a series of knives is placed, against which the rags are 
drawn by the cylinder. In order that by the movement of the cylinder none of the 
material should be thrown out, a cover is provided, the dirty water thrown up 


Fig. 202. 



falling through the sieves, v v, and flowing through the opening, gg. Clean water 
flows in from the top of the hollander. The washing finished, the water pipe is shut 
by means of a sliding partition, each partition having an inner one to prevent the 
pulp passing away. The rags are poured into the top of the hollander with 
the requisite quantity of water. The roller revolves 100 to 150 times a minute, the 



















































































PAPER. 


349 


knives cutting more readily in the fluid. Having passed the cylinders and the lower 
set of knives, the mass flows over the steep slope of the craw, z, while the roller 
continues its work. This mode has this advantage, that the rags have an uninter¬ 
rupted flow, and that all parts have the same resistance under the roller. The work 
of the half-hollander is of two hours duration for soft and clean rags, a longer 
time being requisite for coarse and dirty materials. 

Bleaching the Puip. After this the mass is placed in another machine, the whole- 
hollander, and bleached by a solution of chloride of lime, chlorine water, chlorine 
gas, or other bleaching agents. The lime is retained in the machine until the 
rags are sufficiently bleached; the pulp is then let down into long slate cisterns to 
steep before placing in the beating machine. 

An arrangement for bleaching by means of chlorine gas is exhibited in Fig. 203. 
The gas passes from the generator, a a , into a wooden chamber, A, in which the 
damp pulp is arranged on shelves. These shelves have openings admitting the 
chlorine gas as shown by the 
arrows. The surplus gas escapes 
through opening, c, to a reservoir, 
which is also used for bleaching 
the pulp. The pulp is then re¬ 
moved, washed by a solution of 
soda, potash, or urine, and after 
standing, worked with antichlore, a 
term given by bleachers to any salt 
that neutralises the pernicious 
after effects of chlorine upon the 
pulp. By this means, in each 100 
kilos, of half-stuff, 2-5 to 5 kilos, of 
common salt is developed by the 
action of the chlorine gas upon the 
soda. When bleached by chloride 
of lime, 1 to 2 kilos, are applied to 
100 kilos, of pulp. When greater 
smoothness is required, a little hydrochloric or sulphuric acid is. added, although caro 
must be taken in its use, for applied too largely it destroys the fibre. Orioli employs 
hypochlorite of aluminium, known by the name of Wilson’s bleaching preparation, 
chloride of aluminium being obtained on the one hand, while, on the other, all the 
bleaching effects arise from the delivery of ozonised oxygen (A1 2 C1 6 0 3 = 3 0-f- A 1 2 C 1 6 ). 
Varrentrapp’s hypochlorite of zinc, under the name of Yarrentrapp’s bleaching- 
powder, is worthy of notice as being extensively used. In this powder, chloride 
of lime, decomposed with zinc vitriol, or, better, with chloride of zinc, is employed. 
When bleached by chloride of zinc, the mineral acid decomposes the chloride of 
lime, therefore no risk is incurred by the fibre. 

Antichlore. 'When the bleach retains chlorine, it is washed in soda, potash, or anti¬ 
chlore, to neutralise the adhering hydrochloric acid, which merely washing in water 
would not effect. The chief constituents of antichlore are sulphite of soda, chloride of 
tin, and hyposulphite of soda. A molecule of sulphite of soda (Na ? S 0 3 + 7H 2 0) 
removes 1 molecule of chlorine (Cl 2 ), whilst hydrochloric acid and sulphate of soda 
are formed. A mixture of sulphite with carbonate of soda is employed to neutra- 


Fig. 203. 

















CHEMICAL TECHNOLOGY. 


350 

lise the hydrochloric acid. The sulphate of soda and chloride of sodium are re¬ 
moved by washing. Sulphite of calcium is greatly approved, and is considered 
to be as effective as antichlore, when applied as the corresponding sodium salt. A 
molecule of tin-salt (SnCl 2 +2lI 2 0), is taken up by a molecule of chlorine (Cl 2 ), by 
which chloride of tin (Sn 01 4 ) arises. After the working is completed, so much 
carbonate of soda is added as is required to saturate the hydrochloric acid. A 
molecule of hyposulphite of soda (Na 2 S 2 0 3 -|-5H 2 0), absorbs 4 molecules of chlorine, 
whilst sulphate of soda, hydrochloric, and sulphuric acids are formed. Some salts 
of lime are also commercially known as antichlore. 

Blueing. Notwithstanding the careful chemical bleaching, the pulp has still a 
yellow tinge, and requires a colouring matter which is generally introduced in the 
process of beating. The blues generally used are ultramarine, Paris blue, indigo, 
aniline blue, oxide of cobalt. With 100 kilos, of the dry paper stuff, 0*5 to 1*5 kilos, 
of ultramarine are mixed, according to the strength of the colour required. 

suing. The pulp requires sizing to preserve the colour. It is guided, as it issues 
from the hollander, through a tub of size, and afterwards carried over skeleton 
drums, containing revolving fans to dry it as it passes; heated cylinders are also 
used for drying. Starch is used to give a thicker consistence to the size, which is 
generally made from the best glue, resin being added in quantities, never exceed¬ 
ing 3 kilos, per 100 kilos, of pulp, to impart the desired amount of stiffness. 

a. Hand Paper. 

straining the Paper sheets. There are three ways of straining or filtering the pulp:— 
First, by straining through a brass sieve with fine slits to allow the pulp to pass, 
and retaining all lumps and knots. Secondly, by pressure; and thirdly, by evapora¬ 
tion. In the first operation the sheet is formed by a mould of the size required, 
being dipped into a tub of pulp previously strained. The pulp becomes distended to 
a thin layer and the water filters off. The tub is either round or of a quadrangular 
shape made of wood, lined with lead. A broad board running across the tub is 
called the bridge, and a smaller one under the larger one the little bridge. The 
large bridge has a pointed support, technically termed the donkey, for the form or 
frame to lean against. 

The sifting machine, technically termed the knotter, used in the manufacture 
of hand-paper, consists of an upright cylindrical sieve, in which an inner cylinder 
revolves. As the whole-stuff is taken from the tub, the remainder becomes massed 
together, and steam or other pressure is employed to force the pulp through the sieve 
and cylinder, the latter retaining the lumps and knots. The paper forms, upon which 
the whole-stuff is placed, are constructed with brass wires to allow the water to drain 
off, retaining the pulp. There are two kinds of forms:— 

1. The Ribbed form.—A square or oblong frame of oak or mahogany with parallel 
brass wires and cross wires at intervals to steady them. Lined paper is made on this 
form, and is not much glazed on account of the time and expense, being reckoned an 
inferior paper. 

2. The Yellum Form.—A frame of finer brass wire-work. Yellum paper is made on 
this form, and has a delicate even surface ; it can be made to present any degree of glossi¬ 
ness by pressing and satining. When held to the light it appears uniform, not possessing 
bright and opaque lines as in the former paper. 

A ribbed form similar to the vellum form is employed in the manufacture of paper 
distinguished by trade marks, coats of arms, &c., the impress of the wire forming what is 
termed the water-mark; bank-notes are made separately in a mould in this way. The 
edge of the form makes the edge of the paper, forms being used according to the size 


PAPER. 


35 * 

required; also the quantity of the whole-stuff varies in accordance with the required 
thickness of the sheets. Felt is extensively used in the manufacture of paper; it is un¬ 
like the ordinary felt for hats, being a coarser, looser, white woollen fabric, more suitable 
for rolling. 

The work of the pulp-tub is divided into two parts, the squaring and the scooping; the 
latter is the placing of the pulp in the mould, the former the placing of the sheets between 
felt. The tub is stirred occasionally with a pointed stick, technically termed the scoop 
stick. The pulp is taken out on the form in a sloping position, shaken a little to aid 
cohesion, and finally placed on the small bridge. The next sheet is placed on the large 
bridge. The form is laid in a sloping position against the donkey-rest to drain, and the 
paper finally placed on the felt to dry a little, the empty form returning to the tub. The 
first paper sheet is covered with felt, on which the next is placed; the average number of 
sheets manufactured exceeding 5000 a day. 

pressing the Paper. As soon as there is a sufficient number of sheets, they are made 
into a thick bale and placed under the pres3, the number of sheets comprising a hale 
being generally 181. Three bales, 181 X 3 = 543 sheets; twenty quires ±= 480 sheets 
sized, and 500 unsized. Pressing gives firmness and glossiness, and by continued 
pressing exceeding smoothness is obtained. 

Drying the Paper. The process of pressing has not quite removed the water from the 
paper, which has to be dried in an airy chamber, the sheets being placed separately, 
or two to five together as required. An expert workman can place 800 to 900 layers 
of two to five sheets each in a day, as well as hanging and drying the sheets and 
taking them off the cord. 

sizing the Paper. The paper is not durable unless it is sized, and is only used for filter¬ 
ing, packing, printing, or scribbling papers. Sizing gives the paper substance by 
filling the pores, and making it firmer, stiffer, and harder. Ordinary size dissolved 
in water will not always prove effective, and it is necessary to add a solution of an 
aluminium salt, such as that of alum, sulphate of alumina, or chloride of aluminium, 
to prevent decay. Without chemical preparation the sheets are rendered sticky and 
have to be sized separately, but with the above addition 80 to 100 sheets can be 
successfully sized by hand; a good workman can size 40,000 to 50,000 sheets in 
twelve hours. The sheets-must not be dried too quickly after sizing. 

preparing the Paper. After the sized paper is pressed and dried, it requires further pre¬ 
paration to make it fit for use. The first process consists in the finishing or trim¬ 
ming to remove all the little specks and blemishes, and to smooth the sheets. The 
finished sheets are counted and placed together, the workman by continued practice 
counting 8000 to 15,000 sheets as he places them, and separating them into whole and 
half quires, twenty-four sheets of sized and twenty-five sheets of unsized paper 
making a quire; the upper and under quire of each ream being placed on an extra 
sheet, known as outsides . The even and glazed surface is mostly obtained by hot- 
pressing, when every sized sheet is interposed between two unsized sheets; this is 
called interchanging. The preparation of the various kinds of paper is now accom¬ 
plished, with the exception of the finest letter paper, which requires an extra pro¬ 
cess to give it a final gloss, by pressing between the rollers of the satining machine. 
The different varieties of paper are classed under three denominations :— 

The Different Kinds A. Writing and drawing paper, the smaller kinds of copy paper, deed 

of Paper. paper, the finer post and letter paper, and vellum letter paper. 

B. Printing paper for books, as distinguished from copy printing, deed printing, post 
and vellum printing, note and copper-plate printing paper. Silk papers for valentines, 
ornamented with gold or silver, and printed from engraved copper plates. 

C. The looser textured papers, such as unsized parcel paper; the better kinds are 
filter- and blotting-papers. Packing paper is half-sized, and appears as a yellow straw 
paper, blue sugar paper, and pin and needle papers. 


352 


CHEMICAL TECHNOLOGY. 


13 . Machine Paper. 

Manufacture of Machine Paper. Manufacturing paper by band requires mucb time and 
labour, and machinery is found to be quite as efficient. Endless paper of any breadth 
can be made by machinery with the same amount of strength and firmness as hand 
paper. The straight form and the vibrating machine are used for finer paper. 

1. It is requisite that the machine should make the pulp of a suitable consistence by 
diluting it with water. 

2. Purify the whole-stuff from knots. 

3. When free from knots work the material by means of regulators, delivering the 

stuff from the form, and producing by the uniform flow of the pulp a smooth paper leaf 
of the breadth required. • 

4. Be so regulated that the stream of whole-stuff may form a sharply turned leaf. 

5. Eree the paper leaf from water, so that it only requires drying in an airy chamber 
and pressing. 

6. For removing the water, steam cylinders are principally used. 

7. The finished paper is cut into sheets by the paper cutting machine. 

After the whole-stuff is thinned to a consistence easily moved by water, it flows 
to the knotter, placed in a perforated cylinder of sheet brass, which is supplied with 
an interior mechanism revolving with greater velocity. One of the best knotting 
machines is Mannhardt and Steiner’s, of Munich. After the whole-stuff is 
purified by the knotting machine it passes out, and the whole-stuff reservoir is sup¬ 
plied anew. In course of time the consistence becomes altered, sometimes producing 
a thicker sheet than required; this variation is obviated by the regulator, an 
essential in the paper manufactory. A complete paper machine is shown in Eigs. 204 
and 205. The drawing is divided into two parts; Eig. 205 is seen as the continua¬ 
tion of Eig. 204. After the whole-stuff has passed from the knotting machine, a , it 
flows into the small trough, a', and is forwarded by the regulators to the form. The 
form, a" a", is an endless wire sieve, similar to the vellum form, the upper part 
extending horizontally over a number of copper rollers. The forms are from 3 to 
4 metres long, and 1 to i*6 metres broad, and are moved by means of a band 
passing over pulleys. Next to the regulators, a', the rollers lie closer together. 
The form of course has a double motion, advancing in the direction of the paper 
sheet, which is carried to a vacant part of the wire and deposited, the form completing 
its circuit underneath. Periodically the form receives a shaking or vibratory move¬ 
ment breadthways. The paper has sometimes an uneven margin, and to equalise the 
substance of the layer, two fine brass wires are placed near the under edge of the form, 
while leather bands, mm , kept in place by the pulley, t, are placed on both sides of 
the form to keep the sheet straight, the bands passing through a vessel of water, n, 
to cleanse them of the adhering pulp. The water in the cistern, c, cleanses the wire- 
work forms. It is now necessary to commence the drying of the pulp; this is 
effected by an air-pump, or preferably by suction apparatus placed in the box, d d, 
over which the whole breadth of the paper sheet passes. After the paper leaf passes 
the box, it is pressed under a wirework cylinder, e, under which is a corresponding 
cylinder; these perforated rollers are called dandy rollers. The paper sheet is now 
somewhat pressed and dried; the empty form returns, and the leaf passes free from 
the form over an endless felt to the wet press, h h, which consists of two iron rollers; 
one glazing the paper, the other passing the leaf to another pair of rollers, h■ h', 
Eig. 205, which press and dry the leaf. The paper leaf is finally submitted to the 
dry press, which consists of a larger cast-iron cylinder, u , v, w, interiorly heated to 
nearly 130° 0 . by steam. These cylinders and the corresponding rollers, u\ v', w\ are 


333 


TAPER. 


covered with felt. By the double 
pressing, the paper becomes dry 
and requires damping before the 
final pressing. The press w- iu is 
not so effective as v v , as it dries the 
surface unevenly, causing one side 
to be more glazed than the other. 
The finished paper passes under 
the roller, y, to the windlass, j, and 
is transferred by means of the arm, 
k, to the windlass,/, where it arrives 
at its journey’s end. It is then cut 
into sheets of the size required, by 
the paper-cutting machine. 

Paper-Cutting Machine. When finished 
by the machine, the paper is cut off 
into long lengths and rolled by hand 
for the manufacturers of drawing and 
wall paper, scene-painters, &c. At¬ 
tached to a large wheel is a knife, 
whose regular strokes cut the paper 
into the size required. The clipping 
machine is used for cutting the edges 
of books. 

7. Pasteboard and other Paper. 

Making pasteboard. Pasteboard is made 
in three ways:— 

1. By placing the pulp in a form 
—form-board. 

2. By pressing several damp 
sheets to form a thick card—elastic 
pasteboard. 

3. By pasting together the finished 
paper sheets—sized pasteboard. 

I. Form-board is an inferior kind 
employed for ordinary purposes of 
packing, bookbinding, &c. It is made 
from waste paper, refuse rags, and the 
coarser parts of the pulp. Clay or 
chalk is sometimes present to 25 per 
cent, of the weight of this pasteboard. 
It is made in a coarse ribbed form, 
goes through the same process of 
knotting as the paper sheet, and is 
dried and pressed under a roller. 

2. Elastic pasteboard is of better 
material, and presents a smoother 
surface; six to twelve sheets of paper 
previously damped are placed together, 
and pressed into one compact sheet. 

A separate and harder kind of paste¬ 
board is the thick elastic board used 
for binding books. The inner layer is 
made of coarser stuff, sawdust, &c. 

24 


Fig. 204. 




































































































































CHEMICAL TECHNOLOGY. 


354 


3. Sized pasteboard, or cardboard, is made of two to fifteen sheets of sized paper, 
pressed, and satined. There are varieties of this cardboard, such as Bristol-board, 



London-board, the former being extensively used for water-colour drawings, mounting- 
board, ornamental-board, &c. 




























































STARCH. 


355 


Rapier mache is used for fancy articles, such as the covers for albums, inkstands, 
blotting-books, paper-knives, &c., as "well as for the cells of galvanic batteries. It is 
obtained from old paper made into a pulp with a solution of lime, and gum or starch, 
pressed into the form required, coated with linseed-oil, baked at a high temperature, and 
finally varnished. The pulp is sometimes mixed with clay, sand, chalk, &c., and other 
kinds are made of a paste of pulp and lime, and used for ornamenting wood, inlaying, &c. 

coloured Taper. The papers made from coloured rags are the brown packing paper 
and coarse coloured papers, such as sugar and pin paper. Coloured pin paper 
requires to 50 kilos, of dry pulp the several undermentioned substances :— 


Yellow 


( 2*05 kilos. Acetate of lead 
I ov 


45 

2-05 

1-05 


Blue . 

Green ./ 3*°° 

1 1-05 

Violet . 

Bose . 

Buff . 


Bichromate of potash; 
Sulphate of iron, 
Ferrocyanide of potash; 
Blue, 

Yellow; 


Extract of logwood; 
Extract of Brazil wood; 
Oil of Vitriol, 

Chloride of lime. 


•05 
1-05 
6*oo 
(3'°° 

(3*00 

Ultramarine and aniline blue are also used in colouring the paper. In variegated 
papers, chemical, mineral, and vegetable colourings are used according to the 
required colours. Body colours are rendered fluid by a solution of gum arabic or 
alum in the size, which can be applied by a brush or sponge when only one side is 
to be coloured. Variegated and tapestry papers are an important part of the 


manufacture. 


parchment Paper. Parchment, although made of animal membranes, is often con¬ 
founded with vegetable parchment (phy toper garnet). The latter is made of 
unsized paper treated with sulphuric acid or a solution of chloride of zinc:—1 kilo, 
of concentrated sulphuric acid and 125 grms. of water, in which the paper is immersed 
so as to equally affect both sides. The length of time differs according to the quality 
of the paper, the thicker or firmer paper taking a longer time to saturate; soft paper 
will take five to ten seconds. It is then placed in a weak solution of sal-ammoniac, 
rinsed in water until no trace of the acid remains, and then dried. When these 
operations are effected mechanically, a steam machine first pulls the endless paper 
through a vat of sulphuric acid, then through water, sal-ammoniac, and again 
water, the paper passing on over cloth rollers to dry, and finally over polished 
rollers to press and glaze the surface. 

Parchment paper, as a rule, is of one colour; when dipped into water it is 
rendered soft and limp. . It is used for documents, deeds, records, &c., also for 
drawing plans, charts, bookbinding, printing, and cards. 


Stabch. 

. Starch granules, one of the vegetable substances most extensive in nature, always 
appearing organically, are the foundation which, chemically treated, yield starch as 
commercially known. Starch is found in most organic combinations considered in 
chemistry and morphology, and in which cellulose is necessarily a component, 
being closely allied to, if not really isomeric with, this vegetable substance; its 
formula is C6 H io 0 5 . In following its connections it becomes the starch that, 
by means of chemical and physical agents, in the preparation of starch gum 
(soluble starch-dextrine) and sugar forms one of the most important substances 








CHEMICAL TECHNOLOGY. 


356 


presented to the consideration of the technologist. It seldom appears in a largo 
granular form, hut presents itself as a white glistening powder, w'hich upon micro¬ 
scopic examination seems to he made up of various rounded bodies with rings con¬ 
centric to a central spot; these lines are more plainly indented and cover a greater 
extent in some than in others, whilst the interior of the grain appears hollowed. 
The granules from different plants vary in size and form; those from wheat being 
smaller, whilst those from tropical products are thicker and more lenticular. Payen 
gives the largest dimension of the granules as o*ooi millimetre; from his researches 
we gain also the following examples:— 


Starch granules from close Potatoes 
„ „ „ ordinary Potatoes 

,. „ „ Maranta indica 

„ „ » Beans. 

„ „ „ Sago Palm .. .. 


99 

99 

99 

99 


„ Iceland Moss 
„ Pea 
„ Wheat 
„ Indian com 


185 

140 

140 

74 

70 

67 

50 

50 

50 


Pig. 206 shows, according to Schleiden, granules of potato starch, and Pig. 207 of 
wheat starch. The potato has a larger granule, and sometimes gives a finer powder 
than wheat. 

Nature of starch. The usual starch contains in its dry state nearly 18 per cent. wa‘ter, 
and in this state has a tendency to form itself into globules; it has been proved that 
exposed to a damp atmosphere it absorbs 33 *5 per cent, water. Starch is insoluble in 


Pm. 206. 



Pig. 207. 



cola water, alcohol, ether, and oil. At a temperature of 160° starch yields dextrine.* 
starch mixed with twelve to fifteen times the quantity of warm water at a temperature 
of 55 0 varies little in substance; at a temperature of 55 0 to 58° it begins to change, 
the higher temperature making the fluid thicker. Lippmann says that potato starch 
is affected at 62*5°, wheat starch at 67'5°. When boiled the granules burst and form a 
gelatinous mass, which, largely diluted with water, can be made of a consistence to be 
filtered through paper, and, when allowed to cool, sets in a jelly. A stiffer paste, 
according to J. Weisner (1868} is made from Indian corn than from the potato or 












STARCH. 


357 


wheat. The longer the starch is boiled the stiffer the paste becomes, i part of starch 
separating in 50 parts 'water, and upon cooling setting into paste of a blue or violet 
hue. Dry starch possesses a specific weight of 1*53. Alkalies and dilute acids, 
with lime, tend to re-form the granules; when boiled with 2 per mille of oxalic acid, 
the starch loses its consistence, becoming thin, and changing into a soluble substance 
called dextrine. Starch treated with almost any dilute acid, or with diastase 
obtained from an infusion of malt, at the proper temperature is converted into 
dextrine, forming a liquid which after a few hours’ standing can be made into 
sugar. Starch is soluble in the cold in concentrated nitric acid; water dropped 
into this solution precipitates the granules as an explosive combination. Under 
the name of xylodine , or white gunpowder, this combination has lately been 
. employed for pyrotechnical experiments. By boiling starch with concentrated nitric 
acid, a formation of oxalic acid is obtained; evolving nitrous vapours. Starch paste 
upon exposure to the atmosphere becomes sour, forming lactic acid. 

sources of starch. But few vegetables yield starch in large quantities : the potato 
yields 20 per cent.; wheat 55 to 65 per cent.; rice 70 to 73 per cent.; and the roots of 
Jatroplm Manihot and Maranta arundinacea, palm pith, and the Canna coccinea, 
similar quantities. In Germany starch is prepared only from potatoes, rice, and 
wheat, the latter yielding a greater quantity of gum, and potato starch being thinner 
and not so gelatinous. 

starch from Potatoes. Potatoes form an important material in the manufacture of starch; 
their constitution is as follows :— 



Newly dug 

Potatoes 


Potatoes. 

dried at ioo°. 

Water. 

. 75*1 

— 

Albumen . 

. 2-3 

9*6 

Patty matter 


o-8 

Cellulose . 


i *7 

Salts . 


4 ’ 1 

Starch . 


83-8 


IOO'O 

IOO'O 


They contain 28 per cent, dry substance, or 23 per cent, insoluble substance, and 
77 per cent. sap. The starch found in potatoes is of cellular construction; the cell 
walls require breaking up to fit it for manufacture. Pig. 208 shows, according to 
Schleiden, a fine specimen of a healthy potato under the microscope. On the outside 
of the potato a layer of flat, pressed, brown cells are found, sometimes appearing 
in a patch, a, forming the outer skin of the potato, and covering the cells, b, which 
sometimes contain a finer grain, but mostly a clear fluid. These cells become 
wider as they near the interior of the potato. The series of cells, c, enclose the 
inner cells, d , the pith of the potato. When the potato is dried, the cells separate 
from each other, as in Pig. 209, a specimen of a mealy potato. The starch granules 
swell in each cell, the cells uniting in reticulated streaks. The process of manu¬ 
facturing starch consists in :— 

1. Triturating the fresh potato. 

2. Washing the starch granules from the pulp. 

3. Purifying and drying the starch. 

The potatoes are placed in a grinding cylinder, which formerly consisted of wood, with 
iron plate rollers placed half way in water to cleanse the pulverised potato pulp. Of late 
o-rinding cylinders with saw-teeth are used (Thierry’s machine). The. saw-blades have 
short teeth, lacerating the cells to obtain the starch granules, which mere gentle 
washing and grinding would not effect; the cylinder revolves 600 to 700 times a minut e. 








CHEMICAL TECHNOLOGY. 


35S 

One cylinder with knives 0*50 metre in length and saw-blades of 0*40 metre, can grind 
fourteen to fifteen batches in an hour to a pulp, which is afterwards submitted to tbe 
process of washing*. A cylindrical metal sieve is generally used for separating the 
starch granules from the potato pulp; it contains a pair of brushes slowly rotating, 
whilst water is supplied to the sieve to wash the pulp, which is ground to a consistence 
that will admit of its readily flowing off, in order that fresh pulp may be received on the 
sieve. The starch granules are suspended in the water strained off, and finally settle to the 
bottom as a soft white powder. Laine’s uninterrupted cleansing sieve is now generally 
used ; it consists of a series of wire-work frames placed over a trough. The potato pulp 
flows from the grinding cylinder to a space under the cleansing sieve, from thence over 
two gratings, where the pulp is cleansed by a stream of water playing all over it, the 
granules settling down at the bottom of the trough. The granules are then crushed 
between steel rollers to separate the starch from the fibre. 80 to 100 cwts. potatoes can 
be thus prepared in a day. From the above method of preparing starch from the potato 
we gain the general principles of such operations. The structure of the potato is shown 
to be partly chemical, partly mechanical, and by destroying the latter we gain starch, which 
is separated after tho potato pulp has been standing eight days, when it becomes a white 


Fig. 208. 



pasty mass containing starch. This is placed in a coarse sieve, which retains a greater 
part of the fibre, another finer hair sieve being used to receive the starch and finer 
fibre, separated from each other by means of a cleansing apparatus, which washes the 
fibre away, leaving the starch granules and sugar behind. 

Drying the Potato starch. The result of the washing is a milk-like fluid, which settles at * 
the bottom of the trough as starch; it is then mixed with fresh water and allowed to 
solidify into a hard substance, which is cut into pieces, poured upon a linen cloth placed 
on a hurdle, with a plaster-of-Paris vessel, or a vessel containing gypsum, underneath, to 
dry the starch. After being watered and left to stand for twenty-four hours, the 
starch dries to the thickness of 2 decimetres upon the gypsum. Of late the water has 
been removed by a centrifugal machine. The moist starch contains 33 per cent, water, 
and is called fresh starch. The average temperature of the drying rooms is not over 6o°. 
When the starch is dried it is broken into pieces by iron rollers. The stalk or whole 
starch is made by boiling to a thick paste, which is forced by machinery through a small 
opening into a trough, where it dries in a kind of mould. 

preparation of wheat starch. According to M. 0 . Dempwolf, 1869, the unprepared wheat 


contains:—• 

Water . 10*51 

Ash. 1 50 

Gum . 14*35 

Starch .65.40 

Fatty and woody fibre . 8-24 


100*00 
































STARCH. 


359 


From the constituent parts of wheat it is seen that:— 
Starch 

Gum C are insoluble in water. 
Husk ) 

Salts 
Albumen 
Dextrine 


are soluble. 


The first three are insoluble, the gum, however, being gradually dissolved by the 
lactic acid developed from the seed, while the starch and husk remain unattacked. 
The different modes of preparing wheat starch are, namely:— 

A. By fermentation (old method) of the— 


a. Unground ) 
0. Ground j 


Wheat. 


B. New mode of treatment without fermentation. 


The old method consists of the following operations 

1. Fermenting the wheat. 

2. Washing the starch from the mass. 

3. Washing and cleansing the starch. 

4. Drying the starch. 

The whole wheat is soaked in water until soft. The seed is separated from 
the husk either by treading in sacks in a flat tub of water, or by being placed under 
rollers, and the pulp thinned with water to a milky fluid, in which a greater part of 
the starch and gum are found. After standing a day this fluid turns acid; a part 
of the gum becomes diluted by the action of the lactic and acetic acids, and is taken 
away and replaced by fresh water, the same process being gone through until 
the fermentation ceases, when the starch is washed with water and dried. In the 
fermentating tub it forms with the water a thin, sour pulp. The time varies 
according to the temperature ; all the gum is not separated until about twelve to 
thirty days. The sour water contains acetic acid, lactic acid, butyric acid, succinic acid, 
ammoniacal salts, and the mineral constituents of the wheat. The mass is then placed 
in a sack and trodden, the milky fluid being allowed to escape, leaving the husk and 
refuse gum behind. The milky fluid containing starch is strained through a fine 
hair sieve and washed with water. Another method is that of placing the milky 
fluid in a tub and allowing it to settle. The first layer of the sediment is fine 
starch, next a mixture of starch, husk, and gum, the last layer containing but little 
starch. In the preparation a little ultramarine blue is added during the cleansing 
process. Of late the centrifugal machine has been used for the purpose of drying 
the starch. 

Preparing wheat starch without fermenting :— 

According to E. Martin’s treatment, wheat flour is mixed with water to a paste, 
100 parts flour to 40 parts w r ater; the paste remains l to 2 hours to affect the gum, 
and is then washed in a fine wire sieve placed over a tub. The starch is found at the 
bottom of the tub mixed with water, and is placed in a warm spot to ferment 
slightly. It is dried in a mass, and goes through similar processes to the other 
starch, being made into stalk and powder starch, and sold in packets. 

100 parts of wheat flour yield 25 per cent, of gum {gluten, gluten granuli ), with 
33 per cent, of water; the fresh gluten is mixed with a double weight of flour, the paste 


CHEMICAL TECHNOLOGY. 


560 

rolled into long strips, and ground into granules, which become dry at 30° to 40°, and 
are afterwards sifted. The consumption of this granular gum is extensive, it being 
employed for food (with ordinary flour as macaroni), art purposes, and manu¬ 
facture. 

constituents and usesjof According to M. J. Wolff, the constituents of commercial starch 

Commercial Starch. © 7 

are as follows:— 



1. 

0 

3 - 

4 - 

5 - 

6. 

Water .. 

I 7-83 

15-38 

I 4 - 5 2 

I 7 A 4 

14-20 

17-49 

Gum 


— 

O-IO 

traces 

1-84 

4-96 

Fibre .. 

0-48 

0-50 

1-44 

1-20 

3-77 

2-47 

Ash 

0-21 

o -53 

0-03 

0-40 

°’55 

1-29 

Starch .. 

81*48 

83'59 

83-91 

81-32 

79-63 

73-79 


100-00 

100-00 

100-00 

ioo-oo 

100-00 

1 00-00 


1. The finest white patent starch in stalks, of a bright and crystalline appearance, 
made from pure potato starch. 2. The finest blue patent starch, potato starch 
coloured with ultramarine. 3. Pure wheat powder. 4. Pine wheat starch in pieces 
5. Medium fine wheat starch in yellowish-white pieces. 6. Ordinary wheat starch 
in greyish- yellow coarse pieces, that upon microscopic examination appear as a mix¬ 
ture of potato and wheat starch. Starch is used for stiffening domestic articles in 
washing, for stiffening paper, and extensively in linen and cotton manufacture 
in gum, syrups, sago, vermicelli, &c. It is also a basis from which we can obtain 
sugar. Potato starch is preferred for domestic washing, but where great stiffness is 
requisite, wheat starch is used, as in bookbinding, &c. In wheat starch, the paste is 
formed of closely united gelatinous particles, which are more widely disseminated in 
potato starch, the latter being transparent and more suitable for stiffening fine linen, 
ironing smoother, and not sticking. Wheat starch will keep fresh upon exposure to 
the atmosphere longer than potato starch, the latter turning sour after a day’s 
standing. 

According to C. Wiesner, 1868, maize starch possesses the highest, wheat the next, 
and potato starch the most inferior stiffening qualities. Maize and wheat are consi¬ 
dered the best for forming a smooth equal paste. Sugar can be prepared from 
starch by means of the active principle of malt—diastase. Prom this sugar, again, 
brandy and spirits can be distilled. According to the researches of Ludersdorff:— 
100 pounds of potato starch need 25’5 pounds of dry malt, and 
100 pounds of wheat starch ,, 90*5 ,, ,, 

to effect the full conversion of the starch into sugar. 

suach^ cassava starch! ^ c h starc h i s largely manufactured in England, France, and Bel- 
Arrow-itoot. gium. To extract the guxn, rice is placed in a bath of weak soda 
solution—287 grins, of caustic soda to the hectolitre. After standing twenty-four hours, 
the rice grain becomes softened, and is then washed, ground between rollers or mill-stones, 
and placed on a sieve with brushes to retain the husk or bran. The water strained off 
contains the starch, which is washed, dried, and manufactured into the form required. 
The gum-containing alkaline ley being neutralised with sulphuric acid is fit for inferior 
uses. J. and J. Colman’s rice starch manufacture employs 1000 workpeople, and the 
result of their manipulation is used as the customary washing starch, the stiffer and 
brighter starch for ball dresses, window hangings, and for the size in paper manufacture. 

In France the chestnut is used for the manufacture of starch. Chestnuts produce a starch 
possessing the evenness of potato starch with the stiffness of wheat starch. 100 parts of 
the fresh bitter chestnut give 19 to 20 per cent, dry starch. 

Arrow-root is obtained from the Maranta arundinacea , and M. indica, cultivated in the 
West Indies; it is very like potato starch, and is prepared in a similar manner. Cassava 
starch is made from the root of Jatropha Manihot , or Manihot utilissima, and M. Aipin, 
largely cultivated in South America, the West Indies, and the Brazils. 








STARCH. 


361 


Cassava is used as an article of consumption both in Europe and the tropics. The 
root of the manioc is thoroughly purified from its poisonous juice, being coarsely 
ground to allow the sap to escape, and roasted in an earthenware vessel, 
the cassava forming into granules on the sides of the vessel ( Cassava sago , or 
ManioJea ), the prussic acid contained in the root becoming volatilised. Erom arrow- 
root and the analogous roots containing a poisonous juice, arrow-root derives its 
name, having been used by the Indians as a poison for the tips of their arrows. Its 
components, according to Benzon, in 100parts, are—Volatile oil, 0*07parts; starch, 
26 parts; 89 per cent, of the starch being obtained in a powder, while the remainder 
is extracted from the parenchyma by boiling water; albumen, 1*58 parts ; gum, o*6 
part; chloride of calcium, 0*25 ; insoluble fibrin, 6 parts; and water, 65-5 parts. 
It is known in commerce in several varieties, viz.Portland arrow-root, Arum 
vulgare ; East India arrow-root, Curcuma augustifolia ; Brazilian arrow-root, 
Jatropha Manihot; English arrow-root, from the starch of the potato ; Tahiti arrow- 
root, Tacca oceanica. 

sago. Sago is made from the soft central portion of the stem of the palm, Sagus 
Rumphii. According to J. Weisner, the Guadeloupe sago is prepared from Raphia 
farinifera , and an East Indian variety from Caryota urens. The stem is torn to fila¬ 
ments and elutriated on a sieve with water. The starch obtained is then washed, 
dried, and sifted into a copper plate, where it remains a hard granular substance. A 
greater part of the common sago is manufactured from potato starch, coloured with 
oxide of iron or burnt sugar. 

Dextrine Dextrine, gommeline, moist gum, starch gum, or Alsace gum, isomeric 
with gum arabic, and expressed by the formula, C6 H io 0 3 , is formed by boiling 
starch with a small quantity of almost any dilute acid, which thins its consistence, 
and converts it into a soluble subs'tance similar to gum arabic. It is soluble in cold 
water,.insoluble in absolute alcohol, but slightly soluble in weak spirits of wine. 
Dextrine derives its name from dexter , the right, from the action of this substance on 
polarised light, twisting the plane of polarisation towards the right hand. Dextrine 
in grape sugar is converted into dextrose by the action of dilute acids. Dextrine 
solution does not ferment with yeast; but a little yeast mixed with a large quantity 
of gelatinous starch, at a temperature of 160 0 , quickly liquefies it, dextrine being 
produced, the greater part of which, if allowed to stand, becomes converted into 
grape sugar. From this decomposed dextrine a cheap and largely employed sub¬ 
stitute for gum arabic is obtained. The components of this decomposed dextrine, 
according to the analyses of B. Forster (1868) are:— 



1. 

2. 


Dextrine. 

Opaque 

Starch. 

Dextrine. 

72-45 

7°’43 

Sugar. 

877 

1*92 

Insoluble substances 

I 3 -I 4 

I 9-97 

Water . 

5-64 

7-68 


100*00 

IOO’OO 


3 - 

4 * 

5 - 

6. 

Dark 

Dextrine. 

Gommeline. 

Old 

Dextrine. 

Bright 

Starch. 

63*60 

5971 

49*78 

5*34 

7-67 

576 

1*42 

0*24 

I 4'50 

20*64 

30*80 

86*47 

14*23 

13*89 

18 *oo 

7’95 

100*00 

100*00 

100*00 

100*00 


Potato starch is preferable to wheat starch for the manufacture of this material, 
not only on account of its cheapness, but for its greater purity at an equivalent 
price. 








362 CHEMICAL TECHNOLOGY. 

Dextrine is prepared by:— 

a. Gently roasting. 

b. Carefully treating with, nitric acid. 

c. Boiling with dilute sulphuric acid. 

d. Treating with malt extract (diastase). 

Preparing dextrine by means of gentle heat is an easy operation. The Bunch 
is roasted until it becomes brown-yellow in colour, in a large copper or iron 
plate cylinder, similar to a coffee drum, situated on one side of the oven. Dextrine 
is formed at a temperature of 225 0 to 260°. According to Heuze, the following is a 
better method:—2 kilos, of nitric acid, of 1*4 specific weight, with 300 litres of water, 
are mixed with 1000 kilos. (= 20 cwts.) of starch, and boiled to form a mass, which, 
when exposed to the air, becomes dry. It is sometimes affected at 8o°, but it 
becomes a paste at ioo° to no°. The starch changes into dextrine in an hour or an 
hour and a half at the most; it is white and soluble in water. Sulphuric, hydro¬ 
chloric, and lactic acids will produce dextrine; and by the addition of water to dex¬ 
trine, dextrine syrup, or gum syrup, is obtained. 

Dr. Yogel gives a simple experiment to illustrate the action of dilute sulphuric acid 
upon starch. Nearly all kinds of writing paper are so very largely sized with starch, that 
if figures or letters are traced on the paper with very dilute sulphuric acid, and then dried, 
the application of iodine in a dilute solution will impart a blue tinge to that portion of 
the paper not affected by the acid, the characters remaining white. 

Dextrine is extensively used instead of gum arabic in printing wall papers, for 
stiffening and glazing cards and paper, for lip glue, surgical purposes, wines, and 
in the fine arts it is applied in many ways. 

Sugar Manufacture. 

History of sugar. Sugar has been known in the East Indies and China since xt very 
remote period. In Europe honey was used for sweetening purposes in the olden 
time, and although sugar was known to the inhabitants of Greece and Italy, the 
commercial intercourse with India being limited, it was but little used until the time 
of Alexander the Great. After the conquest of Arabia sugar-canes were propagated 
in Western Asia, Africa, and Southern Europe. The Crusaders became acquainted 
with this useful product, and the Venetians began to cultivate it about that time in 
Europe and Northern Africa. Malta, Cyprus, Candia, and Egypt, yielded the first 
sugar-cane, which was next cultivated in Sicily, Spain, Portugal, and the Canary 
Islands, about 1420. In 1506, sugar was cultivated in the West Indies, Brazil, 
Haiti, and in many islands of the Indian Ocean. Cane sugar, a substance found in 
the juice of various grasses, was first discovered in South America. Bitter mentions 

it as a plant capable of great cultivation, to be found in different parts of the globe_ 

eastwards from Bengal to China; westwards, the Indies, North Africa, Southern 
Europe to America. Slaves were imported to cultivate the sugar-canes in North 
America in 1800, when the first cultivation commenced, and sugar, which until now 
had been a curiosity and a luxury, being chiefly used for medicinal purposes, became 
one of the daily necessaries of life. The art of extracting sugar from the canes and 
refining the raw product soon became known, and this useful article of food was 
extensively manufactured. 

Nature of sugpr. Sugar is known as cane sugar and grape* sugar, dextrose, glucoso 
crumbling sugar, starch sugar, potato sugar, and coarse ]aw sugar or fruit sugar 


SUGAR. 


363 

Cane sugar is prepared from the sugar-cane, maize, the Andropogon glycichylum , 
the sap of the sugar maple, the birch, the sweet turnip, and carrot. According to 
W. Stein, 8 per cent, of sugar is found in the root of the madder. The pumpkin, 
melon, banana, and most of the species of palms yield sugar. Cane sugar has the 
formula C I2 H 22 0 II . The crystallised sugar, known as sugar-candy, is hard and has 
a spr. gr. of i*6; it is unaffected by exposure to the air, and when heated at a 
temperature of 180° it dissolves into a sticky colourless fluid, which upon rapid 
boiling resolves itself into a pliant uncrystallised mass, commonly known as 
barley-sugar. At a very high temperature it becomes black and decomposed. At 
210 0 to 220 0 cane sugar becomes a dark brown substance termed caramel, used in 
colouring spirits, and for other purposes. Sugar has a pure sweet taste, is soluble 
in one-third of its weight of cold water; by continued boiling it loses its power of 
crystallising. It is insoluble in absolute alcohol and ether, but soluble in dilute 
alcohol, especially when warmed. Gerlach, 1864, gives in the following table 
the specific weight of sugar solutions with the corresponding percentage of cane 
sugar at 17*5° 0.:— 

Percentage Specific 
Cane Sugar, weight Sol. 


Percentage Specific 
Cane Sugar, weight Sol. 

1*383342 


75 

74 

73 

72 

7 i 

70 

69 

68 

67 

66 

65 

64 

63 

62 

61 

60 

59 

58 

57 

56 

55 

54 

53 

52 

5 i 

50 


1*376822 

I ’ 37°345 

1*363910 

1*357518 

1*351168 

1*344860 

i *338594 

1*332370 

1*326188 

1*320046 

1*313946 

1*307887 

1*301868 

1*295890 

1*289952 

1*284054 

1*278197 

1*272379 

1*266600 

1*260861 

1*255161 

1*249500 

1*243877 

1*238293 

1*232748 


Percentage Specific 
Cane Sugar, weight Sol. 


49 

48 

47 

46 

45 

44 

43 

42 

4 i 

40 

39 

38 

37 

36 

35 

34 

33 

32 

3 i 

30 

29 

28 

27 

26 

25 


1*227241 

1*221771 

1*216339 

1*210945 

1*205589 

1*200269 

1*194986 

1*189740 

1*184531 

1*179358 

1*174221 

1*169121 

1*164056 

1*159026 

1*154032 

1*149073 

1*144150 

1*139261 

1*134406 

1*129586 

1*124800 

1*120048 

i*ii 5330 

1*110646 

1*105995 


24 

23 

22 

21 

20 

19 

18 

17 

16 

15 

14 

13 

12 

11 

10 

9 

8 

7 

6 

5 

4 

3 

2 

1 

o 


1*101377 

1*096792 

1*092240 

1*087721 

1-083234 

1*078779 

1*074356 
1*009965 
1*065606 
1*061278 
1*056982 
1*052716 
1 *048482 
1*044278 
1*040104 
1*035961 
1*031848 
1*027764 
1*023710 
1*019686 
1*015691 
1*011725 
1*007788 
1*003880 
1*000000 


A watery solution turns the rays of polarised light to the right hand. Dilute 
sulphuric and muriatic acids, with most of the organic and mineral acids, tend to 
convert cane sugar solutions into a mixture of dextrose and levulose according to 
the equation :— 

C I2 H 22 0 ix + H 2 0 = CeHxaOg + 

Cane sugar or Dextrose Levulose. 

sucrose. (glucose). 

From the above it may be deduced that cane sugar is found only in the neutral 
juices of plants, while juices like that of the grape containing free acid, tartaric, 





CHEMICAL TECHNOLOGY. 


364 

malic, and citric acids, can yield only leyulose and glucose. By treating with 
yeast the sugar separates and produces the usual alcoholic fermentation products, 
alcohol, carbonic acid, glycerine, &c. Cane sugar enters into combination with 
the hydroxides of calcium and barium, forming saccharates, which in the prepara¬ 
tion of sugar on the large scale are of great interest. The sugar solution contain¬ 
ing hydroxide of calcium becomes especially interesting as being the origin of the 
application of lime to the refining of cane and beet-root sugars, the hydroxide oi 
calcium forming a clear fluid with a raw sugar solution containing C I2 H 22 0 II} be¬ 
coming dull upon standing, the sediment containing C 12 H 22 0 I1 .Ca 0 . Carbonic acid 
gas has of late been applied to the sugar-lime solution, the lime thrown down as 
carbonate and the sugar separating and becoming colourless in the solution. 
Preparing cane sugars with hydroxides of barium gives rise to sugar barytes, 
C I2 H 22 0 I1 Ba 0 , worthy of notice as being insoluble in water and originating the 
method of extracting sugar from the juice of beet-root and molasses with caustic 
baryta. Sugar barytes is decomposed by means of carbonic acid. An explosive 
mixture is formed with nitric and concentrated sulphuric acids and sugar, and 
known as nitro-sugar. Cane sugar when mixed with a solution of sulphate of 
copper with an excess of caustic potash, is at first but slightly affected; a small 
quantity of red powder is thrown down after a time ; but the liquid long retains 
its blue tinge, while with grape sugar the effects are much increased. 


Cane Sugar. 

Su #u a ga^Tne^ e The sugar-cane, Saccharum officinarum, is a plant of the grass species; 
its stalk is round, knotted, and hollow, and the exterior of a greenish-yellow or blue, 
with sometimes violet streaks. It grows from 2'6 to 6 - 6 metres high, and from 4 to 6 
centimetres in thickness ; the interior is cellular. The leaves grow to a length of 
i*6 to 2 metres, and are ribbed. The plant is grown from seed, and also cultivated 
from cuttings. 

A hectare of land yields raw sugar:— 

By 15 Months’ Cultivation 

Prom Martinique. 2500 kilos. 

,, Guadeloupe.3000 ,, 

,, Mauritius . 5000 ,, 

„ Brazil .7500 „ 

Components Of the The sugar-cane yields the largest amount of sugar, generally 90 per 
Sugar-cane. cent, juice, containing, according to Peligot, 18 to 20 parts crystallised 
sugar. The components of sugar-cane, according to the analyses of Peligot, Dupuy, and 
leery, are as follows :—Martinique (a ); Guadeloupe (b) ; Mauritius (c). 


Sugar 

(a). 

Peligot. 

(b). 

Dupuy. 

X^r. 

.. 180 

17-8 

• 20’0 

Water 

72-1 

72-0 

69-0 

Cellulose.. 

9'9 

9*8 

IO'O 

Salts 

.. — 

0-4 

07—I-2 


Prom 18 per cent, sugar found in the sugar-cane, as a rule not more than 8 per cent 
crystallised sugar can be realised. The loss may be accounted for thus :—90 per cent. 
juice is expressed from the cane, from which only about 50 to 60 per cent, can be clarified 
from the straw, &c.; a fifth part is exhausted by refining; and finally two-1,birds of the 
sugar is obtained by boiling, while the rest goes to the molasses. The 18 per cent, sugar 
may be realised in the following manner :— 


In 1 Year. 
2000 kilos. 
2400 „ 
4000 „ 

6000 ,, 






SUGAR. 


365 


In the refuse sometimes remains .. 6 per cent. 

By skimming.2’5 „ 

In the molasses .3 „ 

As raw sugar.65 „ 


Pr fromthc t su^ir-ca S re! ar The preparation of raw sugar from the sugar-cane consists in 
first expressing and then cleansing and boiling the juice. 

1. Expressing the Juice.— The sugar-canes are crushed in a press consisting of 
three hollow cast-iron rollers, ah c, Fig. 210, placed horizontally in a cast-iron 
frame. By means of the screws, i i, the approximate distance of the rollers is 
adjusted. One roller is half as large as the others, and is moved by three cogged 



Fig. 210. 


wheels fitted on to the axis of the rollers. The sugar-canes are transferred from the 
slate gutter, d d, to the rollers, a c, which press them a little, and from thence they 
are carried over the arched plate, n , to the rollers, c h. The pressed sugar-canes 
fall over the gutter, /, the expressed juice collecting vug g, and running off through 
h. The middle roller is termed the king roller; the side cylinders are individually 
the side roller and macasse. 

2. Refining and Boiling the Juice .—The expressed juice is removed to the boil¬ 
ing-house, which is fitted with five iron or copper vessels. To 15,000 litres of ex¬ 
pressed juice 5 to 9 litres of milk of lime are added. The lime neutralises the 
malic and other vegetable acids, and upon boiling forms with the albumen and the 
other constituents of the juice a thick green scum, which being removed the juice 
is allowed to remain in two of the pans to evaporate. A fresh scum is formed on 
the first pan, which returns after a second or third time of removal. The juice as 
it issues from the press is received into the first pan, in which by slow boiling it 
becomes a thick froth, changing by rapid boiling to a clear colourless fluid; in the 
third and fourth pans the liquid becomes gradually purer, until in the fifth it crys¬ 
tallises. The finger is dipped into the boiled juice to test its consistence, and by 
the length of the pendant drop, which ought to be about 3 centimetres, the thick¬ 
ness is ascertained. The boiled juice is placed in a large open wooden vessel ol 
about 16 centimetres capacity, and termed the cooler, where after standing twenty- 
four hours the sugar crystallises, the cooler being provided with a double per- 














CHEMICAL TECHNOLOGY. 


366 


forated bottom to allow the molasses to escape, leaving the crystals behind. After 
standing five or six weeks, the molasses dries into a mass commonly known as moist, 
raw, or Muscovado sugar. The molasses passes into a cistern placed underneath 
the cooler, capable of containing 15,000 to 20,000 litres of juice, and after standing 
fourteen days is ready for the market. In the Trench and English colonies sugar 
is exported in chests covered with fire-clay under the name of chest or tub sugar. 

Varieties of Sugar. European commerce deals with the following kinds of raw sugar :— 

1. "West Indian—Cuba, San Domingo or Haiti, Jamaica, Porto-Bico, Martinique, 
Guadeloupe, Saint Croix, St. Thomas, Havana. 

2. American—Bio Janeiro, Bahia, Surinam, Pernambuco. 

3. East Indian—Java, Manilla, Bengal, Mauritius, Bourbon, Cochin China, Siam, 
Canton. 

Of late there has been a distinction between sugar cultivated by slave and that by free 
labour; the latter comes from Jamaica, Barbadoes, Demerara, Antigua, Trinidad, Dominica; 
the former from Cuba, Havana, Brazil, St. Croix, and Porto Bico. 

The mode of manufacture varies according to the nature of the foreign sub¬ 
stances that always form part of the constituents of sugar, such as water, fibre, 
gluten, sand or earth, soluble mineral salts, acetic and other acids, all of which 


must be destroyed before the sugar 
in the following sugars from :— 

can be refined. 

According 

to Benner we have 


Java. 

Havana. 

Surinam. 


Baw Sugar 

98*6—83*1 

97*0—8 7-3 

92*3—85*4 

99-6 997 

Slime Sugar .. 

5'5 — 0-3 

37— 0*9 

4*4— i*6 

0*1 0*2 

Water 

6*i— 0*3 

3*5 — o*9 

6*3— 3*6 

0*2 0*1 

Ash. 

2‘I - 0*2 

1*4— o*o 

2*0— 1*2 

0*1 — 

Caramel, gum, vege- \ 
table acids, &c. j 

■ 3'5 — °’5 

. Tl * 

*0 

1 

in 

V 

2*1— II 

- — 


Molasses. The production of molasses is due to the long-continued heating of the 
cane juice, but the quality varies according to the nature and culture of the sugar- 
canes, the heat of the season, &c. By chemical treatment molasses appears as a 
concentrated watery solution of crystallised sugar, slime sugar, with a small admix¬ 
ture of caramel and mineral salts. It is a dull red-brown sweet fluid used princi¬ 
pally in the colonies for the manufacture of rum; it is soon converted to spirit, 
and then quickly becomes acetated. Benner gives the constituents of molasses as : 


Baw Sugar . 


40*36 

Slime sugar .. .... 

.. . . 4*30 

7-38 

Water . 

.. .. 1371 

16*25 

Ash. 

•• •• 3*35 

378 

Caramel, gum, &c. 

.. ., 45*65 

32*22 


Refining the Sugar. Sugar refining consists in:— 

1. Dissolving and refining. The raw sugar is dissolved in water, and during 
the process cf evaporation the apparatus is connected by a gutter to a reservoir 
into which the sugar flows. It is then submitted to a straining apparatus, which 
retains the several impurities. The refined fluid is then heated in a copper pan, 
termed the melting-pan, the water adding 30 per cent, to the weight of the sugar, 
and is afterwards placed in the refining pan, a vessel constructed with a double 
bottom. Eor the purpose of clearing, a mixture of albumen is added in the shape 
of serum of blood, or white of egg, with lime-water and sulphuric acid, an addition 
afterwards being made of 3 to 4 per cent, animal charcoal and £ to 2 per cent. 








SUGAR. 367 

blood, and the whole heated to the boiling-point. The albumen coagulates and 
forms a fibrous scum, containing all the impurities. 

2. Taylor’s filtering apparatus is now much used for filtering the sugar, charcoal 
being employed as the purifying agent. 

3. The boiling of the clear sugar in pans placed oyer a vacuum apparatus, re¬ 
sembles the previous boiling, with the exception that the fluid is rendered purer, 
10 to 12 per cent, water remaining. 

4. Cooling and crystallising. When the sugar begins to crystallise on the sur¬ 
face of the vaccum pan, generally at 8o°, the temperature is lowered to about 50°, 
as too great heat at this stage of the process exercises an injurious effect upon the 
sugar, which now forms an amorphous mass, and is drained, washed with clean 
syrup, and prepared for ordinary loaf-sugar. Sugar-candy is the result of slow 
crystallisation, the crystals by this means acquiring a larger size and more regular 
form. 

5. The shaping of the crystallised mass into the form of a sugar-loaf is accom¬ 
plished by evaporating the sugar and placing it in earthen conical moulds to soli¬ 
dify at a temperature of 25 0 to 30°. After standing ten minutes the sugar sets into 
form. 

6. Drying.the sugar. After standing twelve hours a green-coloured syrup is 
obtained from the crystalline mass, which is removed, and the crystals submitted 
to a centrifugal process of drying, then placed in a drying-stove at a temperature 
of 25°, which is gradually increased to 50°. By thus refining the raw sugar, the 
ordinary loaf sugar is obtained. 

Production of Raw Sugar. The estimated production, of raw sugar in 1870 was 55,000,000 

cwts., the largest instalment being from Cuba. 

Beet-Root Sugar. 

its Nature. In the year 1747 Marggraf, a chemist of one of the Berlin academies, 
discovered crystals of sugar in the red beet, Beta cicla, which he deemed capable of 

• manufacturing into the commercial article. He found that, treated with alcohol, the ’ 
white beet yielded 6*2, and the red variety 4-6 per cent, of sugar. But the prepara¬ 
tion of beet-root sugar was not developed until the close of the year 1800. Achard 
and Hermbstadt, of Berlin, tried many experiments with this new product with 
equal success, always finding that beet-root contained crystallised sugar to the 
amount of 6 per cent., with 4 per cent, of molasses, and sometimes a larger quantity 
of sugar. About the time of the Continental war native products were in request 
on account of the difficulty and expense of obtaining foreign articles. The first 
Napoleon supported the new product in the pursuance of his “ Continental system” 
of excluding cane sugar from the French markets, and a trial of the German 

• method was made, but it was not crowned with the success it has now achieved 
until ten years after his overthrow. The annual production of sugar in 1811 did 
not exceed 13,000,000 lbs.; the present yearly consumption of beet-root sugar ex¬ 
ceeds 15,000,000,000 lbs., this enormous amount being supplied by more than 
eighty manufacturers. 

Species of Reet. The vegetable known as beet-root is a large .fleshy root of the beet, a 
plant of the species Beta maritima , largely cultivated in France, Belgium, and 
Portugal for the production of sugar. There are several varieties of the two species, 
the white beet being preferred on account of its yielding more sugar, and also for 


CHEMICAL TECHNOLOGY. 


368 


its purity of colour, the red beet being chiefly cultivated for culinary purposes. 
There is also the field beet, commonly known as the mangold wurzel, which was 
first used as provender for cattle about the end of the last century. The sugar beet 
has, in course of cultivation, been improved by many new methods of manuring, 
&c., until it yields 13 and sometimes 14 per cent, of sugar. In Germany the follow¬ 
ing varieties of beets are principally cultivated:— 

1. Quendlinburg beet, a slender rose-coloured root, and very sweet; it is matured 
fourteen days before any other kind. 2. Silesian beet is pear-shaped, with bright 
green ribbed leaves; it is known as the green-ribbed beet, and does not produce so 
much sugar as the former. 3. Siberian beet is pear-shaped, with white-green 
ribbed leaves, and is known as the white-ribbed beet. It does not yield so well as 
the Silesian beet, although of a greater weight. 4. The French, or Belgian beet, 
has small leaves and a slender and spiral root, yielding sugar. 5. The Imperial 
beet is slender and pear-shaped, yielding much sugar. The king beet is a bien¬ 
nial ; in the first year the root is merely developed, in the second it bears seed. 

The following is a list of the countries where the beet is cultivated for sugar:— 




Beets 

The manufacture 

Into Sugar 
in pounds. 

In 

According to— 

gathered 
in cwts. 

of suitable Beets 
in cwts. 

Austria. 

Krause 

104—145 

88—123 

770—1084 

Austria. 

Burger 

169—193 

143—164 

1256—1560 

Bohemia. 

Neumann 

112—145 

95— 12 3 

836—1160 

Prussia. 

Ludersdorff 

146 

124 

1088 

Prussia. 

Thaer 

180 

153 

1336 

Baden . 

France:— 

Stolzel 

120—160 

102—136 

896—1196 

Northern Departments ) 

Dumas 

( 193 

168 

1476 

Other „ ) 

l 124 

105 

924 

France . 

Boussingault 

149 

127 

1116 


In general 140 to 160 cwts. are cultivated, cut, and cleaned, per acre, there being four 
Magdeburg acres to one hectare, which usually yields sufficient roots for three days’ w r ork. 


Chemical Constituents 
of the Beet. 


The flesh of the beet consists of a quantity of small cells con¬ 
taining a clear, colourless fluid. The constituents of the sugar-beet, according to 
chemical analyses, are:— 

Water . 

Sugar . 

Cellulose. 

Albumen, caseine, and other bodies. 

Fatty matter. 

Organic substances, citric acid, pectin and pectic acid, 
asparagin, aspartic acid, and betain, a substance having, 
according to M. Scheibler, the formula C I5 H 33 N 3 06 .. 

Organic salts, oxalate and pectate of calcium, oxalate and 

pectate of potash and sodium. 

Inorganic salts, nitrate and sulphate of potash, phosphate 
of lime and magnesia . I 


\ 


827 

11 '3 
o*8 

0*1 


37 


Near Magdeburg, where the beet is extensively cultivated, the general results 
give 

The greatest sugar production, as 13*3 per cent. 

That from inferior beets, as .. 9*2 „ 

The average beet yielding .. .. n*s „ 

















SUGAR . 


36Q 


The components of the beet vary according to the time of the year, it at some 
periods containing more water than at others, from 82 to 84 per cent, being the 
average. In the autumn it does not contain slime sugar; in February and March 
the components intermingle and some decrease nearly 2 per cent., as shown by the 
following analyses:— 

October. February. 


Woody fibre and pectin 

3*49 per cent. 

2*52 per cent. 

Water. 

82*06 ,, 

84*36 ,, 

Sugar. 

12*40 ,, 

io*6o ,, 

Slime sugar. 

0*00 ,, 

0-65 ,, 

Mineral salts . 

075 » 

0*63 „ 

Organic acid and extractives 

1*30 ,, 

100*00 

1*24 ,, 

100*00 


124 cwts. of beet yield on an average 1 cwt. of raw sugar, 
saccharimetry. The measure of the amount of saccharine matter contained in the 
various crude sugar productions can be estimated either by the— 

1. Mechanical, 

2. Chemical, or 

3. Physical method. 

Mechanical Method. The middle part of the beet is cut in thin slices to the weight of 25 
to 30 gnus, each, and dried. From the difference in weight before and after drying, the 
quantity of water contained in the root is ascertained. The dry residue is pulverised, and 
then treated with boiling dilute alcohol of a specific gravity of O' 83. By this means the 
sugar is dissolved, and the weight ascertained. The insoluble residue gives after drying 
the weight of the cellulose, protein bodies, and mineral constituents. If the alcoholic 
solution be placed in a vacuum over caustic lime, it gradually becomes more and more 
concentrated, until after standing about a day, the sugar, owing to its insolubility in abso¬ 
lute alcohol, may be collected in small colourless crystals, only absolute alcohol remaining. 
Good sugar beets give 20 per cent, dry residue, the water amounting to 80 per cent. Of 
the 20 per cent., 13 per cent, is usually sugar, and the remaining 7 per cent, pectin, cellu¬ 
lose, protein, and mineral substances. The higher the specific weight of the juice of the 
beet, the more sugar it contains. The juice of a good beet properly cultivated marks 8’ 
and sometimes 9 0 B. 


chemical Method. The chemical method is based upon the following facts:— 

a. The known proportional solubility of hydrate of lime in cane sugar. 

b. The capability of a cane sugar solution to reduce the hydroxides of copper to 

protoxides, the quantity reduced affording an estimate; and the conversion 
by acids of cane sugar into inverted sugar (a mixture of levulose with 
dextrose or glucose). 

c. The fermentation of sugar, giving rise to the formation of alcohol and 

carbonic acid, the amount of which can be ascertained, 4C0 2 corresponding 
to 1 mol. of cane sugar, C I2 H 22 0n. 

The first of these methods is that of determining the solubility of hydrate of 
lime in a cane sugar solution. The fluid containing sugar is stirred with 
hydrate of lime, the quantity of which dissolved, estimated by titration with 
sulphuric acid, determines the quantity of sugar. The second method is 
grounded on the researches of M. Trommer, who found—(1.) That cane sugar 
in an alkaline fluid does not reduce oxide of copper; but it becomes reduced 
if the sugar has previously been boiled with sulphuric or hydrochloric acid, 
the acid converting the cane into inverted sugar. 2. The quantity of the reduced 
protoxide is proportional to the quantity of sugar. Barreswil and Fehling give a 







37« 


CHEMICAL TECHNOLOGY. 


test based on this law:—An alkaline solution of oxide of copper is made by 
dissolving 40 grins, of sulphate of copper in 160 grms. of water, and adding 
a solution of 160 grms. of neutral tartrate of potash in a little water, with 
600 to 700 grms. of caustic soda ley of a specific gravity == 1*12. The mixture 
should be next diluted to 1154*4 c.c. *5°* A litre of this copper solution contains 
34*65 grms. of sulphate 6f copper, and requires for its reduction 5 grms. of 
dextrose or levulose; or 10 atoms sulphate of copper (1247*5) are reduced, by 
means of 1 atom of dextrose or levulose (180), to protoxide (34*6515 = 1274*5:180, 
or= 6*93:1), 10 c.c. of the copper solution corresponding also to 0*050 grms. of dry 
dextrose or levulose. Mulder prefers a solution in which 1 part of oxide of copper 
corresponds to 0*552 part of dextrose or levulose of the formula C6 Hi 2 06+H 2 0 ; by 
the use of this test-liquor, the amount of sugar may be ascertained with great 
accuracy. By another method 10 c.c. of this copper solution are heated with 40 c.c. 
of water, and placed in a sugar solution till all the oxide of copper is reduced. When 
this point is nearly reached, the precipitate becomes redder, and forms more rapidly. 
Testing the filtrate with ferrocyanide of potassium will throw down a yellow pre¬ 
cipitate if there be sugar in excess. The copper salts are instantaneously reduced 
by the sugar in corresponding quantities; long boiling is not necessary. 100 parts 
dextrose or levulose correspond to 95 parts cane sugar. 

Ferment Test. The third method, the ferment test as it is generally termed, is 
grounded on the fact that a solution of sugar may be preserved for an indefinite 
period in an open or close vessel; but that if decomposing azotized matter be acci¬ 
dentally or intentionally added, the sugar is converted first into dextrose or levulose, 
which suffering vinous fermentation is converted into alcohol with the evolution 
of carbonic acid. 

1 mol. of cane sugar, ) yields by j 4 mols. of carbonic acid = 176, 

CHO = 342, ) fermentation { 4 mols. of alcohol = 188. 

The estimation of the quantity of carbonic acid is easily performed by means of 
the alkalimetric apparatus of Fresenius and Will. The fermentation being com¬ 
plete, the air is sucked out of the apparatus, and the amount of carbonic acid 
estimated from its loss, which 

Multiplied by $ = 1*9432, gives the quantity of cane sugar. 

,, ' S s g ° = 2*04545, gives the quantity of dextrose. 

physical Method. The raw sugar containing dextrose or dextrine rotates the -plane 
of polarised light to the right hand in proportion to the quantity present. A 
sugar solution of 100 c.c. containing 15 grms. of sugar turns the ray of polarised 
light of 200 millimetres length, 20° to the right. Proportionally a solution of 
100 c.c. containing 30 grms. of sugar, turns the ray 40°. The forms of polarimeters 
are very various, and this method of estimation has received attention from many 
eminent physicists. 

i>re f^ r mtheBeet! 8ar The preparation of sugar from the beet consists in the following 
operations:— 

1. Washing and cleansing the beet. 

2. Obtaining the juice from the root. 

a. The root is ground to a pulp and subjected to hydraulic pressure. 

/ 3 . The juice is extracted from the pulp by means of a centrifugal machine. 

y. According to Schiitzenbach, after the maceration juice is separated from, the 
pulp by water. 

S. The root is cut into thin shoes and placed in a vessel (diffusion apparatus'! with 
water at a certain temperature. 


SUGAR. 


37' 


3 . Refining the juice with lime, and removing the lime with carbonic acid. 

4. Filtering the juice through charcoal. 

5. Boiling the refined juice for crystallisation. 

6. The manufacture of raw and refined sugar. 

a. Raw or moist sugar. 

£. Refined or loaf sugar. 

1. Washing and Cleansing the Beet. —The beet when newly dug requires washing 
and cleansing, which takes 10 and sometimes 20 per cent, from the weight of the 
root. Champonnois’s washing machine, is, perhaps, the most successful; it 
consists of revolving drums of open iron- or wood-work placed in a trough supplied 
with water, the drums making from 8 to 40 revolutions in a minute. The beets 
cleansed from all impurities, washed, are cut and submitted to elutriation on a sieve. 
From 1000 to 1200 cwts. beets can be prepared per day of twenty-hour hours with 
2-horse power; the length of the washing drum being from 3*1 to 4 metres with a 
diameter of 1 metre, the drum making from 30 to 40 revolutions per minute. 

2. Separating the Juice from the Root .—There are two methods of effecting this; 
the first by grinding the root to a pulp, and then removing the juice by :— 

a. Pressing. 

/ 3 . Centrifugal force. 

y. Maceration. 

The sugar in the beet-root is contained in the cells, which are easily opened, but 
require a moderate pressure to extract the juice containing the sugar. A hand¬ 
grinding machine is sometimes found sufficient for this purpose, but Thierry’s 
crushing machine, shown in the following illustration, Fig. 211, is generally used. 
The grinding cylinder, Fig. 212, is 0*5 to o'6 metre in length, and o*8 to ro metre 

Fig. 211. 



m diameter, the periphery being set with 250 saw-blades, t (Fig. 211) is a funnel 
to admit water; i the trough into which the roots are placed; m the cistern to 
receive the pulp. The motive power gears with a and s ; and the motion of the 
axis of a is by means of the pinion, h, communicated to the eccentric, d, and friction 
roller, e, thence by the arm, g, and connecting-rod, h, to the plunger,/, which presses 


\ 




























372 


CHEMICAL TECHNOLOGY. 


the roots against the edges of the saw-blades concealed by the case, u, the pressure 
being regulated by the weight, k. The cylinder revolves 1000 to 1200 times a 
minute, reducing from 800 to 1000 cwts. of beets to pulp in twenty-four hours. 

The water from t is necessary, that 
the pulp may be ground to a finer 
consistence. 

a. The juice is obtained by 
pressing the pulp by means of a 
stone or iron roller through a series 
of linen cloths. But in the French 
manufactories the hydraulic or 
Bramah press is most generally 
adopted. The pulp is placed in 
sacks or bags between iron plates, 
and subjected to a pressure of 500 
to 600 lbs. Tne expressed juice flows from the bed-plate into a pipe, which conducts 
it to a receptacle. 100 cwts. of beet, with a pressed residue of 18 per cent., yield 
82 per cent, good juice. 

The Residue. According to the researches of M. Wolff, the residue of the crushers 
used at Hohenheim contains— 

When the beets are pressed with:— 

20 per cent. 14 per cent. Without 
Fresh Roots. Water. Water. Water. 


Water . 81-56 68*oi 67-92 65-94 

Ash. 0-89 5-47 574 5 ' 28 

Cellulose. 1-33 6-25 6-04 6-68 

Sugar . n-88 7'86 7 ‘ 5 8 6-72 

Protein substances.. 0-87 1-05 1.67 11-02 

Other nutritious „.. 3-47 11*36 10-05 14-31 

100 parts of beet leave 23*2 parts residue and 76-8 parts juice of the following compo¬ 
sition :— 

Residue. Juice. 

Water. 15-61 65-95 

Ash . 1-27 (?) 

Cellulose . 1 "47 — 

Sugar . .. .. 1-72 10-17 


Carbon hydrate. 2-84 0*63 

Protein substances . 0-28 0-58 

23-20 76-80 

( 3 . The juice is now generally obtained from the pulp by means of the centrifugal 
machine to the extent of 50 to 60 per cent., water being applied to the residue to 
obtain a thin pulp also used in sugar manufacture. A centrifugal machine 1 metre 
in diameter will express 100 cwts. per day. The power to which the first juice is due 
is 5-1 atmospheres, 60 per cent, juice being expressed. The remainder of the juice, 
after the addition of water to the contents of the machine, is expressed at a pressure 
of i-8 atmospheres, the quantity of water amounting to 50 to 60 per cent, of the 
quantity of beets. Of the roots 50 per cent, remain, 20 per cent, in the residue, 
and 30 per cent, in the clarifying vessel. 

y. Treating the beet-pulp according to Sehiitzenbach’s method of immersion and 
maceration in order to obtain the juice. The roots are cleaned and then cut in 
slices by a cutting machine. They are then passed to a drying chamber heated to 
50°, and subsequently ground to a meal. Four parts of this meal are allowed to 


212 

















SUGAR. 


373 


macerate in g parts water, to which, sometimes sulphuric acid is added. Another 
method is to moisten the dried beet-meal with milk of lime, and afterwards continue 
the operation in a bath of water heated to 8o°. These methods are largely used in 
Germany, where in general practice it is found that 475 cwts. of green roots yield 
1 cwt. of dry beet-meal. The juice is afterwards treated with lime-water for the 
purposes of purification. 

8 . Before any juice can be obtained it is necessary to open the cells in which it is 
confined. This, as it has been seen, may be effected by pressure or by maceration in 
water, by which the cells are broken and to which they yield their sugar. The 
action with each cell is very similar to that of the dialyser used in dialysis; the 
sugar becomes gradually diffused in the water, the insoluble substances remaining 
with the cell. By this means a very pure sugar solution may be obtained and 
afterwards concentrated. The diffusion residues are always very watery, containing 
93 per cent, water and 7 per cent, dry substances. 

components of the juice. The juice after being expressed from the pulp, if allowed to 
remain exposed to the action of the air, throws down a dark flaky precipitate. 
The more free acids the juice contains the lighter will be the colour of the 
precipitate, and the juice will appear of a brown-red. The juice is not only 
a solution of sugar, but contains the soluble constituents of the beet, in 
which nitrogenous and mineral substances are very prominent. Sugar under 
fermentation forms lactic acid and other products; but is is separated from all im¬ 
purities and refined into crystals. The usual method of refining is to boil the 
juice rapidly in copper refining-vessels constructed with double bottoms. The 
rapid boiling separates the coagulated juice, whilst the free acid is neutralised 
by the introduction of dilute milk of lime. The lime also serves to separate 
the nitrogenous substances of the juice, and enters into a combination with a 
small portion of the sugar, forming sugar-lime or calcium saccharate. Lime, too, 
throws down from their salts protoxide of iron and magnesia, while potash and 
soda are set free. The quantity of lime added depends upon the condition of the 
root. As a rule, to 100 pounds of juice, 1 to 2 pounds of lime are added, or to 2 cwts. 
of roots 1 pound of lime. The insoluble combinations of lime are separated from 
the juice as a slime by filtering in a filtering press. 

3. De-Liming, or Saturating the Juice with Carbonic Acid .—The clear juice is by no 
means a pure sugar solution, but contains besides free sugar, sugar-lime, free potash, 
and soda, sometimes ammonia, and a small quantity of nitrogenous organic substances, 
decomposed by the free alkalies, ammoniabeing largely developed by their evaporation. 
The juice also contains various organic acids (as aspartic acid) and alkaline salts (as 
sulphate and nitrate of potash). The decomposition of the sugar-lime effects the 
removal of the extraneous substances from the juice. The physical method of puri¬ 
fying the juice is by filtering it through animal charcoal, while the chemical method 
is effected by means of carbonic acid. The use of carbonic acid was first recom¬ 
mended by Barruel, of Paris, in 1811, and later by Kuhlmann, Schatten, and 
Michaelis. The latter obtained the gas from the action of sulphuric acid upon 
chalk, or better upon magnesite; the former employed the gas resulting from the 
combustion of charcoal or coke. Lately, Ozouf has prepared carbonic acid gas by 
heating bicarbonate of soda. In the German manufactories the decomposition of the 
sugar-lime is effected in a Kleeberger’s pan, Fig. 213. This apparatus consists of a 
cast-iron cistern, b, to contain the juice. The carbonic acid, having been washed in 


374 


CHEMICAL TECHNOLOGY. 


pure water, is admitted by the pipe, m, winch, dips nearly to the bottom of the 
vessel, B, and is divided internally by a partition for the better dissemination of the 
gas. The unabsorbed gas collects in b over the juice, whence it passes through the 
opening, p, into the upper chamber, A= When the juice sinks through p into B, the 
gas there collected passes through A into n, and is thence re-conducted to the 
reservoir. When the juice is sufficiently cleared, the carbonic acid cock, o, is turned 
off, and the juice allowed to flow into a reservoir through q, where the carbonate 
of lime settles. The clear juice is then fit for crystallisation. The man-hole, e, is 


Fig. 213. 



provided for the cleansing of the apparatus from separated carbonate of lime. The 
juice to be de-limed is supplied to the cistern, B, by means of the pipe, s, and the 
gutter, t. 

other Methods of r>e-Liming Instead of employing carbonic acid or animal charcoal, the lime 
the Juice. - 0 f the sugar-lime, may be removed by the addition of a substance 
or an acid which forms with it an insoluble body, but does not affect the sugar. Oxalic 
acid is suitable for this purpose, oxalate of lime being insoluble in the sugar solution, 
but the acid is very expensive, and, besides, the precipitate is too fine, passing through the 
filter. Phosphoric acid is used for the purpose, phosphate of lime separating into flakes 
which can be easily removed by filtering through a thin layer of charcoal. Any free 
phosphoric acid is converted into phosphate of ammonia, neutralising the alkali, while the 
excess of ammonia is volatilised on the application of heat to the juice. Oleic, stearic, and 
hydrated silicic acids, and casein, similarly throw down precipitates. Acar uses pectic acid, 
which forms with the lime an insoluble pectate. Morgenstern has found sulphate of mag¬ 
nesia prepared from the Stassfurt kieserite successful in removing part of the impurities as 
well as a portion of the colouring matter. Frickenhaus tried hydrofluoric acid. In 1811 
Proust recommended sulphite of lime; and in 1829 Dubrunfaut took out a patent for the 
employment of sulphurous acid. Melsens, of Brussels, in 1849, employed hyposulphurous 
acid, which at ioo° separates the lime and most of the protein substances, and disguises 
for a time the colouring matter, the colour, however, returning on exposure to air, and 
remaining permanent. 

rurifying with Baryta. About fifteen years ago Dubrunfaut and De Massy patented a 
method of purifying the juice by means of caustic baryta, which forms with cane sugar 
at the boiling-point the insoluble saccharate, C I2 H 22 0 rr .Ba 0 ; in practice sufficient caustic 
baryta is added to throw down all the sugar. The sugar-baryta is thus separated 
from the supernatant fluid in which all the foreign substances remain suspended ; and is 
next treated with carbonic acid to form carbonate of baryta and set the sugar free. The 
solution is then filtered and some gypsum added, which gives rise to the double decom¬ 
position of the carbonate of baryta into sulphate, and of the gypsum into carbonate of 
lime. 

4. The Filtration of the Juice through Animal Charcoal , and the Evaporation of 
the Juice .—The various apparatus hero play the most important part. 






































SUGAR. 


375 


The Filter Besides acting as a filter, charcoal possesses the property of removing 
the colour from the liquid allowed to percolate through it. "Wood charcoal was 
first used for the purposes of sugar-refining in 1798, but lately has given place to 
the employment of animal charcoal (bone charcoal), which, according to Schatten, 
has a tendency to remove the lime and salts in the juice. At first it was used in 
powder, but now it is employed in the form of lumps. The old method consisted 
in boiling the powdered charcoal with the juice, blood being afterwards added, as 
in the usual methods of sugar-refining. 

Fig. 214 exhibits a section of Taylor’s filter, which has been in use since 1825. 
The juice is admitted to the upper cistern, A, by means of the pipe, 0, and gra¬ 
dually percolates through the long linen bags suspended from the bottom of A in 
13 , and containing charcoal, a layer of charcoal being also placed in A. The mouth 


Fig. 214. 




of each bag is kept open by a funnel-piece shown at P. The filtered juice is received 
into the lower cistern, whence it passes by the pipe, a, into the reservoir. 

Dumont’s Filter. Pajot des Charmes employed animal charcoal in 1822, but Dumont 
was perhaps the first to make its use successful by means of a filter still bearing 
his name, shown in vertical section in Fig. 215, and in plan in Fig. 216. The juice 
is supplied to the filter, A, from the cistern, D, the supply being regulated by the 
ball-cock, d e. The pieces of charcoal in A rest upon the sieve, b bf the percolating 
juice being received into the cistern, and removed by tho tap, 0. c is a man-hole 
for the cleansing of the apparatus. 

Evaporation pans. The pans generally in use for evaporating the juice to crystallisa¬ 
tion are made sufficiently strong to withstand high steam and atmospheric pressure. 
The processes of evaporation are :— 

I. Under the usual air-pressure : 

a. In pans suspended over an open fire; 
h. With high steam pressure ; 
e. By hot air. 



1 








































376 


CHEMICAL TECHNOLOGY. 


II. By diminished air-pressure or vacuum pans, tlie vacuum being produced: 

a. By the air-pump ; 

b. On the principle of the Torricelli vacuum ; 

c. By means of steam and condensation; 

d. By combining the methods a and b. 

Tho pans are constructed to prevent the boiling over of the juice. One of the 
ill effects of an open fire is the danger of over-heating, or burning as it is called. 


Fig. 215. 



which deteriorates the quality of the sugar solution in various ways, forming 
caramel. Fig. 217 is a vertical section, and Fig. 218 the plan of an open pan 
arrangement. D is the evaporating pan, A the fire-place, c the ash-pit, E and a 
the flue. The fuel is placed on the sloping grid, b, through the furnace-door, a. 

Fig. 216. 



The fire-room is arched, the flame and hot gases passing through the openings, e e, 
into contact with the evaporating pan; 11 admit air to the fire-place. The use of 
a suspended pan, as shown in Fig. 219, is preferable for many reasons. When the 
juice is sufficiently concentrated, the workman has only to pull the rope, m, to 
empty the pan. 

The Pecquer evaporating-pan is heated by steam, the pipes, Figs. 220 and 221, 
being placed horizontally under the pan. The steam enters by a into b, passes 
through the pipes, and is conveyed away by d and e. The heating by steam. 



































SUGAR. 


377 

besides the advantage of cleanliness, is more equable and easily managed. When 
the juice is sufficiently heated, the pan, by means of the lever, m, is tilted up, and 
the juice run off by opening g. 

The evaporation by hot air is best exemplified in the pans of Brame-Chevallier 
and Peclet. That of the latter is shown in Fig. 222. The evaporating-pan, A, is 



directly over the fire, the products of the combustion passing by the pipes, B, to the 
chimney, g. The steam from the evaporating-pan passes away through e. By 
means of the axis, a, and sieves, c d , set in motion by steam-power gearing with b> 
the juice is thoroughly exposed to the blast of hot air generated in c, and passes by 

Fig. 220. 



the hot pipes, B, into the pan, A. By this constant stirring the juice is prevented 
from adhering to the pans, and becoming burnt. 

vacuum Pans. An improved evaporation apparatus was invented by Howard, in 
1812, in which the juice was placed in chambers of rarified air, or “vacuum pans. 








































































































CHEMICAL TECHNOLOGY. 




perature the juice loses its power of crystallisation, and forms caramel. The vacuum 
may be considered as two distinct apparatus i. The boiling-pan; 2. The appa¬ 
ratus for exhausting the air and condensing the steam from the juice. 


37b 

The lowest boiling-point of the clear juice in the vacuum pans is 46-1° C.; the 
usual temperature at which the sugar is boiled 65*5° to 71*1° C.; at a higher tem- 

Fig. 222. 


Fig. 223. 



































































































































SUGAR. 


379 


In France, Derosne’s apparatus is extensively used; but that which we shall 
describe meets with general approval in Germany, and has the advantages of being 
simpler in construction and less costly to work. Fig. 223 is a perspective view, 
and Fig. 224 a section of this form of evaporating pan. The boiling-pan, B, con¬ 
sists of two air-tight hemispheres, surmounted by a funnel connected by the tube, 
I, with the condenser, A. The apparatus is supplied with steam by r s, the steam 
circulating in the boiling-pan by means of the pipes, g, Fig. 224. By opening the 
lever valves, /, the juice can be run by means of the pipe, 0, into the pan, p. 
When the pan, after continued boiling, requires to be re-filled, the pipes l and w 
iire connected to an air-pump. The manometer, h, shows the state of the air-pres¬ 
sure, which can be regulated by opening the pipes connected to the vacuum- 


Fig. 224. 



chamber. By means of the gauge-cylinder, G, the quantity of syrup in the boiling- 
pan can be ascertained, the gauge-cylinder being connected to the boiling-pan by 
the pipes a and ?, and the height read off from the gauge-tube, n. The syrup can 
be removed, for the purpose of ascertaining its consistency, from the gauge-cylinder 
by means of either of the three pipes, bed. By u steam can be admitted to the boil¬ 
ing-pan and condenser, e is generally of stout glass, through which the state of 
the juice can be observed, g is the grease-cock, butter or Sostman’s paraffin being 
generally used to prevent the adhesion of the scum to the working parts of the pan, 
the taps, &c., / is the man-hole. The condenser consists of the jacket, B, arranged 
to prevent the mixing of the juice with the water used for condensation, x is the 
gauge. Tho pipe m , conveying water to the condenser, terminates in a rose. 2 is a 
thermometer, showing the interior temperature of the boiling-pan. 

The air-pump being set in operation, the tube c is opened, and the gauge-cylinder 
filled by the juice rising from q. By closing m and opening z the juice is admitted 
to the boiling-pan. When this is half full the steam-pipe, s, is opened, the steam 
quickly heating the contents of the pan to the boiling-point. The condenser is then 






























380 


CHEMICAL TECHNOLOGY. 


placed in working; by opening the pipe, l, the steam of the juice passes into the 
condenser, where it is speedily condensed, passing with the water through ft . 
Trappe’s arrangement is sometimes found useful in working the Torricelli vacuum. 
The condenser is io*6 to 11 metres above the pan; from it reaches a pipe to a water 
reservoir beneath, the height of the water in this pipe indicating the degree of rare¬ 
faction in the pan. 

Evaporating the Notwithstanding the first purifying, many substances still remain 
in the juice, the carbonic acid treatment not completely removing the lime, free 
potassa or soda, ammonia, and nitrogenous organic substances. According to 
Leplay and Cuisinier, 1000 hectolitres of juice yield 300 kilos, of sulphate of am¬ 
monia. Among the former decomposition products are also found nitrate and sul¬ 
phate of potassa, chloride of sodium, &c., besides levulose, and humus substances, 
which impart a brown colour to the juice. The clear juice is, therefore, again 
evaporated to density of 24 0 to 25 0 B., and afterwards filtered through animal char¬ 
coal. During this second evaporation the ammonia is got rid of, as well as the 
organic substances, while the filtration removes the alkaline salts and the lime, and 
also lightens the colour. 

5. Boiling the Evaporated and Filtered Juice to Crystallisation. —After the second 
filtering and evaporation the juice is technically termed “ thin juice,” and is con¬ 
centrated to “thick juice ” by boiling to the point of crystallisation. As a rule, 
the juice speedily begins to seethe and rise in the usual manner of boiling fluids ; 
but if the throbs in this “dry boiling,” as it is termed, sound heavy or dull, 
“ fat ” as it is called, it indicates that some quantity of free alkali still is contained 
in the juice, and a remedy is found in the cautious addition of sulphuric acid. The 
estimation of the specific gravity of the boiled juice is not practically available as a 
means of ascertaining the degree of concentration. This is best arrived at by 
noting the boiling-point of the juice, which varies for pure juice from 112 0 to 120°; 
but generally an empirical test is employed, a small quantity of the juice being 
removed from the pan on a stick of wood, and rubbed between the fingers, a little 
practice soon enabling the workman to estimate pretty accurately the consistence 
of the syrup. In some cases the juice is removed in a ladle, and the consistency 
judged from the tenacity with which the juice clings to the side of the ladle when 
sharply blown with the breath. The juice when sufficiently concentrated is re¬ 
moved to the cooler to crystallise. 

6. Preparation of Moist or Raw Sugar , and of Loaf Sugar. —When the juice has 
been brought to such a degree of concentration that it crystallises on cooling, the 
final processes commence. The crystallisation proceeds gradually, the crystals form¬ 
ing more quickly the purer the juice. The further the purification has been carried, 
the easier is the separation of the sugar into molasses, and loaf or crystallised 
sugar. The loaf sugar is again warmed in a pan and allowed to crystallise in a 
form to which the general name of sugar-loaf is given, variously distinguished 
according to their size into— 

Loaf form, containing 30 to 34 pounds sugar. 

Coarse lump form ,, 60 to 70 ,, 

Inferior form ,, 120 to 150 ,, 

The forms are generally made of clay, Fig. 225, encircled by a band of wood to 
preserve the shape. Sometimes the forms are of polished plate iron; papier machS 
has been used with tolerable success for this purpose. By the old method of boil- 


SUGAR. 


38i 

ing the sugar in an open pan, the crystals formed unequally in the mould, and had 
to be removed in several ways. The vacuum pan, however, does away with this 
process, the sugar crystallising evenly in very large quantities. To heighten the 
whiteness of the loaf sugar, the manufacturer sometimes adds ultramarine in 
quantities of 2\ pounds to 1000 cwts. sugar. 

After standing twenty-four hours the sugar is sufficiently set 
to be removed from the mould. In working on the large scale, 
the moulds are generally arranged as shown in Fig. 226, the 
overflowing syrup falling into m, whence it is conveyed by 0. 

This syrup is known in the trade as green treacle or golden 
syrup. 

Draining the Crystals. It is very necessary that all sugars before being 
moulded should be thoroughly drained from all non-crystallised juice, 
which would, if allowed to remain, injuriously affect the colour, 
firmness, and dryness of the sugar loaf. The method of effecting 
this drying is by first passing a small quantity of water through the 
sugar; the water combines with a small portion of the sugar to 
form a very pure syrup, which supplants the molasses or non- 
crystallised juice in the interstices of the loaf. Practically this 
filtering takes place in linen cloths, or the form is filled with a layer of pure juice to a 
thickness of 2 to 3 inches, water being added till a syrup of the consistency of honey 
is obtained, when the crystallised sugar is forced in, and the form set aside to drain. 
Lately, a suction apparatus, the invention of M. KranschUtz, has been employed. This 
apparatus consists of the usual series of 
forms, to the bottom of each of which is 
attached a tube proceeding to a vacuum 
chamber, serving also as a reservoir for the 
extracted molasses. The vacuum chamber 
is attached to an air-pump in the ordinary 
manner. 

The Centrifugal Drier. The labour and uncer¬ 
tainty attending the above methods of drying 
have given rise to the invention of a ma¬ 
chine by which the non-crystallised juice 
may be extracted before the sugar is moulded. 

Schi'itzenbach’s machine for this purpose merely consists of a cistern, the bottom of 
which is formed by fine metal sieves, admitting the percolation of the juice, the 
damp sugar crystals being removed from the cistern and placed in forms. But the most 
effective Is the centrifugal drier, shown in Fig. 227, the invention of M. Fesca, con¬ 
sisting of an open drum, a , pf fine meshed wire-work, caused to revolve in the cast- 
iron case, b b , by means of the bevel-wheels, c d , gearing with a motive power, the 
drum making 1000 to 1500 revolutions per minute. The motion of the drum can be 
stopped by means of the break, e, and regulated by the weights placed at 0. The sugar 
containing non-crystallised juice is poured into the drum, which being set in revolution, 
the molasses is, by centrifugal force, driven through the sieve, the dry sugar remaining 
in masses of 60 to 100 pounds weight. The action of the machine is aided by the cone, g. 
By means of this apparatus, a hundredweight of sugar can be dried in ten to fifteen 
minutes. 

Removing the Sugar from When all the syrup has been removed, the bottom of the loaf in 
the Form." the form becomes quite dry and hard; the loaf is now loosened in 

the mould by means of a long knife, so that when the mould is inverted, the sugar-lorn 
may standby itself on the “ unloading block,” as the bench is termed where this operatior 
takes place. * From the unloading block the loaf is removed to the drying room, where, 
first at a temperature of 25 0 and finally at 50°, it is dried. The loaf is now ready for the 
market or warehouse. When the pure juice is evaporated to the crystallising point, the 
small granular crystals formed upon cooling are commercially known as the first product; 
the syrup removed still contains a quantity of crystallisable sugar, and is further evaporated, 
the result being known as the second product, and of course considered inferior to the first. 
In the same way a third and a fourth product, known as after-products, may be obtained. 
On an average 100 kilos, of beet-root yield 


Fig. 226. 



Fig. 225. 











382 


CHEMICAL TECHNOLOGY. 


First product at 97 per cent. 5 ‘8o kilos. 

Second „ 92 „ 2 ‘ 2 5 „ 

Third „ 87 „ o-8o „ 


8-85 kilos. 

Fourth product, molasses, &c. 3'^5 » 


Total. 12-50 

And again, the sugars of each refining is distinguished according to its quality, viz., as 
refined sugar, lump or boiled sugar, crystallised sugar, raw or moist sugar, and molasses. 

Beet Molasses. The molasses so largely formed during the manufacture of beet-root 
sugar contains most of the foreign substances—caramel, salts, aspartic acid 
common to the cane-sugar molasses. Beet molasses is used extensively for sweeten¬ 
ing purposes, for the preparation of a coarse spirit, and in many parts of France 
and Germany as fodder for cattle. The quality depends on the mode of preparing 
the beet. 100 parts of molasses contain :— 


Sugar . 

5 0 * 1 49 ’° 

48*0 

507 

Non-saccharine matter . . 

33'3 35*8 

34 *o 

30*8 

Water. 

i6'6 15*2 

18*0 

18*5 


IOO'O 100*0 

100*0 

100*0 

Fig. 227. 

Sugar Candy. 

The large, 

hard cr; 


formed during the various stages of 
sugar manufacture, are known as sugar- 
candy. The commercial article is gene¬ 
rally obtained from cane sugar, the 
crystals of beet-root sugar being too long 
and flat. The amount of sugar-candy 
made from beet sugar does not exceed 
20 per cent, of the entire production. The 
sugar selected for candy is mixed with 
3 to 4 per cent, of animal charcoal, 
then cleared with white of egg, and 
filtered. It is next boiled in a copper 
or an enamelled iron pan over an open 
fire; whence it is conveyed to a crystal¬ 
lising vessel, the sides of which are 
perforated with a series of holes, in eight or 
ten concentric rings, the distance between 
each hole laterally being less than that 
between each ring-. Through these holes 
the candy crystallises, the size of the 
holes being adjusted to the consistency of 
the boiled sugar by means of a paste 
made of fine clay, ashes, and ox-blood. 
The temperature of the drying room 
is maintained at 75 0 for six days, when it 
is reduced to 45 0 or 50°, and in 8 to 10 
days the crystallisation is complete. During the crystallisation the candy must not be moved 
or shaken, or the air allowed to affect it. Upon the completion of the crystallisation, the 
candy is found covered with a mixture of syrup and small crystals; these are removed by 
filling the crystallising vessel with weak lime-water. The rinsing water must be lukewarm, 
as cold water cracks the crystals, and hot water makes them, as it is technically termed, 
blind. The crystallising vessel, when emptied of the rinsing water, is soaked to remove 
all saccharine matter, and if this be not effected with hot water, a smooth stone is used to 
knock away the adhering crystals. After standing a day to dry, the sugar candy is ready 
for the market. It is commercially known as of three kinds:—the finest, refined white, 
nas a large colourless crystal; yellow candy, a straw-coloured crystal; and brown candy 
is similar in colour to ordinary moist sugar. In some parts of France a dark candy 
is manufactured under the name of Sucre de Boer have. Inferior cane sugar is employed 








































































SUGAR. 


383 

for tlie brown, boiled sugar for the yellow, and refined sugar for the white candy. Sugar- 
candy is extensively used, the white principally in preparing “ Liqueur,” a solution of 
candy in wine or cognac, also in champagne manufacture, and in all cases where a clear 
sweetening solution is required in large quantities. The yellow candy is used for sweetening 
tea and coffee in restaurants, and enters largely into the recipes of the pharmaceutist for 
affections of the throat and chest, as well as for making syrups intended as vehicles for 
nauseous medicines. 

The total annual production of beet-root sugar amounted in 1870 to 16,000,000 cwts., of 
which 6,000,000 cwts. are due to Trance. 

Grape Sugar. 

Grape sugar. Grape sugar, potato sugar, starch sugar, glucose, or dextrose, is a 
sugar crystallisable with difficulty, occurring iu a non-crystallised state as levulose 
or chylariose (yvXapiov, syrup) in many sweet fruits, in the vegetable kingdom, and 
it forms the solid crystalline portion of honey. It may be obtained by any of the 
following processes:— 

a. By the conversion of starch, dextrine, cane sugar, or some gums by means 
of dilute acids or diastase. 

h. By treating cellulose and similar vegetable matters with dilute acids. 

c. By decomposing organic substances, such as amygdalin, salicin, phloridzin, 
populin, quercitrin, gallo-tannic acid, &c., that by treatment with dilute 
acids or synaptase (emulsin) are separated into grape sugar and other 
substances. 

Grape sugar is found in the various fruits in the following quantities:— 



Per cent. 

Peach 

.i'57 

Apricot. 


Plum . 


Raspberry. 


Blackberry. 

.4'44 

Strawberry. 

.. 573 

Bilberry . 

.578 

Currant . 


Plum . 


Gooseberry. 

.7 -I 5 

Cranberry.. 


Pear . 


Apple. 

.8‘3 7 (Fresenius). 

» . 


Sour cherry. 

.877 

Mulberry . 

.9*i9 

Sweet cherry 

.1079 

Grape .. : 

.H’93 


Grape sugar, C 6 H I2 06 ,H 2 0 , crystallises from its aqueous solution in granular, 
hemispherical, warty masses. It is less easily soluble in water than cane sugar, 
and requires of its own weight of cold water, while in boiling water it is 
soluble in all proportions, forming a syrup possessing but poor sweetening qualities. 
There are required 2% times more grape sugar than cane sugar to sweeten the same 
volume of water. At 120° grape sugar loses its water, and has the formula CgH I2 06 . 
At 140 3 it is converted into caramel. Heated with caustic alkalies melassic acid is 
formed, together with humus-like substances. Treated with sulphuric acid, grape 
sugar forms sulpho-saccharic acid, and with common salt a soluble compound of 
sweetish saline taste. With caustic potash in excess a grape sugar solution, when 
heated to the boiling-point, reduces the hydrate of oxide of copper to suboxide, 
oxide of silver to metallic silver, and chloride of gold to metallic gold. A mixture of 




















384 


CHEMICAL TECHNOLOGY. 


ferridcyanide of potassium and potash 'with the aid of heat decomposes grape sugar, 
and discharges the original yellow colour of the fluid. Under the influence of a 
ferment grape sugar suffers many changes, the product varying with the ferment 
and method of treatment employed. Beer yeast decomposes grape sugar into alcohol 
and carbonic acid. 

100 kilos, of grape sugar give :— 

Alcohol . . . . 51*11 

Carbonic acid . . 48*89 

There are also found under certain conditions of temperature and concentration 
the homologues of alcohol, viz., propylic alcohol, butylic alcohol, and amylic alcohol, 
and under all conditions glycerine and small quantities of succinic and lactic acids. 
When fermentation is effected in the presence of alkaline reagents, lactic acid is formed 
without any disengagement of gas. Ordinarily the formation of lactic acid is merely 
a stage in the process of conversion, the lactic acid decomposing into butyric and 
acetic acids with development of hydrogen. Under certain conditions mannite 
may be prepared from grape sugar; several other gum-like substances may also be 
obtained. If to a grape sugar solution a small quantity of caseine and of carbonate 
of lime be added, and the mixture submitted to a temperature of 90°, butyrate of 
lime will be thrown down after fermentation, carbonic and hydrogen gases being 
continuously evolved. 

Preparation of Grape sugar. Grape sugar may be prepared from :— 

a. Grapes. 

b. Starch. 

c. Wood and similar vegetable substances. 

When grape sugar is prepared from the grape, the juice of the white grape is 
preferred, and set aside to clear. The cleared must is heated to the boiling-point with 
pieces of marble, chalk (not with burnt lime), or witherite (carbonate of baryta) to 
neutralise a portion of the tartaric acid. It is then allowed to stand for twenty-four 
hours, and during this time the insoluble salts of lime are deposited. The must is 
now cleared with ox blood in the proportion of 2 to 3 litres of blood to 100 litres of 
must, and next evaporated to 26° B. After remaining a short time in a tub to clear, 
the impurities are removed, and the must again evaporated—this time to 34 0 B. 
By these means a syrup is produced, from which the grape sugar can be imme¬ 
diately obtained. The syrup is concentrated by boiling and run into crystallising 
vessels, where after three to four weeks the sugar crystallises out; it is separated 
from the non-crystallised chylariose in a centrifugal machine. For experimental 
purposes the crystals may be separated by placing the concentrated syrup on a 


heated porcelain or glass plate. 

1000 parts by weight of grapes give:— 

Must.800 

Syrup.200 

Baw grape sugar . . 140 

Pure grape sugar . . 60—70 


The preparation of grape sugar from starch is an important branch of the sugar- 
boiler’s art. Dilute sulphuric acid and the fecula of potato starch are the active 
agents. The principal processes are the following 
a. The boiling of the starch-meal with dilute sulphuric acid is effected on a small 
scale in leaden pans, but in an extensive preparation iron pans are employed. The 




SUGAR. 


385 

requisite quantity of water is first heated to the boiling-point, and to this is added 
the sulphuric acid diluted with 3 parts by weight of water. The starch is also 
previously brought by the addition of water to a milky consistency. The liquids so 
prepared are mixed, and the boiling continued until all the starch is converted into 
sugar. An intermediate stage, not usually noticed by the manufacturer, is the 
conversion of the starch into dextrine, which in its turn suffers conversion into 
grape sugar. The entire conversion of the dextrine into grape sugar cannot be 
ascertained with certainty by the iodine test, as sometimes a purple-red tint is 
produced, while in others there is no change. The most reliable test is that with 
alcohol, founded on the known insolubility of dextrine in an alcoholic menstruum. To 
1 part of the solution to be tested there are added 6 parts of absolute alcohol; if no 
precipitate is thrown down there is no dextrine remaining, and the conversion has 
been entire. The proportions of the materials are generally to 100 kilos, of starch 
meal—2 kilos, of ordinary sulphuric acid of 6o° B. and 300 to 400 litres of water. 

The conversion of the starch into grape sugar is hastened by the addition of a 
small quantity of nitric acid. 

b. The separation of the sulphuric acid from the sugar solution is a most important 
operation, for the colour, purity, and flavour all depend upon success in this stage 
of the process. The acid is neutralised by baryta or by lime, with either of which 
it forms an insoluble salt, deposited at the bottom of the neutralisation vessels, and 
leaving a clear supernatant syrup. The baryta can be employed as carbonate 
(witherite), and is without doubt the better neutralising agent, sulphate of baryta 
being very insoluble. Lime, although ordinarily used, forms with the sulphuric acid 
a sulphate (gypsum) that is not perfectly insoluble in water. * It can be employed 
either as marble, chalk, or caustic lime. The neutralisation is completed in the 
boiling-pan while the sugar solution is still hot. Tor every kilo, of sulphuric acid 
(technical atomic weight = 100 to 106) so much pulverised marble (chemical atomic 
weight = 100) is required as the varying strength of the acid may demand. After 
the addition of the marble powder, and when the effervescence has subsided, the 
liquid must be tested with litmus paper, or, better, with tincture of litmus; if 
the sugar solution be neutralised when at 26° B. density, the following evaporation 
will concentrate even the smallest quantity of sulphuric acid which may have 
remained, and render another neutralisation necessary. To ensure perfect neutral¬ 
isation it is useful to add an excess of carbonate of baryta in the proportion of 250 
to 500 grins, to every 10 kilos of sulphuric acid. 

c. Evaporating and Purifying the Sugar Solution. —This part of the process is ac¬ 
complished first in a copper pan over a slow fire, or better, by heating with steam. 
The impurities separate and are absorbed in the scum, which is removed by means 
of ladles. The evaporation is continued until the syrup marks 15 0 to 16 0 B., when it 
is passed through a filter, generally of animal charcoal. It is then removed to a 
large reservoir, and, if a granular sugar be desired, evaporated to 40° to 41 0 B., in flat 
pans, from which it is taken to be placed in the crystallising vessels. These vessels 
are provided at the bottom with twelve to twenty-four holes, into which wooden plugs 
are fitted, by removing which, when the sugar has crystallised, the molasses are 
removed. The crystals are dried, sifted, and either pressed into sugar-loaf forms 
or packed in casks. The crystallisation is effected in eight to ten days. 

The manufacture of grape sugar from wood and similar vegetable substances is 
26 


CHEMICAL TECHNOLOGY . 


336 

only of value iu relation to the production of spirits, and recently as a by-process 
of the manufacture of paper from wood. 

composition of starch sugar. The composition of starch sugar as it occurs in commerce is 
very varied. During inferior seasons the marketable starch sugar may contain 50 
per cent, sugar, 32*5 per cent, foreign substances, and 17*5 per cent, water. 
Gr. Schwaendler found by the analysis of various samples of last year’s (1870) sugar 
the following percentages:— 


1. 2. 3. 4. 5- 

Grape sugar.67*5 64*0 67.2 75*8 62*2 

Dextrine. 9*0 17*4 9*1 9*0 8*8 

Water . 19-5 11*5 20*0 13-1 24*6 

Foreign substances . . 4*0 7*1 37 2*1 4*4 


IOO'O 100*0 ioo*o 100*0 100*0 

Uses of Grape Sugar. The sugar prepared from starch, in addition to the sugar yielded 
really by the grape, is largely employed in wine-making and in the brewing of beer. In 
the latter case the grape sugar is prepared by means of diastase ; that its use is extensive 
may be gathered from the fact that to 3 cwts. of malt 1 cwt. of potato sugar is 
employed. It is also employed instead of honey in confectionery, for colouring liquors 
and vinegars brown, in rum and cognac, beer and wines. In the latter cases it is known 
as sucre couleur , being then a grape sugar that has been re-melted, sometimes with the 
additibn of carbonate of soda or caustic soda to deepen the colour. 

■ Fermentation. 

Fermentation. Fermentation is a term applied to the peculiar changes of complex 
organic substances of the amylaceous and saccharine type under the influence of 
certain putrescible nitrogenous substances or ferments. The decomposition of 
fermentable organic bodies by a ferment effects the separation of their constituents 
into two or more combinations, as when by a yeast-ferment dextrose and levulose 
are converted into alcohol, its homologues, and carbonic and succinic acids; or the 
molecules of the original substances are re-grouped, as in the conversion of sugar of 
milk into lactic acid during lactic acid fermentation; finally, the elements of the 
organic substance may enter into combination with the oxygen of the atmosphere 
either to form new organic combinations, or to separate into its inorganic constituents 
carbonic acid, carburetted hydrogen, &c. This latter decomposition is termed 
mouldeirng when a residue rich in carbon (humus) remains, but when only the 
mineral constituents remain, decay is said to have been reached. These terms are 
thus defined more by custom or usage than by direct etymology—dictionaries hardly 
distinguish between them, but the difference is known to all. If large quantities of 
water be present both these processes are resolved into putrefaction , in which chiefly 
gases carbonic—acid, ammoniacal, sulphuretted hydrogen—and water are disengaged. 
But fermentation always results in the remaining or the formation of other organic 
compounds, and the variety of fermentation set up mostly depends on the state of 
decomposition of the azotised matter employed as a ferment. The most important 
ferment is undoubtedly yeast, but the ferment may be either an organic substance 
(yeast) or a protein body in a putrescent state—it is always a nitrogenised body. In 
a technological work the varieties of fermentation may be classed as— 

1. Yinous or alcoholic fermentation, including the changes observed during 
the processes of wine-making, beer-brewing, and the production of alco¬ 
holic liquors or spirits. 





FERMENT A TION. 


387 

2. Lactic acid fermentation, taking place during the souring of milk; and at a 

higher temperature changing to 

3. Butyric acid fermentation. 

To these fermentations may be added— 

4. Putrescence, noticeable only in technological chemistry as a stage to be 

most carefully avoided. 

vinous Fermentation. Vinous or alcoholic fermentation is the result of the decomposi¬ 
tion of saccharine matter, dextrose or glucose, levulose or chylariose, and lactose 
into several products, principally alcohol and carbonic acid. According to the 
recent researches of Lermer and Yon Liebig (1870) dextrine in the presence of 
sugar is converted into equal parts of alcohol and carbonic acid. This will be seen 
from the following table, which gives the result for 100 parts by weight:— 


Alcohol. Carbonic Acid. 


Crystallised dextrose, C 6 H I4 0 7 , 
Anhydrous dextrose, CgH^Oe, 
Cane-sugar, Ci 2 H 22 0 u, 

Starch-meal, C 6 H io 0 5 , 

1 mol. dextrose, CeH I2 06 =: 180, gives j 


46-40 -f 44*40 = 90*86. 
51*10 48*90= IOO’OO. 

53‘8o -f 51*46 = 105*26. 
56-78 + 54*32 == iii-io. 
2 mols. alcohol, 2C 2 HeO 
2 mols. carbonic acid, 2C0 2 


= 92 
= 88 


180 

Becently Pasteur has shown that lactic acid does not result from alcoholic fermen¬ 
tation, but that succinic acid is a constant product of this fermentation in quantities 
never less than o*6 to 0*7 per cent, of the weight of the sugar employed. Glycerine 
is another constant production to the extent of 3 per cent, of the sugar; this 
substance occurs in all wines. The 5 to 6 per cent, of substances remaining may 


therefore be thus divided:—• 

Succinic acid. .o*6 to 0*7 

Glycerine.3*2 to 3*6 

Carbonic acid. .*. .. o’6 to 0*7 

Cellulose, fatty substances, &c.1 *2 to 1*5 


5-6 to 6-5 

Yeast. The nature of alcoholic fermentation was first investigated by Cagniard- 
Latour, while our present knowledge is due chiefly to the researches of A. de Bary, 
J. Wiesner, Hoffman, Bail, Berkley, Pasteur, Hallier, Bechamp, Lermer. Yeast 
on being introduced into a fermentable fluid rapidly throws out fermenting arms, as 
it were, until the fluid is covered with a superficial ferment, termed in German 
the Oberhefe, while at the bottom of the vessel a viscid sediment is deposited, known 
in German as the Unterhefe. The oberhefe or superficial ferment, is employed as 
barm by the baker, for the purpose of leavening his bread ; while the unterhefe or 
sedimentary ferment is that employed in the fermentation of wines and of Bavarian 
beers; these beers differ from the general beers of England, France, and Germany, 
in not souring *by exposure to air, this quality being due to the peculiarity in the 
process of fermentation, Untergahrung, or fermenting from below, during which the 
gluten, the substance absorbing the oxygen of the air, is removed. In the distilla¬ 
tion of brandy, the yeast employed is a mixture of barm and bottom yeast, as the 






38S 


CHEMICAL TECHNO LOG Y. 


terms run m tliis country. Fresh yeast appears as a grey-yellow or red froth of 
strong odour, and with an acid reaction. Under the microscope the two kinds of 
yeast are easily distinguished. The superficial yeast or barm consists of globular or 
ellipsoidal cells of equal size, and about o*oi millimetre diameter. They float partly 
alone, partly in groups in the fluid. The walls of the cells are so transparent that 
the inner cells can be seen through the upper. In the centre of each cell appears a 
dark speck or grain, the protoplasma , sometimes consisting of more than one grain. 
The bottom yeast or sedimentary ferment also consists of cells, but these do not 
cling together so tenaciously as the cells of the barm, and are generally isolated, 
while the adhesion is merely mechanical between those that do cling together, a 
slight concussion being sufficient to effect their separation. Sometimes a large cell of 
the bottom yeast contains two, three, or even four smaller cells, the dimensions of these 
cells varying greatly, and not being nearly so constant as in the cells of the barm. 

“ I found,” says Dr. Wagner, “ from the researches of Mitscherlich, communicated 
to the Philosophical Faculty of the University of Leipsig, that the sprouting ortrans- 
planting of the cells had been actually witnessed under the microscope—that a parent 
cell had been observed to put forth little cells, which gradually grew in size. These 
observations had been made with barm or superficial yeast, and I wished to 
ascertain if the cells of the bottom yeast or sedimentary ferment were propagated in 
the same manner. For this purpose I placed a sedimentary yeast-cell, containing a 
germ, under the microscope in a bath of concentrated beer-worts. The temperature 
varied between 7 0 to io°. The cell remained unaltered for some time, but finally 
there appftred 30 to 40 small cells. These cells were either separated from the 
mother-cell by the bursting of the cell walls, or had been introduced as spawn into 
the field of the microscope in the beer-worts; which was the true case the microscope 
could not reveal, for no separated spawn were visible. An analysis of the two 
yeasts gave:— 



Barm. 

Sedimentary Yeast. 

Carbon. 

44’3 7 

4976 

Hydrogen . 


6-8o 

Nitrogen. 


Q‘i 7 

Oxygen, sulphur, and ash .. 

40*38 

34’26 


The barm contained 2*5 per cent., the sedimentary yeast 5*29 per cent, of ash. 
The amount of sulphur was 0-5 to 0'8 per cent. The ash consisted essentially of 
potash, phosphoric acid, silica, and magnesia.” 

According to the recent researches of Liebig, Pasteur, Lemaire, and others, 
alcoholic fermentation is essentially due to the formation of yeast-cells, and to the 
development of organic substances. There are two cases to be considered. Yeast, 
with its botanical names, Saccharomyces cerevisice, or Hormiscium cerevisice, a 
descendant of the fungi, Penicillium glaucum, Ascophora Mucedo , A. elegans, and 
Periconia hyalina , the spawn of which is always occurring in the atmosphere, ferments 
either with a pure sugar solution, without the existence of protein substances, or 
in the presence of albuminous substances. The latter case occurs also when 
a solution of sugar containing an albuminous body is so situated as to be partially or 
wholly open to atmospheric influence. The local ferment floating in the air in the 
shape of yeast-spawn finds in this solution a ready agent for its extension. But in the 
first case, where the sugar solution is mixed with the yeast, without the necessary 





FERMENT A TION. 


3^9 

protein substance as food or nourishment for the cells, the fermentation is after 
a time exhausted, and is not again set up. It is for a similar purpose that during 
the process of brewing the yeast cells are fed with a substance formed in the germi¬ 
nation of barley. During this germination the gluten of the seed passes over into 
diastase, of all nutriment that upon which the yeast cells flourish best. 

The nature of the yeast cell is a most interesting question. Is it more nearly allied to 
the animal or to the vegetable kingdom P The line of demarcation is not always defi¬ 
nite, yet there would appear some interesting analogies that should not be overlooked. 
“ Plants,” says Professor Williamson, “build up complex substances from simple. 
All the most complex substances that we can get are made in the organisms of 
plants. They may have been taken over by animals from plants, but they are 
formed in the main by plants. And the chief chemical activity of animals is 
precisely opposite ; they take those complex substances and break them down, 
by means of their vital functions, to the simple products which are exhaled and 
given off in the processes of animal life. Therefore, the question whether tho 
process which the yeast carries on is a synthetical process—a building up—or whether 
it is in the main an analytical process, is certainly one of the most important which 
can guide us. Prom what we know best regarding the nature of the yeast cells, the 
food which we know they take in large quantities, and upon which they thrive, 
is certainly exceedingly complex, and the products which they give off are exceed¬ 
ingly simple in comparison. Their functions are in the main (those which we know 
best at any rate) analogous to those which take place in animal organisms, and 
are most remote from those which take place in vegetable organisms.” 

Among the most remarkable deconrpositions effected with the aid of yeast cells are 
those described by Liebig in a recent paper, in which it is stated that yeast cells will 
assimilate tartaric acid, malic acid, and nitric acid; the latter it deprives of a portion 
of its oxygen, converting it to nitrous acid. 

conditions of Alcoholic or The conditions of alcoholic fermentation are the general conditions 

Vinous Fermentation. 0 f the vegetation of the yeast plant, with the distinction that by vinous 
fermentation the largest amount of alcohol is obtained. The following conditions must 
be fulfilled when alcoholic fermentation is the desideratum :— 

1. An aqueous solution of sugar , in the proportion of 1 part of sugar to 4 to 10 parts of 
water. The sugar can be employed as grape sugar, dextrose, or levulose, which is always 
capable of fermentation, or an unfermentable sugar, cane sugar, or sugar of milk, may be 
converted by means of an acid or suitable agent into fermentable sugar. However 
gradual the process may seem, cane sugar is always converted into grape sugar before fer¬ 
mentation sets in. 

2. The presence of yeast, or spawn. In the first case, 1 part of yeast to 5 parts of sugar 
is sufficient to effect a strong fermentation. If spawn only is present, there must also 
be present substances upon which the spawn may feed or develope—protein substances, 
phosphoric acid, humus, and alkalies. If no ferment exists, the only other condition 
under which fermentation is effected is by exposure to— 

3. The atmosphere , which introduces the before-mentioned ferment and furnishes life. 

4. A hnown temperature, the limits of which are 5 0 and 30° C. As a rule vinous fermen¬ 
tation is effected between 9 0 and 25 0 . The lower the temperature the longer the time 
required for the fermentation to subside, and conversely. At 30° and at higher tempera¬ 
tures, tho vinous fermentation easily goes over into butyric acid fermentation. The 
making of wines is based on a practical acquaintance with alcoholic fermentation; but 
in this case only a portion of ilie sugar of the must goes over into alcohol and carbonic 
acid. The alcohol remains, while the greater part of the carbonic acid escapes. 

In beer-brewing the substance forming alcohol is mostly starch, part of which goes over 
into unfermentable dextrine, bus the greater into easily fermentable dextrose. It is 
arranged that the beer shall hold a small portion of the dextrose unchanged until the after- 
fermentation at a lower temperature, during which much of the carbonic acid is expelled, 
the alcohol remaining in the beer. 


39° 


CHEMICAL TECHNOLOGY. 


In the brewing- of beer, only a part of the raw material or starch employed goes over 
into dextrose, and finally into alcohol and carbonic acid; but in the manufacture of 
spirituous liquors the given material—starch or sugar—is converted into the greatest 
possible quantity of alcohol in the shortest time, and afterwards separated by distillation. 
The aim of the wine maker is, of course, to produce the greatest quantity of wine; of the 
brewer, the maximum amount of beer; and of the distiller, the largest yield of spirit. 
The residue from the distillation of spirits is often employed in making concentrated food 
for animals. 

In the baking of bread and confectionery the lightening or leavening of the dough is 
effected by alcoholic fermentation, but only the carbonic acid, and not the alcohol, is 
of use. In the foregoing illustrations of the application of fermentation, it will have 
been perceived that the object is the generation of alcohol or of carbonic acid, or of both, 
according to the requirements of the case. The particulars we will consider under 
separate divisions. 


Wine-Making. 

wine. By the name of wine is generally distinguished an alcoholic fluid prepared 
without distillation by the fermentation of grape-juice. In the widest meaning 
of the term is included the result of the vinous fermentation of all natural juices. 

The vine and its cultivation. The vine, Vitis vimf era , is generally cultivated in Europe at 
a temperature of 50°, while the best and ripest drinking wines are obtained from 
grapes grown at a temperature of 51 0 to 52 0 . It requires an average temperature of 
io° to ii°, and an average summer temperature of 18 0 to 20°; but it is the summer’s 
sun that forms the sugar. A climate with severe winters and hot summers is therefore 
as favourable to the cultivation of the grape as a temperate climate. England, with a 
mean average annual temperature of 11°, is consequently very unsuited to the growth 
of the vine. The weather has the greatest influence upon the vine: during the 
growth rain is required, but during the ripening only the sun’s rays should reach the 
grape. The soil is not so much a matter of consequence if a quantity of potash be 
present; but a warm, loose soil is the best. Clay shale, clay marl, gypsum, lime, 
and chalk formations are very suitable to the vine. The uses of the grape are 
numerous in the highest degree; it serves chiefly in the preparation of must foi 
wine, the preparation of grape sugar, French brandies or cognacs, wine-vinegars, &c. 
Oil is prepared from the seeds, and the lees are burnt for their potash. 

vintage. The sugar is found at an early stage of the growth of the grape. When 
unripe the grape contains malic, citric, and tartaric acids, bitartrate of potash and 
lime, organic salts in smaller proportions, and a little colouring and extractive 
matters. Successive analyses have been made of the grape during its period of 
growth by C. Neubauer, from samples obtained from the Neroberg, near Wiesbaden 
(1868), and have given the following results:— 


July 27 th 

o'6 per cent. Sugar and 27 per cent, free acid. 

August 9th .. 

o *9 

) > 

y y 

2-9 

t » », 

„ 17th .. 

27 

yy 

yy 

2*8 


,, 28th . 

8*2 

y y 

yy 

rg 

>> >» 

September 7th 

n*9 

y • 

y y 

1*2 

>» 

„ 17th 

18*4 

yy 

y y 

°*95 

>> »* 

,, 28th 

I 7*5 

yy 

yy 

o-8 

>> »> 

October 5th .. 

16*9 

yy 

yy 

o*8 

>> »> 

„ 12th.. 

i8*6 

yy 

y y 

0-9 


,, 22nd 

I 7‘9 

y y 

yy 

0*9 

*> »> 






WINE. 


391 


It appears that the riper the grape the more sugar it contains, and it produces a 
wine richer in alcohol, so that the grapes are never gathered until perfectly ripe. The 
grapes of the white vine are of a brown-yellow when ready for gathering for wine, 
and the red and blue grape must be extremely dark before the seed will separate 
from the fleshy part of the grape sufficiently for wine-making purposes. 

The grapes are sometimes plucked, and sometimes left on the stalk. The separation 
of the grape from the stalk is effected either by hand or by the aid of a hurdle, the 
openings between the bars of which are only sufficiently wide to admit of the passage of 
the grape, or by a wooden or brass trellis-work, or finally with a large wooden fork 0’5 to 
o-6 metres in length. The stalk contains much tannic acid, and it is therefore necessary 
that all the grapes should be thoroughly separated before pressure; but in some cases 
when the grape contains too little of this acid, a few stalks are purposely allowed to 
remain. 


TheP GrapeI. ofthe After the grapes are stripped from the stalks, they are placed in a 
vat and stamped with a wooden maul or pestle to express the juice. They are 
generally allowed to remain for some time, and afterwards submitted to a second 
bruising, the maceration being for the purpose of softening the skins and fleshy part 
of the grape. The whole of the juice and grape-skins, or marc, is then put into a 
butt with perforated sides, through which the must trickles into the fermentation vat 
beneath. If a white wine is being operated upon, to prevent it becoming stringy , as 
the term runs, from an insufficient supply of tannic acid, small quantities of stalks 
are added from time to time. This addition renders the wine more easily clarified 
by the addition of white of egg or isinglass in a subsequent stage of the process. While 
the wine is in the vat, the fermentation is allowed to proceed, and the slight acidity 
generated reacts upon the colouring matter and aromatic constituents of the grape, 
these being taken up in the alcohol set free. 


The wiue-presses are of very various construction. The most general is the beam-press, 
roughly constructed with a pole 12 to 16 metres in length, and four to six oaken cross beams. 
The'se presses have considerable power, but they are tedious to work, and soon get dirty. 
The lever-press is more efficacious, and is made in many forms, the pressure being mostly 
from below. The hurdle- or sledge-press is of the rudest kind, consisting merely of 
hurdles and rough heavy stones. The best presses are the screw-presses made of wood 
or cast iron. 100 parts of grapes yield 60 to 70 parts of must. The ripest grapes yield 
the first juice in the press; the results of stronger pressure are more acid. The.result of 
the first pressure is termed the wine or the first wine; then comes the press wines; and 
finallv the after wines. The residue or marc is sometimes treated with water to obtain 
an inferior wine. 


The centrifugal Machine. In 1862 Steinbeis, of Stuttgart, with the co-operation of 
Eeihlen, endeavoured to express the juice cf the grape with the aid of the 
centrifugal machine instead of the press. They were enabled in ten minutes to 
express the juice perfectly from 100 to 120 pounds of grapes, including the time 
required to fill and empty the machine. In 1869, Ballard and Aloan obtained 
equally successful results, some of which were made comparative with those ob- 


good press;— 

Centrifugal Machine. 

Press. 

Must. 

. . . 79-141 

77*086 

Eesidue .. 

20*214 

18*601 

Less. 

. . • 0*645 

4 * 3 1 3 


100*000 

100*000 


cbemicoiConstituents Besides the stalk of the grape, there are the outside skin, the 
Jiull. the seeds, and the juice. Of the composition of all these substances, with the 
exception of the grape juice, our knowledge is very deficient. Besides cellulose, 





392 


CHEMICAL TECHNOLOGY. 


the stalks contain much tannic acid, and an acid very sour to the taste. The hull c.f 
the grape contains the colouring matter and a small quantity of tannic acid. The 
seed contains a peculiar acid, oenanthic acid, and an ether, bearing the same name, 
to which the bouquet of the wine is due. 

The Grape° f the The wine grape contains more sugar than any other kind of grape. 
The quantity of sugar—a mixture of dextrose and levulose—is seldom than 
12 per cent., while it is sometimes as much as 26 to 30 per cent. The proportion of 
acid to sugar is in good years and in a good grape, according to Fresenius, 1 : 29; 
in average years and cases, 1:16; 1 nd when the proportion is only as 1 : 10, the 
grapes are useless for the production of wine. The proportion between the acid and 
sugar in wine-must from the same kind of grape for different years is, according to 
this eminent chemist:— 

In a very inferior year, 1847, as 1 : 12 
In a better year, 1854, ,, 1 : 16 

In a good year, 1848, ,, 1 : 24 

during the fermentation of the must, bitartrate of potash is deposited, and from 
this source most of the tartar of commerce is obtained. This salt is insoluble in 
dilute alcohol; consequently as the sugar changes into alcohol it is thrown down. 
It is from the fact of containing tartaric acid, which, by combining to form an 
insoluble salt, is thus prevented exerting an unfavourable influence on the wine, that 
grapes possess so much the property in proportion to other fruits of making a good 
wine. The malic and citric acids contained in currants and gooseberries cannot be 
withdrawn in this manner : hence the addition of sugar to wines made from these 
fruits to veil the acidity; the addition, however, giving rise to the danger of a second 
fermentation, and consequent acidity. According to Al. Classen, 1 kilo, of ripe grapes 
gave (in 1868) 577 to 688 grins, of juice; and 1 litre of juice contained :— 

Water.860 to 830 grms. 

Sugar (dextrose and levulose) .. .. 150 ,, 300 ,, 

Pectin, gums, extractive matter, I 
Protein substances, organic acids, > 30 ,, 20 ,, 

and mineral matters. J 


1040 to 1150 

1000 parts of juice of ripe (Itkine, 1868) grapes contained :—■ 



1. 

2. 

3 - • 

Solid matter .. 

.. .. 164-4 

1897 

204-6 

Sugar 


162-4 

174-0 

Free acid.. 

.. .. 7-2 

6-8 

4-8 

Ash. 

.. .. 27 

3-0 

4-0 

ts of the ash were 

contained:— 




1. 

n 

3 - 

Phosphoric acid 

. 16-6 

i6’i 

14*0 

Potash 

.. . . 64*2 

66-3 

71*4 

Magnesia .. 

.... 47 

2**S 

2'C 










WINK 


393 


C. Neubauer (1868) analysed two kinds of grapes, and found—- 

Neroberger Steinberger 
(large grapes), (selected grapes). 

Sugar . 

Free acid. 

Albuminous substances 
Mineral constituents (potash, \ 
phosphoric acid, &c.).. .. \ 

Combined organic acids and | 
extractive matter .. .. ) 


Total of soluble constituents 
Water . 


i8’o6 

24-24 

0*42 

°'43 

0*22 

0-18 

0*47 

°’45 

4 ' 11 

3-92 

23-28 

29-22 

76*72 

7 ° 7 8 

IOO'OO 

IOO'OO 


TheF Grape juice. ofthe The fermentation of the grape juice is spontaneous; that is, it 
is consequent upon the exposure of the grape juice to the atmosphere, without the 
addition of yeast. The albuminous matter of the must forms, under the influence 
of the atmospheric spawn or yeast germ, the well-known fungus Penicilium glaucum , 
or yeast cells. The fermentation begins at a temperature of io° to 15 0 , and is effected 
more or less rapidly according to the temperature. Too low a temperature will 
retard the progress of fermentation, as also will the addition of sulphurous acid; 
the same effect is obtained by the addition of other sulphur compounds, as, for 
instance, the essential oil of mustard, which contains sulphocyanide of allyl. The 
must is left in open vats; bubbles of carbonic acid soon appear, scum collects upon the 
surface of the juice, and an alcoholic odour pervades the wine at this stage. About 
the seventh day the fermentation commences to decrease, and about the tenth or 
fourteenth day the fluid begins to clear, no more carbonic acid or scum appearing. 
The yeast cells formed are carefully removed from the bottom of the vessel, and the 
wine run into casks, where it undergoes a slight after-fermentation. If there be 
much sugar contained in the grape, and a small quantity of azotised matter, the 
resulting wine will be sweet; but if the proportion of sugar be small and albumen 
large, a dry wine is the result. 

Drawing^ofifand^caskmg After the principal fermentation the greater part of the sugar 
of the must is found to be separated into alcohol and carbonic acid. There is still 
likely to arise, unless the temperature be considerably decreased, a fresh fermenta¬ 
tion, known as the after-fermentation. Should this after-fermentation continue too 
long, vinegar is formed, and to prevent this, the wine, after the disappearance of the 
bubbles of carbonic acid upon the conclusion of the principal fermentation, is at 
once “ spigotted off” from the lees into casks, the object being to cut off communica¬ 
tion with the atmosphere as much as possible. The casks are nearly filled, and are 
bunged loosely, being filled completely a day or two after. Wines casked in Decem¬ 
ber will often continue fermenting till February or March. Strong wines rich in 
alcohol can be kept in cask until they have become quite clear; but weak wines 
must be soon bottled, as the oxygen of the air is liable to convert the hydrate of the 
oxide of ethyl or alcohol into trioxide of acetyl or vinegar. 

constituents of wine. Constituents that were not found in the must are characteristic of 
the wine—the chief of these is alcohol. Succinic acid and glycerine, the constant 
products with alcohol and carbonic acid of vinous fermentation, are also to be found. 
A “ dry ” wine, such as the French and Ehenish wines, is one in which all the sugar 
has been decomposed; a “ sweet” wine, on the other hand, is one in which some 
sugar has remained undecomposed either from an insufficiency of albuminous matter 









394 


CHEMICAL TECHNOLOGY. 


to nourish the yeast cells, or from the checking of the fermentation by exposure to a 
low temperature. A very sweet and thickly fluid wine is termed a ‘ ‘ liqueur.” The 
difference in colour is due to three substances—a blue colouring matter, a brown 
colouring matter, and tartaric acid. The brown colouring matter is present in all 
light or white wines, while the blue colouring matter, found in the skins of purple or 
black grapes, is in the wine a red colour, the change arising from the contact with 
the tartaric acid. Wines of the first year after growth are termed new or “ green ” 
wines. The average composition of wines, in 1000 parts, is the following:— 

Water . 

Alcohol*. 

Homologues of alcohol (propylic, butylic alcohol)* 

Ethers (acetic, cenanthic)*. 

Essential oils. 

Grape sugar (dextrose and levulose). 

Glycerine* . 

Gums . 

Pectin . 

Colouring and fatty substances. 

Protein bodies . 

Carbonic acid* . 

Tartaric and racemic acids. 

Malic acid . 

Tannic acid.. 

Acetic acid*. 

Lactic acid (?)* . 

Succinic acid* . 

Inorganic salts . J 

Those substances marked (*) are formed during the principal fermentation. 

The quantity of alcohol contained in a wine is due partly to the quantity of sugar and 
partly to the quantity of albuminous matter contained in the must. It is chiefly ethylic 
or ordinary alcohol. The specific weight of the wine gives only appi’oximately the 
alcoholic contents; a better method of estimation is by means of an alcoholometer. Of 
these instruments, Geissler’s Vaporimeter is, perhaps, one of the best, in which the 
pressure exerted by the vapour of the wine upon a column of mercury gives a measure 
of the alcohol contained. The vapour of absolute alcohol at a temperature of 78’3° 
exerts a tension equal to that exerted by aqueous vapour at ioo°. It is therefore only 
necessary to ascertain the height of the column of mercury and the temperature to 
arrive at the quantity of alcohol. The apparatus is shown in Eig. 228, and consists 
essentially of four parts, viz.—1. A brass vessel, a, half-filled with water, heated by 
means of the lamp to the boiling point. 2. A bent glass tube, b, to which a wooden scale 
is fixed. 3. A cylindrical glass vessel, o, filled with mercury and the wine to be tested. 
4. A cylinder of sheet brass, in the upper part of which a thermometer, t, is fixed. The 
glass vessel, o, is filled with mercury to the mark, a, and then completely filled with the 
liquid to be tested. The boiling-vessel is now affixed, the brass cylinder drawn over the 
mercury tube, and the thermometer inserted. Heat is applied, and the water raised to 
the boiling-point; the steam ascends into the brass cylinder, and heats the wine and 
mercury to the boiling-point of water. The wine expands, and is partly vaporised, 
forcing the mercury up the arm, b, which has been previously' graduated by experiments 
with fluids of known alcoholic contents ; the mercury of course rises the higher the more 
alcohol there is contained in the wine. The variable constituents of the wine, the 
extractive matter, &c., do not influence the result. The carbonic acid must have been 
removed previously by filtering the wine tlirough freshly-burnt lime. Equally good, if 
not better, results are, however, to be obtained by the distillation test, effected by 
distilling 10 c.c. of the wane, and adding to the distillate sufficient water to make a total 
of 10 c.c., the specific weight of the fluid giving the alcoholic contents of the wine. The 
alcoholometer most generally employed is the Ebullioscope of Tabarie, Eig. 229. With 
the barometer at 760 m.m. water boils at -j- ioo°, and alcohol at -}- 78-3° C. The nearer 
therefore the boiling-point of the fluid tested approaches 78-3°, the greater the alcoholic 
contents. The wine is poured into the vessel, c, and the cover, e h, replaced. The fluid i3 
heated by means of the lamp, l, and the steam ascends round the thermometer, t t', the 
height of the mercury of which when the fluid boils varies inversely as the alcoholic contents 
of the wines tested. The vessel, m m', is filled with cold water to hasten the condensation 


\ 


900—891 
80—70 






















WINE. 


395 


of the vapours. If the boiling point ot pure water be taken at 99*4° C., the following 
boiling-points show the quantity of alcohol contained:— 


96-4° 

C. 3 per cent, alcohol. 

91-1° 

C. 9 per cent, alcohol. 

95-3 

» 4 

99 99 

go-2 

„ 10 

99 

94-3 

>> 5 

99 99 

897 

» 11 

99 

93-5 

» 6 

99 99 

89-3 

„ 12 

99 99 

927 

»» 7 

99 99 

88-8 

» 13 

99 99 

9 1 '9 

„ 8 

99 99 

88-4 

„ 14 

99 99 


Red French wines contain 9 to 14 percentage by volume of alcohol; Burgundy, 9, 10, 
and 11 per cent.; Bordeaux, 10, 11, and 12 per cent. Other French wines contain 8 to 10 
per cent.; the wines of the Palatinate, 7 to 97 per cent.; Hungarian wines, 9 to 11 per 
cent. Champagne contains 9 to 12 per cent.; Xeres, 17 per cent.; Madeira, 17 to 237 
per cent.. Acids exist in all wines, and are generally carbonic, succinic, tartaric, malic, 
and acetic acids; these acids are found partly free, partly combined as salts; tartaric 


Fig. 228. 



acid, for instance, as cremor tartari , bitartrate of potash, and other acid tartrates. Faure 
found an essential gum, which he termed cenanthin, and which with glycerine—first 
shown by Pasteur in 1859 to be a normal constituent of wine—helps to give a certain con¬ 
sistency to the wine. Pohl found (1863) in Austrian wines 2’6 per cent, glycerine. As 
wine ages the glycerine disappears. The colouring matter of wine is of interest in the 

























































































39^ 


CHEMICAL TECHNOLOGY. 


case of red wines only, as the yellow-Lrown colour of some wines is undoubtedly due to 
oxidised extractive matter. The colouring 1 matter of red wines has received from Mulder 
and Maumene the name of cenocyan, while it is commonly termed wine-blue ; it is a blue 
substance similar to litmus, possessing the property of turning red in the presence of 
acids. It is insoluble in water, alcohol, ether, olive oil, and oil of turpentine ; but soluble 
in alcohol containing small quantities of tartaric or acetic acid. With a trace of acetic 
acid the solution is practically blue, turning red upon the addition of more acid; 
neutralised with alkalies the solution remains blue. On the evaporation of a wine to 
dryness the extractive matter remains, consisting of a mixture of non-volatile acids, the 
salts of organic and inorganic acids, with cenanthin, colouring matter, sugar, protein 
substances, and extractive matter, the nature of which is unknown. The quantity of 
extractive matter differs greatly, varying with the kind of wine and the degree of fermen¬ 
tation of the sugar. Fresenius found in Rhine wines a maximum of io - 6, and a minimum 
of 4-2 per cent, of extractives; Fischern, in the wines of the Palatinate, 107 to 1*9 per 
cent.; in Bohemian wines, 2 - 26 ; in Austrian, 2'64; in Hungarian, 2 - 62 per cent. The 
mineral constituents of wines exist in but small quantities—as an average in old 
Madeira to 0-25 per cent.; in old Rhine wines, cr 12 per cent.; and in old ports, o - 235 per 
cent. Van Gockom, Yeltmann, and Mosmann found in 1000 parts of wine :— 


Madeira.275 parts of ash. 

Teneriffe.2‘9i „ „ 

Rhine wine . 1-93 „ „ 

Port.275 „ „ 


Polil estimated the following number of parts of ash in 100 parts of wine :— 


Bohemian .. 1-97 parts. Slavonian . .. 1’91 parts. 

Croatian .. .. i - 68 „ Styrian. i - 63 „ 

Craniola .. .. rSi „ Tyrol. 1-84 „ 

Lower Austrian .. 2 - oo „ Hungarian.. .. rSo „ 


The ash contains potash, lime, magnesia, soda, sulphuric acid, and phosphoric acid. 

The “ Handworterbuch der Reinen und Angew r andten Chemie” (B. ix., Seite 676), gives 
the following analyses of wine-ash, the first four being by Crasso, and the fifth by 
Boussingault:— 



1. 

2. 

0 

J- 

4 - 

5 - 

Ash (per cent). 


0‘34 

0-41 

0-29 

o-i8 

Potash . 

•• 65*5 

63-9 

71-3 

62*0 

45 ‘o 

Soda. 

.. 0-3 

°'4 

12 

2'6 


Lime. 

.. 5-2 

3'4 

3'4 

51 

4’9 

Magnesia. 

•• 3’3 

47 

4-0 

4 *o 

9-2 

Oxide of iron. 


04 

o-i 

0-4 


Oxide of manganese 

.. 08 

07 

O'I 

0-3 

— 

Phosphoric acid 

•• I 5'4 

16-6 

141 

170 

22*1 

Sulphuric acid. 

.. 5’2 

5'5 

3-6 

4'9 

5 ' 1 

Silica. 

2‘0 

21 

1-2 

2‘2 

0’3 

Chloride of potassium .. 

i '5 

2‘I 

IO 

I ’5 


Carbonic acid. 


— 

— 


I 3 o 


IOO’O 

IOO’O 

100-0 

IOO'O 

100-0 


The bouquet of wines or their peculiar odour is due to oenanthic ether mixed with 
the alcohol. According to C. Neubauer (“ Chemie des Weines; ” Wiesbaden, 1870, Seite 97), 
this oenanthic ether is a combination of various substances, of which caprylic and caproic 
acid ethers are the most important, and is a product of the fermentation of the must. 
Duiing the fermentation of the sugar there are formed, besides ordinary alcohol, propylic 
and butylic alcohols, anil succinic acid as a constant product, while in the juice of "the 
grape there occur tartaric, malic, and racemic acids; these with acetic, propionic, and 
butyric acids, and the aldehydes of these acids, together with the oil of the seed of the 
grape (oleic and palmitic acids), cannot but greatly influence the bouquet of the wine, 
which of course will vary according to the proportion of these constituents. 

Maladies of wines. Wines are subject to various causes of deterioration, termed 
maladies, distempers, or diseases. That most commonly occurring is ropiness or 
viscidity , the cause of winch was for a long time unknown. • Francois show r ed that 
it was due to the decomposition of the glucose into azotised matter and mannite, 























WINE. 


397 


and at the same time indicated the proper remedy, the addition of tannic acid. He 
employs 15 grms. of tannin to 230 litres of wine. This is well mixed with the wine, 
which is allowed to stand for a few days. At the end of this time the tannin will 
have separated the azotised matter, and the wine may be bottled off. 

The souring of wine is due to the conversion of the alcohol into acetic acid, caused, 
according to Pasteur, by the formation of the vinegar plant or Mycoderma aceti , 
which he found in all sour wines. This disease is very common, and may result 
from too small a proportion of alcohol, too high a temperature of the cellars, or 
exposure to the atmosphere. The wine, if too far soured, is fit only for making 
vinegar; but slight cases can be remedied by an addition of sugar. The formation 
of vinegar may be somewhat delayed by impregnating the wine with sulphurous 
acid. In some cases the acetic acid may, by the addition of tartaric acid, be removed 
as acetic ether; but the acetic acid can never be neutralised with alkalies, as the 
salts formed are very easily soluble. 

The bidering of wine, or its acquirement of a bitter flavour, is due to another 
cause, the formation of a bitter substance, which developes as the wine ages, or at 
too high a temperature. Maumene suggests as a remedy the addition of slaked 
lime in the proportion of 0^25 to 0*50 grm. per litre. Littering is due also to the 
formation of brown aldehyde resin. Mould in wines appears as a white vegetable 
(fungus) film covering the surface, and arises from an insufficiency of alcohol; 
consequently weak wines are more subject to this malady. The film of mould 
should be removed and the wine used as soon as possible, for wine affected with 
this disease soon turns sour. The decaying of a wine is due to the dissipation of 
the alcohol and the decomposition of the acids of the wine; the wine obtains an 
astringent taste, and a dim, thick colour, finally turning sour. The bitartrate of 
potash is converted into carbonate of potash, affecting the colouring matter and 
tannic acid, which pass over into humus substances. At the commencement of 
this decomposition a remedy may be found in the addition of a small quantity of 
sulphuric ether. Caskiness, or the taste of the cask, due to an essential oil formed 
in casks that have long stood empty, is best removed by the addition to the wine of 
a small quantity of olive oil and agitation; the olive oil absorbs the essential oil, 
and brings it to the surface of the wine, whence the oily matter may be skimmed, or 
the wine may be filtered through freshly burnt charcoal. All casks and vessels that 
have stood long empty should be well steamed before use. 

AgeingandConscrvatioa The Pasteuring, a term which usage has substituted for 
pasteurisation, or the conservation and artificial ageing of wines, according to 
Pasteur’s method, is a great improvement in the general treatment of wines to 
ensure their keeping. It consists essentially in heating the wine to 6o° C., and for 
this purpose the apparatus designed by Eossignol is best suited. A metal cask, t, 
Pig. 230, contains at the bottom a copper vessel, c, with a trumpet-shaped cover 
extending in the open tube, c, above the top of the vessel, t. t is a thermometer. 
Water is poured into the vessel, c, until the tube, c, is three parts full. The wine 
is placed in the metal cask, T, and by means of the tap, r, and the tube, /, run ofl 
into the cask, F, when sufficiently heated. The water in the copper vessel, c, is em¬ 
ployed to prevent the direct heating by the flame of the vessel containing the wine, 
and the consequent burning of any insoluble matter settling to the bottom of the 
vessel. Pig. 231 shows in detail the manner of fastening the vessels together. A 
copper ring, a, encircles the vessel, T, and beds with the walls of this vessel into the 


CHEMICAL TECHNOLOGY. 


398 

india-rubber band, d, into which it is pressed by the tightening of the bolts, e, 
binding the ring of angle-iron and lower iron ring, b, together,. The joint is thus 
rendered water-tight. The vessel, T, is not quite filled with wine to allow for 
expansion under heat; by this means the wine is exposed to a known quantity of 
air. Wine should not be artificially aged in contact with air, as Pasteur has proved 

Pig. 230. 



that such processes deteriorate the colour and the flavour of the wine; and in 
ordinary cases, where part of the process of ageing consists in heating the wines 
for a short time in an open vessel with a full exposure to air, the wine acquires a 
peculiar boiled flavour, gout de cuit , easily recognisable by the connoisseur. By 
Pasteur’s method, however, neither the flavour nor colour of the wine is deteriorated; 
indeed, the latter is improved by the expulsion of the carbonic acid. 

Pasteur has shown that most of the diseases of wine, acetification, ropiness, 
bitterness, and decay or decomposition, are due to the growth of different fer¬ 
ments, consisting of minute vegetable cells always existing in wines, and becoming 
active and destructive under certain conditions, such as a change of temperature 
and oxidation. He recommends (“ Comptes Rendus,” May 1st, 29th; August 14th, 
1865), that these plants of fungi should be killed , as the best means of ensuring the 
keeping of the wine, and the particular modus operandi selected is essentially the 
following, differing considerably from the foregoing method. The bottles are quite 
filled, the wine touching the cork, which is inserted with such a degree of firmness 
that the wine in expanding may force the cork out a little, but not so much as 
to admit air into the bottle. The bottles are then placed in a chamber heated to 
45 0 to ioo°, where they remain for an hour or two, after which they are removed, set 
aside to cool, and the cork driven in. By this means the life or active principle of 
the fungi is destroyed, while the wine acquires an increased bouquet, is of a more 
beautiful colour, and, in fact, is to a considerable extent aged. Both new and old 
wines can be thus treated. 





















WINK 


399 


v.earm^or Ruing the Most wines are self-clearing, the ferment settling to the bottom 
of the cask, and leaving the wine clear and pure. This applies chiefly to dry wines 
which have less sugar than sweet wines. The sweet wines are generally more 
thickly fluid on account of the quantity of sugar they contain, and consequently 
more frequently need clearing. Fining, as it is sometimes called, or clearing, 
consists in adding to the muddy wine some albuminous or similar substance that will 
mix with the suspended matter and carry it to the bottom or bring it to the sur¬ 
face of the wine. The substances most generally employed are white of egg, ox- 
blood, and milk, or mixtures of these substances. Liming, or the addition of 
gypsum, is fqr the purpose of heightening the colour, chiefly of red wines; further, 
it converts the soluble potash salts of the wine into insoluble lime-salts and sulphate 
of potash. 

The Residue or Wa-te The waste of wine-making consists of the stems, husks, and seeds of 
of Wine-making, the grapes, as well as of the fermentary sediment and tartar. Both 
descriptions of waste find numerous applications. The lees left from the pressing of the 
wine contain a not unimportant quantity of must, which (i) is employed in preparing an 
inferior wine. 2. In the making of an inferior brandy. 3. In the preparation of ver¬ 
digris (see p. 58). 4. In vinegar making, and for promoting the formation of 

vinegar from saccharine or alcoholic fluids. 5. In wine-making countries the lees are 
much employed as fodder for horses, mules, and sheep. While (6) the residue of the 
after-pressing or final pressing is used as manure. 7. The grape seed yields an oil 
in quantities of 10 to 11 per cent.; or (8) tannic acid in large quantities. The oil can be 
extracted by pressure or by treatment with benzole, or with sulphide of carbon. The 
tannin obtained can be employed for the preservation of hides, &c. 9. Potash is prepared 

from the calcined lees. 10. The stalks and seeds when calcined are employed in 
the preparation of a black colouring material (vine black). 11. The ferment and stalks 
are in some wine-producing- countries, besides being employed in the preparation of tartar 
and potash, also used in the distillation of a peculiarly rich brandy, in which an oil 
is found possessing highly the flavour of cognac, and known in commerce as wine oil, 
cognac oil, huile de marc. 12. Crude tartar is found with tartrate of lime, colouring 
matter, and yeast, forming a more or les 3 thick crust on the walls of the wine cask or in 
the crust deposited in the wine, but not firmly attached to the vessel, and is the chief 
source of the pharmaceutical bitartrate of potash (C 4 H 5 K 0 6 ), and tartaric acid. 

Effervescing wines. Effervescing wines have been known for many centuries. Some of 
Rembrandt’s paintings exhibit among the accessories, a champagne glass with 
effervescing wine. And from Yirgil— 

“ Ille impiger hausit, 
fipumantem pater am —” 

it would appear that this description of wine was known to the Romans. In 1870, 
there were in Germany fifty producers of effervescing wines, with a production 
of 2| to 3 1 millions of bottles, i| millions of which were exported. In France the 
production amounts yearly to 16 to 18 millions of bottles. 

All wines are capable of being produced as effervescing wines if bottled before the 
fermentation is over. By bottling at this period the carbonic acid is retained in the 
wine, and when the bottle is opened the disengagement of this gas causes the appear¬ 
ance of effervescence. In this country the effervescing wine most generally known 
is champagne; but Hocks, Moselles, and even red wines are very admirable when 
thus treated. If the wines contain much sugar, the fermentation is arrested in the 
bottle before all the sugar is consumed, producing a sweet effervescing wine. On 
the other hand, if the sugar is all exhausted in producing the carbonic acid, 
the result is a dry effervescing wine. These wines are very agreeable to the 
palate, and may be supposed to assist the digestion of the food with which they 
are taken; but when new, they are dangerous as being likely to communicate their 
state of change to the contents of the stomach, interfering seriously with digestion, 


400 


CHEMICAL TECHNOLOGY. 


and producing what is well known as “ acidity.” Dry effervescing wines are less 
likely to disagree than sweet wines of this class containing much sugar and 
fermentable matter. The connoisseur places great reliance in his judgment of a 
champagne upon the loudness, or rather sharpness, of the report when the cork 
is drawn, and upon the “bead ” or bubble formed on the side of the glass by the car¬ 
bonic acid gas. These effects are not proportionate, for while a loud report results 
from an extended fermentation, a good bead may be obtained with a very weak fer¬ 
mentation. The gas in a bottle of champagne exerts a pressure of some five 
atmospheres, and it will at once be evident that if the bottle be made a little 
smaller, reducing the space between the cork and the wine only one-twentieth, 
a considerable increase in loudness of the report will ensue. 

The process of manufacturing effervescing wines is in general the following:—The 
best grapes are used for this purpose; for champagne, the black grape, called by the 
French noirien , is employed. The juice is expressed from the grape as soon 
after gathering as possible, in order to prevent the colouring matter of the skin 
affecting the wine; while the fruit is pressed as quickly and as lightly as possible. 
The juice from the second and third pressings is reserved for inferior, or red-tinted 
effervescing wines. The expressed juice is immediately poured into tuns or vats, 
where it is left to stand for twenty-four to thirty-six hours. In this time any earthy 
matter or vegetable impurities will have settled, and the juice is ready to be trans¬ 
ferred to the fermenting vats, where it remains for about fifteen days. It is then put 
into casks, which are securely bunged; sometimes brandy is added in the proportion 
of one bottle to one hundred bottles of juice or must. Towards the end of December, 
the wine is fined with isinglass, and a second time in the ensuing February. About 
the beginning of April the clear wine is fit for bottling. It now contains, if a good 
wine, 16 to 18 grms. of sugar, n to 12 per cent, of the volume of alcohol per bottle, 
and an equivalent to 3 to 5 grms. of sulphuric acid in free acids. 

Great care is necessary in the manufacture of champagne bottles; they must be 
free from flaws, and made of pure materials. Generally each bottle is from 850 to 
goo grms. in weight, and equal in thickness throughout. Formerly the flawed bottles 
amounted to 15 to 25 per cent., but recent improvements in manufacture h&ve reduced 
the percentage to 10. Before the wine is introduced, the bottle is rinsed with a 
liqueur of white sugar-candy 150 kilos., wine 125 litres, cognac 10 litres, the liqueur 
being allowed to remain in the bottle : according to F. Mohr the cane sugar of the 
liqueur becomes converted into grape sugar in the champagne. It is doubtful 
whether glycerine might not be advantageously substituted for a portion of the sugar 
of the liqueur. The liqueur employed varies with the flavour of the wine: port, 
Madeira, essence of muscatels, cherry water, &c., are used, but rarely unmixed with, 
some other favourite solution of the manufacturer, as, for instance, water 60 litres, 
saturated solution of alum 20 litres, tartaric acid solution 40 litres, tannin solution 
80 litres. About 2 litres of this mixture would in practice be added to a butt of 
wine. The bottles are filled by women, the proportion of liqueur introduced being 
about 15 to 16 per cent, of the wine. A space of about 2 to 3 inches is left between 
the wine and the cork, which, after being thoroughly moistened, is next inserted by a 
machine. The bottle is then passed to a man, termed in the French establishments 
the maillocher , who drives the cork home with a mallet. Another process, now gene¬ 
rally effected by the aid of a machine, is the “ wiring,” or securing the cork with 
wire or string. The bottles are now conveyed to the cellar, where they are laid in 
horizontal racks against the wall. In about eight or ten days a deposit, termed 


WINE . 


401 


“ griffe, ” is formed, and shows that the time has arrived for the wine to be transferred 
to the cellar, where it is to remain until sold to the merchant. The deposit is allowed 
to form during the summer, and in the ensuing winter means are taken for its 
removal. The bottles are well shaken, and placed with their mouths downwards, to 
cause the deposit to settle on the cork. The cork being removed, the sediment falls 
out, when more liqueur is added, and the bottle re-corked and again wired. The 
bottle is now laid upon its side at an angle of about 20°, and in about eight to ten 
days the inclination is gradually increased until the vertical position is attained, 
when, by a dexterous movement of the cork, the gas is permitted to force out the 
remaining sediment. This process is repeated as many times as may be necessary, 
until the wine is perfectly clear. Wine thus prepared, generally known as sparkling 
wine, vin mousseux , is ready for the consumer at the end of 18 to 30 months, the time 
varying with the temperature of the season. One of the greatest causes of loss is 
the bursting of the bottles, sometimes as much as 30 per cent, of the wine being 
wasted. This in some measure accounts for the dearness of these wines. 


By the analysis of several sparkling wines (1867 and 1870) the following results 
were obtained:— 



1. 

2. 

3 - 

4 - 

5 - 

6. 


Permille. Permille. 

Per mille. 

Permille. Permille. 

Per mille. 

Free acid .. 

• • 5 ’ 3 °° 

5’900 

7*600 

7*800 

6*200 

5’600 


Per cent. 

Per cent. 

Per cent. 

Per cent. 

Per cent. 

Per cent. 

Alcohol 

.. 8*400 

9*500 

8*700 

8*400 

9*800 

8*400 

Sugar. 

. . 8*200 

4*300 

7*900 

9*100 

7*500 

5*400 

Extractive matter 

.. 11*600 

7*500 

10*300 

12*000 

n*6oo 

15*200 

Specific gravity .. 

.. 1*036 

1*029 

i ’039 

1*046 

1-039 

1*041 


1. From Chalons. 3 and 4. From Wirtzburg. 2. From the same place, but intended 
for export to India ; 3 being the manufacture of J. Oppman, and 4 of Silligmuller, both 
well-known German firms. 5. From Sutaine and Co., of Rheims. 6. From a well-known 
Rhenish firm, glycerine being substituted for a portion of the sugar. 

The improving of the Tim worth or character of a wine is determined by its aroma 
and the amount of alcohol and free acid contained—decreasing with an increase of the 
latter, and increasing with increase of the former. The proportion between the 
chief constituents of the grape-juice, sugar, acid, and water, is nearly equal in all 
good wines, and this proportion is never accidental, but always belongs to a good, 
wine. The grapes not fitted for making good wines are treated in two ways: either 
the expressed juice is allowed to ferment as it is, in which case an inferior wine is 
obtained; or, by the study of chemical analyses of good wines, the incomplete con¬ 
stituents are supplied, and others injurious to the wine removed, to make the must 
of that quality which will yield a good wine. The following are the best methods 
of improving the must:— 

1. The addition of sugar to wine poor in this constituent, and the neutralisation of an 
excess of acid by means of pulverised marble (Chaptal’s method). 

2. The addition of sugar and water to must poor in sugar and rich in acid (Gall’s 
method.) 

3. Repeatedly fermenting the husks with sugar-water (Petiot’s method.) 

4. Removing the water by means of freezing, or by treatment with gypsum. 

5. Removing the acid by means of a chemical reaction. 

6. Addition of alcohol to poor wines. 

7. Treating the prepared wine with glycerine (Scheele’s method). 

The addition of sugar to must poor in this constituent is the oldest method of improve¬ 
ment, and appears to have been known to the Greeks and Romans. At that time cane 
2 1 




402 


CHEMICAL TECHNOLOGY. 


sugar was unknown, honey being used for sweetening purposes, and which, being added 
to the wine, gave it a peculiar flavour, and rendering it thick. In years when honey 
was scarce, we are informed that the wine was inferior. Chaptal, in 1800, wrote a work 
on the cultivation of the grape, in which he gives a recipe for adding sugar to an inferior 
must, to render the wine equal to that of better years, the acid being neutralized with pieces 
of marble. In Burgundys, Chaptal’s method is not much required to be used, as these 
wines rarely contain more than 6 parts per 1000 of free acid. The amount of pulverised 
marble (carbonate of lime) required to neutralise 60 parts of free acid is, as a rule, 50 
parts; and the amount of sugar to be added, when the acid is in excess, is 100 parts for 
each 50 parts of alcohol required after fermentation, it being found that 15 per cent, of 
sugai in the must produces 7*5 per cent, of alcohol in the prepared wine. Thus should it 
be desired to heighten the alcoholic contents from 7-5 to 10 per cent., to every 1000 kilos, 
of must are added 50 kilos, of sugar. 

The cause generally of the poorness of the must in sugar is a wet or cloudy season, during 
which there has been but little warmth from the sun to ripen the grapes. Most German 
vines show, besides a lack of sugar, a superabundance of acid, malic and tartaric acids; 
and while the addition of a sugar solution increases the alcoholic contents, it does not 
remove these acids, which impart a flavour to the wine and lessen its worth. The addition 
of a saccharine solution does not, as might be expected, enfeeble the bouquet of the wine, 
if pure starch sugar, containing no dextrine, be employed. The use of impure starch sugar 
causes a quantity of unfermented matter to remain in the wine, imparting to it a tendency 
to decay. Gall’s method is found to be economical, as a flavouring material can be added 
to very inferior must. According to Gall a normal must should consist of— 


Sugar 


Free acid 

o-6 „ 

Water .. 



IOO'O „ 


1000 kilos, of such a must contain, therefore 240 kilos, of sugar, 6 kilos, of free acid, and 
75*4 litres of water. If, by analysis, the must to be improved yields only i6’7 per cent, 
sugar and o - 8 per cent, acid, there are to be added— 

153 kilos, of sugar, and 
180 „ or litres of water, 

by which addition 1333 kilos, of normal must are obtained, corresponding to an increase 
in quantity of 33 per cent; while in some years, when the acid contents are as much as 
12 to 14 per cent., the increase in quantity rises to 100 to 115 per cent., but seldom more. 

Petiot based his method on the fact that, according to the usual process of preparing 
the must, the colouring and bouquet constituents remaining in the maro are sufficient to 
give the flavour and odour of wine to a lixivium of sugar-water. This method may, 
therefore, very justly be considered as yielding a wine without the aid of grape-juice. To 
the marc left after the expressure of the grape-juice cold water is added, equal in quan¬ 
tity to the must removed: in this water the marc is allowed to macerate for 2 to 3 days. 
The water takes up the various soluble constituents of the marc; after the time speci¬ 
fied the liquor is removed, and the amount of sugar and acid it contains ascertained. 
There is usually only 2 to 3 per cent, of sugar, consequently an addition of 17 to 18 per 
cent, must be made; and if there should be too little acid, tartaric acid must be added to 
approximate the acid contents of a normal must. The ai'tificial must, as it may be con¬ 
sidered, is then put into the fermenting vat, while the marc is again treated in a similar 
manner, a longer immersion being this time required. The resulting wines are darker 
in colour than wines prepared from the natural must, in consequence of a larger propor¬ 
tion of tannin. The flavouring of these wines is a matter of experience, and does not fall 
under any chemical consideration. 

Freezing is employed in the improvement of wine, for the purpose of reducing the 
aqueous contents. According to the experiments of Verg-nette-Lamotte and Boussin- 
gault, the effect of cold upon wine is of a very complicated nature. By cooling the wine 
at a temperature of o-6° there first occurs the precipitation of those substances that are 
insoluble at this temperature. These consist of cream of tartar; colouring matter, and 
nitrogenous substances, and a fluid possessing the property of becoming solid at 6°. 
When these substances are removed the wine becomes more ardent, richer in alcohol, aud 
its peculiar merit is that it is not liable to after-fermentation, and can be kept in vats and 
half-empty casks. The removal of the acid from wine is effected best by means of car¬ 
bonate of lime (pulverised marble, chalk), sugar of lime, or neutral tartrate of potash. 
An addition of carbonate of lime to the must, or to the wine, is not detrimental, in so far 
that the wine retains none, or a very small quantity, of the lime-salt. Carbonate of lime 
will not be of service in the case of so-called acid fermentation, as acetate of lime will 





BEER. 


403 


then bo formed, and the wine is no longer worthy the name. Liebig recommends the use 
of neutral tartrate of potash for this purpose, as bitartrate of potash is formed, which 
settles as an insoluble salt to the sides of the vessel or bottle. The use of this neutral¬ 
ising agent has the merit, moreover, of not injuring the flavour and odour of the wine. 
Sugar of lime can be employed in the case of wines not containing acetic acid. To pre¬ 
pare the sugar of lime, slaked lime is diluted with ten times the quantity of water, to 
form a thin cream. This cream is thinned with sufficient water £0 obtain a milk of lime, 
in which sugar-candy is dissolved. The solution is left to stand, and the clear supernatant 
liquor—a solution of sugar of lime—decanted to mix with the wjme as required. "When 
the wine is treated with the sugar of lime solution, the lime forms with the acid of the 
wine an insoluble salt, which is precipitated, while the sugar remains in the wine. 

Another addition to wine, hardly bearing upon its improvement, but effected as a means 
for its preservation during removal or exportation, is that known in France as the vinage , 
a certain quantity of brandy being mixed with the prepared wine. When the wine is to be 
exported from France, the law permits the addition of 5 litres of brandy to each hecto¬ 
litre of wine, provided the alcoholic contents after the addition do not exceed 21 per cent. 
But experiments have proved that the wine delivered to private consumers does not on the 
average contain more than 10 to 11 per cent, of alcohol, while the 'wine delivered to retail 
firms averages 16 to 17, and to wholesale firms 22 to 24 per cent. To prevent this fraudu¬ 
lent proceeding, the operation of vinage is permitted only in the Departments of the 
Pyrenees Orientales, A ude, Herault, Garde Bouches du Rhone, and Var, immediately under 
the inspection of the Commissioners appointed to this duty. In 1865, Scheele introduced 
his method of improving wine by the addition of glycerine, the addition being made after the 
first fermentation has subsided. The limits of the addition lie between I to 3 litres of 
glycerine to 1 hectolitre of wine. But the expense will not permit of extended operations. 

Beer Brewing. 

Beer. Beer is a well-known liquor obtained from germinated grain—chiefly barley 
and wheat, sometimes from rice, maize, potatoes, and starch sugar—and hops, by 
means of a yeast fermentation, but without distillation of any kind. It contains the 
constituents of the grain employed, which constituents by decomposition form 
dextrose, dextrine, and albuminous substances, alcohol, carbonic acid, small quan¬ 
tities of succinic acid and glycerine, organic matter, with phosphates of the alkalies 
and alkaline earths, besides the constituents of the hops. 

In Bavaria, the Schenk, or pot beer, is brewed in the winter, and the Lager, or store 
beer, in the summer. The winter beer is brewed during October to April, when the 
highest range of the thermometer is 12° to 13 0 . A part of the beer by a short storing is 
set aside for winter consumption, while the remainder is used during the summer months. 

1 volume of malt gives on an average 2‘5 to 2-6 volumes of winter beer. 

I „ „ „ 2-0 to 2'i „ summer beer. 

In some of the North German States, potato-sugar and syrup are much employed in brew¬ 
ing, sometimes supplying a third part of the malt. But generally 1 cwt. of the malt gives— 

300 quarts light heer. 

200 „ double beer. 

180 „ Bavarian or bock beer. 

Materials of Beer Brtwinj. The materials of beer brewing are:—1. Grain, or amylaceous 
substances. 2. Hops. 3. A ferment. 4. Water. 

The Grain .—The grain selected for this purpose is generally barley, as containing 
the proportion of sugar and starch best adapted to form alcohol. Many substitutes 
have been suggested, but with inferior success. In Bavaria, the large double barley 
(Hordeum distichon ), is preferred. According to Lermer. 100 parts of dried barley 


contain:— 

Starch .. .68 ’43 

Protein substances. 16’25 

Dextrine. 6*63 

Fat . 3’o8 

Cellulose. .. .. 7*10 

Ash and other constituents .. 3*51 






4o4 


CHEMICAL TECHNOLOGY. 


The ash of barley contains in ioo parts:— 

Potash. 17 

Phosphoric acid.30 

Silicic acid .33 

Magnesia . 7 

Lime . 3 

with other constituents. Potatoes, rice, maize, glycerine, and potato- or starch- 
sugar, are employed in some modern breweries. 

Hops. The hop (Humulus lupulus), is a disecious plant of the natural order o ’ 
Urticacese, the female flowers of which, or catkins, are used for flavouring beer. 
The catkins, or strobils, are composed of a number of bracts or scales, which are 
green, afterwards changing to a pale yellow. At the base of each flower is seated 
the pistil containing the seed, while surrounding the pistil are a number of little 
grains, embedded in a yellow powder, the farina, containing the active property of 
the hop, essentially lupuline, the grains being termed lupulinic grain. This yellow 
pulverulent substance contains an essential oil, tannic acid, and mineral con¬ 
stituents. The essential oil, the flavouring principle of the hops, is found in air- 
dried hops, to the amount of o - 8per cent.; it is yellow-coloured, with an acrid taste, 
without narcotic effect, of a sp. gr. = 0*908, turning litmus paper red. It requires 
more than 600 times its weight of water to effect a solution. It is free from Sulphur, 
and belongs to th*e group of essential oils characterised by the formula, C 5 H8, and 
can become oxidised under contact with the air into valerianic acid (C 5 H io 0 2 ), this 
oxidation being the cause of the peculiar cheesy odour of old hops; it is a mixture 
of a hydrocarbon, C 5 H8, isomeric with the oils of turpentine and rosemary, with 
an oil containing oxygen, C IO H I 80, having the property of oxidation alluded to 
Tannic acid is found in the several kinds of hops, in quantities varying from 2 to 5 
' per cent., and is an important constituent, as it precipitates the albuminous matter of 
the barley, and serves to clear the liquor. It gives with the per-salts of iron a green 
precipitate; treated with acids and synaptase, does not separate into gallic acid and 
sugar; and by dry distillation does not give any pyrogallic acid. The hop reein is 
the important constituent of the hops, and contains the bitter principle or lupuline* 
It is difficultly soluble in water, especially in pure water, and when the lupuline or 
essential oil is absent. But water containing tannic acid, gums, and sugar 
dissolves a considerable quantity of the resin, especially when the essential oil is 
present. It is intensely bitter in taste, and becomes foliated when exposed to the 
atmosphere. Hop resin and the essential oil are not identical; the former is soluble 
in ether, the latter is not. In the course of long exposure it becomes insoluble. The • 
gum and extractive colouring matter are of little use. The mineral constituents of 
hops dried at ioo 0 are :—in ash, 9 to 10 per cent.; 15 per cent, of phosphoric acid; 

17 per cent, potash, &c. 

Quality of the Hops. The quality of the beer is almost proportionate to the quality of 
the hopp. A rich soil is required for the growth of the hop-plant, well exposed to 
the influence of the sun’s rays, and protected from easterly winds, which are highly 
detrimental. The hops must on no account be gathered until the seed is perfectly 
ripe, as it is only then that the bitter quality is fully developed. The ripeness of 
the hops can be ascertained by rubbing them between the fingers ; if an oily matter 
remains, with a strong odour, they are fit for gathering. When gathered, the next 
most important operation is the drying, which is effected in kilns or stoves, at a 







BEER. 


405 


temperature of 40°, with a good ventilation. When sufficiently dried, the small stem 
attached to the flower snaps readily. The temperature must be carefully regulated; 
not permitted to range so high as to run the risk of burning the hops, nor allowed to 
fall so low that the hops may afterwards become mouldy from under-drying. Wkm 
dried the hops are carefully packed, the finer kinds being put into canvas pockets, 
and the inferior into hop-bags of a coarser texture. The bags are then subjected to 
slight pressure in a hydraulic or screw press, to render them more impervious to air. 
To preserve the hops they are sometimes sulphured, that is, subjected to the action 
of vapours of burning sulphur, 1 to 2 lbs. of sulphur being employed to 1 cwt. of 
hops. Old hops are sometimes treated in this manner, to impart the colour and 
appearance of freshly-dried hops, but the fraud can be detected by the odour. The 
best method of testing for sulphur in hops is as follows :—A sample of the hops is 
placed in a sulphuretted hydrogen apparatus, with some zinc and hydrochloric acid; 
the disengaged gas is passed through a solution of acetate of lead. If the hops 
contain sulphurous acid, sulphuretted hydrogen will be disengaged— 

(S0 2 + zH 2 = SH 2 + 2 H 2 0), 

and black sulphide of lead thrown down from the lead solution. Better still is to 
receive the disengaged gas in a solution of nitroprusside of sodium, to which a few 
drops of potash-ley have been added; the slightest trace of sulphuretted hydrogen 
imparts a beautiful purple-red colour to the solution. 

Substitutes for Hops. Other substances have been used as substitutes for hops, as the bark of 
some species of the pine, quassia, walnut leaf, wormwood, bitter clover, extract of aloes, 
&c.; recently picric acid has been employed. Although all these substances impart a bitter 
taste to beer, they are inferior to hops. They contain the same constituents, namely, 
tannic acid, a resin, a bitter extractive, and an essential oil. 

Wa-er. Water is employed for steeping the barley for the purpese of inducing ger¬ 
mination. Brewers are careful as to the usual distinction of hard and soft waters. Soft 
water contains fewer mineral constituents. Rain, like distilled water, is a very soft water, 
containing traces only of organic matter, nitrates and carbonate of ammonia. Spring and 
well water are in most cases hard waters, while river water is often soft. Soft water, or 
nearly so, is best adapted for brewing. River water is preferred for malting. According 
to Mulder, in water containing lime an insoluble phosphate is deposited, while in the 
course of time lactic acid is formed. The water employed is usually purified by filtra¬ 
tion through sand, gravel, and charcoal. 

The Ferment. The yeast of former operations is generally employed in fermenting the 
beer-worts. The preparation of the yeast, and the rationale of the process of fermenta¬ 
tion, given in a previous section of this work, should be consulted. 

T Bee^B?ewing. f The brewing of beer may be considered to consist of the following 

operations:— 

1. The malting. 

2. The mashing. 

3. The fermentation of the beer-worts. 

4. The fining, ripening, and preservation of the beer. 

The Malting. i. Malting is the process during which the grain—barley—is germi¬ 
nated, by means of steeping in water until it swells a,nd becomes soft. The non- 
germinated grain possesses only in a very small degree the property of changing its 
starch into sugar (dextrose): this property is very fully developed during the germi¬ 
nation, so much so that it would be an easy matter to distinguish between the 
germinated and non-germinated seed by the degree of this property alone. As has 
been already stated, barley is the grain preferred, on account of its forming sugar in 
larger quantities than any other kind of grain. The germination of the seed takes 
place in three well-marked periods. In the first, the seed is enveloped in an outer 


40 6 


CHEMICAL TECHNOLOGY. 


organ, which, becomes exhausted and withered. In the second, the growth of the 
germ is shown by the swelling at the end by which it was attached to the stalk ; and 
in the third period, the little plumule or acrospire , which would form the stem of the 
new plant, is put forth. The germinating seed is similar to an egg, with its white, 
yolk, and embyro ; the shell corresponds with the outer or hard coating of the seed ; 
the white and yoke of the egg appear as the albumen, or meal of the grain; while 
the embyro of the egg has its analogue in the germ of the grain. A remarkable 
change takes place during germination; the glutinous constituent has passed from 
the body of the grain to the radicula , or rootlet, which has grown to nearly the length 
of the grain, while about one-half of the starch has been converted into sugar. 
This conversion is the aim of the malting, as by its means the sugar can be readily 
dissolved. The grain is supposed to have been sufficiently treated when the plumida, 
or acrospire, has attained a length equal to two-thirds of the entire length of the 
grain. The operation of germination is the same with all kinds of grain employed 
in brewing. The conditions of success are—the saturation of the grain with mois¬ 
ture, and a temperature of not higher than 40° nor lower than 4 0 , with access of air 
and exclusion of light. 

a. The softening or soaking of the grain is accomplished in large cisterns of wood, 
sandstone, or cement, half-filled with water. The grain is poured into the water, 
and after the lapse of an hour or so, sinks to the bottom of the tank, only the infe¬ 
rior and diseased'Seed remaining on the surface, to be removed with wooden shovels, 
and thrown aside for use as fodder for horses, cattle, &c. The steep water receives 
the soluble constituents of the husk of the seed, and becomes of a brown colour and 
peculiar flavour, with a decided inclination to lactic, butyric, and succinic acid fer¬ 
mentation. The duration of the softening varies according to the age of the grain ? 
the temperature of the water, &c. A young fresh grain requires 48 to 72 hours’ 
soaking, while an older grain, containing more gluten, is not thoroughly softened 
under 6 to 7 days. Grains of equal age and constitution must be soaked together, to 
obtain an equally softened product. After sufficient soaking the grain is allowed to 
drain for 8 to 10 hours, then taken out and thrown into heaps on the floor of the malt- 
house. The sufficiency of the soaking is ascertained—1. By pressing the grain 
between the finger and thumb-nail, when, if sufficiently moistened, the germ or 
embyro will be projected. 2. The husk is easily destroyed by pressure between the 
fingers. 3. When crushed with a piece of wood the grain yields a floury mass. 
The grain when softened has a peculiar aroma, resembling that of apples. The 
quantity of water usually absorbed by the barley amounts to 40 to 50 per cent, of its 
weight, while the grain correspondingly increases in volume 18 to 24 per cent. 
During this absorption the grain loses 1 *04 to 2 per cent, of its own weight in solid 
matter. Lermer states, that in fresh steep water he has found succinic acid in the 
proportion of 30 grms. to 1 bushel of grain soaked. 

b. The Germination of the Softened Grain .—As soon as the grain is thoroughly 
saturated with moisture, the conversion of the starch into sugar commences. When 
germination has proceeded far enough it must be stopped, as about this time the 
formation of sugar has reached a maximum. The softened barley is, as before 
stated, transferred to the floor of the malting-room, where it is “ couched,” or placed 
in a layer 4 to 5 inches in thickness. Here the germination proceeds till the plumules 
have attained the desired length. The temperature rises some 6° to io°, on account of 
the heat developed during germination, and consequently much of the moisture is 


BEER. 


407 


dissipated. The chief art of the maltster consists in stopping the germination at 
that point when the plumules and roots commence to draw upon the constituents of 
the grain. The duration of the germination varies, during the warmer months of 
the year, from 7 to 10 days, while towards autumn the process will not be completed 
under 10 to 16 days, but the average duration is 8 days. The grain during the ger¬ 
mination loses about 2 per cent, of its weight, probably by the oxidation of the 
carbon to carbonic acid by the oxygen of the air. 

c. The Drying of the Germinated Grain .—The grain is now removed to the drying 
floor ( ivelkboden ), where it is exposed to the air in layers 3 to 5 centims. in depth, and 
turned about with rakes 6 to 7 times daily. When the malt becomes dry it is 
cleared from the rootlets, some of which drop off by themselves, while others have 
to be removed by winnowing. Malt must be dried for the making of most kinds of 
beer, and has to undergo a roasting process before quite fitted for use. This drying 
or roasting is effected in a malt kiln or cylinder heated by flues to the boiling-point 
of water. During the roasting the malt acquires a darker colour, due to the con¬ 
version of the remainder of the starch into sugar. The equality of the temperature 
is of the utmost importance, so that one part of the malt may not be more strongly 
heated than another. Before the malt is submitted to this operation, however, it is 
first heated to 30° or 40°. By this means some of the starch is converted into gluten, 
and forms a coating to the grain impervious to water, the malt being in this stage 
known as “ bright malt from its,smooth glossy appearance. • 

The malt kilns consist essentially of the drying plates upon which the malt is 
laid, and the heating flues. The plates used to be of stone or sheet-iron, but 
modern brewers employ wire-wove frames, placed one above the other, so that the 
hot air from the flues beneath may ascend through the interstices. The flues are 
generally of sheet-iron for the better conduction of heat to the surrounding 
atmosphere. Coke is used as fuel on account of the absence of smoke; as with coal 
or wood in the event of a leakage in the flues considerable damage would be done 
to the malt. 

The malt is not all dried at the same degree (50° to ioo° C.), but is distinguished 
as pale, amber, brown, or black malt, according to the degree of heat to which it has 
been exposed. Pale malt results from heating to 33 0 to 38°; amber, from a tempera¬ 
ture of 49 0 to 52 0 ; and brown from the rather high temperature of 65*5° to 76‘5°. 
Black malt, commonly called patent malt, is prepared by roasting in cylinders, like 
coffee cylinders, at a temperature of 163° to 220°. These darker malts are used in 
England for colouring porters and stouts. 

100 parts of barley give 92 parts of air-dried malt. The loss of 8 parts may be 
thus accounted for:— 


In the steep-water . 1*5 

During malting.3*0 

During germination.3^0 

Other losses.o’5 

Total loss . 8*c 


The moisture in air-dried malt amounts,to 12 to 15*2 per cent., which is expelled 
during the kiln drying. According to C. John (1869) 100 parts of dried barley 
give- 







408 


CHEMICA L TECHNOLOGY. 




I. 

II. 


Malt .. 


. . . 83*09 

85-88 


Plumules 

. 

• • • 3*56 

3-09 

* 

Radicules (rootlets) . 

• • • 4’99 

4*65 


Permentary products 

.. 8-36 

6-38 




100'00 

100-00 


The change undergone during the drying or roasting of 

the malt 

is shown in the 

following table, the result of Oudeman’s 

analyses:— 




Air-dried Malt. Kiln-dried Malt. Strongly dried Malt. 

Products of roasting 

0*0 

7*8 


14-0 

Dextrine. 

8*o 

6*6 


10*2 

Starch . 

58*1 

58*6 


47-6 

Sugar . 

o *5 

07 


0-9 

Cellulose. 

14-4 

io-8 


ii *5 

Albuminous matter 

iy 6 

10*4 


10-5 

Fat. 

2*2 

2*4 


2*6 

Ash. 

y 2 

27 


2-7 


The amount of sugar is undoubtedly increased during the process; and the 
dextrine appears to increase with decrease of starch, and vice versa . The conversion 
of starch into dextrine and sugar is effected, as far as is known, by the agency of 
diastase. Dubrunfaut has only lately (1868) shown that malt presents another 
substance similar in its effect to diastase, and which he termed maltin. This principle 
is found to be much more active than diastase, so that with the same quantity 
of maltin which a known quantity of malt contains, ten times as much beer can be 
obtained as when diastase only is employed. Dubrunfaut has also found a second 
but less active substance. Its behaviour with respect to the decomposition of starch 
is similar to that of diastase; malt contains i^- per cent., while only 1 per cent, of 
maltin is found. The treatment with alcohol necessary to obtain diastase destroys 
the maltin. Dubrunfaut believes diastase to be only a less active modification of 
these new substances. 

Preparation of the 2 . Under this head is included the preparation from malt of the 
wort—a saccharine fluid containing dextrine— and the flavouring with hops. The 
general method of preparation is in three operations :— 

a. The bruising of the malt. 

b. The mashing. 


c. The boiling and flavouring of the wort with hops. 

Tllc Bri Mau" of the a ' Deer-wort, or the wort, as it is generally termed, is obtained 
by means of the extraction of the bruised malt with water. To the end that all the 
active principles may be extracted from the malt, it must be bruised or ground to a 
fine meal. The obtaining of a clear liquor after the extraction is effected by 
means of filtration. The grinding is ordinarily performed in a malt mill, a machine 
with rollers being preferred as affording a more equable product. 

Mashing. b. The mashing is a most important operation, on success in which 
depends many of the good qualities of the beer. It is during this operation that 
not only the sugar and dextrine already existing in the malt are set free, but 
also the unconverted starch, by the aid of diastase, the water, and a favourable 








BEER. 


409 


temperature, suffer conversion into sugar and dextrine. Lermer found in the best 
cases of mashing that only half the starch was converted into a corresponding 
quantity of sugar. The operation is very variously performed, but generally may be 
considered as effected by either of two methods:— 


a. The Infusion Method, according to which the mash is prepared at a certain degree 

of heat, but never attains the boiling-point. The crushed malt is thrown into hot 
water (first cast) in the mash tun, and when the mash has reached a certain 
saccharine condition, a further addition of water is made (second and third cast). 
The infusion method is much employed in North Germany, France, England, 
Austria, and Bavaria. 

b. The Decoction Method .—After the infusion has been made the mash is baought to the 

boiling-point, and 

a. A portion of the water evaporated to form a thick mass {thick mash 
boiling). At a subsequent stage, only a portion of the mash having been 
thus treated, the remainder of the mash is added, and 
/ 3 . The whole of the mash is heated to the boiling-point {clear mash boiling). 
During the clear mash boiling the hops are added. 


The fnashing vessels are either round tubs or wooden cisterns with a double 
bottom, the upper being perforated, and about an inch above the true bottom. Between 
the bottoms is a tap through which the wort is drawn off. In large breweries these 
bottoms are of metal instead of wood. The hot water is supplied from the bottom 
and not from the top of the vessel. Under the mashing vessel is situated a large 
reservoir, either of stone, cement, wood, or masonry, and destined to receive the 
fluid run off from the mash. The continuous stirring of the contents of the mash- 
tun or tub is effected either by hand or machinery driven by water or steam power. 

Decoction Method. The general description of the mashing process having been given, 
we now pass on to the particular method of preparing the wort by decoction. The 
infusion takes place in the mash-tun, in which the required quantity of water is 
placed, and the malt to be mashed shaken in. The quantity of water employed in 
making the infusion is generally in the proportion of 202 volumes of water to 100 
volumes of malt, both at the ordinary temperature. After the bruised malt has 
been well stirred in the water, the whole is allowed to stand for 6 to 8 hours. 
During this time the necessary quantity of water is heated to the boiling-point in 
the copper. The quantity of water used to prepare an estimated quantity of beer is 
termed the “ cast,” and the quantity of malt the “ yield.” In Bavaria the quantity 
of beer prepared from a defined quantity of malt is as follows:— 

•. « 202*3 volumes of Schenk beer. 

100 volumes of malt yield _ |>Lagerbe er. 

’In order to produce this quantity of beer an equivalent quantity of water must of 
course be employed, so that in a Bavarian brewery to 100 volumes of malt there are 


taken of water— 

For infusion 
For mashing 


Schenk beer. 
202*3 vols. 
170*0 „ ■ 


Lager beer. 
202*3 vols. 
130*0 „ 


372*3 vols. 332*3 vols. 

These proportions vary according to the quality of the grain, the state of the 
weather, the length of time of keeping, &c. 

The various modifications of the decoction method are:—1. The Bavarian or Munich 
method. 2. The Augsberg-Nuremberg’, or Swabian method, sometimes termed “ sediment 
brewing ” {satz brauen). 

Thick .Mash Boiling. According to the Munich method (thick mash boiling) the cast of water 
is divided into three portions, two of which are poured into the mash-tun to form a 





4 io 


CHEMICAL TECHNOLOGY . 


paste with the bruised malt. After this mash has stood for two to four hours, the re¬ 
maining third of the water, which during this time has been heated to the boiling-point, in 
the copper, is added, the whole of the mash attaining thereby a temperature of 30° to 40°. 
Then follows the first thick mash boiling; for this purpose the brewer draws the mashed 
grain to one side of the tun, and removes a portion to the copper, where for schenk bee v 
it is boiled for thirty minutes, and for summer beer for seventy-five minutes. The quantity 
of mash boiled at each operation is generally about half the cast. The boiling mass is 
returned to the mash tun. Then follows the second thick mash boiling, which for schenck 
beer last seventy-five minutes, and for summer beer an hour. By means of the first 
boiled mash the contents of the mash tun are raised to a temperature of 48° to 50°, and 
by the second addition to 6p° to 62°. After the finishing of the second mashing the clear 
■mashing begins, that is, the thinly fluid part of the mash is placed in the copper and boiled for 
about fifteen minutes, and is then returned to the mash tun. The temperature of the mash 
is now 72 0 to 75 0 , and is most suited for the formation of sugar. The mash remains in 
the covered tun 14 to 2 hours. During this time, and as soon as the clear mash has been 
removed from the copper, the latter is re-filled with a sufficient quantity of water for the 
purposes of brewing small beer. When the sugar has been properly formed and dis¬ 
solved in the wort the latter is removed from the mash tun to the fermenting vessels. 'The 
remaining mash is then treated with hot water to yield small beer, 1 bushel of malt yielding 
35 to 50 quarts of this beer. The residue of the small beer is again treated with water, 
the resulting infusion being employed in vinegar-making. The residue from this process 
is used as fodder for cattle. 

The thick mash boiling is by no means a rational method, as the separation of the mash 
and the several removals are unnecessary labour, and do not contribute so much to the 
complete extraction of the malt as is generally supposed; the high temperature renders 
a portion of the diastase ineffective, while much of the starch remains unconverted into 
dextrine and dextrose. 

All who have tried to reduce the brewing process to simple methods based upon sound 
chemical and physical principles declaim against the process of thick mash boiling, 
stating—and with good sound reason proved by experiments—that the advantages of 
this method are absurdly overrated; and that in order to lessen the bad effects of this 
method as much as possible it should be replaced by a method of hot mashing, viz., 
at a temperature of from 6o° to 65°. 

Augsburg Method. Distinct from the foregoing mash methods is the so-called “ sediment 
brewing” used in many Swabian and Franconian breweries. It essentially consists in 
treating the bruised malt with cold, and then with hot water to obtain a saccharine 
wort. The bruised malt is mixed with cold water in the mash tun in the proportion of 
7 Bavarian bushels to 30 to 35 eimers (each — 68'41 litres of water. After standing for 
four hours, two-thirds of the fluid is drawn off. During this time a quantity of water 
(48 eimers to 7 bushels of bruised malt) is brought to the boiling-point in the copper; a 
portion of this water is now added to the contents of the mash tun, which thus attains a 
temperature of 50° to 52 0 , while the liquor or weak wort drawn off from the mash 
tun is poured along with the rest of the water in the copper. The liquor that has 
been drawn off contains albumen, diastase, dextrine, and dextrose. The mash is allowed 
to stand for a quarter of an hour in the tun, when the fluid is entirely drawn off, 
transferred to the copper, and h:ated to the boiling-point. This is termed the “first 
mash.” While this is going on enough fluid will have drained from the malt in the mash 
tun to fill the space between the double bottoms of the tun; this fluid is at once removed 
to the cooling vessels. The fluid .heated in the copper is now returned to the mash tun, 
the entire contents of which attain a temperature of 72 0 to 75 0 . This “ second mash” is 
after an hour’s interval followed by a “third mash.” The wort is then run into the 
cooling vessels. 

infu»on Method. The infusion method is distinguished from the decoction method by 
a slight difference in the procedure, the bruised malt being treated with water at a 
temperature of 70° to 75 0 , but without any portion of the mash being boiled. The 
method is that usually employed in this country, North America, France, Belgium, 
and North Germany. 

The quantity of w r ater intended to be used for the mashing process is, according 
to the initial temperature of the water the brewer has at hand, heated either whdlly 
or only a portion in the copper, the temperature of this fluid being raised in winter 
to 75 0 , in summer to from 50° to 6o°. The necessary quantity is first poured into the 
mash tun, the bruised malt being next added, and the mixture made up so as to 


BEER. 


411 

form a moderately thin paste. Water is heated to the boiling-point in the copper in 
order to proceed further with the mashing process. As soon as a sufficient quantity 
of water boils it is —usually by means of properly constructed pipes—allowed to 
run into the mash tun, wherein it is considerably cooled owing to the colder water 
(liquor) present in that vessel; the increase of temperature of the contents of 
the tun to 75 0 (the most suitable for saccharification) is generally made in order to 
prevent the formation of starch paste, whereby the formation of diastase would be 
interfered with. Since the conversion of amylum (starch) into dextrine and dextrose 
proceeds gradually only, it is clear that the contents of the mash tun should be kept 
at the temperature suitable for that process; while, however, on the other hand, care 
has to be taken to prevent the mash becoming sour by the formation of lactic 
(probably also propionic) acid. 

The progress of the formation of dextrine and dextrose is best ascertained by the 
help of an aqueous solution of iodine, or preferably of iodine dissolved in iodide of 
potassium, in the proportion of o’i grm. of iodine and ro of iodide of potassium to 
100 c.c. of water; this solution will at first give with a sample of the mash a dark 
blue colouration, next a wine red, and finally, when only dextrine and dextrose are 
present, no colouration at all. The addition of two to three drops of the clear 
wort to a small quantity of this iodine solution is sufficient for testing. When 
the mash has been kept for about ono hour’s time at the temperature most suitable 
for the saccharification, the wort is run either into a large reservoir, or into a 
vessel kept expressly for this purpose, or lastly, at once into the copper; and a 
fresh quantity of water is then poured into the tun, and the contents of the tun 
are allowed to remain for half to one hour at a temperature of 75 0 . It is as a 
matter of course quite evident that the infusion method may be varied as regards 
the quantity of water and repeated number of infusions; but in order to brew 
a beer of a certain and fixed brand it is requisite that the degree of concentration 
of the wort be always the same. For the purpose of ascertaining the degree of 
concentration, Balling’s saccharometer is generally employed, which instrument when 
put into sugar solutions indicates the percentage of sugar they contain. Balling 
has shown that solutions of dry extract of malt have the same specific weight as 
cane sugar solutions of equal percentage. For use in a brewery the saccharometer 
need only be graduated for solutions varying between 20 to 30 per cent. 

Extractives of the wort. The quantity of extract which a wort should contain depends, 
of course, upon the quality of the beer which the brewer desires to make, and diffeis 
according to the nature of the beer, whether it shall be thick, heavy (rich in 
extract), or strong (of great alcoholic strength). The quantity of malt extract varies 
in different beers from 4 to 15 per cent., that of the alcohol from 2 to 8 per cent. 
1 per cent, of sugar in the wort yields after fermentation o’5 per cent, of alcohol. To 
produce a beer containing 5 per cent, of alcohol and 7 per cent, of malt extract, the 
wort should, before fermentation, mark the degree on the saccharometer corre¬ 
sponding to 17 per cent. A beer of 3-5 per cent, of alcohol and 5*5 per cent, of malt 
extract will have resulted from a wort containing 12*5 per cent, of sugar. 

Boiling the Wort. c. The prepared but not yet boiled wort contains dextrose, dextrine, 
some unconverted starch, protein substances, extractive matter, and organic salts. 
The colour of the wort is a brown or yellow-brown, according to the variation of 
colour of the malt from which it has been obtained. The odour is agreeable and the 
taste sweet. The wort exhibits an acid reaction to test-paper, owing to the presence 


412 


CHEMICAL TECHNOLOGY. 


in that fluid of small quantities of free phosphoric, lactic, and probably other acids; 
but in case the wort has by accident become sour, or if wort is made purposely 
from already exhausted grain which has become sour, this reaction is far stronger, 
and may be ascertained by the odour, owing to the formation of volatile acids, 
among which butyric, and in the latter case, lactic and propionic acids are present 
in large quantity. The boiling of the wort aims at its concentration, and also 
at the extraction of the bitter principle of the hops; further also for the purpose 
of coagulating and precipitating a portion of the albuminous substances, by the aid 
of the tannic acid contained in the hops. This latter reaction renders the wort 
clear. In many breweries gypsum is added to the boiling wort to reduce the whole 
of the nitrogenous substances. The boiling is generally effected in copper cauldrons 
(technically, also simply, “ the copper”), set in masonry over a fire-grate. The fire 
is very carefully disposed to prevent the burning of the wort, as the pans are 
exposed to the direct action of the flame. The manner of hopping (as it is termed), 
that is to say, the mode of adding the hops to thewort, varies in different breweries, 
and depends as regards quantity also upon the quality (strength) of the hops, the 
larger or smaller amount of extract contained or desired to be retained in the beer, 
and last, but not least, the mode of preservation and length of time it is intended to 
keep the beer. 

Adding the Hops. To winter beer, which in Germany, as a rule, is consumed in four to 
six weeks after brewing, the old hops (viz. one year old), are added in the proportion 
• of 2 to 3 pounds to a Bavarian bushel of malt (2*22 hectolitres). !For summer beer, to 
be consumed in May and June, 4 to 5 lbs. of new hops are added to the bushel of 
dried malt; while for the beer for September and October consumption, 6 to 7 pounds 
of new hops are employed with each bushel of malt. Among the constituents of 
hops which are active in the process of brewing, we mention in the first place the 
bitter ingredient it contains (not correctly known, notwithstanding recent research) 
and which as well imparts to beer its bitter taste as its narcotic property; further, the 
tannic acid which combines during the boiling of the wort with a portion of such 
of its protein compounds as are not rendered insoluble by the boiling alone, and 
form together a precipitate, rendering the wort—previously turbid—quite clear, 
and also regulating the first and second (so called after) fermentation. The essential 
oil and resin met with in hops act to a certain extent as retarding the fermentation, 
and thus as preventatives of converting the wort into a sour liquid; as regards the 
inorganic constituents of hops they do not appear—at least cannot be directly 
proved—to be of much consequence. As regards the degree of concentration to 
be given to the wort by the process of boiling, it should be observed that the degree 
of concentration as ascertainable by the saccharometer should remain from 0*5 to 1 
saccharometrical percentage under the degree of concentration which the wort 
should indicate at the beginning of the fermentation, because while cooling, the 
wort gains in concentration just the percentage alluded to. The separation of the 
coagulated albumen does not take place until the temperature of the wort has 
reached 90°; and the quantity separated is greater from wort prepared by the 
infusion method than from that prepared by the decoction method. As soon as it 
appears that in a sample of the boiling wort taken from the pan and poured into a 
large test-glass the suspended flocculent matter settles rapidly to the bottom of 
the glass, the boiling can be discontinued, the wort being then ready; but in the 
case of the infusion method, the boiling is continued for the purpose of further 


BEER. 


413 


concentrating the liquor, and the boiling for this purpose may even last for from 
5 to 8 hours. If the boiling only aims at the coagulation of the albuminous 
compounds, one hour’s boiling in winter, and three-quarters of an hour in summer, 
is quite sufficient. As regards the hops, it is best to add them in a somewhat cut 
up state, and not before, by a good boiling of the wort, the greater part of the albu¬ 
minous compounds have been, as far as possible, precipitated. In order to extract the 
hops, the wort is either passed through a basket filled with hops or through any 
suitably constructed perforated vessel retaining the hops, this vessel being placed in 
communication with the coolers; or the hops are boiled along with the wort; or 
again, several portions of the wort are boiled successively along with the samequantity 
of wort; and lastly, even with the weakest wort or after-run. 

cooling the wort. The cooling of the wort to the degree necessary for the commence¬ 
ment of the fermentation is effected in large wooden, stone, or iron cisterns. As 
at a temperature of 25 0 to 30° 0. the wort has a great tendency to set up lactic acid 
fermentation, the cooling has to be very rapid in order that the temperature of the 
liquid may be soon much below 25 0 to 30°, and thus any danger of souring 
prevented. 

The cooling of the wort is an operation which is performed in well constructed 
and in all directions well ventilated buildings, protected from rain, in which 
buildings the coolers are placed. Owing to improvements in the modes of cooling, 
it is now possible even to brew beer in localities (as for instance Montpellier and 
Marseilles, Barcelona, and Naples) where formerly, on account of the prevailing 
high temperature during the greater portion of the year, brewing could not take 
place at all; while also for the same reason *in various countries (America, 
United States especially), excellent lager beer is brewed. The cooling vessels 
are generally only 6 to 8 inches deep, of wood, iron, or copper, and are placed in 
an airy situation near or immediately under the roof of the brewery. Metallic 
vessels are of course more effectual in cooling the wort in a short time than wooden 
ones; they are also more cleanly, and less liable to get out of order. In some 
breweries, where a constant stream of cold water is available, the coolers are placed 
therein; but this is of course a matter entirely depending on tho locality of the 
brewery. Without doubt the surest means of cooling the wort rapidly is by 
employing ice, either in blocks in the wort or in pans placed in the cooling tuns. 
But for economic reasons this plan is not generally available. The temperature 
to which the wort is to be cooled is that best suited to fermentation, the next process 
to which the wort is subjected. The following are the temperatures at which fer¬ 
mentation most readily sets in, depending upon the temperature of the locality and 
upon the kind of fermentation:— 


Temperature of the locality 
where the fermentation 
takes place. 

6° to 7 0 
7 0 to 8° 

8° to 9 0 
9 0 to io° 
io° to 12° 


Temperature of the wort. 


In sedimentary 
fermentation. 


In superficial 
fermentation. 


12° 15 0 

n° 14 0 

io° 13° 

9 0 12° 

7 0 to 8° 12 0 to ii° 

The concentration of the boiled and hopped wort is expressed in degrees percent 
of the saccharometer. 




414 


CHEMICAL TECHNOLOGY. 


According to J. Grschwandler’s researches (1868), the undermentioned Bavarian 
beer worts had the following composition :— 



Decoction. 

Bock. 

Sedimentary 

Method. 

Infusion. 

Sugar . 

4-850 

7*100 

4*370 

5*260 

Dextrine . 

6-240 

8*6oo 

7-610 

6-68o 

Nitrogenous substances 

0-790 

1*350 

— ■ 

— 

Other constituents . 

0-410 

0*630 

0-950 

0*700 

Specific weight. 

1-050 

1-073 

1-052 

1-051 

Extract (direct estimation).. 

11-870 

17-050 

11-980 

11-940 

,, (according to Balling) .. 

, 12*290 

17-680 

12-930 

12*640 


While the wort remains in the cooler a yellow-grey or brown sediment is 
deposited, consisting of a compound of coagulated albumen with the tannic acid of 
the hops, and some starch similarly combined. This sediment during the first 
cooling is formed in quantities varying between 3 to 4 per cent, of the quantity of 
the cooled wort; the sediment when washed and dried amounts to 0*5 per cent, of 
the quantity of malt employed. 

The Fermentation. III. The Fermentation of the Beer Wort. —The wort when cool is run 
into the fermenting tanks, where fermentation sets in either spontaneously, or is 
induced by the addition of yeast. The first kind—spontaneous fermentation—sets in 
as soon as the wort, having been cooled down to the temperature most suitable for 
fermentation, is left to itself, and this fermentation is induced by the sporules of 
yeast (ferment cells) always present in all fermenting localities, which meeting with 
the wort, find in that liquid the pfoper conditions suited for their growth. This kind 
of spontaneous fermentation is applied usefully in the brewing of the Belgian beers 
known as Faro and Lambick, which are rich in lactic acid. Usually, however, 
yeast is added to the wort, and there is avoided the dangerous first stage of 
spontaneous fermentation, for by the addition of the yeast a regular and rapid 
fermentation is set up, but yet so regulated that the yeast only gradually converts 
the dextrose into alcohol and carbonic acid/ 

The higher the temperature of the wort and of the locality the smaller the quantity 
of yeast required. A yeast formed by a violent fermentation and at a high tempera¬ 
ture, has more active qualities than yeast formed at a lower temperature and by a 
longer fermentation. The first spreads itself rapidly over the surface of the fluid, 
and is termed superficial yeast ( oberhefe ) ; while the second sinks to the bottom of the 
vessel, and there continues its action; this is termed— sedimentary , or bottom yeast 
(unterhefe ). The fermentations resulting from these two yeasts are respectively 
termed superficial fermentation (< oberydhruna ), and sedimentary fermentation [unter- 
gdhrung). The latter fermentation is induced in worts that are intended to yield 
beers of great durability, such as the Bavarian beers. The superficial fermentation 
is induced in such beers as are intended to be soon drunk. Where fermentation 
is induced in a wort at a low temperature and with deposit only (bottom-yeast) the 
so-called surface fermentation— that is to say, a vinous fermentation whereby yeast 

* The results of the researches made by Von Lenner and Liebig (1870), are of oreat 
importance for a rational basis of the brewer’s business. According to these savants an 
addition of sugar to a solution of dextrine, to which previously beer-veast has been added 
causes a large quantity of the dextrine to be converted into alcohol and carbonic acid just 
as if the dextrine were sugar. ’ J 







BEER. 


415 

is carried to the surface of the fermenting fluid—is employed chiefly for such 
kinds of worts as are intended to produce a beer which is not required to be 
kept for any length of time, but rapidly consumed after having been brewed. The 
wort is in this instance generally rich in sugar (glucose); and while only a portion 
of this sugar is converted into alcohol (sweet beer being formed), the formation 
of a small quantity of alcohol (the wort being only lightly hopped),, contributes 
largely to the preservation of this kind of beer. Surface fermentation is also 
induced in such kinds of worts as are either very concentrated or contain sub¬ 
stances which to some extent retard, or might even altogether impede, fermentation; 
as, for instance, the empyreumatic substances present in a very highly roasted malt 
or a large quantity of hops, these conditions obtaining in the brewing of porter, 
stout, and, as regards hops, the bitter ale. Worts of this description come com¬ 
paratively very difficultly into fermentation. Fermentation, no matter whether 
surface or sedimentary (the yeast is in this case slowly deposited as a sediment on 
the bottom of the vessel), exhibits the thrse following phases, viz. :— 

1. The chief fermentation, beginning soon after the addition of the yeast, 
characterised by the decomposition of glucose, by the formation of new yeast, and 
by an increase of temperature. 

2. The after-fermentation, during -which decomposition of glucose continues 
slowly, while the formation of new yeast cells does not ensue so energetically as 
in the first phase, the suspended particles of yeast settling down, and the beer 
becoming clear. 

3. The quiet or imperceptible fermentation taking place when the after-fermenta¬ 
tion is finished is characterised by a further decomposition of glucose, while the 
formation of yeast is not perceptible to any extent. 

sedimentary Fermentation. Sedimentary fermentation is employed in the brewing of the 
Bavarian schenk and lager beers, taking place in large fermentation vats con¬ 
taining 1000 to 2000 litres of wort. Becently, upon the suggestion of G. Sedlmayer, 
these vessels have been constructed of glass. The addition of yeast may be effected 
in two different ways : yeast may be either added to the wort, or a small portion of 
the wort is first separately brought into a state of fermentation, and next added to 
the bulk of the liquid. In the first case, dry yeasting, as it is termed, the yeast is 
placed in a small tub and wort poured over it, and these substances haying been well 
mixed, the whole of the contents of the vessel are thrown into the fermentation vats, 
and there worked about by the aid of a stirring pole. According to the second 
method, wet yeasting or yeast carrying, to 1000 maas* of wort, 6 to 8 maas of yeast 
are added and well mixed with about 3 eimers of wort, the mixture being allowed 
to stand for four to five hours. After fermentation has set in, the fermenting liquid 
is mixed with the wort in the fermentation tank. The yeast intended to be used 
for this purpose should be obtained from a former and normal fermentation; it should 
not be too old, and should possess a pure odour (not be foul), thick consistency, and 
be frothy. 

After the wort has been mixed with the yeast the following phenomena are exhibited:— 
After ten to twelve hours the decomposition of the dextrose becomes apparent by the 
evolution of bubbles of carbonic acid gas, which forms a wreath of white froth at the 
edge of the vessel. In another twelve hours larger quantities of a more consistent froth 
are formed, causing the surface of the liquid to exhibit a very peculiar appearance, which 


* The Bavarian maas is equivalent to 1*25 English quarts. 



416 


CHEMICAL TECHNOLOGY 


mi ght, be compared to that of irregular masses of broken up rocks; at the same time a 
more vivid evolution of carbonic acid takes place and becomes perceptible by the smell. 
The G-erman term for this phase of the fermentation, Las Bier Steht im itrdusen , can 
hardly be expressed in English, but the meaning is the fermentation is in full force; these 
phenomena to continue with a regularly proceeding fermentation in full activity for from 
•two to four days, and then gradually subside, there remaining on the surface of the liquid 
a somewhat brown-coloured film of froth, much contracted, and chiefly consisting of the 
resinous and oily constituents of hops. 

The yeast formed is only to a very small extent present on the surface of the liquid, 
as in the case of sedimentary fermentation the carbonic acid evolved cannot carry the 
isolated yeast cells to the surface. The temperature of the fermenting liquid increases 
at the beginning of the fermentation, so that the liquid becomes several degrees 
warmer than the air of the locality where the fermenting vats are placed. By the 
fermentation the wort loses the greater portion of its dextrose, about half of which is 
evolved in the shape of carbonic acid, while the remainder is converted into alcohol ; 
further, a portion of the albuminous substances dissolved in the wort is rendered 
insoluble and deposited in the shape of yeast. On being tested with the saccharometer 
the liquid—for reasons just explained—exhibits after fermentation a less degree of 
strength than before. The difference in percentage shown by the saccharometer before 
and after fermentation is in direct proportion to the quantity of dextrose decomposed, 
and provides a means of ascertaining the course of the progress of the fermentation. 
If this difference be made the numerator of a fraction, the denominator of which is the 
percentage indicated by the saccharometer before fermentation, the value of the fraction 
will increase proportionately with the completeness or efficacy of the fermentation; if, 
for instance, a wort before fermentation marks a saccharometrical percentage of 11*5, 
and afterwards gives 5 per cent.; the difference 6*5 divided by 11*5 gives the coefficient 
0*565, that is, of 100 parts of malt extract 56^5 per cent, are decomposed during fermentation. 

Afte infheCasks Uon After the chief fermentation is completed, which for summer or lager 
beer requires nine to ten days, and for winter or schenk beer seven to eight days, the 
young or green beer is put into barrels, after having become quite clear by the sepa¬ 
ration of the yeast. Before the beer is vatted the scum present on its surface is 
removed. The yeast, settling to the bottom of' the vat in which the fermentation took 
place consists of three layers, the middle being the best yeast; the lowest, decomposed 
yeast and foreign matter, is mixed with the yeast of the upper layer, and if not other¬ 
wise saleable is sometimes employed in the distilleries of malt spirits. The middle 
layer serves for further fermenting operations. In breweries where pure water (the 
reader should bear in mind that Bavaria is alluded to) is not to be had, this yeast is 
occasionally obtained fresh from other breweries. It is usual to fill casks or vats 
with winter beer at once quite full; but as regards summer beer several brewings 
are mixed in smaller vats in order to obtain an uniformly coloured mixture. The 
barrels are usually coated with pitch on the inside, the aim being to prevent the beer 
soaking into the wood, and thus giving rise when the cask is emptied to the forma¬ 
tion of acetic acid. For the after-fermentation the beer is placed in stone cellars, 
which should be as cold as possible, so as to cause the after-fermentation to proceed 
as slowly as possible, and thus admit of the .beer being kept until the brewing season 
opens. 

In all parts of Germany, but mostly so in Bavaria, great attention is paid to the 
construction of the cellars : often these cellars are excavated in rocks, and some 
times ice-pits are placed in the cellars to keep them very cool. The after-fermenta¬ 
tion of the beer sets in when it is vatted, the moment of the beginning of this 
process partly depending upon the condition of the beer when vatted and partly upon 
the temperature of cellar. The after-fermentation, which becomes apparent by the 
appearance of a bright white-coloured foam at the bung-hole, may set in imme¬ 
diately after the vatting of the beer, or may only become apparent some eight days 
after. Should the beer happen not to exhibit any sign of incipient after-fermen- 


BEER. 


417 


tation, green, young, or new beer is added for the purpose of inducing this process. 
"When the after-fermentation is finished, the bungs of the casks or tuns are not 
tightly fastened, and the beer is left in this condition (in the cellars of course) 
during the summer months. About a fortnight before the beer in the casks is 
intended to be tapped, the bungs are tightly closed in order to cause as much car¬ 
bonic acid to accumulate in the fluid as will occasion the beer to foam on being 
tapped; but.if beer happens to be vatted in very green condition, the bung-hole 
should not remain closed for so long a period, because then so violent a fermenta¬ 
tion may set in that, on tapping the cask, its contents become too much agitated, 
and thereby a very turbid (full of yeast) beer is served to the customers. Some¬ 
times the addition of liqueur (a solution of white sugar) is resorted to for the 


purpose of setting up a strong 

fermentation 

in very 

old beer. . 

According to 

J. Gschwandler (1868) beer obtained by the processes alluded to has the following 
composition:— 

Sedimentary 

Decoction. Bock. Method. Infusion. 

Alcohol 

.. 2*810 

3*380 

2-940 

3*130 

Sugar. 


2*320 

1-460 

1*330 

Dextrine .. 

.. 4-610 

6*910 

4*770 

4-800 

Nitrogenous substances .. 

.. 0*380 

0-740 

— 

— 

Other constituents .. 

.. 0-380 

0-400 

0*890 

0*550 

Sp. gr. of solution of extract 

. . I'022 

1*042 

1*028 

1*026 

Extract (direct estimation) 

• • 6-570 

9-980 

6*230 

. 6*130 

,, (according to Balling) 6*950 

10*380 

7-120 

6 -68o 


surface rermeiitation. Surface fermentation is that induced in the worts intended for 
the brewing of the bottled beers of North Germany, Bohemia, Alsace, England, and 
Belgium. Beer obtained by this process of fermentation is not so lasting as that 
prepared by the sedimentary fermentation process. This difference is due to the 
fact that the surface fermentation goes on at a higher temperature, proceeds more 
rapidly, while the elimination of the nitrogenous compounds is also less complete. 
The reason why this process is preferred to the sedimentary'fermentation process is 
that brewing, by the application of the last process, is so greatly dependent upon a 
low temperature that this mode of brewing cannot be continued throughout the 
whole year; while as regards the other process it may be continuously carr ied on, 
and the stock of beer kept ready for use can thus be considerably decreased. Sur¬ 
face fermentation, however, is the only plan for preparing briskly foaming and 
strong beers. Porter, stout, and ale could be brewed as well by the sedimentary 
method—although in the English climate this process would be more difficult to 
conduct successfully—but the main reason why the surface fermentation is em¬ 
ployed for English malt liquors is that this method—by a great saving of time—is 
cheaper. The phenomena of the surface fermentation are similar to those of the 
sedimentary, with the exception that the process is by far more violent, the froth 
surging more to the surface of the wort. The yeast is employed in the same 
manner. An ingenious contrivance is adopted in the London breweries for the 
purpose of carrying off the yeast from the beer after it has undergone the process of 
fermentation. The wort is placed in large hogsheads, or rounds , the tops of which 
are fitted with wooden troughs. Into these troughs the yeast runs as it rises, and 
is carried away. The beer now becomes clear, and is pumped into the stone vats. 

28 








CHEMICAL TECHNOLOGY. 


AlS 

b team Brewing. The extensive application of steam to the manufacture of beet-root sugar 
and alcoholic spirits has given rise to many suggestions for the substitution of heating by 
steam for direct firing in brewing. The heating is effected by a system of tubes similar 
to that described in the preparation of beet-root sugar (see p. 377). In brewing, how¬ 
ever, though much would be gained by uniformly heating the worts, and by reducing the 
chances of burning, there would not ensue any great economising of fuel; but much 
labour might be saved. Steam could not be employed directly without a series of tubes, 
as the condensation would cause a great dilution of the mash. 

constituents of Beer. The constituents of a normal beer prepared fiom malt and hops 
(not from substitutes) are : —Alcohol, carbonic acid, undecomposed dextrose, dex¬ 
trine, constituents of the hops (oil and bitter substance, no tannic acid), protein 
substances, a small quantity of fat, some glycerine, and the inorganic matter of 
the barley and hops. The acid reaction which a normal beer exhibits after the 
carbonic acid has been expelled from it by boiling is due to succinic and lactic acids, 
with traces of acetic acid, and perhaps propionic acid. The sum of all the consti¬ 
tuents of a beer after the abstraction of the water is termed the total contents ; the 
sum of the non-volatile constituents, the extractive contents. Beer rich in malt 
extract is termed rich, fat, or full-bodied beer; and that which is poor in extract, 
but contains much alcohol, the wort having been rich in sugar which has all been 
converted, is termed a dry beer. 

The proportion of alcohol in beer can be estimated by distillation and the testing 
of the distillate with an alcoholometer, or by means of an ebullioscope, or with 
the help of a vaporimeter (see Wine-testing, p. 394). The following table shows 
the average weight per cent, of the alcoholic contents of several beers :— 

Per cent. 


Wirtzburg lager beer (1870) . 40—4*3 

,, schenk beer. 3-3—4*2 

Stuttgardt lager beer (1865). 4*1 

Culmbach lager beer (1865). 4-5 

Coburg lager beer. 4*4 

Munich lager beer. 4*3—5*1 

,, schenk beer . 3*8—4*0 

Bock (Munich, 1870). 4*3—4*8 

Porter (Barclay, Perkins, and Co., London, 1862) 5-5—7-0 

Strasburg beer (1870). 4*21 

Vienna beer (1870).. 4*1 

Bice beer of the Bhenish Brewery ” in Mentz 3-6 


The quantity of carbonic acid in beer varies between ou to 0*2 per cent. 
According to C. Prandtl (1868) dextrose is found in beer in quantities varying from 
0-2 to rg per cent. The quantity of dextrine, according to Grschwandler’s analyses, 
varies from 4*6 to 4'8 per cent. The proportion of sugar to dextrine is never 
constant. The occurrence of protein substances in beer has not been sufficiently 
investigated to warrant an exact conclusion. It may be said that on an average 
malt extract contains 7 per cent, protein substances, from which Mulder deduces that 
1 litre of beer should contain 5*6 percent, albuminous substances. A. Vogel (1859) 
found that 1 Bavarian maas ( = 1*069 litres) of beer on an average contained 
1 to 1*2 grms. nitrogen; and Peichtinger (1864) obtained from 1 Bavarian maas 
of several Munich beers between 0*467 and 1*248 grms. nitrogen. Succinic acid, 
acetic acid, and lactic acid occur in Belgian and Saxony beers in large quantities. 
Tannic acid occurs in Bavarian beers only in small quantity. The inorganic 












BEER. 


419 


constituents of beer have received great attention. Martius obtained from 1000 parts 
of Bavarian lager beer 2*8 to 3*16 parts asb, containing one-tbird potasb, one-tbird 
pbospboric acid, and one-tbird magnesia, lime, and silica. J. Gschwandler and 
0. Prandtl (1868) found an average extractive contents in 100 parts of— 


Parts. 

Scbenk beer (Munich). 5-5—6‘o 

Lager beer (Munich) . 6*i 

Scbenk beer (Wirtzburg . 4-6 

Lager beer (Wirtzburg). 4-4 

Bock (Munich) . 8*6—9*8 

Salvator (Munich). 9*0—9-4 

Rhenish rice beer. 7*3 

Porter (Barclay, Perkins, and Co., London) .. 5*6—6*9 

Scotch (Edinburgh) . io-o—iro 

Burton ale . 14*0—19-29 


100 parts of extractive matter contain, according to A. Yogel (1865) 3-2 to 3-5 parts 
of ash; 100 parts of ash contain 28 to 30 parts phosphoric acid. 1 litre of beer 
contains 0-57 to 0*93 grm. of phosphoric acid. 

Lermer (1866) subjected several Munich beers to analysis with the following 


results:— 

1. 

2. 

3 - 

4. 

5 - 

6. 

7 * 

Sp.gr . 

1*02467 

1-0141 

1-01288 

I *0200 

1-02678 

1-03327 

1*0170 


per ct. 

per ct. 

per ct. 

per ct. 

per ct. 

per ct. 

per ct. 

Extractive matter 

773 

4*93 

4*37 

4*55 

8*50 

9-63 

5*92 

Alcohol 

5-08 

3-88 

3 * 5 i 

4-41 

5*23 

4*49 

3-00 

Inorganic constituents 0*28 

0-23 

0-15 

0-18 

— 

— 

— 

Nitrogen:— 

In 100 parts extract 

11-15 

871 

12-19 

8*85 

_ 

6-99 


,, 100 ,, beer 

0-87 

0-43 

o *53 

039 

— 

0-67 

— 


1. Bock beer. 2. Summer beer. 3. White beer. 4. White Bock beer (superficially 
fermented, obtained by surface fermentation from malted wheat). 5. Another sample of 
Bock beer. 6. Salvator beer. 7. Winter beer. 

The analysis of the ash of five of these beers gave:— 



1. 

2. 

3 - 

4 - 

5 * 

Potash. 

.. 29-31 

33*25 

24-88 

34-68 

29*32 

Soda . 

i *97 

o *45 

20-23 

4-19 

o-n 

Chloride of sodium 

. . 4-61 

6*00 

6*56 

5*06 

6-oo 

Lime . 

.. 2-34 

2*98 

2*58 

3*14 

6*21 

Magnesia 

.. n’87 

8*43 

o *34 

777 

775 

Oxide of iron 

.. I'OI 

0*11 

o *47 

0*52 

0*84 

Phosphoric acid 

.. 34-18 

32*05 

26-57 

29-85 

29*28 

Sulphuric acid .. 

1-29 

2*71 

6-05 

5*i6 

4-84 

Silicic acid 

• • 12-43 

14-12 

770 

2-86 

8*oi 

Sand 


0*67 

2*30 

5*20 

6*27 

Carbon .. 

.. 0-49 

o*8i 

0-40 

0-65 

0-28 


100*33 

101-47 

98-03 

99-08 

98-91 
























420 


CHEMICAL TECHNOLOGY. 


The high importance of beer, both as regards its value as nutriment as well .as regards 
the enormous trade done in this article, has given rise to attempts to find proper and 
suitable means for testing that liquid in respect of its quality and purity. 

Beer-Testing. The experiments proposed for ascertaining the strength as well as 
freedom from adulteration of beer, is termed beer-testing; it is desirable that these 
operations should be easily executed and yield sufficiently reliable results. The 
strength of a beer is judged according to the quantity of alcohol, extract, and car¬ 
bonic acid it contains; it is evident, however, that an intimate knowledge of the 
real constituents of the extract, viz., the therein contained quantities of dextrine, 
hop constituents, the by-products of alcoholic fermentation, such as, for instance, 
succinic acid and glycerine, not to mention such substances as, for instance, 
glucose and glycerine purposely added to the wort, as substitutes for malt, largely 
influence the quality of any kind of beer, and therefore ought to be determined 
when any rigorously exact analysis of that liquid is wanted. 

Beer-testing is effected partly by ascertaining certain physical qualities of the 
beer, partly by chemical means. To the former belong its flavour, odour, colour, * 
consistency, transparency, specific gravity, refractive power to light, &c. By 
chemical analysis we ascertain and determine the immediate constituents, viz., 
carbonic acid, alcohol, extractives, and water. The carbonic acid contained in the 
beer is first eliminated either by repeatedly pouring a quantity of beer from one 
tumbler or beaker-glass into another, care being taken to let the beer fall from 
some height, or the carbonic acid is removed by shaking the liquid up in a bottle and 
pouring it out of the same and into it again. The gas having been driven off, the 
specific gravity of the beer is taken by means of the hydrometer or saccharometer ; 
the beer is next boiled down to half its original bulk; next there is added to it 
it as much water (best distilled) as is required to restore the liquid to its original 
bulk, and of this liquid the specific gravity is again determined; this will be found 
greater than that previously obtained. The difference between the two determina¬ 
tions gives the amount of alcohol contained in the beer. 

Bailing’s^saccharometricai gi nce by fermentation ioo parts of malt extract yield 50 parts 
alcohol, twice the quantity of alcohol found will indicate the quantity of malt ex¬ 
tract necessary for its formation. This quantity of malt extract added to that still 
existing in the beer indicates the whole of the malt extract existing in the wort 
before fermentation. 

The specific gravity of the beer-wort becomes lower by fermentation, partly 
because the specifically lighter alcohol is formed, partly by the loss of some of the 
extractive matter, and partly also by the loss of the substances taken up in the yeast. 
This decrease of the specific gravity, or attenuation , as it is termed, can be estimated 
either directly by weighing, or by means of the saccharometer. The degree marked 
by the saccharometer in a beer freed from carbonic acid we will call m; the malt- 
extract of the wort, p. Subtracting m from p, the difference ( p — m ) gives the 
apparent attenuation , which is the greater the mere thorough the fermentation. 
The quantity of alcohol in a beer varies in direct proportion with the apparent 
attenuation. The empirical alcohol factor, a, by which the apparent attenuation 
must be multiplied to obtain the alcoholic contents of the beer 1= A in weight per 

* Very recently, C. Leyser has invented a colorimeter with which, by means of a 
normal solution of iodine (127 grms. iodine to a litre) after having brought the beers to 
an equal colouration with water, he estimates the relative degree of the original colour. 
The invention is fully described in the “ Jahresberichte der Chem. Technologie” for 1S69 
p. 467 


BEER. 


421 


cent. [(p — m)a — A] becomes the greater, the higher the original degree of concen¬ 
tration of the -wort. For worts between 6 to 30 per cent, of extractive matter, this 
factor varies from 0*4079 to 0*4588. The alcohol factor can be found by the follow¬ 
ing equation, when the apparent attenuation (p — m) and the alcoholic contents of 

the prepared wort (A) are known; then a = ^). With the help of the 

alcohol factor, a, the alcoholic contents in weight per cent, can be calculated. A 
quantity of beer being boiled to volatilise the alcohol, and the residue having been 
diluted with water to the original bulk or weight, if a weighed quantity were 
operated with, the specific gravity gives the quantity of extractive matter contained 
in the beer, which Balling terms n. The difference between the extractive matter 
contained in the wort (p) and that of the beer («), or (p— n), gives the actual 
attenuation, which, multiplied by the alcohol factor for the actual attenuation (&), 
likewise gives the quantity of alcohol contained in the beer expressed in percentage 

bv weight. The alcohol factor for the actual attenuation is h =. ( —^— \ . Sub- 

J & \p — n) 

tracting from the apparent attenuation (p — m) the actual (p — n), the difference {d) 

in the attenuations is obtained :— 

d=z(p — m) — (p — n) ; or d = m — n. 

d is known, when the extractive matter contained in the beer (n) and the saccharo- 
metrical percentage (m) of the beer free from carbonic acid are known; d is the greater 
the more alcohol the beer contains. The alcohol factor multiplied by the difference 
in attenuation gives the percentage (A) of alcohol, from which the alcohol factor for 
the difference in attenuation can be obtained by the following equation :— 

A 

c= - 

(p—m) 

It averages 2*24. Finally, with the help of c the difference in attenuation of the 
alcoholic contents of a beer can be calculated approximatively, even when the quantity 
of extractive matter of malt contained in the wort is not known. The apparent 
divided by the actual attenuation gives a quotient (d), which is the ratio of the 

attenuations, d= ^~ t7 ~ and can be calculated with the help of the alcohol factor 
p — n 

for the apparent attenuation (a), and of the original extractive contents of the wort 
(p). First— (a) is obtained by the division of the alcohol factor for the actual 
attenuation by the corresponding attenuation quotient or ratio. Assuming the 
alcohol factor for the difference in attenuation to be rr 2*24, and next doubling the 
approximative alcoholic contents thus obtained, we arrive at the quantity of the 
extractive matter of the wort from which the alcohol was formed. Adding to this 
the extract yet met with in the beer, the sum thus found expresses the approximate 
percentage of the extractive contents of the wort. When (p) has thus been approxi¬ 
mately obtained, Balling’s tables give the corresponding attenuation quotient q, 
reckoning all decimals above 0*5 as units, and neglecting those under 0*5. If only 
the original concentration of the wort (p) is to be calculated, the percentage of the 
alcohol of the beer may be obtained from the equation to the actual attenuation 
A = (p — n) b. If the degree after fermentation is 975 (or 16*29 — 6*54), the 
eaccharometrical percentage (see p. 363) 

975 


= 0*542. 





*22 


CHEMICAL TECHNOLOGY. 


Fuchs’s Beer Test. Hallivietrical Beer Test. —Fuchs’s test, based upon the presumption 
that tbe beer has been brewed from malt and hops only, starts from the fact 
that ioo parts of water, independently of temperature, dissolve 36 parts of pure 
common salt (=2778 :1), and that a fluid dissolves the less salt the greater the 

quantity of alcohol and extractive matter it contains. 
It is therefore possible to estimate by this means the 
quantity of water in a beer by determining the quantity 
of common salt which remains undissolved; this is done 
by means of the hallimeter, Fig. 232, an instrument con¬ 
sisting of two glass tubes, one very wide and cup-shaped, 
the other narrower and attached to the bottom of the 
former. The smaller tube is so graduated that the 
larger divisions correspond to a quantity of 5 grains of 
common salt, while the smaller divisions correspond to 
1 grain of salt. In all hallimetrical experiments it is 
very essential that the pulverised common salt be 
always as much as possible of the same degree of 
fineness, while care has also to be taken that this sub¬ 
stance be reduced to its smallest bulk when put into 
the tube by gentle taps, so as to expel air 5> and thus 
cause the salt to occupy exactly the space intended 
for it. It is therefore required to pass the pulverised 
salt through a wire-gauze sieve, after which the pre¬ 
pared salt is kept for use in a glass-stoppered bottle. 
The testing requires two experiments. By the first is estimated the amount of 
water together with the entire quantity of carbonic acid, alcohol, and extractive 
matter contained in the sample ; while the second experiment gives the quantity 
of extractive matter, which when the carbonic acid is deducted from the total 
contents, yields the amount of alcohol contained in the beer. The alcohol is 
not anhydrous, but is mixed with a certain quantity of water. 1000 grains (62*5 grins.) 
of the beer to be tested are poured into a flask with 330 grains (20-46 grms.) of the 
common salt. The flask, lightly closed with a stopper or cork, is frequently 
agitated, and having been placed on a water-bath is heated to 38°. After six to ten 
minutes the flask is removed from the water-bath, the carbonic acid being 
expelled by gently blowing into the flask, which is next weighed ; the loss of weight 
indicates the quantity of carbonic acid, which in good beer averages 1*5 grains. 
The mouth of the flask having been closed with the thumb is turned upside 
down in order thereby to collect any non-dissolved salt in the neck of the flask, 
and the salt along with the fluid transferred to the hallimeter, the non-dis¬ 
solved salt settling down in the graduated tube, this movement being promoted 
by gently shaking the instrument. As soon as the volume of the undissolved salt 
ceases to increase, the number of grains is read off and deducted from 330, the 
difference being the number of grains dissolved from which the quantity of water 
present is calculated. 

Example: 1000 grains (=62*5 grms.) of beer dissolve 330— 18=312 grains common 
salt; therefore these 1000 grains of beer contain 866 6 grains of water; for 

36 : 100= 312 : x, 

. • . x = 866 - 6 

1000 — 866-6 = 133-4 grains indicate the total quantity of carbonic acid, extractive matter. 


Fig. 232. 













BEER. 


423 


and alcohol present in the beer. If the contents of the flask by heating- have lost 15 
grains in weight, the extractive matter and alcohol together amount to 131-9 grains. 
The second experiment is now made to estimate the amount of extractive matter. For 
this purpose 1000 grains (62-5 gnus.) of beer are weighed off and poured into a flask, and 
boiled down to half the quantity, that is, 500 grains. Both the carbonic acid and the 
alcohol are driven off. 180 grains of common salt are now added, and the experiment 
proceeded with as before. Supposing 180 — 20 =160 grains of common salt to be dis¬ 
solved, there will have remained 444-4 grains of water ; for 

18 : 50 r= 160 : x 

. • . ‘ x = 444-4, 

which shows the quantity of the extractive matter to bo 55-6 grains. If the preliminary 
estimation of the carbonic acid has been correct, the quantity of alcohol contained in the 
beer will be 76-3 grains, for I33'4 — 55-6 — i'5 — 76-3. This corresponds, according to a 
table published with each instrument, to 42-27 grains of absolute alcohol. The beer 
would, therefore, contain in 1000 parts :— 


Carbonic acid. 1-50 

Free water . 866-6o 

Combined water . 34-03 

Extractives . ... 5 5'60 

Alcohol . 42-27 


iooo-oo 

The hallimetrical assay of beer is entirely worthless when beer is made with the addition 
of glucose or glycerine. 

By-products of the Among the by-products of brewing the residue of the mash tuns is 

lire wing Process, perhaps the most important. 100 parts of kiln-dried malt leave on an 
average 133 parts of residue, which being dried at the temperature to which the malt 
was subjected give 33 parts. It is used as fodder for cattle under the name of brewers’ 
grains. This material yet contains, in addition to the husks and cellulose of the grain, 
undecomposed fatty matter and protein substances, upon which its value depends. 
Exhausted mashed grain from a Munich brewery used to prepare summer beer (by the 


thick mash method) had the following 

composition: — 




Wet Grains. 

Air-dried. 

Dried at ioo°. 

Water. 

7471 

7-28 

— 

Ash . 

1 -06 

3"§7 

4-18 

Cellulose. 

3-06 

11-22 

I 2 TO 

Fat . 


6-23 

6-72 

"Nitrogenous nutritive matter.. 

6-26 

22-89 

24-71 

Non-nitrogenous nutritive matter 13-21 

48 - 5 I 

52-29 


ICO-OO 

100-00 

IOO'OO 


The rootlets and plumules of the germinated malt present in the proportion of about 
3 per cent, of the weight of the dried malt, form a very concentrated and rich fodder. 
Accor din g to the analyses of Scheven, Way, and Lermer (Hungarian barley), the 
following is the composition of that substance :— 



Scheven. 

Way. 

Lermer. 

Water. 

7-2 

37 

10-72 

Ash. 

, 6-8 

5 ' 1 

6-91 

Cellulose. 

17*0 

i 8-5 

— 

Protein substances . 

45'3 

48-9 

32-40 

Non-nitrogenous nutritive matter 

23-6 

23-8 

49-77 


The sediment of the cooling tun3 (see p. 414), part of which is used as fodder and part 
in the preparation of brandy, amounts to about 3 per cent, of the wort. The after- 
washes are also used in malt spirit making, as well as in the preparation of vinegar. The 
thick mash processes yield an after wash containing from 4 to 8 per cent, extract, 
while by the infusion methods this amounts only to 2 to 3 per cent. Much of the yeast 
formed "during brewing is employed in bread-making, as well as in the manufacture of 
vinegar and brandy 


















424 


CHEMICAL TECHNOLOGY. 


The Preparation or Distillation of Spirits 

Alcohol. Since alcohol happens to be in almost all countries an article which in a 
nearly pure state (that is to say more or less diluted with water) is a fluid used as an 
article of consumption, and therefore very properly submitted to a more or less 
heavy duty or impost, the mode of manufacturing alcohol on the large scale, and 
the raw materials from which it is obtained, vary in different countries, and conse¬ 
quently these conditions very greatly influence the industry of alcohol production. 
When a fluid containing alcohol is distilled, alcohol and water are collected in the 
receiver, while the non-volatile constituents remain in the retort in a concentrated 
condition. The act of distillation of an alcoholic fluid is termed the brennen* while 
the product of the operation is designated as brandy, a fluid which contains on an 
average from 40 to 50 per cent, of alcohol. A distillate which contains more alcohol 
than the quantity just alluded to is designated as spirits of wine, or simply 
spirit. Originally, that is to say when spirits (now some two and a half 
centuries ago) were first commenced to be made industrially on the large scale, 
it was only made for the purpose of being drunk, and the liquor prepared in 
the comparatively dilute state in which it is offered for sale for consumption. 
More recently (within the last forty or fifty years), the use of alcohol in various 
branches cf industry (varnish-making, ether preparation, perfumery, preparation of 
cordials, liqueurs, &c.) is so great, that as a rule distillers at once prepare strong 
alcohol, which, if required for consumption as a beverage, is suitably diluted and 
sweetened if desired. Since the distillation of alcohol has been carried on on the 
large scale the apparatus have been very greatly improved; and those now in 
use in the best arranged distilleries are constructed upon scientific principles, while 
care is also taken that the surveillance on the part of the excise officers is rendered 
an easy task, and fraud almost impossible. The whole art of the production of 
alcohol—its ready preparation from grain (partly malted), from beet-roots, potatoes, 
refuse of saccharine liquors from sugar works, the proper utilisation of the residues 
of the distillation, either as food for cattle or otherwise—is now brought to a degree 
of perfection almost unequalled in any other branch of industry. 

A 1 Tmpofte d ntPropeuTes^ y The formula of alcohol (as a chemically pure substance) is 

C 2 H 60 , or 2 j 0 . It is a colourless, thin, very mobile fluid of 0792 sp. gr., 
boiling at 78*3°, while water boils under the same atmospheric pressure at ioo°; thus 
there is afforded a means of ascertaining by the boiling-point of an alcoholic fluid, the 
quantity of alcohol contained. Between o° and 78 ‘3° (its boiling-point), alcohol 
expands o'og^6 of its volume; while the coefficient of expansion of water between 
the same degrees is o'02j8. The expansion of alcohol is thus 3J times greater than 
that of water; and this fact is made available in alcoholometry. The tension of the 
vapour of alcohol at 78*3° is equal to an atmosphere, while water must be raised to a 
temperature of ioo° to obtain the same pressure. Thus, the variation in height of a 
column of mercury subjected to the pressure of these vapours may be made a mea¬ 
sure of the quantity of alcohol contained in a fluid. On this principle the vapori- 
meter (see p. 395) is constructed. Alcohol is readily inflammable, and burns with a 
pale blue flame without giving off soot. Its heat of combustion corresponds to 7183 

* There is no equivalent term for this word in English neither also in the French lan¬ 
guage ; the real meaning is “the firing,” in Dutch {branded); the term Brennerei 
(German), and brandery (Dutch), meaning “ a distillery.” 


SPIRITS. 


425 


units of heat. It eagerly absorbs water, and upon this property is based its use for 
the preservation of articles of food, cherries, and other fruit, and also anatomical 
preparations. It mixes with water in all proportions, whereby a decrease of bulk 
of the mixture and increase of specific gravity is observed— 

53*9 volumes of alcohol, with 

49*8 ,, water, form a mixture not of 

103 7, but of 100 volumes. 

Alcohol is a solvent for resins (upon which property is based its application to the 
manufacture of varnishes, cements, and pharmaceutical preparations), and also a 
solvent of many essential oils. These solutions are employed either as perfumes, such 
as eau de Cologne, or as liqueurs, cordials, and aqua vitae, or as spirits for burning 
in lamps, as, for instance, the mixture of oil of turpentine and alcohol, so-called fluid 
gas; alcohol also dissolves carbonic acid gas, a property made available in the 
making of effervescing wines. 

By the influence of certain oxidising agents alcohol u converted first into aldehyde 
and next into acetic acid, as illustrated in the so-called quick vinegar-making 
process. Alcohol does not dissolve common salt, and upon this property Fuch’s test 
(see p. 422) is based. 

By the action of most of the stronger acids aided by heat alcohol is converted 
into what are termed ethers ; as regards the action of sulphuric acid upon alcohol, 
it depends upon the relative quantities and degree of concentration of these liquids, 
whether sulphovinic acid, ether, or bicarburetted hydrogen gas, be formed. 
Hydrochloric acid forms with alcohol chlorine of ethyl or hydrochloric ether. 
Butyric and oxalic acids form ethers directly when heated along with alcohol; but 
most of the other organic acids require the addition and the aid of sulphuric or 
hydrochloric acid for this purpose. Alcohol is the intoxicating principle of all 
spirituous liquors. 

1Uw Manufac S ture. Spirit Alcohol is always the product of vinous fermentation. The 
manufacture of spirits therefore includes three principal operations :—■ 

1. The preparation of a saccharine fluid. 

2. The fermentation of this fluid. 

3. Separation of the alcohol by distillation 

All saccharine fluids, therefore, or those substances which yield alcohol by fermen¬ 
tation, can be employed in the manufacture of spirit; and all materials so employed 
contain already either completely formed alcohol, or cane sugar and dextrose, or 
finally substances which by the influence of diastase or dilute acids are converted 
into dextrose. Such substances are starch, inuline, lichenine, pectin compounds, and 
cellulose. The raw materials of spirit manufacture may be generally classed in the 
three following groups : — 

1 st Group .—Fluids in which the alcohol is already present, requiring only distil¬ 
lation to effect its separation. Such fluids are wine, beer, and cider. 

2nd Group .—Substances either solid or liquid which contain sugar, which may be 
either cane sugar, or dextrose and levulose, or sugar of milk. In this group are 
included the beet-root, carrot, sugar-cane, maize stalk, the Chinese sugar-cane 
(, sorghum ),. some kinds of fruit—viz., apples, cherries, figs, some berries (grapes, 
mountain ash berries, &c.), the melon and gourd, some fruits of the cactus tribe, tho 


426 


CHEMICAL TECHNOLOGY. 


molasses of cane and of beet-root sugar manufacture, the marc of grapes and refuse 
grain of beer-making, honey, and milk. 

3rd Group .—All substances which originally contain neither alcohol nor sugar, but 
the constituents of which may be converted into sugar and dextrose. Such are 
starch, inulioe, lichenine, pectin compounds, and cellulose, chiefly found in— 

a. Eoots and bulbs: Potatoes, dahlia roots, &c. 

I). Cereals: Eye, wheat, barley, oats, maize, and rice. 

c. Leguminous and other seeds : Buck-wheat, millet, black or negro millet, peas, 

lentils, beans, vetch, chestnut, horse-chestnut, oak leaves, &c. 

d. Substances containing cellulose: Sawdust, paper, straw, hay, leaves, osier, 
moss. 

In the future a— 

4 th Group may perhaps be added, which will embrace all substances as probably 
may enter into the synthetic preparation of alcohol, and thus form what might be 
called a mineral spirit. Berthelot in 1855 proved that alcohol can be formed from 
olefiant gas and water (C 2 H 4 + H 2 0 = C 2 H 6 0 ). Olefiant gas, when agitated for a 
length of time with concentrated sulphuric acid, gives rise to the formation of 
sulphovinic acid; and from this liquid after having been diluted with water 
a dilute alcohol can be distilled. This experiment has as yet only a scientific 
interest; the process has been tried on the large scale in Prance, but failed to be 
commercially available. 

a. Preparation of a Vinous Mash. 

Vinous Mash from cereals. Grain brandy (corn brandy) maybe prepared from either 
wheat, rye, or barley. Generally more than one kind of grain is used, because 
experience has proved that a larger quantity of alcohol is obtained when two kinds 
of grain—for instance, wheat and barley, rye and barley—are mixed. A mixture of 
lye with wheat or barley malt, or wheat with barley malt, is very generally used, at 
least abroad. To 1 part of malt from 2 to 3 parts of non-malted grain are usually 
taken. Either, as is done in England, wort is made, the grain being first malted, 
next mashed, and the wort drawn off, or the mixture of malted and unmalted grain is 
allowed to ferment together. The latter method is more usual in Germany, and will 
be that described in this work. In Eussia and Sweden brandy is prepared without 
malting; by properly mashing rye meal a reaction ensues between its constituents, 
the effect of which is the same as if it had been acted upon by diastase of malt— 

The preparation of a mash from grain may be considered as consisting of the following 
four operations:— n 

1. The Bruising —The materials, malted as well as unmalted grain, are first bruised. 
As it is not essential in the manufacture of spirits that a clear wort should be prepared* 
the grain may be broken up very small, whereby the formation of sugar is rendered more 
complete. Green malt is now generally considered preferable by many distillers. 

2. The Mixing with Water.—Making of Mash .—This operation is almost identical with 
that of the mashing of the brewer ; the only distinction being that the distiller aims at the 
entire conversion of the starch into glucose, while the brewer does not require this as he 
also wants some dextrine. The complete saccharification, and next the complete conversion 
of the glucose into alcohol during fermentation, are possible only with a certain decree 
of dilution of the mash. The quantity of water to be mixed with the grain cannot be 
reduced too much, because that would involve a loss of spirits. 

3. The Cooling of the Mash .—When the saccharification is complete, the mash should 
be rapidly brought to the temperature suitable for fermentation by bein°- placed in 
cooling vessels, just as is done with the wort in brewing, by being placed in an apparatus 
termed a refrigerator, or by the application of ice or cold water. The temperature 
to which the mash has to be cooled varies according to the locality and the duration of 


SPIRITS. 427 

tlie fermentation, but it averages 23 0 C. When sufficiently cooled the liquid is placed in 
the fermenting vats. 

. 4. The Fermentation of the Mash. —The fermentation vat is generally made of wood and 
sometimes of stone. The first possesses the property of retaining the heat for a longer 
time, and for the same reason large vessels are preferred. The capacity seldom exceeds 
4000 litres. Either beer yeast in its fluid condition or dry yeast is used to set up 
fermentation. The latter is mixed with warm water before being added to the contents of 
the fermentation tanks. Of the fluid beer-yeast, there is usually taken to 1000 litres of 
mash 8 to 10 litres ; while for 3000 litres of mash 15 to 20 litres of yeast are a sufficient 
quantity. Of the dry yeast, ^ a kilo, is employed to 1000 litres of mash, or 1 kilo, of 
yeast to 3000 litres of mash. In large distilleries artificial yeast is sometimes employed, 
as beer yeast of the requisite quality cannot always be procured at a remunerative price. 
The mode of adding the yeast is the same as that employed in breweries. After 
standing 3 to 5 hours the temperature of the mash will have increased to 30° to 32 0 . 
Carbonic acid is then given off, and the heavier substances settle to the bottom of the 
tank. This continues for about four days, when the clear fluid may be considered ready 
for further operations. 

Mash froiA Potatoes. Potatoes consist of about 28 per cent, of dry substances, 21 per 
cent, of which is starch, with 2*3 per cent, of albuminous matter, and 72 per cent, 
of water. The active principle under the influence of which the starch is converted 
into dextrose is diastase, but this substance is not found even in the germinated 
potato. It therefore becomes necessary, in order to convert the starch of the pota¬ 
toes into dextrose, to add malt, or to treat the potatoes first with dilute sulphuric 
acid. Accordingly, the preparation of a mash from potatoes may be performed by 
either of these two operations. The former is that most generally employed. The 
preparation ordinarily includes the following operations :—1. The washing and boil - 
ing of the potatoes. —Before the potatoes can be boiled or steamed, they must bo 
cleansed from the adhering earth. After the washing the potatoes are boiled with¬ 
out previous paring. Finally, they are steamed. 2. The chopping of the boiled 
potatoes. —As soon as the potatoes are boiled they are placed in a chopping machine, 
and cut into small pieces, care being taken to keep them hot by the aid of steam, 
so that the cut up mass admits of being readily mixed with hot water into a uniform 
mass, which is the best condition for the potato starch to be most readily converted 
into dextrose. In some cases the boiled potatoes are passed between two hollow 
cast-iron cylinders, the axles of which are so arranged and fitted in a frame-work 
as to admit of the cylinders being moved in an opposite direction, and thus capable 
of converting the boiled potatoes into a uniform mash. 3. The mashing .—After 
the addition of the grain or diastase-containing material, the mashing proceeds as in 
the case of malt. The grain or malt added is sometimes rye malt, sometimes barley 
malt, and generally a mixture of the two. Green malt has greater power of con¬ 
version than air-dried malt, ultimately producing a larger quantity of alcohol. The 
proportion of bruised malt to be employed varies in many instances; while in some 
cases only 2 to 3 per cent, of barley as malt is added to 100 parts of potatoes; in 
others as much as 10 per cent, is used. A medium quantity between these two ex¬ 
tremes, or about 5 per cent., is perhaps that most in use. 100 parts of potatoes con¬ 
taining about 20 per cent, of starch yield on an average 17*3 parts of dry extractive 
matter in the mash wort, 5 parts of barley malt yielding 3 parts of dry malt ex¬ 
tract ; the yield of spirits has therefore to be calculated from these two substances. 
When a thick mash of potatoes is made a different proportion of the dry substances 
to the water to be added is obtained from that which obtains when malt or raw 
(unmalted) grain is made into a mash ; these proportions are in the case of potatoes 
as 1 : 4*5, 1: 4, even 1:3. It is clear that the large quantity of water contained in 
potatoes (viz., 72 to 75 per cent.) has to be taken into account. 


*28 


CHEMICAL TECHNOLOGY . 


The operation of cooling is performed as already described. While the mash is 
placed in the cooling vessels it undergoes changes which are partly favourable and 
partly unfavourable to the yield of alcohol. The increase of sugar is f course 
favourable; this increase can only be accounted for by the action of the protein 
compounds contained in the malt, whereby the dextrine is converted into dextrose. 
All albuminous substances possess the property of converting starch into dextrose; 
and this the more so if the albuminous substances are themselves already in a 
state of decomposition. Blood, brain, albumen of malted barley, saliva, meat in a 
state of incipient decay, are all capable of converting starch into dextrose. When 
Mulder suggests that the word diastase should be banished from science, and for it 
substituted that of starch converter, he is right in a scientific sense, because 
diastase does not exist as a chemical body by itself; but the word diastase may be 
conveniently used in technology for the purpose of indicating an albuminous body, 
which being itself in a state of decomposition, is capable of converting starch into 
dextrose. Another change of the mash consists in the formation of lactic acid, 
always readily formed from sugar under the influence of a peculiar ferment. The 
quantity of this acid is increased by slowly cooling to the suitable temperature for 
fermentation ; it is therefore best to cool the mash as rapidly as possible. Recently, 
an aqueous solution of sulphurous acid is employed, some of this being added to the 
mash mixture, the effect being the prevention of the formation of lactic acid, and 
thus increased yield of alcohol. 

Mash wiai sulphuric j,j ie Preparation of a Mash by means of Sulphuric Acid .—We 
have already seen that some dilute acids are as capable of converting starch into 
dextrose as the so-called diastase cf malt: dilute sulphuric acid is usually applied 
for this purpose. Leplay first recommended this mode of preparing mash. The 
raw potatoes are first converted into a pulp, which is thrown into a large vessel 
containing water. The starch cells separate, some settling to the bottom of the 
vessel, others becoming mixed with the cellular tissue of the pulped potatoes. The 
brown-coloured supernatant fluid (wherein is also contained the albumen of the 
potatoes, which would, if left, interfere with the action of the sulphuric acid upon 
the starch) is first syphoned off. This liquid is given as drink to cattle, or is used 
for the purpose of moistening dry fodder. While this operation is in progress there 
is heated to the boiling-point in another vessel the required quantity of dilute sul¬ 
phuric acid, the heating apparatus consisting generally of steam pipes. To every 
hectolitre of potatoes from 1*5 to 2 kilos, of strong sulphuric acid diluted with 
3 to 4 litres of water is usually taken. The previously more or less washed green 
potato starch is gradually and by small quantities at a time added to this boiling 
fluid. The boiling is continued until the whole of the starch as well as all the 
dextrine are converted into glucose, the course of the progress of the conversion 
being ascertained by means of iodine water, while the insolubility of dextrine in 
alcohol affords a means of ascertaining whether the conversion of this substance is 
complete. A sample of the fluid when agitated with alcohol should exhibit no milky 
appearance. After about five hours’ boiling the formation of sugar will be complete. 
The fluid is then .first run into a vessel with double bottoms, one of which is 
perforated with small holes so as to admit of acting as a strainer to retain cellulai 
tissue, &c., after which the fluid is run into another vessel, and while therein is 
neutralised by the addition of chalk. The gypsum having settled down, the fluid 
is again transferred to another vessel. The wash water of the sediment having 
been added, the liquids are ready to undergo fermentation. 


SPIRITS. 


429 

4. The Fermentation of the Potato Mash .—The addition of yeast to the cooled 
mash in the fermenting vat takes place in the same manner as with malt. To 100 
kilos, of mash are added 1 to 2 litres of beer yeast, or to 1 kilo, of dry yeast. The 
potato mash contains besides the husk of malt and grain some finely divided cellular 
tissue; these substances during fermentation are carried to the surface of the mash 
and form a scum, the appearance and behaviour of which gives an opportunity of 
judging the progress of the fermentation. The fermentation is said to be regular or 
irregular; the former begins some four to six hours after the yeast has been added, 
and proceeds in a regular manner, the end depending upon the quantity of yeast 
added and upon the temperature. The progress is quiet, not violent, the scum which 
appears on the surface sinking or being drawn down at one side of the vat and thrown 
up at the opposite side, while bubbles of air or gas appear and burst on the surface, 
much as bakers’ dough heaves under the influence of the ferment. Irregular fermen¬ 
tation is so far opposed to the former that the surface of the mash is only partly 
covered with froth, which remains in one position, and does not move of itself. The 
result of suck a fermentation is generally defective, the reason being the incomplete 
saccharification of the mash, the addition of too small a quantity of yeast, or finally 
working at too low a temperature. After about 60 to 70 hours with a regular fer¬ 
mentation, the mash is ready for distillation. Recently large quantities of spirits 
have been prepared from maize ^and also from rice. 

Mash from Roots. % the use of those vegetables which contain alcohol-forming bodies, 
either in the shape of cane sugar or as dextrose, the mashing process is avoided, and 
the prepared fluid is immediately ready for fermentation as soon as the saccharine 
fluid has been completely squeezed out of the cells wherein it is contained in the 
vegetable. The great advantage of the preparation of spirits with the avoiding of 
the mashing process is too important to be overlooked, and it is therefore clear that 
every effort should be made to substitute for the starch-containing vegetable products 
those which contain sugar, the more so as it has been recently proved in England 
perfectly possible to arrange this industry in every way to tbe satisfaction of the 
excise authorities. 

One of the most important of such roots is the sugar-beet so largely employed 
in the manufacture of beet-root sugar. Although it would appear -to be a 
simple matter to extract the juice from the previously pulped juice, this is yet— 
notwithstanding even the large quantity of juice, viz., 96 per cent, of the 
weight—a difficult matter, because the remaining 4 per cent, of substance have 
all the properties of a sponge and tenaciously retain the juice; it is this spongy 
nature of the solid constituents of the root which prevents the conversion of 
the whole root into a sufficiently concentrated mash. If it were possible to set up 
fermentation in the thick pulp obtained from the roots 100 kilos, of the pulp would 
yield 6 litres of alcohol, a quantity sufficiently large to be remunerative even with 
a very low market price of spirits. Indeed it is maintained by the advocates 
of beet-root distilleries, that the distillation of spirit is a more profitable business 
than the manufacture of beet-root sugar. In Belgium and Germany, distilleries 
are frequently to be found attached to the beet-root sugar manufactories; and 
the combination of the industries possesses the advantage that, in a season when the 
proportion of sugar in the roots is too poor to yield much profit to the manufacturer 
as sugar, ho may ferment the sugar-containing juice and obtain a fair yield of 
spirit. Beets to be available to the distiller may contain only 5 to 6 per cent, of 


430 


CHEMICAL TECHNOLOGY. 


sugar; but for the purposes of the manufacturer of sugar they must contain at 
least 8 to 9 per cent. The products of the first distillation of the fermented beet¬ 
roots contain, in addition to water, oils known as fusel oils, of very unpleasant 
taste and smell and of poisonous quality. These oils, however, disappear during 
rectification. The methods of obtaining the juice are the following:— 

<*. By pulping and 

a. Pressure, or 

b. By treatment in a centrifugal machine. 

By maceration, or by the dialytical method. 

a. The sliced roots being treated with cold or with hot water (Siemens’ and 

Dubrunfaut's methods). 

b. The sliced roots being treated with hot wash from former distillations. 

y. According to Leplay’s method, somewhat modified by Pluchart, the sliced roots are 
submitted to fermentation without previous extraction of the juice, and also without 
addition of yeast, the alcohol being afterwards distilled from the sliced roots with the aid 
of steam. 

Spirits from the By-Products In the East Indies the scum from the boiled sugar, the molasses, 
of sugar Manufacture. &c., are brought to fermentation and the fermented fluid distilled. 
The product is in the English colonies known as Rum, in Madagascar and the Isle of 
France as Guildine. The peculiar aroma of rum is contained in the portion which first 
distils over. By the fermentation and distillation of the scum from the boiling of the 
s ugar-cane juice, a coarse, sour, dark brown or black-coloured acrid tasting brandy is 
obtained; it is known as Negro rum. In England and Germany rum is frequently made 
from the diluted molasses of the sugar refineries fermented with yeast, the fermented 
fluid being distilled after about 3 to 4 days’ fermentation. The aroma peculiar to rum 
is obtained by the addition of some pelargonic ether or essence of pine-apple. Beet-root 
molasses are also largely used for the purpose of obtaining spirits. By itself the beet-root 
sugar molasses are difficult to ferment, but if the alkalinity of this material is first 
neutralised by the addition of some sulphuric acid, and the material next boiled with a 
further addition of acid for the purpose of converting the cane sugar it yet may happen 
to contain into inverted sugar, the fermentation may be readily set up and regularly pro¬ 
ceed. ioo kilos, of molasses yield on an average 40 litres of spirit. The very objectionable 
odour of this spirit is due to fusel oil, which contains small quantities of propyiic, butylic, 
and amylic alcohol, pelargonic acid, and caprylic acid, while later researches have added 
to this fist oenanthic, caproic, and valerianic acids. The residue left in the retort is used 
for the preparation of potassa (see page 118). The addition of sulphuric acid has not only 
the effect of converting the cane sugar into an easily fermentable sugar, but also prevents 
the setting up of lactic acid fermentation. 

Spirits from wine and Marc. The distillation of spirits from wine is chiefly carried on in 
France, Spain, and Portugal. The yearly production of spirits from wine or 
French brandy ( alcool de vin) in France alone, amounts to 450,000 hectolitres of 
85 per cent., and 400,000 hectolitres of 60 per cent. The quality of the spirit is 
indirectly affected by the degree of ripeness of the grapes, and directly by the care 
bestowed upon the fermentation and distillation, the more or less intimate mixture of 
the volatile principles of the wine with the alcohol, and by the age of the wine. Old 
wine yields a spirit of better quality than new wine. The freshly distilled brandy is 
colourless, and remains so even when bottled ; but since the spirit is kept in oaken 
casks it extracts therefrom some colouring and extractive matter. The best kinds of 
brandy are distilled in the Departement de Oharente, and the brand known in 
commerce as Cognac (name of a town) is the most valued. From the marc and 
wine-lees spirit is also distilled. By the distillation of spirits from wine a residue 
is left in the retort (the vinasse ) which contains a large quantity of glycerine which 
may thus be obtained as a by-product. 


SPIRITS. 


431 


b. Distillation of the Vinous Mash. 

instillation of the Mash. The fermented mash (as obtained from potatoes is a mixture or 
non-volatile and volatile substances. To the first belongs the fibre, malt, husks, 
inorganic salts, protein substances, undecomposed and decomposed yeast, succinic 
acid, lactic acid, glycerine, &c.; to the volatile, the alcohol, fusel oil, water, and 
small quantities of acetic acid. The volatile constituents of the mash, the products 
of the fermentation, are separated from the non-volatile by distillation, during 
which the volatile constituents are converted into vapour afterwards cooled and con¬ 
densed in another vessel. When a vinous mash, is heated to the boiling-point, 
vapours are generated which consist essentially of alcohol and water; by condensing 
these vapours there is obtained a mixture of alcohol and water. 

Water boils at-}- ioo° C., barometer 760 mm. 

Alcohol,, „+78*3°C.. „ „ „ 

Thus it might be thought that while the boiling-point of water is 2170° C. higher 
than that of alcohol, it would follow that when a vinous mash is heated to 8o 3 C., 
only the alcohol would be converted into vapour, the water remaining behind. But 
this is not the case, for under all circumstances the boiling-point of a mixture of 
alcohol and water is higher than that of pure alcohol alone, and the vapour formed 
consists of both alcohol and water. The reason is partly due to the affinity of alcohol 
for water, partly also to the fact that water evaporates at a lower temperature than 
its boiling-point; the former (affinity) retains alcohol and prevents it to escape at 
proper boiling-point (78*3°) in the shape of vapour. If the mixture of alcohol and 
water be heated to its boiling-point (suppose 90° C.) much more alcohol will be con¬ 
verted into vapour, because its boiling-point is lower, while of water only just so much 
is evaporated as would be the case were it when pure to be heated to this temperature, 
while simultaneously a current of air is passed through it, because the vapours of 
alcohol evolved from the mixture act exactly in the same manner as would a current 
of air carried through the mixture of alcohol and water, the former substance taking 
up just as much water as will be volatilised at the boiling-point of the mixed liquids. 
As the quantity of vapour evolved from a liquid bears a direct relation to the 
temperature of that liquid, the quantity of aqueous vapours in the mixture of 
vapours will increase according to the increase of temperature, until at last, as soon 
as the boiling-point rises to that of water (= ioo°) no more alcohol will be present in 
the vapours which are given off. At the commencement of the distillation the vapour 
given off contains much alcohol and very little water; presently more water comes 
over, and finally only water. It is therefore quite evident that we cannot by distil¬ 
lation separate alcohol at once from the rest of the volatile constituents of a vinous 
mash liquor. By interrupting the distillation at the proper time, there is obtained 
in the distillate all the alcohol contained in the mash along with a certain quantity 
of water, while the residue of the distillation will not contain any trace even of 
alcohol. The liquor obtained by the first distillation is generally very weak alcohol, 
and requires further rectification, as it is termed, to increase the proportion of 
alcohol. This rectification (another process of distillation) may be continued till the 
alcohol contains only a small quantity of water, which can only be eliminated by the 
aid of such substances as have a greater affinity for water than the alcohol, which 
retains that liquid very tenaciously. Anhydrous, or absolute alcohol, can only be 


432 


CHEMICAL TECHNOL OGY. 


obtained by treating highly rectified alcohol with some substances which have a 
great affinity for water, such as caustic lime, fused chloride of calcium, &c.; but 
really absolute alcohol is never used on the large scale in industry. The first 
portions of liquid obtained by the distillation of vinous mash are rich in alcohol, and 
termed fore-run or first-run, while the last portions of the fluid yet containing alcohol 
are termed after-run. A doubly-rectified alcohol contains 50 per cent, pure spirit; 
but by means of rectification alone a stronger alcohol than of 95 percent, cannot be 
obtained. The residue of the distillation is called fluid-wash. 

The Distilling Apparatus. A distilling apparatus as usually employed consists in its 
simplest form of four parts, namely, the still or retort, the head or cap of the still, 
the cooling apparatus, and the receiver. 

The still or retort is generally constructed of sheet copper—more rarely of iron boiler¬ 
plates. The shape of the vessel varies, but is generally a somewhat flattened cylinder, pro¬ 
vided with a round opening of 12 to 14 inches in diameter, fitted •with a collar about I inch 
in height forming the neck, on which the cap or head is placed. The bottom of the still 
is either somewhat bulged inwards at the centre or is quite flat. The residue of the 
distillation is removed through a waste-pipe fitted with a stop-cock attached to the 
bottom of the vessel. From the cap or head a pipe conveys the volatilised alcohol to the 
receiver, while jutting obliquely from the top of the still is a pipe for the introduction of 
the mash. The head carries the vapours from the still into the cooling or condensing 
apparatus; although a simple tube might answer this purpose, it is preferred to make 
the head of the stills large and wide, not only for the purpose of separating any particles 
of mash which might happen to be carried off with the vapours of the boiling liquid, but 
also to obtain a distillate richer in alcohol, because an increased surface is favourable to 
the cooling of the vapours, whereby thus the aqueous vapour is first condensed; more¬ 
over, large heads are advantageous in case, by a rapid evolution of vapours, the mash 
might boil up (priming) ; roomy space in the head prevents then the liquid passing over 
into the worm. Since the volume of the vapours decreases during the condensation, a 
somewhat conically-shaped head would be the best form for this portion of the apparatus. 
The cooling apparatus is not simply destined to convert the vapours carried into it from 
the head into liquid, but it is also required that this liquid be so far cooled down as to 
prevent—at least as much as possible—the evaporation of the distillate; the condensing 
apparatus should not be too roomy ; that is to say, there should not be too much 
space for the vapours, because this would cause air to enter the cooling apparatus, 
and this air, while mixing with the vapours of alcohol, carries off along with it some of 
this fluid, thereby causing a loss of the fluid. It is also requisite that the cooling- 
apparatus be strongly made, yet at the same time so constructed as to admit of being 
readily taken down for cleansing purposes and easily fitted up again; usually the cooling 
apparatus—technically termed worm—consists of a series of spirally bent tubes made of 
either block-tin or copper, seldom of lead; this apparatus is placed in a large wooden 
or metal vat containing cold water, or as in the more recently constructed distilling 
apparatus, cold vinous mash, which is thus made warm previous to being transferred into 
the still, whereby of course a saving of fuel is effected. 

improved^Distaiins However much the shape and details of construction of the apparatus, 
with the aid of which strong alcohol can at once be obtained by one distillation, may 
vary, these apparatus all agree in this respect, that the mixture of vapours of alcohol 
on their way from the still to the condenser become continuously richer in alcohol, so 
that on reaching the cooling apparatus strong alcohol is the result of the operation. 
This result can be attained in two different ways, viz.:— 

1. By causing the mixture of vapours to pass repeatedly through alcoholic liquids 
formed by the condensation of the vapours first given off; when afterwards the 
temperature increases in consequence of the continued rush of vapours into the 
liquid, a new process of distillation begins, the vapours generated by it being far 
richer in alcohol than when the first distillation took place (principle of rectification). 

2. By so cooling the mixed vapour that the water only is condensed, the alcohol 
passing on as vapour (principle of dephlegmation). 


SPIRIT. 


433 


When, in former days (sixty to sixty-five years ago), it was desired to prepare 
strong alcohol, a repeated process of distillation was adopted; this of course was a 
costly affair both as regards consumption of materials, fuel, &c.j and loss of time. 
At the present day distillation apparatus are generally so arranged that by a kind 
of dissociation of the mixture of vapours, alcohol of any desired strength can be at 
once prepared. 

Most of the recent distillation apparatus may be considered to consist of the 
following parts:— ^ 

1. The still or vessel in which the fermented mash is placed. 

2. Two condensing apparatus, one of which serves as rectifier, while the other 
completes the condensation of the products. 

3. A dephlegmator in which the mixed vapour separates, a portion of the water 
becoming condensed and a vapour richer in the alcohol being carried on; this latter 
is carried into the cooling apparatus, while the former flows back into the still. 

Among the many distilling apparatus employed in Germany for distilling fermented 
potato mash, we propose to describe those of Dorn, Pistorius, Gall, Schwarz, and 
Siemens. 

Dom’s Apparatus. Dorn’s apparatus, Fig. 233, consists of the still, a, the helm, b, which 
acts as dephlegmator, the condensing apparatus, d, and between the still and con¬ 
densing apparatus, a copper vessel divided by a partition into two compartments, 


Fig. 233. 


n 



c and f, the upper of which, c, is termed the fore-warmer, the under, f, the recti- 
ficator. Connected with the helm is a small condenser, n, for the purpose of taking 
an occasional sample of the distillate which passes over. The fore-warmer is filled 
with mash to a level with the tube, 0, and usually contains as much mash as is 
necessary to fill the still. With the help of the revolving arms, x x, the mash is 
from time to time kept stirred, and thus equally heated throughout to about 85° by the 
vapour passing through the pipe, i i, from the still. When the distillation is finished 
the wash (waste residue) is run off by opening the tap a, the still being re-filled with 
mash from the fore-warmer. As soon as the distillation commences the vapour is 
condensed in the worm, i i, the condensed fluid flowing into f. When the steam is 
no longer condensed in i, which occurs as soon as the mash has reached a certain 
temperature, the vapours pass over into the low wine, which thus becomes rapidly 
29 































434 


CHEMICAL TECHNOLOGY. 


heated to the boiling-point. By this means a second distillation is effected, really a 
rectiiication, the Vapour or steam from which passing by the tube, y. is carried to the 
worm, z z, placed in the condenser, d, and having been converted into a fluid flows 
off at p. The distillation is continued until the fluid which comes over (the distil¬ 
late) contains only 35 to 40 per cent of alcohol; a sample is then taken at tho 



small cooling apparatus, k, to test the quality of the mash, and in order to 
ascertain whether it contains any more alcohol. When the distillate collected at n 
is found to be only water the operation is finished. The wash is run off from the 
still, and it is then re-filled with fresh mash from the fore-warmer through 7 , and 



















































SPIRIT. 


435 


the distillation again proceeded with. The low wine contained in the vessel f flows 
through the tube j or q back into the still. As may be seen in the cut, Dorn’s appa¬ 
ratus has not a separate dephlegmator and only one still or retort. This apparatus 
is now rarely used for distilling mash, but frequently for rectifying spirits. 

Pistorius’s Apparatus. . Pistorius first introduced in Germany a distilling apparatus 
fitted with two stills ingeniously connected with rectificators and deplilegmators. 
When a distilling apparatus is required which not only extracts all the alcohol from 
the mash, but also produces the alcohol in a very pure and concentrated state, 
performing this work with the least possible expenditure of fuel and labour, 
Pistorius’s apparatus answers the purpose admirably, a and b, Fig. 234, represent 
the two stills, a is the main still, which is either placed qn a furnace and heated 
directly by fire or by means of steam. Heating by steam-pipes instead of direct 
firing possesses many advantages. The second still, b, is placed at a somewhat 
higher level than the first, and when not heated by steam-pipes is situated 
on the flue of the furnace fire of the first still. The main still, a, is fitted with a 
large helm, n, fastened on the still with bolts and nuts, p is a tube projecting from 
the helm and provided with a safety valve which opens inwards, in order to give 
access to air as soon as towards the end of the distillation a vacuum might ensue in 
the interior of the apparatus in consequence of the condensation of the vapours. 
There is also connected with this tube, p, a small condenser, q, as in Dorn’s 
apparatus, from which samples showing the progress of the distillation may be taken. 
In both stills stirring apparatus, m and n, are fitted to prevent the mash burning. 
By the tube x the vapour of the “ low wine ” is admitted to the second still, the 
mash-still. From the helm, f, of the mash-still a curved pipe, s, conveys the vapour 
to the mash fore-warmer, which, as in Dorn’s apparatus, is divided into two parts, the 
upper, e, containing the mash, the lower, g (the “ low wine ” cistern); the vapour 
ascending along the narrow passage, v, to the rectification apparatus, h. Frequently 
the vapour is conveyed to a third still before entering g ; this still is not shown in the 
drawing. The rectification apparatus, h, consists of two or three conically-shaped 
vessels, made of sheet-copper and connected together, and is provided with a cistern 
filled with water, w; it is connected with the condenser, 11, by the tube c. The 
tube x conveys cold water to the rectification apparatus, and the short tube, y, does 
so to the fore-warmer. The pump, r, is employed to pump the mash from the 
cistern, l, to the fore-warmer; thence it is carried to the second still, and thence 
again to the first still. When both stills and the fore-warmer are filled with mash, 
the fire is lighted under the first still. The steam or vapour from the mash in a 
passes to the mash in b, which is thereby heated to the boiling-point. The still b 
serves, therefore, the purpose of a rectificator. When the distillation has begun, the 
vessel, w, on the rectificator is filled with cold water, which is re-supplied when it 
has become warmed by the passing vapours. As soon as the steam reaches tlie upper 
rectificator, the real distillation commences. The condensed fluid drops into a 
cistern in which a hydrometer is placed. 

Gail’s Apparatus. In most apparatus for distilling from a vinous mash the distillate 
becomes gradually weaker and is not throughout of the same strength. Gall and 
Marienbad have endeavoured to avoid this defect in their apparatus, Figs. 235 and 
236, so as to obtain a more uniform product during each distillation. Two stills are 
placed in a suitable manner in a steam-boiler and the stills are connected with the 
separator (low wine cistern), bb are the stills; c is a boiler with flues, i i. 


436 


CHEMICAL TECHNOLOGY. 


the stills, in order to prevent them cooling, are fixed into the boiler; d is a third 
still placed on, not in, the boiler ; e is the low wine cistern; f and g two dephleg- 
mators or separators ; a is a condenser with a worm, h. The mash is put first into 
the still d by means of the tube a a , this still serving as a fore-warmer and recti- 
ficator. From this still both the stills b b are filled. From the boiler a current of 
steam is conveyed through the bent tube, b, into the three-way-cock, c, whence the 
steam is either passed into one or both the stills b b or is conveyed upwards by the 
tube cl to the vessel destined to steam the potatoes. The vapour from one or both of 
the stills b b proceeds to the still d, and thence into the low wine cistern, e, and 
passing through the dephlegmators, f and g, finally enter into the condenser. The 


Fig. 235. 



peculiarity of Gall’s apparatus consists in that by the peculiar arrangement of 
tubes and stop-cocks, each of the two stills may at will be brought into action, it 
being possible to turn the steam at pleasure into the right-hand still, and next 
into the left-hand still, or vice versa. Each still may be also disconnected, the 
wash therefrom discharged and re-filled without in the least interrupting the 
working of the other portions of the apparatus; the distillation can therefore 
proceed uninterruptedly, one part of the apparatus being filled while the other is 
at work. 

Schwarz’s Apparatus. Schwarz’s apparatus is in very general use in the south-west of 
Germany. It consists, Fig. 237, of the steam boiler, d ; two mash stills, a and b; the 


















SPIRIT. 


437 


fore-warmer, c ; the “ low wine” cistern, or receiver, e ; the rectificators, h and f; and 
the condenser, o. m is a reservoir for cold, n one for hot water. The steam generated 
in the "boiler, d, passes through the pipe, g, into the under compartment, a, of the 
double still, through the mash contained there ; becoming mixed with vapours of 
alcohol, it arrives in the helm, z, and further makes its way by means of the tube u 
into the upper part of the double still; thence after a double rectification it is 
conveyed by means of the tube t to the fere warmer, c; the upper part of this 
vessel provided with the tubes aaa acts as a dephlegmator or separator, the con 
densed fluid flowing into e. The steam which arrives from the upper part of the 
still passes through e, and thence by way of the tubes a a into the helm, and 
the tube n, which latter is surrounded with the vessel h kept cold by means of cold 


Fig. 236. 



water ; the dephlegmation continues here. From h the steam passes through v to r, 
an apparatus corresponding to the fore-warmer, c, but of smaller dimensions; 
because here the quantity of vapour has become greatly reduced while it has become 
richer in alcohol. The dephlegmator tubes are here surrounded by cold water, not 
by cold mash, the former liquid being constantly renewed so as to keep cold. The 
steam or vapour collected in the helm, b, is sufficiently laden with alcohol to 
admit of being at once conveyed to the condenser, g, the condensed distillate flowing 
out at i. The vinous mash is first poured into the fore-warmer, c, wherein it is 



























































































43 8 CHEMICAL TECHNOLOGY. 

occasionally stirred by the arms, dd, and crank, cl, so as to keep it uniformly mixed 
and heated. When the mash has become warm it is conveyed into the upper com¬ 
partment of the double still by the pipe, e, and into the lower compartment through 
■ the open valve; this compartment also serves as cistern for the phlegma from all 
other parts of the apparatus; the fluid flows backwards from the compartments h and l 



of the rectificators, h and r, byway of the tubes in' and n, into the low wine cistern, k, 
thence into the upper compartment of the double still, where it mixes with the mash. 
As soon as the mash has given up all its alcohol, which can be ascertained by testing 
the inflammability of the vapour issuing from the test stop-cock, o, the residue is 


































































SPIRIT. 


439 


removed by opening the tap, p. By means of the tubes qqq the rectificators and 
condensing apparatus are supplied with cold water. The warm water from the con¬ 
denser is conveyed by the tube r into the boiler. By means of r, the steam csn be 
admitted to the potato vessels, and by s into the reservoir n, when it is desired to 
heat the water it contains to the boiling-point. Schwarz’s apparatus possesses the 
advantage of being easily taken to pieces and cleansed. But, on the contrary, 
among its disadvantages are the following:—the construction of the mash-warmers is 
not quite suited for the purpose, while also the condensed liquid in e is not brought 
sufficiently into contact with the hot steam to affect a thorough distillation or rectifi¬ 
cation. The steam passes so quickly through the liquid that it is only very 


Fig. 238. 



imperfectly deprived of its water (deplilegmated) when it reaches the dephlegmation 
apparatus, where it will consequently be but imperfectly rectified, while the vertical 
steam-pipes offer too few points of contact, and allow much steam to pass off with¬ 
out being fully condensed ; while even the partly condensed vesicular steam is 
carried off along with the condensation escaping steam. The condenser itself is 
imperfect, being constructed of a number of vertical pipes, through which the con¬ 
densed liquid rapidly falls without becoming quite cold, and in order to obtain a 
sufficient condensation an immense quantity of cold water has to be used. 
















































440 


CHEMICAL TECHNOLOGY. 


Siemens’s Apparatus. Among the apparatus capable of producing a large quantity of 
spirits at a small cost is that of Siemens. This apparatus is much used in the dis¬ 
tillation of brandy. It consists, Fig. 238, of two mash-stills set in a boiler, and 
capable of being alternately used (by means of the three cocks, a, b, and c), in the 
same manner as in Gall’s apparatus, while the fore-warmer and dephlegmator is 
constructed according to Siemens’s plan, l is the boiler ; p one of the mash-retorts; 
k is the low wine receiver; n the fore-warmer; a, a reservoir in which the condensed 
water intended as feed water of the boiler is collected; c is the dephlegmator ; b a 
reservoir for the vapours condensed in c. From the dephlegmator the vapour 
passes to a condenser not shown in the engraving. This apparatus is constructed of 
such dimensions that it can perform the work about to be mentioned. The 
boiler has to steam about 5000 kilos, of potatoes in four lots, during from 40 to 
45 minutes each, and should thus be cax^abl® to yield in three hours the fifth 
part of the weight of the potatoes = 1000 kilos., or in one hour 333 kilos, of 
steam, which renders necessary a steam-generating surface of about n square metres. 
But since the distillation requires steam also, this generating surface has to be 
increased by about 20 per cent, and should consequently be 135 to 14 square metres. 
The size of the mash stills should be sufficiently large to contain with ease 500 litres 
when properly filled; because, as already stated, the fluid from a is not returned to 
the still but to the steam-boiler, the stills being set into the last-named vessel not 
becoming externally cooled, whereby the quantity of water carried along with the 
vapours of spirit is compensated for. 

The mash warmer consists of a cylindrical portion, i i, the lower part of which 
has an indentation, c. In the cylinder is placed a narrower portion, 0 0, of the real 
mash-containing vessel fitted with the heating tube, f n. The upper part of the 
fore-warmer is fitted to the lower part by means of the flange, li h. r is a stirring 
apparatus, which is frequently set in operation during the process of distillation. 
The vapours from the second still are carried into the depression, c, under the fore¬ 
warmer, which in order that the vapours may come into contact with the phlegma is 
covered with a sieve. The vapours surround the under part of the mash reservoir 
and enter into the tube, /, through which they pass to the lower cylinder of the 
dephlegmator. The condensed water of the dephlegmator is conducted into the 
reservoir, a. The upper and under part of the fore-warmer are made of cast-iron, 
but the interior bottom and heating surfaces are made of copper. This kind of 
fore-warmer has the advantage of uniformly distributing the heat, while it can be 
easily cleansed. The dephlegmator, c, is so contrived that the rectified vapour can 
be conveyed to the condenser by two separate pipes placed in an opposite direction 
to each other, and are joined again in close proximity to the condenser. The 
remainder of the details will be seen on studying the drawing. 

Contl Appara?u8* imng Among the distilling apparatus intended for the distillation of 
wine (not of mash), and so constructed as to be fit for continuous working, we 
must not neglect to mention the apparatus of Cellier-Blumenthal, as improved 
by Derosne, and represented in Fig. 239. This apparatus consists of two stills, 
a and a'; the first rectificator, b; the second rectificator, c; the wine warmer and 
dephlegmator, d; the condenser, f; the regulator, e; a contrivance for regu¬ 
lating the flow of the fluid wine from the cistern, g. The still a', which as 
well as the still a is filled with wine, acts as a steam boiler. The low wine 


SPIRIT, 


441 


vapours evolved come, when they have arrived in the rectificators, in contact 
with an uninterrupted stream of wine, whereby dephlegmation is effected; the 
vapour thus enriched in alcohol becomes still stronger in the vessel d, and thence 


Fig. 239. 



arrives at the cooling apparatus, f. In order that a real rectification should take 
place in the rectificators, the stream of wine should be heated to a certain 
temperature, which is imparted to it by the heating of the condenser water. 








































































442 


CHEMICAL TECHNOLOGY . 


The steam from the still a' is carried by means of the pipe z to the bottom of 
the still a. Both stills are heated by the fire of the same furnace. By means 
of the tube b' the liquid contained in the still a can be run into the still a'. The 
first rectificator, b, contains a number of semi-circular discs of unequal size, placed 
one above the other, and which are so fastened to a vertical centre rod that they can 
be easily removed and cleansed. The larger discs, perforated in the manner of 
sieves, are placed with their concave surfaces upwards. In consequence of this 
arrangement the vapours ascending from the stills meet with large surfaces moistened 
with wine, which, moreover, trickles downwards in the manner of a cascade from 
the discs, and comes, therefore, into very intimate contact with the vapours. The 
second rectificator, c, is fitted with six compartments; in the centre of each of the 
partition walls (iron or copper plates) a hole is cut, and over this hole by means of a 
vertical bar, is fastened an inverted cup, which nearly reaches to tlie bottom of 
the compartment wherein it is placed. As a portion of the vapours are condensed 
in these compartments the vapours are necessarily forced through a layer of low 
wine, and have to overcome a pressure of a column of liquid 2 centimetres high. 
The fore-warmer and dephlegmator, d, is a horizontal cylinder made of copper 
fitted with a worm, the convolutions of which are placed vertically. The tube m 
communicates with this worm, the other end of which passes-to o. A phlegma 
collects in the convolutions of this tube, which is richer in alcohol in the foremost 
windings and weaker in those more remote : this fluid collecting in the lower part 
of the spirals may be drawn off by means of small tubes, thence to be transferred at 
the operator’s pleasure, either all or in part, by the aid of another tube and stop¬ 
cocks to the tube 0, or into the rectificator. By means of the tube l the previously- 
warmed wine of the dephlegmator can be run into the rectificator. The condenser, f, 
is a cylindrical vessel closed on all sides, and containing a worm communicating 
with the tube 0. The other end of the condensing tube carries the distillate away • 
On the top of this portion of the apparatus the tube k is placed, by means of 
which wine is run into the dephlegmator. The cold wine flows into the cooling- 
vessel by the tube 1. When it is desired to work with this apparatus, the first 
tiling to be done is the filling of the vessels a and a' with wine. The stop-cock, e. 
is then opened, whereby the tube j, the condenser, f, and the dephlegmator are filled 
with wine. The wine in the still a' is next heated to the boiling-point; the steam 
enters the tube z and is condensed in a until the wine here is heated to the boiling- 
point by the combined effect of the steam and the hot gases circulating in the flue. 
The low wine vapour then passes to the rectificator, b, and thence into the worm of 
the dephlegmator, d, where the greater portion of it is condensed, the phlegma flowing 
backwards into the rectificator As soon as the fore-warmer is so far heated that the 
hand cannot be kept in the hot wine, the stop-cock of the vessel e is opened, and 
the distillation commences. The wine which is conveyed by the tube j into the 
cooling vessel, f, soon begins to become hot, and is then conveyed to the fore¬ 
warmer, where its temperature becomes nearly as high as the boiling-point; by 
means of the tube l this fluid is conveyed into the rectificator, b, and thence into 
the still a. 

As soon as the wine in the still a' contains no more alcohol, the stop-cock, fitted to 
the lower part of the vessel is opened, and the vinasse run off at it, the still being 
re-supplied by opening the stop-cock, b'. The vapour proceeds in the same 
way, but in a reversed direction; when the vapour has been condensed in f it is 


SPIRIT. 


443 



first collected, as alcohol, in the small vessel, n, provided with an areometer, and 
thence conveyed to the cistern, n. The strength of the alcohol obtained by means 
of this apparatus increases with an increase of the number of the windings of the 
condenser placed in the dephlegmator and connected with the rectificator. Practical 
experience decides, according to the alcoholic strength of the wines to be distilled, 
and the quantity of pure alcohol desired in the distillate, the opening or shutting 
of the various stop-cocks of this apparatus. Derosne’s apparatus may be readily 
made continuous; for this purpose it is onty necessary to fill the reservoir, conden¬ 
sing apparatus, and rectificator with cold water, while the lower portion of the tube l 
is closed. 

Laugier’s Apparatus. Laugier’s apparatus, shown in section in Fig. 240, is also of great 
interest. Notwithstanding the fact that Derosne’s apparatus is exceedingly com¬ 
mendable for great economy of fuel, rapidity of distillation, and excellence of product, 

Fig. 240. 


the apparatus is rather of a complicated construction, because it is arranged to 
distil all lands of wine, be they -weak or strong, while at the same time alcohol of 
any desired strength may be obtained. Apparatus of the construction of Laugier’s, 
arranged for the distillation of one kind of fluid, wine or mash, and for the pro¬ 
duction of a distillate which is always of the same strength of alcohol, may be 
far more simply constructed. The fluid to be distilled flows from the tube, s, 
into the funnel,^*, thence into the vessel a, entering its lower part and serving to 































444 


CHEMICAL TECHNOLOGY. 


condense the alcoholic vapour. From this vessel the warmed fluid passes 
by means of the tube r into the lower part of the second vessel, b, where 
dephlegmation takes place by means of a condensing tube. Thence the fluid 
flows by way of the tube c into the second still, c, which is heated by the hot 
gases evolved from the fire kept burning under the first still, d ; in the still c the 
fluid undergoes a rectification, and the vinasse flows by the tube e into the 
still d. m is the pipe conveying the hot vapour from d into c; the tube b conveys 
the alcoholic vapours into the dephlegmator. By means of the tube cl the phlegma 
is conveyed into the still c ; f serves as a means of emptying the still d ; g and h 
are glass-gauging tubes for indicating the height of the fluid in the interior of the 
still; the tube l conveys the non-condensed vapours from the dephlegmator into the 
condensing apparatus ; while i conveys the vapours formed in the vessel b into the 
condensing apparatus. The alcohol condensed in the cooling apparatus flows, as is 
exhibited in the cut, into a vessel, o, provided with an areometer to indicate the 
strength of the fluid. The cooling apparatus of the vessel b consists of seven 
compartments or divisions formed by wide spirals, each of which is at its lower 
level fitted with a narrow tube, all of which are connected to the tube d, by way 

of which the condensed fluids are 
made to flow back into the still. By 
properly regulating the boiling of 
the liquid in the first still and by 
adjusting the flow of wine, the 
condensation of the vapours in the 
dephlegmator can be arranged at 
will, so that either brandy of 50 
per cent or alcohol of above 80 per 
cent be obtained. 

Sometimes an apparatus of even 
more simple construction is em¬ 
ployed, in which the fluid to be 
distilled is heated by a spiral tube, 
through which high-pressure steam 
is made to circulate. Such an 
apparatus is exhibited in Fig. 241. 
a is a cast-iron or copper cylinder, 
in which the fluid to be distilled 
is heated by a spiral tube made 
of copper; the inlet of this tube is at 
b, and the outlet at a; by means of c 
the vinasse, devoid of alcohol, is run 
off. b is the dephlegmator, through 
which the fluid to be distilled con¬ 
tinually flows in a downward direction, while the vapour of the low wine evolved in a 
ascends uninterruptedly. In order to increase the surface and points of contact the 
arrangement in the deplegmator is very different. The vapour ascends to the reservoir, 
e, and by way of the tube f enters the rectificator, c, which is arranged as usual ; the 
condensed portion returning through h to the dephlegmator, while the uncondensed 
vapour passes on to the condenser of the vessel n there to become condensed 









































SPIRIT. 


445 


and carried off through m. The fluid to he distilled is kept in a tank (not represented 
in the cut) placed higher than the apparatus, being conveyed to the latter by way of 
the tube l i fitted with the stop-cock k, so that the liquid arrives first in d, is next 
conveyed to c, thence through g into the dephlegmator, and lastly into the cylinder. 

EemoYinR f the Fusel oils. It has been already mentioned (see p. 431) that in addition to 
etliylic alcohol there are formed during vinous fermentation—under conditions not at 
all clearly understood nor scientifically elucidated—larger or smaller quantities of 
alcohols homologous with etliylic alcohol; such, as, for instance, propylic, butylic, 
amylic alcohols, which, when mixed with larger or smaller quantities of complex 
ethers, bear the name of fusel oil, a fluid which imparts to the etliylic alcohol (in 
the shape of brandy, gin, whiskey, &c.) a very unpleasant flavour, also rendering 
these spirits when crude very injurious to the human system. Fusel oil differs 
according to the nature of the mash, potatoes, grain, and beet-roots being used 
in its preparation. Fusel oil is formed in large quantity only when fermentation 
takes place at a high temperature in a concentrated saccharine fluid, while no 
tartaric acid is simultaneously present. A fluid which ferments at a low temperature 
and is very dilute does not yield fusel oil, at least no amylic alcohol, which also is 
never formed in such wines as have been fermented when tartaric acid has been 
present in the fermenting fluid. 

As it is a property of all fusel oils that they are less volatile than water and 
alcohol, they are only condensed when brandy, gin, whiskey, &c., are distilled towards 
the end of the distillation ; while as regards the distillation of the alcohol these oils 
are chiefly met with in the products of the condensation of the deplilegmators. A 
portion, however, of the fusel oils comes over along with the alcohol, and being 
very intimately mixed therewith is not readily removed from these fluids. Potato 
fusel oil is essentially amylic alcohol (C 5 H I2 0 j, a colourless, very mobile fluid 
of 0 818 sp. gr., of penetrating odour, provoking coughing, and of a burning taste; 
it boils at 133 0 . By means of oxidising agents, such as manganate and per¬ 
manganate of potash, a mixture of sulphuric acid and bichromate of potash, or 
manganese as well as platinum black, amylic alcohol is converted into valerianic 
acid (C 5 H 10 0 2 ). By the action of acids this amylic alcohol is converted into peculiar 
kinds of ethers in the same manner as this effect is produced by acids upon ordinary 
(ethylic) alcohol. Some of the ethers thus formed exhibit a highly agreeable 
odour, and are therefore used in perfumery, and for the flavouring of sweetmeats, 
bon-bons, &c. 

As for many of the applications of potato-spirit the fusel oil is a disadvantage, 
the spirit has therefore to be submitted to an operation of rectification whereby the 
fusel oil is got rid of. The suggestions which have been made for this purpose refer 
either to the destruction of the fusel eil by oxidation or the action of chlorine, or the 
masking of the oil and its conversion into less disagreeable compounds; partly 
also to a real removal of the fusel oil from the spirit. "When the fusel oil con¬ 
taining spirit is rectified over chloride of lime (bleaching-powder), permanganate of 
potassa, &c., valerianate of fusel-ether is formed; but since the action of these 
reagents is not limited to .the amylic alcohol but extends to the ethylic, it is 
very difficult to adjust the quantity of these reagents so that only the amylic 
alcohol be acted upon. If the spirits from which the fusel oil is to be re¬ 
moved are treated with a mixture of sulphuric acid and vinegar, there is formed, 




446 CHEMICAL TECHNOLOGY. 

C H 0) 

besides some acetic ether, acetate of amyl, q 2 jj 3 [ 0, of a pleasant fruity flavour. 

Hydrochloric and nitric acids, also used to remove fusel oil, act in a somewhat 
similar manner. The most approved method of removing the fusel oil is by means 
of well-burnt charcoal (vegetable charcoal, charred peat, bone-black), which, when 
brought into contact with the crude spirit, absorbs the fusel oil mechanically. By 
the aid of charcoal, spirits and brandy (no't when obtained from wine), are purified 
either in the state of vapour, or by digestion with the charcoal, and filtration at the 
ordinary temperature of the air; rectification at boiling temperature over charcoal 
is altogether unsuitable, owing to the fact that the fusel oil absorbed by the 
charcoal is again readily dissolved at that temperature. The charcoal to be 
employed is granulated and passed through a sieve in order to remove adhe¬ 
ring dust. The granulated charcoal is placed in a copper cylinder, fitted at top 
and bottom with a perforated plate or disc; this cylinder is connected with the 
distilling apparatus between the dephlegmator and rectificator in such a manner that 
the vapours pass through the charcoal. To ioo litres of brandy to be purified 3 to 5 
litres of granulated charcoal are generally required; this can be again employed after 

having been re-burnt at a bright red heat. Falkman’s 
apparatus consists of a helm-shaped vessel, a, Fig. 242, 
in which the perforated diaphragms, bbb, are placed ; 
upon each diaphragm a layer of charcoal, surmounted 
with a cover, c, is placed. The apparatus is closed 
with a hollow cover containing a layer of charcoal, 
del. The vessel a is surrounded by a cooling appa¬ 
ratus, which in the cut is represented by the cold water 
tubes,///, and the hot water (which becomes hot by the 
passage of alcoholic vapours through a) tubes, eeee; 
these serve the purpose of regulating the temperature 
of the layers of charcoal. 

Yield of Alcohol. The quantity of alcohol obtainable from 
any given substance does not only depend on the rela¬ 
tive quantity of the alcohol-forming constituents 
(starch, dextrose, or cane sugar) of the raw material applied for the purpose 
of distillation, but depends very largely also on the more or less suitable mode 
of conducting all the operations of the spirit distillation (mashing, fermentation), in 
properly constructed apparatus. Leaving out of the question the small quantities 
of glycerine and succinic acid formed by vinous fermentation, chemistry teaches 
that 

100 parts of starch yielfl. 5678 of alcohol. 

100 „ cane sugar „ 53'8o „ 

100 „ dextrose „ 5i’oi „ 

Experience teaches that the yield of alcohol is in practice less than it should be, 

premising that every 1 mol. of starch or sugar yields 2 mols. of alcohol; 100 parts of 

cane sugar do not yield in practice the quantity of alcohol above indicated—viz. 53 8 
parts, but only 51*1. 


Fig. 242. 



SPIRIT . 


447 


ioo kilos, of barley give 44 64 litres of corn brandy at 50° Tralles. 

100 „ barley-malt „ 54-96 „ M 

100 „ wheat „ 49-22 „ 

J oo » r ye .. 45'8 o „ 

100 „ potatoes „ 18*32 „ potato spirit ,, 

6 litres (quart or maas) of brandy, from the metrical hundredweight (hectolitre, &c.), 
is reckoned to yield 6 X 50 = 300 per cent alcohol; 7 litres, consequently, 350; 
S litres, 400. 8 litres at 48 per cent Tralles = 384 per cent alcohol. The number of 

litres of brandy or spirit multiplied by the alcohol in percentage according to 
Tralles therefore yield:— 


1 metrical cwt. of 

barley 

44-64 X 50 = 2232 per cent alcohol. 

1 „ 

barley-malt 

54-96X50 = 2748 

1 

wheat 

49*22X50 = 2461 

1 » »> 

rye 

4580X50 = 2290 „ „ 

1 

potatoes 

1832X50= 916 


Usually 1 Bavarian maas is taken as equal to 1*069 litres, 1 Prussian quart = 1*145 
litres. 

In quoting the prices in the following foreign markets, it is usual to take as 
a unit— 

In Breslau 4,800 ( 60 quarts at 8o°). 

In Berlin j.0,800 (200 „ 54°). 

In Magdeburg 14,400 (180 „ 8o°). 

Recently it has become general to adopt as a unit 8000 (100 quarts at 8o°). 

Aicohoiometry. For the purpose of ascertaining the quantity of alcohol contained in a 
fluid which consists only of alcohol and water, the areometer, or alcoholometer, is 

Areometer, generally employed. The vaporimeter and the ebullioscope (see p. 395) 
are seldom used. The application of the areometer is based upon the principle that a 
body immersed in a fluid (for instance, water) always displaces a quantity of water 
equal to its own volume, and loses in weight proportionately to the quantity of water 
displaced. It therefore follows, that by the depth to which the areometer sinks, as 
noted by the degrees on the spindle, we can determine the quantity of absolute 
alcohol contained in the fluid under examination. The areometer of Tralles and that 
of Richter are most generally used in Germany. Stoppani’s is similar to that of 
Richter. Both are centesimal alcoholometers and show by the number of the degree 
to which they sink the percentage of pure alcohol. The difference between these 
two instruments consists in that the areometer of Tralles indicates percentage by 
volume, and Richter’s percentage by weight. Tralles’s alcoholometer is much used 
in the Zollverein (German Custom’s Association, viz. of the various States constitu¬ 
ting, with the exception of Luxemburg, the German Empire) for the purpose of 
ascertaining the alcohol contained in spirituous liquors (at 14*44° R) l i n Austria the 
same instrument is used, with a difference, however, in the temperature at which 
the observation is made, the degree of the thermometer being usually taken at 
12° R. (=15° C.) 

The following table exhibits a comparison of both scales, and with the true 
weight per cent, along with the corresponding specific gravity at a temperature of 

15° C.:- 


CHEMICAL TECHNOLOGY. 


443 


Sp. gr. 

True weight 
per cent. 

Approximate weight 

Percentage of 

per cent according 
to Eichter. 

volume according 
to Tralles. 

0-990 

4‘99 

5 

6-23 

0-981 

irn 

10 

1373 

0-972 

i 8 'I 2 

15 

22*20 

0964 

24-83 

20 

30-16 

0956 

29-82 

25 

36-50 

0-947 

35'29 

30 

42"I2 

°'9 37 

40-66 

35 

48-00 

0926 

46-00 

40 

53'66 

°’ 9 I 5 

51-02 

45 

58*82 

0-906 

54‘85 

50 

62-65 

0-899 

60-34 

55 

67-96 

0-883 

64-79 

60 

72-12 

0-872 

69-79 

65 

76*66 

0-862 

74*66 

70 

80-36 

0-850 

78-81 

75 

84*43 

0838 

8372 

80 

8874 

0-827 

88-36 

85 

91*85 

0815 

92*54 

90 

95’°5 

0-805 

96-77 

95 

97*55 

°795 

99-60 

IOO 

9975 


The most usual alcoholometer is that which indicates the percentage of volume, or how 
many volumes of absolute alcohol there are contained in ioo volumes of the alcoholic 
fluid.. Brandy of 50° Tralles is therefore understood to he a spirit, 100 litres of which 
contain 50 litres of alcohol; and from which by distillation these 50 litres of alcohol can 
be extracted. Considering that when alcohol and water are mixed a considerable contrac¬ 
tion and decrease of bulk is the result, it is clear that 50 litres of alcohol (absolute is here 
meant) and 50 litres of water will only yield a mixture measuring 96-377 litres ; and 
accordingly 100 litres of such a fluid contain instead of 50 litres of alcohol, 51-88 litres of 
that liquid. 

Relation of Brandy The relation of the distillation industry to agriculture, and more 
Distilling to Agriculture, especially as a means of providing fodder for cattle, is very interesting 
and important. The distillation of spirits leaves a residue which may be usefully employed 
as fodder for cattle ; the distillatory process extracts from the starch-containing materials 
which are employed only the alcohol which is formed in the mash by fermentation, but it 
leaves behind in a concentrated state all the nutritive substances (especially albumen 
compounds), which not being acted upon by the fermentation, are left in the residues in 
almost the same state as they were originally present in the potatoes and grain made use 
of by the distiller. It is evident that when the expenses of the production of the spirits 
are paid to the distiller, the residues of the operation become a valuable material obtained 
cost.free, the production of which is an important item in this industry. 

"Viewed in the light of agricultural industry the preparation of spirits from potatoes 
becomes in reality a chemical decomposition of the substances of which potatoes are com¬ 
posed, and a product of a relatively far greater value, and more readily transportable 
and preservable—viz., spirits and wash, and fodder material. 

The Residue or Wash. The wash is a fluid in which starch, dextrine, pectin substances, pro¬ 
tein compounds, fat, small quantities of sugar, husks of grain, succinic acid, glycerine, 
salts, and some of the constituents of yeast are met with, partly in solution, partly sus¬ 
pended, while some of these materials are more or less decomposed and altered. The 
quantity of dry substance only amounts to from 4 to 10 per cent; this is due to the 
varying nature of the raw material, to the quantity of water used in mashing, and to 
the unequal quantity of water absorbed by the fermented mash during the process of dis¬ 
tillation. 


SPIRIT. 


449 


Ritthausen analysed several varieties of wash with the following results, the proportion 
of dry substance to the water being in (I.) as i :y'3 ; in (II.) as i: 6 ; in (III.) as i: 4*08; 
in (IV.) as 1:4 ; in (Y.) as 1: 3 :— 



I. 

n. 

HI. 

IV. 

V. 

Non-nitrogenous substances 

278 

3-23 

3-08 

4' x 4 

5 ‘ 3 i 

Protein compounds .. 

0*82 

1-04 

1-26 

i -39 

178 

Cellulose . 

0*46 

o -43 

o -94 

0*78 

1*00 

Ash . 

0*52 

o -59 

072 

0*79 

1*01 

Water. 

95 ' 4 ° 

947 1 

94*00 

92*90 

90*90 


When in a distillery potatoes and malt are always used in equal quantities and of the 
same quality, and the mash made at the same degree of concentration, the wash will 
always be of nearly as possible the same composition. It may be assumed that, on an 
average, three-fourths of the solid matter met with in the wash is nutritive; the 
proportion of nitrogenous to non-nitrogenous matter is on the average as 1:3, while 
in the potato it is only as 1:8. When the potatoes are converted into wash they lose 
the greater part of their non-nitrogenous matter, and thus become a fodder rich in 
protein compounds. In practice, 150 to 250 kilos, of potato mash are considered 
equivalent to 50 kilos, of hay. 

Dry Yeast. By the fermentation of the beer-wort containing hops, yeast is pro¬ 
duced in large quantities, and this is used in most cases when it is desired to induct 
a vinous fermentation; but for some purposes, such as bread-making for instance, 
this yeast is not applicable owing to its containing much of the bitter principle of 
the hop, and therefore possessing a very disagreeable flavour. This bitter principle 
may be removed by thoroughly washing with cold water, or, as recommended by 
Trommer, by first dissolving the yeast in a solution of caustic alkali, and then pre¬ 
cipitating it therefrom by means of dilute sulphuric acid : such proceedings, how¬ 
ever, always impair the efficacy of the yeast as a ferment, and the additional amount 
of time and labour required necessarily enhances the price of the yeast. The pro¬ 
duction of yeast in breweries is, moreover, only a subordinate affair, the main 
point being the preparation of beer of good quality. The production of yeast, 
although it can only be obtained by vinous fermentation, is best combined with the 
distillation of spirit, whereby, if desired, the preparation of dry yeast may be made 
a principal, and the production of spirit to a certain extent a subordinate, 
affair. 

We have in a former portion of this work, while treating on fermentation in general, 
explained the mode of formation and the nature of the yeast, and that this yeast has 
been proved by experience to be best fed and most rapidly propagated by the glutei 
and other protein compounds of the cereals in solution. Yeast may be made in various 
ways. At Schiedam (Holland) it is made of excellent quality by a mode which is to 
a certain extent a trade secret—and differs materially from the following process :— 
A mash is made in the ordinary manner of 1 part of bruised barley malt with 
3 parts of bruised rye, the mash being cooled with the fluid portion of the wash. 
To 100 kilos, of the bruised grain is added 0*5 kilo, of carbonate of soda and 0*35 
kilo, of sulphuric acid diluted with water; these ingredients having been added to 
the mash it is brought to fermentation by the aid of yeast. The newly-formed 
yeast is removed from the strongly-fermenting fluid by the aid of perforated ladles 
it is then strained through a linen cloth or fine sieve, and poured into cold water, 
wherein it is allowed to form a sediment. The sediment thus produced is col¬ 
lected after the supernatant water has been run off, is placed in a stout canvas 
bag under a press, and formed into a stiff clayey dough, to which usually 4 to ic 

30 





CHEMICAL TECHNOLOGY. 


450 

(sometimes as much as 24) per cent of dry potato starch is added. Sometimes tlio 
water is removed from the yeast by placing that substance upon slabs made of 
gypsum or other absorbent materials, care being taken to keep the yeast in a 
cool place; by the use of the hydro-extractor—expressly arranged as regards its 
construction for this purpose—yeast may be very rapidly rendered dry. As regards 
the use of the carbonate of soda, it appears to assist in the separation of the glu¬ 
tinous constituents of the cereals; the action of the sulphuric acid is partly 
similar, and it also prevents the formation of lactic acid, which, if formed, causes 
a loss of bs»t.h starch and spirit; the sulphuric acid also accelerates the separation of 
the yeast. According to communications by some of the most eminent distillers at 
Schiedam to Dr. G. J. Mulder, neither soda nor sulphuric acid are used at 
Schiedam in the preparation of what the trade terms dry or German yeast, some of 
which is imported into this country from Hamburg. Assuming the researches of 
Pasteur and others on fermentation to be correct, these observations are of great value 
in reference to the manufacture of yeast. It is found that the yeast sporulse become 
properly developed when they are placed in a fluid which, instead of containing 
protein compounds, consists of aqueous saline solutions mixed with a sugar 
solution, such as, for instance—tartrate of ammonia, phosphate of potash, gypsum, 
phosphate of magnesia. It would hence appear that under such conditions yeast 
cells take up the material for the propagation of new cells, partly from inorganic 
substances, partly from organic, viz., the decomposing sugar which yields 
carbonic acid: in this respect the yeast cells agree, then, with higher organised 
plants. As regards the quantity of yeast obtainable from a given weight of 
materials, it may be stated that from 100 kilos, of rye, including the bruised malt, 
about 15 to 16 kilos, of dry yeast can be obtained. As the quantity of real yeast 
or of the nitrogenous matter for sale present in the ready prepared dry yeast amounts 
at the most to 20 per cent, the nutritive value of the wash obtained after the dis ¬ 
tilling off of the spirits from the fermented liquid is but little impaired. 

so-called Artificial Yeast. We have yet to refer to what is termed artificial yeast, in reality 
a substance only intended for transferring the fermentation' of the wort or mash in 
activity to-day to a fresh batch to-morrow, so that it bears the same relation to the 
spirit preparation as leaven does to bread-baking. There are a great number of 
recipes for the preparation of artificial yeast and of artificial fermentation-inducing 
substances; as far as these are known they may be brought to the following cate¬ 
gories:—1. A small quantity of fully and strongly fermenting masli is mixed with 
fresh mash. 2. A small quantity of the fluid portion of the fermenting mash 
is cautiously drawn off by the aid of a syphon, and this portion having been set 
into fermentation, is added to the freshly made mash of the next day. 3. As soon 
as in the last-made mash the fermentation is strongest and most active, a small 
quantity of the ferment (yeast) separated from the fluid, and floating on its surface, is 
mixed with freshly made mash, the temperature of which has been purposely made 
sufficiently high to start the fermentation. The mash thus prepared may be used after 
a few hours to induce fermentation in a freshly made mash. A really artificial yeast, 
that is, yeast only prepared for the purpose of obtaining that substance by itself and 
independent of either brewing or distilling, is made in various ways, but always by a real 
process of fermentation. As an excellent instance of this mode of preparation, we quote 
the mode of preparing Vienna yeast:—- 

Vienna Yeast. This yeast is prepared in the following manner:—Previously-malted 
barley, maie, and rye are ground up and mixed, next put into water at a temperature of 
Cj° to 75 0 ; after a few hours, the saccharine liquid is decanted from the dregs, and 
the clear liquid brought into a state of fermentation by the aid of some yeast. The 
fermentation becomes very strong, and, by the force of the carbonic acid which is evolved, 
the yeast globules (the size of which averages from 10 to 12 m.m.) are carried to the 


BREAD . 


451 


surface of the liquid, and, forming a thick scum, are removed by a skimmer, then placed 
on cloth filters, drained, washed with a little distilled water, and next pressed into 
any desired shape by means of hydraulic pressure, and covered with a strong and well 
woven canvas. This kind of yeast keeps for eight to fourteen days according to the season, 
and is, both for bakers and brewers, very superior to that ordinarily used ; the extra good 
qualities of Vienna beer and bread are partly due to the use of this yeast in preparing 
these articles. 

Duty on Spirits. In the original work a couple of pages are devoted to an uninteresting 
discussion on this subject, which, as might be expected, has been treated not from a 
general point of view but from one bearing upon conditions which are altogether 
different from those existing in this. country. There can be no doubt that a duty 
on spirits is a very excellent thing; indeed, in this country this tax brings in such an 
enormous sum as to lead to the inference that spirits are consumed in larger quantities 
than is consistent with healthy conditions of body and social comfort. 


Bread Baking. 

Modes of Bread Making. The preparation of bread aims at the production in the flour 
obtained by grinding up the cereals of such a chemical and physical condition as 
will tend to render it most readily masticated by the teeth, and after having 
been duly mixed with saliva in the mouth, digested by the juices of the stomach. 
When flour is mixed with water so as to form a dough, and this mixture dried at the 
ordinary temperature of the atmosphere, a kind of cake is obtained which contains the 
starch unaltered and in an insoluble state, so that this kind of cake is very difficult 
to digest, while, moreover, its taste is so unpleasant as to create no appetite. 
Again, if the cake is dried at the boiling-point of water, it becomes like a dried 
starch paste, which is also very difficult to digest. 'When this temperature only acts 
upon the surface of such dough, and does not penetrate into the interior, the resulting 
cake will be a mixture somewhat similar to ship’s biscuit, which may always be 
considered as a strongly-dried dough, and although it may be preserved for almost 
any length of time, it is far less digestible than bread. The object of the baking 
process is to impart to the dough so high a degree of heat as to render the starch 
soluble, while it is further desired to form a light spongy mass, instead of a 
brittle or watery paste; the heat should be strong enough to terrify and roast the 
outer surface of the bread mass to such an extent as to form a deeply coloured 
crust, whereby not only the taste of the bread is greatly improved, but it can 
also be kept in good condition for some time. The usual means of rendering 
dough spongy is by vinous fermentation set up by the addition of a ferment, this 
being either leaven or yeast; a small portion of the starch of the flour is thus 
converted into glucose, which is then decomposed, yielding alcohol and carbonic acid 
gas; the latter, -while trying to escape, is prevented from doing so by the toughness 
of the dough, which is thereby rendered spongy. 

The alcohol is of no consequence whatever. White bread is prepared with 
wheaten flour and yeast; rye meal or a mixture of rye meal and wheaten flour with 
leaven, yields “black” or rye bread. Heeren found that flour in the state in 
which it is usually applied for bread baking contains an average of 13 per cent 
moisture. 

The Details of Bread Baking. The raw materials employed in the preparation of bread are 
flour, water, and a ferment , salt, spices, &c., are also used. The composition of the 
most important lands of flour and meals is as follows:— 


452 


CHEMICAL TECHNOLOGY. 



a. 

b. 

c. 

d. 

Water . 

I 5-54 

14*60 

14*00 

11*70 

Albumen . 

i *34 

1-56 

1*20 

1*24 

Vegetable glue . 

176 

2‘92 

3-60 

3-25 

Casein.' 

o '37 

090 

i *34 

015 

Fibrin . 

5 -i 9 

7 '36 

8-24 

14*84 

Gluten. 

350 

— 

— 

— 

Sugar . 

2*33 

3-46 

3*04 

219 

Gum . 

625 

4 - io 

633 

2‘8i 

Fat . 

1'07 

r8o 

223 

5-67 

Starch . 

63-64 

64'28 

53 -I 5 

58*13 

Sand . 

— 

*— 

685 

— 

a. Wheat flour, b. 

Bye meal. 

c. Barley meal. 

d. Oatmeal. 



In addition to these kinds of meal, those derived from zea-mais (Indian com) 
beans, peas, &c., are occasionally employed for making bread. 

The principal phases of the preparation are :— 

The and x thf Knead^g Ugh I * The m i x i n o °f the flour with water is the first manipulation 
of the baking process. The object of this operation is first to render dextrin and 
sugar (owing to the action of the gluten upon the starch, the quantity of sugar 
becomes increased while the mixing process is going on) and some albuminous 
substances soluble, and next to mix the solution thus formed thoroughly with 
the starch and gluten of the flour, and to soak and somewhat dissociate these 
substances; dry yeast or leaven are at the same time added to the bread mass, the 
former ferment being used when it is intended to make white; the latter when 
black bread is desired to be made. 

By sour dough or leaven is understood that portion of the already fermenting 
dough which is set apart and kept for the next baking operation; it consists of a 
mixture of flour and water, in which a portion of the starch is converted— 
partly into sugar, which is again changed by vinous fermentation, and acetic 
acid—but chiefly into lactic acid, by a process of fermentation set up by the 
peculiar conversion into active ferments of the protein, compounds of the flour 
itself. Leaven therefore acts as a fermentation-producing substance in a fresh 
batch of dough, its action being similar to that of yeast, or of already fermenting 
wort when added to a freshly made wort. After a length of time the leaven 
becomes putrid and unfit for use as a ferment. As regards the quantity of leaven 
to be used with the dough nothing definite can be said, since it depends as 
much on the degree of sourness of the leaven as on the quality of the bread in¬ 
tended to be made; usually 4 parts of leaven are added to 100 parts of flour, or to 
80 parts of bread 3 parts of leaven. In the case of white bread, 100 parts of flour 
require 2 parts of dry yeast. The mixing of the flour is effected with ^lukewarm 
w^ter, at a temperature of from 21 0 to 37 0 . 

Kneading The thin dough obtained from flour, water, and ferment, is dredged over 
with dry flour, and placed in a warm situation for a time, generally during the 
night. Fermentation is thus set up by the action of the ferment upon the dextrose 
of the dough, the carbonic acid developed rendering the dough spongy. The 











BREAD. 


453 


sponge thus prepared, is next mixed with more flour to bring it to the consistency 
required for the baking, this operation being known as the kneading of the 
sponge. The method usually employed in these operations is that one-third of 
the total quantity of flour required for a batch is mixed first with water and 
ferment, and when this mass has come into full fermentation, the two other thirds 
of flour are kneaded up along with the sponge, sufficient water being added to 
form a normal dough. After the kneading operation the dough is again dredged 
over with some dry flour, and left in a warm situation for the purpose of becoming 
thoroughly spongy: for this continued fermentation only about half the time is 
required as for the first-mentioned fermentation. In most bakeries, however, this 
second fermentation is not proceeded with, but the dough is, immediately after 
having been kneaded, cut up and shaped into loaves. 

By means of the kneading the dough becomes squeezed together, and has, there¬ 
fore, again to be left in a warm situation for further fermentation, during which 
it heaves up and increases to double its size. The dough is generally put either into 
a basket or tied in a stout cloth, which is previously dusted over with bran to 
prevent the pasty mass adhering to the cloth. The bulk of the dough increases 
twofold. When rye bread is made, the dough is frequently moistened on its 
external surface with lukewarm water, applied by the aid of a brush, in 
order to prevent cracks in the outer coating of the dough by the evaporation 
of the water; just before putting the loaves into the oven this brushing over 
with water is repeated. The water softens the outer surface of the dough, 
and dissolves some of the dextrine it contains, which substance, after the evapo¬ 
ration of the water from the surface, remains as a glaze upon the crust of this 
kind of bread. When the loaves have risen sufficiently and exhale a vinous 
peculiar odour, it is time to commence the baking process. Since the bread loses 
considerably in weight during the baking, the baker must proportion so much dough 
to each loaf before baking as will yield the legal weight of the baked bread. The 
weight of dough to be proportioned to a loaf of a certain fixed weight varies 
according to the size of the loaf, but increases comparatively with decrease in the 
size of the loaf. The dough generally loses in baking about 25 per cent of its 
weight. The smaller the loaf, the more crust in proportion to crumb; and since the 
crust contains less moisture, and, consequently, weighs less than the crumb, 
the loss of weight is greater in a small than in a large loaf. » 

Kneading Machines. The kneading of the dough by hand is not only very heavy 
work, but is unhealthy and objectionable on account of being unclean; the 
uniform quality of the dough is, moreover, by no means to be depended upon. 
Although it is impossible to perform by machinery any labour which absolutely 
requires the touch of the human hand, bread-kneading machines have been 
introduced wherever the making of only one and the same kind of bread is 
required. Among the numerous kinds of machines invented for this purpose we 
select for description that of Clayton (see fig. 243.) The constituents of the dough 
are placed in the cylinder, a, mounted in the framework, b b, and provided with 
hollow axles, c and d, turning in their bearings at e. The interior of the cylinder is 
fitted with the framework,/, which may be made to revolve by aid of the axles g and h. 
The two halves of this framework are connected together by the diagonal knives, i i, 
which, when the machinery revolves, work tip the dough; the trough or outer 
cylinder revolves in the opposite direction to the revolution of the framework. The 


454 CHEMICAL TECHNOLOGY. 

crank, o, is connected with the axle of the trough or outer cylinder; the crank, j) 
with that of the inner framework. As the two cranks are turned in opposite 
directions they impart opposite movements to trough and framework. The revolving 



Fig. 243. 


of the machinery may be performed by one man by the aid of one crank, since the 
axle, h, of the crank, o, which is fitted to the inner frame by means of the hollow 
axle-tree, and revolves along with it, carries a conically-shaped wheel, m, fitted to 
the wheel Je, which being connected with l causes the trough also to revolve; when, 
therefore, the wheel m turns towards the right, the wheel t will revolve towards 
the left. 

The oven. The conversion of the prepared dough into bread by baking is effected 
in an oven, ordinarily a circular or oval hearth or furnace, spanned by a vault, 
constructed with an opening at one end termed the mouth, serving alike for the 
introduction both of bread and of the fuel.* The oven is built of bricks cemented 
together with fire-clay, the sole of the hearth being laid with tiles or lined with 
fire-clay. The vault is usually elliptical, in order to reflect the heat as much as 
possible. The mouth is closed with a door made of boiler-plate or of cast-iron; 
and as the mouth also serves as an exit for the smoke, a flue is constructed at some 
short distance above it, and made to communicate with the chimney. Two small 
openings in close proximity to the mouth of the oven serve to bum therein small 
pieces of wood to afford light, while the bread is being placed in the oven. The air 
necessary for the combustion of the fuel enters the oven from the lower part of the 
mouth, while from the upper the gases of combustion and the smoke escape. 
It is preferable, however, to construct these ovens with a separate flue and 
chimney communicating- with another part of the vault, and to fit the flue with a 
damper to regulate the draught of the fire. Fig. 244 exhibits the vertical sec¬ 
tion, and Fig. 245 the plan of the sole of a baking oven. The sole, a, which 
is made so as to slope upwards towards the back of the oven, has a breadth 
of 31 metres, and a depth of 4 metres; it is spanned by a vault 05 metre 
high. The mouth is o*8 metre wide, eee are the flues through which the gases 
of combustion pass into the chimney, d, the draught being regulated by means of 
the damper, u. The trench, x, affords standing-room for the baker. Under the oven 
is a chamber serving as a store-room for the coal. The space e serves as a hot 
room wherein the bread is placed previous to being put into the oven in order that 
the dough may rise. Thoroughly dried wood is used as fuel; it is placed cross¬ 
wise upon the hearth. Coals are used in England as fuel for this purpose. The 






















bread; 


455 


oven lias reached the required temperature, when a piece of wood rubbed on the 
hearth gives off sparks. The glowing charcoal is removed through the mouth of 
the oven, and extinguished in the lower chamber. Before the bread is put into the 
oven the sole is carefully cleaned with a wet swabber fastened to a pole, and ash and 


Fig. 244. 



cinders having been removed the bread is put into the oven with the aid of an 
oven-shovel, fixed to a very long handle. The proper temperature of the oven for 
baking is between 200° and 225 0 C. Before the loaves are put into the oven they 
are brushed over with water wherein a small quantity of flour has been mixed, in older 
to prevent the crust of the bread formed by the first action of the heat flying off 
and cracking by the rapid expansion 
of the vapours formed by the heat 
to which the bread is exposed. The 
steam, which after some time fills 
the oven, materially assists the 
baldng process, and very greatly 
aids the chemical changes which 
are especially apparent in the crust, 
which owes its glazed appear¬ 
ance thereto. The time necessary 
for the baking varies according to 
the size of the loaves, the form, 
and the kind of bread. The nearer 
the bread approaches to a globular 
form, and its surface therefore 
relatively smallest in relation to its contents, so much the longer time is 
necessary for the baking. Black bread takes a longer time to bake than white 
bread. These ovens are, however, not of the best construction: it is evident 
that they cannot be uniformly heated throughout, while they cool unequally also, and 
of course most so at the front part by the rushing in of cold air. After every batch 
of bread baked it therefore becomes necessary to fire the oven again for a short time 


Fig. 245. 






































45 ^ 


CHEMICAL TECHNOLOGY. 


before a fresh batch of bread is put into it; of course less fuel is required to bring 
up the requisite temperature again than will be required when firing is commenced. 
When the baking of bread is carried on continuously and on a manufacturing 
scale, ovens are employed in which the baking- and the fire-rooms are separate and 
distinct. 

substitutes for the Ferments. Substitutes for the Ferments in the “ Raising" of Bread. —We 
have seen from the preceding details that the preparation of bread is essentially 
based upon the fact that by the act of fermentation the gluten of the flour forms a 
kind of cellular tissue by which the escape of the carbonic acid is prevented, and thus 
the bread rendered porous and spongy, whereby its digestibility is increased. This 
quality of the bread is obtained at the cost of a portion of the starch of the flour, 
which is first converted into starch-sugar, and then by means of fermentation into 
alcohol and carbonic acid gas; to the expansion of the latter the bread owes its 
spongy texture. Many attempts have been made for the purpose of effecting 
the “ raising ” of the bread, as it is termed, without the use of a ferment, by 
introducing into the dough some gas- or vapour-producing substance, which 
would have the same mechanical effect at least as the carbonic acid derived from 
the fermentation. Although the problem of preparing bread of good quality without 
the aid of fermentation cannot be said to be quite settled, many proposals have 
been made in this direction, and some of these deserve notice; we therefore quote 
the most important. When sesquicarbonate of ammonia (the so-called sal cornu 
cervi of pharmacy) is added in small quantity to the dough, it will cause the raising 
of the same, partly because some acid is always present in the dough, whereby 
the salt is decomposed and carbonic acid set free, partly because by the heat of 
the oven the salt is volatilised, and by assuming the state of vapour causes the 
expansion and consequent sponginess of the dough. Liebig recommends the 
addition of bicarbonate of soda and hydrochloric acid to the dough, the carbonic 
acid being evolved according to the formula (NaHC 0 3 +HCl=NaCl+H 2 0 + C 0 2 ) 
with the formation of common salt which remains in the dough. The proportions 
are as follows:—To ioo kilos, of meal for making black bread i kilo, of bicarbonate 
of soda is taken, and 4*25 kilos, of hydrochloric acid of ro63 sp. gr. (= B. = 13 
per cent C 1 H), yielding 175 to 2 kilos, of common salt; the quantity of water to be 
added amounts to from 79 to 80 litres. From this mixture is obtained 150 kilos, of 
bread. The proportion of the bicarbonate of soda to the hydrochloric acid is so 
arranged that 5 grms. of the former are fully saturated by 33 c.c. of the latter, leaving in 
the bread a faintly acid reaction. The substance known and sold as Horsford’s yeast 
powder, also recommended by Liebig, is preferable and more readily applied. This 
powder consists of two separate preparations, viz., the acid powder (acid phosphate 
of lime with acid phosphate of magnesia), the other the alkali powder (a mixture of 
500 grms. of bicarbonate of soda and 443 grms. of chloride of potassium). To 
100 kilos, of flour, 2'6 kilos, of the acid powder, and r6 kilos, of the alkali powder 
are added. During the kneading the following changes occur: the bicarbonate of 
soda and chloride of potassium are first converted into chloride of sodium and 
bicarbonate of potash, the latter salt being in its turn decomposed by the acid 
phosphate, whereby carbonic acid is set free. By the use.of this baking powder it 
is possible to make flour into bread within two hour’s time, while, moreover, 100 
pounds of flour yield 10 to 12 per cent more bread than with the best method of 
baking in the usual way. The plan of incorporating pure carbonic acid gas with 


BREAD. 


457 


the dough has been frequently taken up and abandoned again; many trials have 
been made in this direction, and the process has its opponents as well as its 
defenders. Of later years the late Dr. Dauglish and Mr. Bousfield have taken this 
subject up, and after having obtained a patent have started the Aerated Bread 
Company. This process as carried out in practice is best described by an extract 
from Dr. Dauglish’s pamphlet, using his own words:— 

“ I first prepare the water which is to be used in forming the dough by placing it 
in a strong vessel capable of bearing a high pressure, and forcing carbonic acid into 
it to the extent of ten or twelve atmospheres, taking advantage of the well-known 
capacity of water for absorbing carbonic acid, whatever its density, in quantities 
equal to its own bulk. The water so prepared will of course retain the carbonic acid 
in solution so long as it is retained in a close vessel under the same pressure. I there¬ 
fore place the flour and salt of which the dough is to be formed also in a close 
vessel capable of bearing a high pressure. Within this vessel, which is of a 
spheroidal form, a simply constructed kneading apparatus is fixed, working from 
without through a closely packed stuffing box. Into this vessel I force an equal 
pressure to that which is maintained on the aerated water vessel; and then, by 
means of a pipe connecting the two vessels, I draw the water into the flour and set 
the kneading apparatus to work at the same time. By this arrangement the water 
acts simply as limpid water among the flour, the flour and water are mixed and 
kneaded together into paste, and to such an extent as shall give it the necessary 
tenacity. After this is accomplished the pressure is released, the gas escapes from 
the water, and in doing so raises the dough in the most beautiful and expeditious 
manner. It will be quite unnecessary for me to point out how perfect must be the 
mechanical structure that results from this method of raising dough. In the first 
place, the mixing and kneading of the flour and water together, before any vesicular 
property is imparted to the mass, render the most complete incorporation of the flour 
and water a matter of very easy accomplishment; and this being secured, it is evident 
that the gas which forms the vesicle, or sponge, when it is released, must be 
dispersed through the mass in a manner which no other method—fermentation not 
excepted—could accomplish. But besides the advantages of kneading the dough 
before the vesicle is formed, in the manner above-mentioned, there is another and 
perhaps a more important one from what it is likely to effect by giving scope to the 
introduction of new materials into bread making; and that is, I find that powerful 
machine kneading continued for several minutes has the effect of imparting to the 
dough tenacity or toughness. In Messrs. Carr and Co.’s machine, at Carlisle, we 
have kneaded some wheaten dough for lialf-an-hour, and the result has been that 
the dough has been so tough that it resembled bird-lime, and it was with difficulty 
pulled to pieces with the hand. Other materials, such as rye, barley, &c., are 
affected in the same manner; so that by thus kneading I am able to impart to 
dough, made from materials which otherwise would not have made light bread, from 
their wanting that quality in their gluten which is capable of holding or retaining, 
the same degree of lightness which no other method is capable of effecting. And I 
am sanguine of being able to make from rye, barley, oatmeal, and other wholesome 
and nutritious substances, bread as light and sweet as the finest wheaten bread. 
One reason why my process makes a bread so different from all other processes 
where fermentation is not followed is, that I am enabled to knead the bread to any 
extent without spoiling its vesicular property, whilst all other unfermented breads 


45 8 


* 


CHEMICAL TECHNOLOGY . 


are merely mixed, not kneaded. The property thus imparted to my bread by 
kneading renders it less dependent on being placed immediately in the oven. 
It certainly cannot gain by being allowed to stand after the dough is formed; but it 
bears well the necessary standing and waiting required for preparing the loaves for 
baking. 

‘‘There is one point which requires care in my process, and that is the baking: as 
the dough is excessively cold, first, because cold water is used in the process, and 
next because of its sudden expansion on rising. It is thus placed in the oven some 
40° F. in temperature lower than the ordinary fermented bread. This, together with 
its slow springing until it reaches the boiling-point, renders it essential that the top 
crust shall not be formed until the very last moment. Thus, I have been obliged to 
have ovens constructed which are heated through the bottom, and are furnished 
with means of regulating the heat of the top, so that the bread is cooked through 
the bottom; and, just at the last, the top heat is put on and the top crust formed. 

“ With regard to the gain effected by saving the loss of fermentation, I may state 
what must be evident, that the weight of the dough is always exactly the sum of the 
weight of flour, water, and salt put into the mixing vessel, and that in all our 
experiments at Carlisle we invariably made 118 loaves from the same weight of 
flour which by fermentation made only 105 and 106. Our advantage in gain over 
fermentation can only be equal to the loss of fermentation. As there has been 
considerable difference of opinion among men of science with respect to the amount of 
this loss—some stating it to be as high as 17! per cent and others so low as 1 per 
cent—I will here say a few words on the subject. Those who have stated the loss to 
be as high as 171 per cent have, in support of their position, pointed to the extra 
yield from the same flour of bread when made by non-fermentation compared with 
that made by fermentation. Whilst those who have opposed this assertion, and 
stated the loss to be but 1 per cent or little more, have declared the gain in weight to 
be simply a gain of extra water, and have based their calculations of loss on the 
destruction of material caused by the generation of the necessary quantity of carbonic 
acid to render the bread light. Starting, then, with the assumption that light bread 
contains in bulk half solid matter and half aeriform, they have calculated that this 
quantity of aeriform matter is obtained by a destruction of but 1 per cent of solid 
material. In this calculation the loss of carbonic acid, by its escape through the 
mass of dough during the process of fermentation and manufacture, does not aiypear 
to have been taken into account, that our calculations may be correct. 

“ One of the strongest proofs that the escape of gas through ordinary soft bread 
dough is very large arises from the fact, that when biscuit dough, in which there is a 
mixture of fatty matter, is prepared by my process, about half the quantity of gas only 
is needed to obtain an equal amount of lightness with dough that is made of flour 
and water only, the fatty matter acting to prevent the escape of gas from the dough. 
Other matters will operate in a similar manner—boiled flour, for instance, added in 
small quantities. But the assumption that light bread is only half aeriform master 
is altogether erroneous. Never before has there been so complete a method of 
testing what proportion the aeriform bears to the solid in light bread as that which 
my process affords. The mixing vessel at Messrs. Carr and Co’s. Works, Carlisle, 
has an internal capacity of 10 bushels. When 31 bushels of flour are put into this 
vessel, and formed into spongy bread dough, by my process it is quite full. And 
when flour is mixed with water into paste, the paste measures rather less than half 


BREAD. 


459 


tlio bulk of the original dry flour. This will, therefore, represent about i£ bushels of 
solid matter expanded into io bushels of spongy dough, showing in the dough 
nearly 5 parts aeriform to 1 solid: and in all instances, if the baking of this dough 
has not been accomplished so as to secure the loaves to spring to at least double their 
size in the oven, they have always come out heavy bread when compared with the 
ordinary fermented loaves. This gives the relative proportion of aeriform to solid in 
light bread at least as 10 to 1, and at once raises the loss by fermentation from 1 to 10 
per cent, without taking into account the loss of gas by its passage through the mass 
of dough. 

“I may be allowed here to state, what will be evident to all, that the absence 
of everything but flour, water, and salt, must render it absolutely pure; that its 
sweetness cannot be equalled except by bread to which sweet materials are super- 
added ; that, unlike all other unfermented bread, it makes excellent toast; and, on 
account of its high absorbent power, it makes the most delicious sop, puddings, &c., 
and also excellent poultices. Sop, pudding, and poultice made from this bread, how¬ 
ever, differ somewhat from those made from fermented bread, in being somewhat 
richer or more glutinous. This arises from the fact of the gluten not having been 
changed or rendered soluble in the manner caused by fermentation; but that this is a 
good quality rather than a bad one is evident from the fact, that the richer and purer 
fermented bread is, the more glutinous are the sops, &c., made from it; and the 
poorer and more adulterated with alum it is, the freer the sops, &e., are of 
this quality.” 

It should be observed that the alcohol formed during the fermentation of the 
bread and volatilised by the heat of the oven, acts along with the carbonic acid 
in rendering the dough spongy; upon this action of the alcohol is based the applica¬ 
tion of rum or brandy, which in small quantities are added to pastry and puddings 
made with flour, suet, eggs, sugar, butter, &c. 

Yield of Bread. As regards the quantity of bread obtained from a given quantity 
of flour, it varies according to the quality of the latter; 100 kilos, of flour usually 
yield from 125 to 135 kilos, of bread. 

composition of Bread. The flour from various kinds of grain contain in its ordinary 
air dry condition from 12 to 16 per cent of water; by its conversion into bread the 
flour takes up much more water. 100 pounds of fine wheaten flour combine with 50 
pounds of water, and give 150 pounds of bread. The composition of the flour and 


of the bread is, therefore, as follows:— 

Wheaten Flour. 

Wheaten Bread. 

Dry flour . 

84 

84 

Water originally contained in the flour 

16 

16 

Water added for making the dough ... 

— 

50 


100 

150 


According to Heeren, 100 pounds of wheaten flour yield at least 125 to 126 pounds 
of bread; 100 pounds of rye meal, 131 pounds of bread. Fresh wheaten bread con¬ 
tains 9 per cent of soluble starch and dextrin, 40 per cent of unchanged starch, 6 5 
per cent of protein compounds, and from 40 to 45 per cent of water. As is generally 
known newly baked bread possesses a peculiar softness, and is at the same time 
tough; does not yield crumbs readily; after one or more days’ keeping, the bread 
loses this softness, becomes dry, crumbles readily, and is then called stale or old 




460 


CHEMICAL TECHNOLOGY. 


bread; it is usually supposed that this change is due to a loss of water; but, 
according to the researches of Boussingault, stale bread contains just as much water 
as fresh bread; the alteration is solely due to a different molecular condition of the 
bread. 

impuritiesjind Adulteration "When the flour intended for the preparation of bread is more 
or less decayed, the gluten it contains is thereby altered; the carbonic acid evolved 
during the fermentation of the bread does not render the dough spongy, but it 
becomes, owing to the altered state of the gluten, a more or less slimy mass, which 
yields a tough and far less white-coloured bread; in order to counteract this defect, 
and to impart a good appearance to the bread made from flour which has been damaged 
by damp, or by having been too closely confined in casks and thereb} r heated, 
the bakers in Belgium and Northern France (and may we not say of England too), 
add to the dough a small quantity of sulphate of copper, tsotttt to ; the base of 
this salt combines with the gluten, forming therewith an insoluble compound, thus 
rendering the dough tough and white, and capable of taking a large quantity of 
water. In order to detect the sulphate of copper in the bread, a portion of the bread 
to be operated upon is first dried, then ignited, and the copper separated from 
the ash by gentty washing away the lighter particles, leaving the metallic copper 
in the shape of small shining spangles. In England alum is very generally added 
to bread. In Germany the addition of sulphate of copper and alum (o’5 per 
cent) to bread is prohibited by law, but in some parts of that country leaven is 
kept in copper vessels, whereby verdigris is formed, the appearance of which is by no 
means disliked by the bakers. 


The Manufacture of Vinegar. 

vinegar, and its origin. The fluid known in common life as vinegar is essentially a mix¬ 
ture of acetic acid and water. Acetic acid, C 2 H 4 0 2 . or C 2 H 3 j 0 , consists, in its 
highest degree of concentration, in 100 parts, of— 


Carbonic acid . 

24 

40*0 

Hydrogen ... . 

4 

67 

Oxygen . 

5 -* 

533 


60 

1000 


and is formed by the oxidation of alcohol as well as by the dry distillation of cellu¬ 
lose. 

As regards the first mode of formation, the process of the conversion of alcohol 
into acetic acid may be represented by the following formula :— 

1 mol. alcohol C 2 HeO = 46 j . ,, ( 1 mol. acetic acid C 2 H 4 0 2 = 60 

2 „ oxygen 2O = 32 J yie tt 1 1 „ water H 2 0 = 18 


78 78 

Accordingly 100 parts of alcohol should give 129'5 parts of acetic acid of the highest 
degree of concentration. The process of conversion is, however, by no means 
so simple as just mentioned, because the alcohol is not at once converted into acetic 
acid, but first converted into a body which contains less oxygen than the acetic acid, 
viz., aldehyde, C 2 H 4 0 . The conversion of the alcohol into acetic acid may be eluci¬ 
dated in the following manner:— 




VINEGAR. 


461 


Alcohol C 2 HeO = 46 
Subtract H 2 = 2 


Remainder 
Aldehyde 
Add 
Result— 
Acetic acid 


} C 2 H 4 0 =!= 44 
O = 16 
| C 2 H 4 0 2 = 60 


H 2 becomes, by the aid of 0 taken up 
from the air, oxidised to H 2 0 . 


from the air. 


100 kilos, of alcohol therefore need 300 kilos. (= 2322 hectolitres) of air, con¬ 
taining 69 kilos, of oxygen, for the conversion of the alcohol into acetic acid. It is, 
however, evident, that in practice this quantity of air is insufficient, and only that 
portion of the oxygen which is in the state of ozone is capable of performing 
the duty of acetification. Alcoholic liquids, in order to become converted into 
vinegar, require the presence of a peculiar fungus (cryptogamic plant), known as 
My coderma aceti, which appears to act as the carrier of the oxygen of the air, 
which is also by it rendered active and given up to the alcohol. 

The origin of vinegar or acetic acid as a product of the dry distillation of cellu¬ 
lose cannot be elucidated by a simple formula, because there are formed in 
addition to acetic acid a large number of other compounds, among which are gaseous 
and fluid hydrocarbons, wood spirit, aceton, creosote, oxyphenic acid, tar, &c., 
the relative quantity of which depends not only upon the temperature at 
which the distillation took place, but also upon the shape of the retorts used, 
the quantity of hygroscopic water contained in the wood, &c. 


a. Preparation of Vinegar from Alcoholic Fluids. 
vinegar from Alcohol When alcohol is left exposed to air or to pure oxygen it is not 
converted into acetic acid. Nevertheless the conversion is due to the alcohol 
becoming oxidised; therefore it is evident the alcohol must be placed under such con¬ 
ditions as are most favourable to the formation of vinegar. In this, as in many other 
chemico-technical processes, practical experience is the best teacher. The most 
important points are, of course, the preparation of vinegar in the shortest time with 
the least expenditure of alcohol. The conditions most favourable to the formation of 
vinegar on the large scale are the following:— 

1. The alcoholic fluid—prepared from grape wine or fruit wine, fermented malt 
infusion, beer, and brandy—should be sufficiently diluted; it should contain not more 
than 10 per cent of alcohol. Experience has proved that fluids prepared by 
the direct application of alcoholic fermentation, viz. wine, beer, &c., are more 
readily converted into vinegar than mixtures of brandy or alcohol and water. But 
too great a dilution should be avoided ; for although a liquid containing 3 per cent or 
less alcohol can be converted into vinegar, the acetification proceeds very slowly in 
so dilute liquids. 

2. A suitable temperature—not above 36° C., not below io° to 12 0 C. At a tempe 
rature of 7 0 C. and less the formation of vinegar no longer takes place, a fact 
usually overlooked when the advantages, of keeping beer and other fermented 
liquids in ice pits or very cool cellars are enumerated. Above 40° to 6o° the acetifi¬ 
cation proceeds very rapidly, but there is a loss of alcohol and vinegar by evapo 
ration. 

3. A plentiful supply of air or oxygen to the alcoholic fluid and an intimate con¬ 
tact between the two. Small quantities of alcoholic fluid with an extended surface 




CHEMICAL TECHNOLOGY. 


4 t>2 

are more readily converted into vinegar than large bulks of fluid, because the former 
present a larger number of points of contact. 

4. The presence of substances which conduce to the formation of vinegar; they 
are as regards their action similar to the ferments, and are therefore called acetic acid 
or sour producing ferments ; but the acetification is not a physiological process, as is 
vinous fermentation, but simply one of oxidation. The best ferment is vinegar, and 
all substances impregnated with it, such as for instance the so-called vinegar plant, 
the Mycoderma aceti ; it was formerly thought that the vinegar mycoderms stood to 
alcohol and vinegar in the same relation as yeast stands to sugar and alcohol, but this 
opinion is correct only so far as the addition of Mycoderma aceti to an alcoholic 
(luid, as proved by Pasteur’s-experiments (1862), is alike in the action of small quan¬ 
tities of vinegar and other acetification-inducing substances upon wooden vats and 
chips of wood thoroughly impregnated with vinegar; many of these substances con¬ 
tain particles which are undergoing a process of oxidation (1 molecule en mouvement ), 
and by coming into contact with alcohol they draw that fluid into a course of oxidation 
also. Pure acetic acid is therefore incapable of inducing acetification, but vinegar, on 
the contrary, is capable of doing so because it always contains smaller or larger quan¬ 
tities of the protein compounds alluded to; but unless these are in a peculiar 
state of activity they are useless ; this is shown by platinum black and spongy 
platinum, both of which are capable of converting alcohol immediately into acetic 
acid. We may therefore conclude that, by the presence of Mycoderma aceti as well 
as of spongy platinum, the oxygen of the air is rendered active—ozonised—and that 
only ozonised oxygen is capable of converting alcohol into vinegar. Acetic acid is, 
therefore, an oxidation product, not one of the Mycoderma. A more accurate inves¬ 
tigation of the behaviour of peroxide of hydrogen and other ozone-containing or 
producing materials with mixtures of alcohol and water, will no doubt lead to a 
better knowledge of the theory of acetification, and may lead also to a more rational 
and improved mode of vinegar making. 

phenomena of vinegar Formation. Acetification exhibits phenomena which are important 
for observation because they indicate the progress of the conversion of the alcohol 
into acetic acid; these phenomena are partly of a chemical, partly of a physical 
kind. In proportion as the formation of vinegar advances, the alcoholic fluid loses 
its peculiar flavour and odour, and acquires the refreshing sour taste of vinegar. To 
the physical phenomena belong:—1. An increase in the specific gravity of the fluid ; 
and (2) an increase of the temperature. The increase of temperature is due to the 
conversion of the oxygen from a gas to a fluid. The more active the absorption of 
oxygen the higher the temperature. 

Th VineglrM e aM°ng? f According to the substance from which vinegar is prepared the 
following kinds are distinguished:—1. Wine vinegar, prepared from wine, anc 
containing in addition to acetic acid mpny of the other constituents of wine, namely, 
tartaric acid, succinic acid, and certain kinds of ethers, the latter imparting to wine 
vinegar its peculiarly agreeable flavour and odour. 2. Brandy vinegar, spirit 
vinegar, or artificial wine vinegar, generally only a mixture of acetic acid and water 
with a small quantity of acetic ether. 3. Fruit vinegar, prepared from cider and 
perry and containing acetic and malic acids. 4. Beer, malt, or grain vinegar, 
prepared from non-hopped beer wort, and containing, besides acetic acid, also 
extractive matters, such as, for instance, dextrin, nitrogenous constituents and 
phosphates. 5 Vinegar from the sugar beet-root. The roots are converted into 


VINEGAR. 


463 

a pulp and tlien pressed ; the juice is next diluted with water and afterwards boiled. 
When sufficiently cooled, yeast is added and alcoholic fermentation set up; this 
having been finished the alcohol contained in the liquid is converted into vinegar. 
The vessel in which the acetification takes place is connected with a blowing fan ; by 
the aid of a plentiful supply of air and the keeping up of a uniform temperature the 
alcoholic liquid to which some vinegar has been added is rapidly converted into 
acetic acid. 6. Vinegar prepared from the so-called wood vinegar or acetic acid 
obtained by the dry distillation of wood. 

As regards the so-called old method of vinegar making it is without doubt an 
imitation of the spontaneous souring of beer, wine, and fermented liquors generally 
and on conditions which are conducive to the improvement of the product; 
such conditions are—a suitable temperature, intimate contact of the souring 
liquor with air, and a so-called acetification-inducing ferment. This method is 
very generally employed for making wine vinegar, French vinegar as it is termed in 
England, but may of course be used for malt or fruit vinegar making as well. 
Generally a “ souring” vessel or “ mother” vessel made of oak wood is employed; 
this vat is first, when newly made, thoroughly scalded with boiling hot water, and 
when thereby the extractive matter of the wood is exhausted the vessel is filled with 
boiling hot vinegar; when the wood is soaked with vinegar there is poured into the 
vessel 1 hectolitre of wine, and after eight days again 10 litres of wine are added, 
and this operation continued weekly until the vessel is filled for two-thirds of its 
cubic capacity. About fourteen days after the last addition of the wine the whole of 
the contents will have become converted into vinegar. Half this quantity is with¬ 
drawn from the souring vessel and carried to the store: to the remainder more wine 
is added, and the preparation of vinegar proceeded with uninterruptedly by the opera¬ 
tion described. A souring vessel may continue to serve its purpose for six years, 
and often longer, but generally at the end of this time there is collected in the vessel 
so large a quantity of yeast sediment, argol, stone, and other matter as to 
render the thorough cleansing of the vessel necessary; after this operation it is 
again fit for further use. Although it might appear that in this process of 
acetification there is no great contact of air, and the fluid is apparently quite at rest, 
there is a constant change pf the particles of the surface of the fluid, owing to the 
fact that every drop of vinegar formed sinks to the bottom of the vessel, or at least 
below the surface, owing to its increased specific gravity; while as regards the air, 
that portion of it from which the oxygen has been absorbed by becoming specifically 
lighter (o'9 sp. gr.) has a tendency to rise upwards, and to be replaced by heavier 
air (ro sp. gr.) ; thus a constant circulation of air is provided. 

Quick vinegar Making. The so-called quick vinegar process, founded on an older 
method of vinegar preparation suggested by Boerhaave in 1720, was first introduced 
by Schiitzenbach in 1823. The chief principle of this method consists in bringing 
the fluid, generally brandy, to be converted into vinegar into ultimate contact with 
the atmosphere at the requisite temperature, or, in other words, the oxidation of the 
alcohol to acetic acid is effected in the shortest time and with the least possible loss. 
The intimate contact of the fluid with the air is effected by;—1. Increasing the 
quantity of air admitted by means of a continual current of air being made to meet 
the drops of the fluid intended to be converted into vinegar in opposite direction to 
that in which these drops fall downwards. 2. By causing the liquid to be operated 
upon to trickle down drop by drop. A peculiarly constructed vessel is required for 


464 


CHEMICAL TECHNOLOGY . 


this operation ; according to the strength of vinegar desired to he made two to foui 
of these vessels are employed, these constituting a group or battery as it is termed. 
A sectional view of such a vessel is exhibited in Fig. 246 ; it is made of stout oaken 


staves, the vat being from 2 to 4 
metres in height, and from 1 to 1*3 in 
width ; at a height of from 20 to 30 
centimetres from the bottom of the 
vessel are bored at equal distance 
from each other six holes — air 
holes—of about 3 centimetres in 
diameter, so cut that the inner 
mouth of the hole is situated a little 
deeper than the outer, that is to 
say, the holes are bored towards 
the bottom in a slightly sloping 
direction. About one-third of a 
metre above the real lower bottom 
a false bottom is placed, similar in 
construction to a sieve, and af a 
height of a centimetre above the 
air-holes; upon the false bottom is 
a layer of beech-wood shavings 
extending upwards to about from 15 


Fig. 246, 



to 20 centimetres below the upper edge of the vat. The false bottom is sometimes 
constructed of laths of wood, forming a kind of gridiron-like network. Before their 
application the wood shavings are thoroughly washed with hot water and next 
dried. The tub is then nearly filled with the dry wood shavings, which are next 
“ soured.” For this purpose warm vinegar is poured over them, and allowed to 
remain in contact with the wood for twenty-four hours so as to cause the acetic 
acid to soak into the wood. At from 18 to 24 centimetres below the upper edge 
of the vat is fixed a perforated wooden disc, the holes of which are as large 
as a goose-quill, and are bored from 3 to 5 centimetres apart from each other. 
In order that the liquid intended to be converted into acetic acid may trickle slowly, 
and in fine spray, as it were, over the wood shavings, or thin chips of wood, 
through the holes, strings of twine or loosely spun cotton yarn are passed so 
us to penetrate downwards for a length of 3 centimetres, while at the top a knot 
is tied which prevents the strings slipping through the holes; by the action of 
the liquid, dilute spirits of wine usually, which is poured into the vessel, the 
twine becomes more or less swollen, and thereby obstructs the passage of the 
fluid so as to divide it into constantly trickling drops. The sieve bottom is fitted 
with from five to eight larger holes, each about 3 to 6 centimetres wide, which by 
means of glass tubes, each of from 10 to 15 centimetres in length, inserted and 
firmly fastened therein act as draught tubes, so placed that no liquid can pass 
through them. The vat is covered at the top with a tightly-fitting wooden lid, 
in the centre of which a circular hole is cut, which serves as well for the 
purpose of pouring the liquid into the vessel as for the outlet of the air which 
enters the vessel from below. In consequence of the absorption of the oxygen so 
















































VINEGAR. 465 

much heat is generated in the interior of the vessel that the air streams strongly 
upwards, causing fresh air to enter by the lower air-holes. 

After the vinegar tub has been soured the fluid to be converted into vinegar— 
generally brandy, more rarely malt liquors or wine—is poured in; the fluid flowing 
off from the first vessel is poured into the second, and if the original liquid did 
not contain more than from 3 to 4 per cent of alcohol the fluid which runs off from 
the second vessel will be completely converted into good vinegar. The vinegar 
collects between the true and false bottoms. As will be seen from the woodcut the 
vinegar cannot flow out until its level is equal to that of the mouth of the glass 
tube. In consequence of this arrangement a layer of about 16 to 20 centimetres 
in depth of warm vinegar assists in the acetification by the evolution of acid 
vapours which ascend into the fluid above. The tube must dip into the lower part 
of the fluid in the interior of the tub,* as it is there that the specifically heavier 
vinegar collects. The arrangement will be readily understood from Fig. 247, 
c p is the perforated bottom, just below which is situated the wooden tap, h, fastened 
to the bent glass tube, m m, the free open end of which touches the bottom of 
the tub. 

Recently (1868) Singer’s vinegar generator has been introduced. It consists of a 
number of vessels, one placed above the other, and so connected together by wooden 


Fig. 247. 



tubes that the liquid intended to be converted into vinegar tricldes drop by drop 
from the one vessel into the other; in each tube is cut a longitudinal slit, through 
which air freely circulates ; the apparatus is placed in a suitably constructed shed, 
wherein a convenient temperature is kept up and from which draught is excluded. 
By the use of this apparatus the loss of alcohol experienced in the use of the 
vats above mentioned is prevented. Singer’s apparatus is fully described in the 
“ Jahresbericht der Chem. Technologie,” 1868, p. 580. 

The composition of the fluid to be acetified varies very much; one of the mixtures 
very generally used is made up of 20 litres of brandy of 50 per cent Tralles, 40 
litres of vinegar, and 120 litres of water, to which is first added a liquid, made by 
soaking a mixture of bran and rye meal in water in order to promote the formation 
of the vinegar fungus {Mycoderma aceti). The room in which the vats are placed 
should be heated to 20° to 24 0 ; the temperature in the vats rises to 36° and more, 
consequently the alcohol, aldehyde, and acetic acid are volatilised, and this loss 
may amount to about one-tenth ; taking this loss into account we may assume 
81 



































4 66 


CHEMICAL TECHNOLOGY. 


that i hectolitre of brandy at 50 per cent Tralles (= 42 per cent according to weight) 
yields by weight— 

13*0 hectolitres of vinegar of 3 per cent acetic acid contents. 

99 
7 9 
6-6 
5’6 
4'9 
4*4 
39 

When required for transport it is, of course, most advantageous to prepare, very 
strong vinegar, which at the place where it is to be consumed can be diluted with 
the requisite quantity of water. 

vinegar from the Sugar-Beet. Vinegar from the sugar-beet is prepared from the expressed 
juice, having a sp. gr. of ro35 to i'045, diluted with water to 1*025 sp. g r -> fermented 
with yeast, the fluid being next mixed with an equal volume of prepared vinegar. This 
mixture being well exposed to the influence of the oxygen of the atmosphere, acetification 
soon sets in. 

vineg Mycoderma Aceti. of the Pasteur, who refers acetification, as Dr. Wagner thinks 
erroneously, to a physiological process, has in 1862 described a new method of pre¬ 
paring vinegar with the help of the vinegar fungus, the Mycoderma aceti. This 
fungus is first propagated in a fluid, consisting of water and 2 per cent of alcohol 
with 1 per cent of vinegar and a small quantity of phosphate of potash lime and 
magnesia. The small plant soon spreads itself over the entire surface of the fluid, 
without leaving the smallest space uncovered. At the same time the alcohol is aceti¬ 
fied. As soon as half of the alcohol is converted into vinegar, small quantities of 
wane or alcohol mixed with beer are added daily. When the acetification becomes 
weaker, the complete conversion of the free alcohol still present in the fluid is allowed 
to take place. The vinegar is then drawn off and the plant again employed in 
the same apparatus. Vinegar prepared by this method possesses much of the aroma 
characteristic of wine vinegar. An essential condition to the rapid formation of 
vinegar by this method is a strong development of the plant. A vessel with 1 square 
metre of surface, and capable of containing 50 to 100 litres of fluid, yields daily 
5 to 6 litres of vinegar. The vessels are circular or rectangular wooden tanks, 
with but a slight depth, and covered with lids. At the ends are bored two 
small openings for the entrance of the air. Two tubes of gutta-percha, pierced 
laterally with small holes, are carried down to the bottom of the tank and used 
to pour alcohol into the tank -without opening the lid. The tank which 
Pasteur employed had a surface of 1 square metre and a depth of 20 centims. 
He found phosphates and ammonia necessary for the growth of the plant. When 
wine or malt liquor, &c., is employed, these substances are present therein in suffi¬ 
cient quantity; but when only alcohol is used, sulphate of ammonia, phosphate of 
potash and magnesia are added in such quantity that the fluid contains njJ^tli 
of this saline mixture, to which also some vinegar is added. It has been long 
known that the addition of bread, flour, malt, and raisins to alcoholic fluids about to 
be acetified greatly promotes the formation of vinegar, as these substances contain 
the requisite organic and inorganic food suited for the propagation of the vinegar 
fungus. 




VINEGAR. 


467 


Vi of e ifatinum Biackl p Dobereiner was the first who pointed out that, with the aid of 
platinum black, alcoholic vapours could be acetified in a very short time ; and to this 
process the following apparatus is especially adapted. Fig. 248 shows a small glass 
house, in the interior of which are seen a number of compartments. The shelves 
forming these compartments support a number of porcelain capsules. The alcohol to 
be acetified is poured into these capsules, in each of which is placed a tripod, also of 
porcelain, supporting a watch-glass containing platinum black or spongy platinum. 
In the roof and at the bottom of the apparatus are ventilators, so constructed as to 

admit of regulating access of air. 
By means of a small steam pipe 
the interior of the house is heated 
to 33 0 . By this means the alcohol 
is gently evaporated, and coming 
into contact with the platinum black 
or sponge, is acetified. So long as 
the ventilation is maintained, the 
platinum black retains its property 
of oxidising the alcohol. With an 
apparatus of 40 cubic metres capa¬ 
city and with 17 kilos, of platinum 
black, 150 litres of alcohol can daily 
be converted into pure vinegar. 
If it be desired to prepare the 
vinegar without any loss of alcohol, 
it becomes necessary to pass the 
outgoing air through a condenser in 
order to collect the vapours of alcohol and acetic acid which otherwise would be 
carried off. 

Testing Vinegar. The value of a vinegar is dependent upon its flavour and upon 
its strength, or upon the quantity of acetic acid it contains. According to its con¬ 
taining more or less acetic acid the vinegar tastes more or less sour. The colour 
varies with the fluid from which the vinegar has been prepared; wine vinegar is 
of a yellow or red-yellow colour, fruit vinegar exhibits a golden colour, brandy 
vinegar is colourless; but as a rule the latter is coloured with caramel in imitation 
of wine vinegar. Freshly made vinegar contains besides small quantities of uncon¬ 
verted alcohol, some aldehyde, which always occurs largely in vinegar not properly 
prepared. Recently it has become customary to add a small quantity of glycerine 
to the prepared vinegar. 

The quantity of acetic acid contained in a vinegar depends upon the alcoholic con¬ 
tents of the fluid to be acetified, and also upon the more or less perfect conversion of 
the alcohol into acetic acid. Malt vinegar contains from 2 to 5 per cent, brandy 
vinegar from 3 to 6 per cent, wine vinegar from 6 to 8 per cent, of acetic acid. The 
specific gravity of various kinds of.vinegars differs from roio to 1*030; the more 
alcohol a vinegar contains the lighter is it, the more extractive matter the 
heavier. The densities of mixtures of acetic acid (C 2 H 4 0 2 ) and water are, at 
15 0 C., according to Oudemans, the following :— 


Fig. 248. 






















































4 68 


CHEMICAL TECHNOLOGY. 


Per- 


centage. Dens. 

0 

0-9992 

1 

1-0007 

2 

1-0022 

3 

I-OO37 

4 

I-0052 

5 

1*0067 

6 

1*0083 

7 

1-0098 

8 

IOII3 

9 

1*0127 

10 

I-OI42 

11 

i'oi 57 

12 

1-0171 

13 

1-0185 

14 

1*0200 

15 

I-02I4 

16 

1*0228 

17 

1*0242 

18 

1*0256 

19 

1*0270 

20 

1-0284 

21 

1-0298 

22 

I- 03 II 

23 

IO324 

24 

1-0337 

25 

IO35O 


Per- Per- Per- 

Diff. centage. Dens. Diff. centage. Dens. Diff. centage. Dens. 


+ 15 
*5 
15 
15 

15 

16 
15 
15 

14 
x 5 

15 

14 

14 

15 
14 
14 

14 

14 

14 

14 

*4 

13 

13 

13 

13 

13 


26 

10363 

12 

T O 

27 

1-0375 

28 

1-0388 

12 

29 

1-0400 

12 

30 

1-0412 

12 

31 

1*0424 

T O 

32 

10436 

JL 4 

I I 

33 

1-0447 

12 

34 

1-0459 

I j 

35 

1-0470 

T T 

36 

1-0481 

JL 1 

I I 

37 

1*0492 

IO 

38 

1*0502 

II 

39 

1*0513 

IO 

40 

1-0523 

IO 

4i 

1*0533 

IO 

42 

i-o543 

0 

43 

1-0552 

y 

Tn 

44 

1*0562 

Q 

45 

1*0571 

y 

n 

46 

1*0580 

9 

n 

47 

10589 

y 

48 

1-0598 

y 

n 

49 

1*0607 

y 

8 

50 

10615 

0 

g 

5i 

1-0623 

8 


52 1-0631 

53 1-0638 ' 

54 1-0646 

55 1*0653 ' 

56 1*0660 L 

57 ro666 ° 

58 1-0673 l 

59 1-0679 

60 1-0685 g 

61 10691 

62 1*0697 

63 1-0702 ^ 

64 1*0707 5 

65 1*0712 5 

66 1*0717 ^ 

67 1-0721 4 

68 1-0725 4 

69 1-0729 4 

70 1-0733 4 

7 1 1-0737 J 

72 1-0740 ^ 

73 1-0742 g 

74 1-0744 * 

75 1-0746 * 

76 10747 

77 1-0748 q 


78 

79 

80 

81 

82 

83 

84 

85 

86 

87 

88 

89 

90 

91 

92 

93 

94 

95 

96 

97 

98 

99 
100 


1*0748 

1-0748 

1*0748 

10747 

1*0746 

1-0744 

1-0742 

1-0739 

10*736 

10731 

1*0726 
1-0720 
1*0713 
1-0705 
1*0696 
1*0686 
1-0674 
ro66o 
1*0644 
1-0625 
1 *0604 
1-0580 
1-0553 


Diff. 

o 

o 

1 

1 

rt 

2 

3 
3 
5 

5 

6 

7 

• 8 

9 

10 

12 

14 

16 

19 

21 

24 

27 


Acetometry. Commercial vinegar varies greatly as regards the quantity of acetic acid 
it contains. The specific gravity of a commercial vinegar is no certain indication of 
the quantity of acetic acid, owing to the fact that the vinegar nearly always con¬ 
tains foreign matters. The testing of the strength can therefore only be accurately 
effected by means of saturating it with an alkali. According to the ordinary method 
first introduced for this purpose by Otto, ammonia is added to the vinegar to be 
tested until the previously added tincture of litmus becomes again blue; although 
this method is not absolutely correct—owing to the fact that the neutral alkaline 
acetates exhibit an alkaline reaction—this does not much impair the correctness 
of this process. Otto’s acetometer is a glass tube sealed at one end, 36 centims. 
long by 1*5 wide, whereon is engraved a double scale of divisions, one of these 
towards the bottom of the tube serving for measuring the vinegar coloured by 
litmus, while the other upper scale is intended for measuring the test liquor. When 
it is intended to apply the test with this measuring tube, a certain quantity (indicated 
by the divided scale) of litmus tincture is first poured into the tube, next vinegar is 
added in sufficient quantity to fill the tube up to the second division; afterwards so 
much of the test-liquor is added as to restore again the blue colour of the litmus. 

The quantity of test-liquor employed indicates the percentage of acetic acid con¬ 
tained in the vinegar. The test-fluid should contain 1*369 per cent of ammonia. 
According to Mohr’s method there are taken of the vinegar to be tested 

( 2 C 2 H 4 O a - 11*0 = IH2 = 51 ); 

and usually having a sp. gr. varying between roio and i on, 5*04 c.c., 

( for JlL=5-o4 \ 

' ron / 










VINEGAR. 


469 

or simply 5 c.c., to which is added tincture of litmus, the whole being titrated with a 
normal alkali blue (a titrated caustic potassa solution rendered blue with litmus). It 
is better to take 10 c.c. of the vinegar and halve the number of c.c. of potassa 
employed. 

Examples:—1. io*o c.c. of a Wurtzburg table vinegar required 

11 *8 c.c. of potash solution, and the vinegar therefore contained 
5-9 per cent of so-called anhydrous acid, or 67 per cent of acetic 
acid (C2H4O2). 

2. io’o c.c. of a vinegar prepared from wood vinegar required 
12*5 c.c. of potash solution, corresponding to 
6’25 per cent of anhydrous acid, or 7-3 per cent (C2H4O2). 

( 3 . Preparation of Vinegar from Wood Vinegar. 
wood vinegar. From the dry distillation of wood a portion of the carbonised matter 
remains in the retorts as charcoal, while the remainder of the constituents of the 
wood are eliminated partly in the state of gases and vapours, such as carbonic oxide, 
carbonic acid, hydrogen, light and heavy carburetted hydrogens—partly in the shape 
of a condensed matter, consisting of a thick, brown, oily fluid floating upon a stratum 
of a watery liquor. The latter, wood vinegar, consists essentially of impure acetic 
acid, some propionic and butyric acids, small quantities of oxyphenic acid, creosote, 


Fig. 249. 



and an alcoholic wood spirit, a mixture of methylic alcohol, aceton, and acetate of 
methyl, the brown, thickish fluid substance known as wood tar, consisting of a 
number of both fluid and solid bodies, paraffin, naphthalin, creosote, benzol, toluol, &c. 
A well-conducted distillation will yield as much as from 7 to 8 per cent of the weight 
of the wood acetic acid. According to the researches of IT. Vohl, peat can be employed 
in the preparation of wood vinegar and of wood spirit. 10 cwts. of peat yield 3 kilos, 
of acetic acid and 1*45 kilos, of wood spirit. The Table on the next page shows the 
principal products of the destructive distillation of wood. 

Raw wood vinegar contains in solution a not inconsiderable quantity of resin, and 
also small quantities of phenol and guaiacol; all these bodies impart a more or 
less brown colour and empyreumatic odour and flavour, but they also render it a 














































47 o 


CHEMICAL TECHNOLOGY. 


(a. Wood 

Wood \ b. Hygroscopic 
( Water 


a. Illuminating 
Gas 


Acetylen, C 2 H 2 
Elayl, C 2 H 4 
Trityl, C 3 H 6 
Ditretyl, C4H3 
Benzol, C6H6 
'Toluol, C 7 H 8 
(-Benzol, CeHe 
Toluol, C 7 H 8 
Styrolen, C 8 H 8 
Naphthalin, C I0 H 8 
Betene, C i 8 H i8 


Xylol, C 8 H io 
N aphthalin, C I0 H 8 
Carbonic oxide, CO 
Carbonic acid, C0 2 
Hydride of Methyl, CH 4 
Hydrogen, H 2 


Paraffin, C 20 H 42 , or C 22 H 4 6 

Carbolic acid, CgHgO 
Cresylic acid, C 7 H 8 0 
v Phlorylic acid, C 8 H io O 


( 3 , Tar *1 Phenol ■ 


) 


j 


Guaicol 


Resin 


Oxyphenic acid, C 6 He 0 2 

( r tt n Combinations of 

§!&■ s 

I2Uz J acids with methyl* 


y. Wood Vine¬ 
gar 


r Acetic acid, C 2 H 4 0 2 
Propionic acid, C 3 Hg 0 2 
Butyric acid, C 4 H 8 0 2 
Valerianic acid, C 9 H io 0 2 
. Caproic acid, C io Hi 2 0 2 
Aceton, C 3 H 60 
Acetate of methyl, C 3 Hg 0 2 
Wood spirit, CH 4 0 
L Phenol, Guaicol, and Resin 


l 


8 . Charcoal 


/ Carbon .. .. 85 per cent. 

J Hygroscopic water 12 „ 

(Ash .3 


valuable antiseptic. Where the principal aim is to obtain wood vinegar, an 
iron retort, somewhat similar to a gas retort, is employed for the distillation 
of the wood; but in France, a vertical retort of boiler plate, exhibited at a. 
Fig. 249, is employed, fitted at the upper part with a tube, o, to which is fastened 
the projecting part, b. When the iron cylinder is filled with wood, a lid is tightly 
screwed on to it, it being next lifted up and placed into the cylindrical furnace, b, 
by means of the crane, d, after which the furnace is closed at the top with 
the firebrick lid, e. The products eliminated from the wood contained in the 
retort pass into the tube b, Fig. 250, and thence into the condensing apparatus, c, 
placed in a framework, d, which condensing apparatus is kept continually supplied 
with cold water by the tube /, while the warm water flows off at k. Vinegar, tar, 
and wood spirit are condensed and flow into the vessel g, in which the tar separates, 
the lighter fluids flowing into li through the tube m. The non-condensed gases 
pass through the tube i into the fireplace, where they assist in heating the retort, 
^0 that but very little fuel is required. In large factories, instead of the wooden 
receivers, large stone or brickwork cisterns are employed, generally several of such 
tanks being used, the largest quantity of tar being condensed in the first cistern, 
while the wood vinegar, mechanically freed from the tar and Heating on its surface, 


* According to S. Marasse (1868), Rhenish beech-wood tar creosote is a mixture of equal 
parts of— 

Cresylic acid, C 7 H 8 0 , boiling at 203°, 
and Guaiacol C 7 H 8 0 2 ,, 200°. 

The latter is methylic ether with oxyphenic acid, j 0 2 . 











VINEGAR. 471 

finds its way into a second cistern. Pettenkofer’s patent wood-gas generators 
produce a not inconsiderable quantity of wood vinegar. 

Purifying wood vinegar. Raw wood vinegar is a clear dark brown fluid, having a tarry 

taste and smoky odour. It is employed in small quantities in the preservation 
of meat, also for the preservation 
of wood, ropes, &c.; but by far 
the largest quantity is employed in 
the preparation of the various 
acetates used in dyeing and calico 
printing, chiefly as crude acetate of 
iron and crude acetate of alumina. 

It is also used in the preparation of 
concentrated acetic acid for indus¬ 
trial purposes, that is, for the pre¬ 
paration of aniline from nitro-ben- 
zol, and of sugar (acetate) of lead. 

Lastly, it is largely used in the 
preparation of table vinegar, an 
operation economical only where, 
as in England,- there is a high 
duty on alcoholic fluids. 

Among the means of purifying 
crude wood vinegar, the most 
simple—leaving out of the question the filtration of the crude liquor over 
coarsely granulated wood charcoal as recommended by E. Assmus—is distillation, 
an operation usually carried on in a still made of copper fitted with a copper 
condensing apparatus. At first a yellow fluid comes over—raw wood spirit from 
which the wood spirit of commerce is prepared—and next the distillate becomes 
richer in acetic acid. 

The principal methods at present employed for the purification of wood vinegar 
may be considered as falling under either of two classes:— 

a. The first includes the purifying of wood vinegar without saturation with a 
base; while 

( 3 . The second includes those methods in which the wood vinegar is purified by 
conversion into an acetate, the acetic acid being next separated by distillation 
with an acid possessing greater affinity for the base. 

To the first class belongs Stoltze’s method, consisting in first obtaining by dis¬ 
tillation 10 per cent of a liquid which is employed for the preparation of wood 
spirit; 80 per cent of the liquid is next distilled off and the empyreumatic 

substances contained are destroyed by the action of either ozone or chlorine. 

The purification of the crude wood vinegar by the second method is more 
generally in use among manufacturers, the inventor of the system being Mollerat. 
The crude wood vinegar is first saturated with lime and the solution next 

precipitated with Glauber’s salt to obtain acetate of soda; this salt is purified by 

crystallisation, and when in a dry state is so far heated that the empyreumatic 
matter it is mixed with becomes carbonised and is thus rendered insoluble; the 
acefate of soda is then extracted with water, and the acetic acid separated from it 
by distilling the previously crystallised and dried salt with sulphuric acid. Instead 


















472 


CHEMICAL TECHNOLOGY. 


of acetate of soda tlie acetate of lime is frequently employed in the preparation of 
acetic acid from crude wood vinegar, the latter being saturated with lime, and the 
salt formed evaporated to dryness. The dry salt is roasted and treated similarly to 
the acetate of soda to calcine any empyreumatic products. The acid employed in 
the distillation is, according to the method invented by C. Volckel, hydrochloric 
acid. The distillation can be effected in a retort with a helm of copper and a 
condenser of lead, tin, or silver. Upon ioo parts of acetate of lime 90 to 95 parts of 
hydrochloric acid at ri6 sp. gr. are used. When hydrochloric acid is used in this 
preparation instead of sulphuric acid, any contamination of the crude acetate of lime 
with empyreumatic or tarry matter 'does not affect the purity of the acetic acid 
which is obtained, provided the crude acetate be first so well dried as to be free 
from all other volatile substances; when sulphuric acid is used for this purpose 
the result is that an acetic acid is obtained, which contains not only a large quantity 
of sulphurous acid, but also other offensive volatile compounds due to the decompo¬ 
sition (by the sulphuric acid) of empyreumatic resins and tarry matter present in 
the crude acetate of lime. 

wood spirit. When the acid liquid obtained by the dry distillation of wood is 
distilled on the large scale, there comes over at first a certain quantity of a 
yellow fluid, lighter than water, and exhibiting an etliereo-empyreumatic odour. 

CH ) 

This fluid (wood spirit) consists chiefly of methylic alcohol, CH 4 0, or jj 3 |0, 

aceton, acetate of methyl, and other substances to which no reference need be 
made. Wood spirit was first discovered by Taylor in 1812, and was for a long 
time only employed for burning in spirit-lamps ; it was not until 1822 that Taylor found 
this body was a new substance. Wood spirit is in a pure state a colourless fluid of 
o'8i4 sp. gr., boiling at 66° C. It is in all respects very similar to alcohol, and can 
be employed as a source of heat in spirit-lamps; it evaporates, however, more 
rapidly and gives a less intense heat, for whereas 1 part by weight of alcohol yields 
by its complete combustion to carbonic acid and water 7189 units of heat, an equal 
quantity of wood spirit only yields 5307 units of heat. It is employed in the 
preparation of furniture polish and in varnish making; for these purposes, how¬ 
ever, it requires to be well purified, and its rapid evaporation is a drawback to its 
extensive use; confirmed spirit drinkers have now and then used it instead of 
whiskey and the like, and, it appears, without bad effects. Its most recent use is in 
the preparation of iodide and bromide of methyl, which substances are employed 
in the manufacture of violet and blue coal-tar colours. 


The Preservation of Wood. 

0 woodiagener^ of The durability of wood, viz., its power of resisting the destructive 
influences of wind and weather, varies greatly, and depends as much upon the 
particular kind of wood and the influences to which it is exposed as upon the origin 
of the wood (timber), its age at the time of felling, and other conditions. Beech- 
wood and oak placed permanently under water may last for centuries. Alder wood 
lasts only a short time when in a dry situation, but when kept under water it is a 
very lasting and substantial wood. Taking into consideration the different lands 
and varying properties of wood and the different uses to which it is applied, we have 
to consider as regards its durability the following particulars:— 


WOOD. 


473 


1. Whether it is more liable to decay by exposure to open air or when placed in 
damp situations; 

2. Whether it is when left dry more or less attacked by the ravages of insects which, 
while in a state of larvae, live and thrive in and on wood. 

Pure woody fibre by itself is only very slightly affected by the destructive 
influences of wind and weather. When we observe that wood decays, that decay 
arises from the presence of substances in the wood which are foreign to the woody 
fibre, but are present in the juices of the wood while growing, and consist chiefly 
of albuminous matter, which, when beginning to decay, also causes the destruction 
of the other constituents of the wood; but these changes occur in various kinds 
of wood only after a shorter or longer lapse of time; indeed, wood may in some 
instances last for several centuries and remain thoroughly sound; thus the roof of 
Westminster Hall was built about 1090. Since resinous woods resist the action of 
damp and moisture for a long time, they generally last a considerable time; next 
in respect of durability follow such kinds of wood as are very hard and com¬ 
pact, and contain at the same time some substance which—like tannic acid—to 
some extent counteracts decay. The behaviour of the several woods under water 
differs greatly. Some woods are after a time converted into a pulpy mass. Other 
kinds of wood, again, undergo no change at all while under water, as, for instance, 
oak, alder, and fir. 

Insects chiefly attack dry wood only. Splint wood is more liable to such attack than 
hard wood ; while splint of oak wood is rather readily attacked by insects, the hard 
wood (inner or fully developed wood) is seldom so affected. Elm, aspen, and all 
resinous woods are very seldom attacked by insects. Young wood, which is full of 
sap and left with the bark on, soon becomes quite worm-eaten, especially so the ald,er, 
birch, willow, and beech. The longer or shorter duration of wood depends more or 
less upon the following conditions:— 

a. The conditions of growth. Wood from cold climates is generally more durable 
than that grown in warm climes. A poor soil produces as a rule a more ^durable 
and compact wood than does a soil rich in humus, and therefore containing also 
much moisture. 

b. The conditions in which the wood is placed greatly influence its duration. The 
warmer and moister the climate the more rapidly decomposition sets in ; while a dry, 
cold climate materially aids the preservation of wood. 

c. The time of felling is of importance : wood cut down in winter is considered 
more durable than that felled in summer. In many countries the forest laws enjoin 
the felling of trees only between November 15 and February 15. 

Wood employed for building purposes in the country, and not exposed to either 
heat or moisture, is only likely to suffer from the ravages of insects ; but if it is placed 
so that no draught of fresh air can reach it to prevent accumulation of products of 
decomposition, decay soon sets in, and the decaying albuminous substances acting upon 
the fibre cause it to lose its tenacity and become a friable mass. Under the 
influence of moisture fungi are developed upon the surface of the wood. These fungi 
are severally known as the “house fungi” ( Thetephora clomestica and Boletus 
destructor ), the clinging fungus ( Cerulius vastator ). They spread over the wood in a 
manner very similar to the growth of common fungi on soil. Their growth is greatly 
aided by moisture and by exclusion of light and fresh air. A chemical means of 
preventing such growths is found in the application to the wood of acetate of oxide of 


474 


CHEMICAL TECHNOLOGY. 


ircfn, tlie acetate being prepared from wood vinegar. Wood is often more 
injuriously affected when exposed to sea water, when it is attacked by a peculiar 
kind of insect known as the bore-worm, Teredo navalis. This insect is armed with 
a horned beak capable of piercing the hardest wood to a depth of 36 centimetres. 
These insects originally belonged to and abound in great number in the seas 
under the tropical clime: but the Teredo navalis is met with on the coasts ot 
Holland and England. 

pre serYation of w °°d The means usually adopted to prevent the destruction of wood by 
decay are the following:— 

1. The elimination, as much as possible, of the water from the wood previously 
to its being employed ; 

2. The elimination of the constituents of the sap ; 

3. By keeping up a good circulation of air near the wood so as to prevent its 
suffocation, as it is termed; 

4. By chemical alteration of the constituents of the sap; 

5. By the gradual mineralisation of the wood and thus the elimination of the organic 
matter. 

Drying wood. i. Thoroughly dried wood remains for a long time unaltered while in 
a dry situation, more especial]3' so when dried by so strong a heat that it 
becomes browned. When timber has to be put into a damp situation, it should, 
after having been well dried, be first coated with a suitable substance to prevent 
the moisture penetrating into the wood. This purpose is attained by coating 
the wood with linseed oil, so-called Stockholm tar, coal tar, creosote, and other 
h} r drocarbons. Hutin and Boutigny adopt the following method to prevent the 
absorption of moisture by wood that is put into the ground. The portion of 
the post or wood to be buried is first immersed in a vessel containing benzol, 
petroleum, photogen, &c., and when taken out is ignited and thus charred. 
When extinguished the wood is put to a depth of from 3 to 6 centimetres into a 
mixture of pitch, tar, and asplialte, and next the entire piece of wood is thorough^ 
painted over with tar. 

Elimination^of^the^constituents 2 . The constituents of the sap are tire chief cause of the 
decomposition of wood, and they should consequently be removed: manj" plans are 
adopted. In order that the wood may contain the smallest quantity of sap, it should 
be felled during the winter months. The constituents of the sap can be eliminated 
from the felled tree by three methods :— 

a. By treatment with cold water, with which the wood must be thoroughly saturated 
to dissolve the constituents of the sap, which are removed when the wood is exposed to a 
stream of water. It is evident that with large timber a long time is necessary to ensure 
perfect saturation. 

b. By employing boiling water the sap is removed much more quickly and efficientl}'. 
The pieces of wood are placed in an iron vessel with water and boiled. Large pieces of 
timber cannot be treated in this manner, but are immersed in a cistern in which the fluid 
is heated by means of steam. According to the thickness of the wood, the boiling 
occupies some 6 to 12 hours. 

c. By treatment with steam (steaming of wood)—the most effectual method of removing 
the constituents of the sap, the h) r groscopicity of the wood thus treated being rendered 
much less, while the wood is far more fitted to resist the effects of weather. The 
apparatus employed in carrying out the method consists of a boiler for the generation of 
steam, and a cistern or steam chamber, for the reception of the wood, this chamber being 
constructed of masonry and cement, of boiler plate, or being simply a large and very 
wide iron pipe. In most cases a jet of steam is conveyed from the boiler to the steam- 
chamber, where it penetrates the wood, and dissolves out the constituents of the sap, 
which on being condensed is allowed to run off. In the case of oak, this fluid is of a 


WOOD. 


475 


black-brown colour ; vnth mahogany, a brown-red; with linden wood, a red-yellow; and 
with cherry tree wood, a red, &c. The operation is finished when the outflowing water is 
no more coloured. The steamed wood is dried in the air or in a drying room ; it loses 
5 to io per cent in weight by the process, and becomes of a much darker colour. 
The steam is sometimes worked at a temperature of above ioo°, but generally the con¬ 
tents of the steam chamber are maintained at 6o° to 70°. Towards the end of the 
operation some oil of coal-tar is introduced into the boiler, and is consequently carried 
over with the steam, impregnating the wood. 

The removal of the sap can also be effected to some extent by means of mechanical 
pressure between a pair of iron rollers, which are gradually brought more closely 
together. Another method is by means of air pressure. Barlow employs for this 
purpose a metal case in which the wood is enclosed, and to one end of which an air 
pump is attached. Air being forced into the tube or case, the sap flows away at the end 
opposite to which the pump is attached. But both these methods are costly and not in 
all cases applicable. 

Air Drains. 3. The construction of air drains or passages around woodwork to be 
preserved is, where the method is applicable, a great aid to the preservation of the wood. 
The consideration of the best means of effecting ventilation in this respect, is not a 
matter with which we can deal in this work. It is sufficient to say, that in many 
instances, the air channels are connected on the one hand with the open air, and on the 
other with the chimney. 

^ckmstftuenta of'the sap? 4- One the mos t usual and most effective means of pre¬ 
venting the decomposition of wood is by effecting a chemical change in the 
constituents of the sap, so that fermentation can no longer be set up. To this class 
belongs the well-known plan of protecting woodwork that is to be exposed to 
the action of the moisture of the earth by charring the wood, either by fire or 
by treatment with concentrated sulphuric acid, so that the wood is coated to a certain 
depth with a layer of charcoal, the charcoal acting as an antiseptic. The charring 
or carbonisation of the wood can be effected either with the help of a gas flame or 
the flame from a coal fire. The apparatus of De Lapparent, invented for this purpose, 
became very generally employed in 1866 at the dockyards of Cherbourg, Pola, and 
Dantzic. According to another method the wood is impregnated throughout its 
whole mass with some substance that either enters into combination with the con¬ 
stituents of the sap, or so alters their properties as to prevent the setting up of 
decomposition. To this class belong the four following methods, these being the 
only ones that have met with any more extensive use. 

1. Kyan’s preserving fluid is a solution of bichloride of mercury of variable 
degree of concentration. In England a solution of 1 kilo, of corrosive sublimate in 
80 to 100 litres of water is generally employed for railway sleepers. The timber is 
laid in a watertight wooden trough, containing the solution, where, according to its 
size, it remains a longer or shorter time. In Baden the wood remains in the 
kyanising solution, when it is to be impregnated to a depth of— 

82 m.m. for 4 days. 

85 to 150 ., 7 „ 

150 to 180 „ 10 „ 

180 to 240 „ 14 „ 

240 to 309 „ 18 „ 

the solution consisting of 1 kilo, of sublimate to 200 litres of water. The prepared 
wood is washed with water, rubbed dry, and then placed in sheds free from exposure 
to rain and strong sunlight. The principal action of the bichloride of mercury is to 
convert the albumen of the sap into an insoluble combination, capable of With¬ 
standing decomposition, while the bichloride becomes gradually reduced to proto¬ 
chloride of mercury (calomel). A great objection to this method is the danger to 


CHEMICAL TECHNOLOGY. 


47 6 

which the carpenter or joiner who may afterwards shape the wood is exposed, the 
free chemicals acting upon his system through his hands, nostrils, and mouth. In 
England wood to be varnished is seldom kyanised. 

Erdmann remarks upon this plan of preserving wood that the interior of the log is 
still left in its original condition. To answer the objection the kyanising has been 
made more effective by placing the wood into a water-tight trough, with the solution 
of sublimate, and by a great pressure of air thoroughly impregnating the wood. 
Kyanising by this method becomes, however, as expensive as any other impregnation 
method. Recently there has been substituted for the pure bichloride of mercury a 
double salt of the formula HgCl 2 -fKCl, obtained by decomposing a solution of 
carnallite with oxide of mercury. 

2. Burnett’s patent (1840) fluid consists of 1 kilo, of chloride of zinc dissolved in 
go litres of water. Wood treated with Burnett’s fluid has been buried in earth for 
five years without undergoing any change, while unprepared wood buried for the 
same length of time has been totally destroyed. Chloride of zinc has been much 
used in Germany as an impregnating material. Besides this salt sulphate of copper 
and acetate of oxide of zinc—pyrolignite of zinc (Scheden’s method), have been 
employed. The action of the copper and zinc salts may be explained by considering 
that the metallic oxides of the basic salt formed during seasoning, separates and 
combines with the colouring matter, tannic acid, resin, &c. of the wood, to form an 
insoluble compound. 

3. Bethell’s (1838) patented method consists in treatment under strong pressure 
with a mixture of tar, oil of tar, and carbolic acid, this mixture being known com¬ 
mercially by the name of gallotin. In and near London wood thus treated has 
remained eleven years in the earth without undergoing change; other pieces of 
timber so treated were subjected to the action of the sea for four years and still were 
in good condition. Yohl employs for preservation peat and brown coal creosote; 
Leuchs uses paraffin. Such agents, however, render wood treated with them highly 
inflammable. 

4. Payne’s method. This includes two patents, the first having been taken out in 
1841. Both are based on the impregnation of the wood—first with one salt, and 
next with another salt, which is capable of forming a precipitate insoluble in water 
and sap of the wood with the first. The first solution is usually one of sulphate of 
iron or of alum, then follows a solution of chloride of calcium or of soda. The wood 
to be impregnated is placed in a vessel from which the air is exhausted, the 
first solution being then admitted, and subsequently pressure is applied. The first 
solution being removed, the second is admitted, and pressure again applied. It is 
necessary to dry the wood partially between the two impregnations. Payne’s 
method, much used in England, possesses, moreover, the advantage of rendering the 
wood somewhat uninflammable. The same effect results with the methods of Buchner 
and Yon Eichthal, who impregnate the wood with a solution of sulphate of iron, 
and then with a water-glass solution, whereby the pores of the wood are filled with 
ferro-silicate. Ransome attains the same end by an impregnation with a water-glass 
solution and subsequent treatment with an acid. It is found that the treatment of wood 
according to the above methods is generally attended with good results. A method 
of impregnation with materials forming an insoluble soap, oleate of alumina, oleate of 
copper, &c., patented in 1862, has given some moderate, results on the small scale. 

Mineralising Wood. 5. When the terms mineralised, petrified, metallised, or incrusted 
are applied to wood, they include the meaning that the wood has undergone impreg- 


TOBACCO. 


477 


nation with an inorganic substance, which has so filled the pores of the wood that it 
may be said to partake of the characteristics of a mineral substance. Suppose that 
the wood has become impregnated with sulphate of iron, when exposed to the rain 
the sulphate will be gradually dissolved out, in time leaving only a basic sulphate. 
By the researches of Strutzki (1834), of Apelt in Jena, and of Kuhlmann (1859), the 
influence of oxide of iron upon wood fibre has been rendered very clear. Wood 
impregnated with basic sulphate of iron ceases to be wood after some time. 

BoU top1egnl I tion < ! d ° f 6 - This method consists in the impregnation of the wood with 
the necessary substance, in a manner similar to the natural filling of the pores with 
sap ; that is to say, the solution is introduced into the tree from its roots, and is thus 
made to take the place of the sap in all parts of the timber. When the tree is felled 
the root end is placed in a solution of the salt (sulphate of copper, acetate of iron), 
and allowed to remain for some days; at the end of the required time the wood will 
have become completely impregnated with the salt. Occasionally this method is 
employed in colouring woods, colouring matter being used instead of, or as well 
as, the salt. The linden, beech, willow, elm, alder, and pear tree can be treated in 
this manner. The fir, oak, ash, poplar, and cherry tree do not, however, absorb the 
impregnating fluid sufficiently. 


Tobacco. 


Tobacco. Tobacco, as employed for snuff and for smoking and chewing, is the 
product of various kinds of annual plants belonging to the genus Nicotiana, of the 
family of Solanea, generally cultivated in warmer parts of the globe, but capable of 
growing in countries situated under 52 0 N. lat. The best tobaccos are grown in 
America, and are chiefly exported from the southern states of North America, viz., 
Maryland, Virginia, &c., from Orinoko, Havanna, and Cuba, &c. The European 
tobaccos are those of Holland, Hungary, Turkey, and France. In Europe three 
separate botanic varieties are cultivated. They are:— 

1. Common or Virginian tobacco [Nicotiana tabacum), with a large lancet-shaped 

ribbed leaf. 

2. Maryland tobacco (Nicotiana macrophylla ), with broad and not so strongly pointed 

leaves as those of the common tobacco plant. 

3. The farm or violet skin tobacco [Nicotiana rustica ), with an oval leaf and long stalk. 

The quality of the tobacco is dependent upon the climate, upon the soil, and upon 
the seed it is obtained from. Next to the vine, the tobacco plant is that requiring the 
most care in its cultivation. The influence of careful culture is so great, that plants 
grown in some parts of Germany yield tobacco unequalled by some of the richest 
tropical produce. 

According to the most recent researches, tobacco contains the following sub¬ 
stances :— 

I Potash 

Magnesia ^base^ 1 Nicotine 

Oxides of iron and manganese ' 

Ammonia 


Mineral a fids 


Nitric acid 
Hydrochloric acid 
Sulphuric acid 
Phosphoric acid 


Malic acid (Tobacco acid ?) 
Citric acid 
Organic Acetic acid 
acids Oxalic acid 
Pectic acid 
\Ulmic acid 




478 


CHEMICAL TECHNOLOGY . 


'Nicotianin 

Other mineral ( Silica Other organic / eUow resin 

substances i Sand substances 1 Nitrogenous subs tances 

.Cellulose 

chemiC T 1 obacco°LeL°f n of the The cliicf characteristic constituents of the tobacco leaf are 
the three following:—namely, nicotianin, nicotine, and malic acid. Nicotianin, or 
tobacco camphor, is a fatty substance, possessing strongly the odour of tobacco, and 
a hitter, aromatic flavour. Experience has shown that the varieties of tobacco con¬ 
taining the most nicotianin are those most preferred. It is generally considered that 
nicotianin is identical with cumarin (CgHsOj,), found in the tonka bean {Dipterix 
odorata) , in the Asperula odorata, in the Melilotus officinalis, and Anthroxantham 
odoratum, as well as in the leaves of the Angraecum fragrans, and the Liastris odora- 
tissima. Nicotine (Ci 0 H I4 N 2 ) is an organic base, and exists in a pure condition as a 
colourless oil, possessing the odour of tobacco and a caustic flavour; it is soluble in 
water, alcohol, ether, and some oils. It is even in very small doses a deadly poison; 
and in the very smallest quantities it will cause convulsions and paralysis. The pro¬ 
portion of nicotine met with in the various kinds of tobacco leaves varies greatly. 
From the experiments of Schloesing, made with many kinds of French and American 
tobaccos, the following quantity per cent of nicotine is found in the dry leaves of 
tobacco from:— 


Departement Lot . 




Nicotine. 

7-96 

„ Lot-et-Garonne ... 




7*34 

„ Nord . 




6-58 

,, Ille-ef-Yillaine ... 




6*29 

Pas de Calais . 




4*94 

Alsace . 




3*21 

Virginia ... 




6*87 

Kentucky. 




609 

Maryland . 




2'29 

Havanna . 


less than 

2 ' 0 O 


Dried snuff-tobacco contains about 2 per cent of nicotine, and contains on an 
average in its undried (usual) condition 33 per cent of water, the nicotine then 
amounting to 1*36 per cent. The nicotine is contained in the tobacco in the form of 
a salt. The characteristic acid is nicotic or tobacco acid, C 3 H 4 0 4 , which recent 
numerous researches have proved to be identical with malic acid. The tobacco leaf 
also contains albumen, woody fibre, gums, and resin. The leaves are also very rich 
in mineral constituents, these amounting to 19 to 27 per cent of the weight of the 
dried leaf. Merz obtained about 23*33 P er cent ash with several varieties of 
tobacco leaf. 100 parts of this ash contained potash, 26'96; soda, 2*76; lime, 39'53 ; 
magnesia, 9*61; chloride of sodium, 9*65; sulphuric acid, 278; silica, 4*51 ; and 
phosphate of iron, 4-20 parts. There is found, also, nitrate of potash, the quantity of 
which does not, however, influence the combustibility of the tobacco. 

Manufacture of Tobacco. Good smoking tobacco should give off an agreeable odour, 
should not deflagrate while burning, and not bite the tongue. Taste differs consider¬ 
ably in the respect of strength in this country from abroad; nowhere but in the 














TOBACCO . 


479 


United Kingdom are such strong smoking tobaccos met with. The freshly dried 
tobacco leaves are not suited for smoking, because they contain a'very considerable 
amount of albuminous matter, and on burning give off an odour of burnt horn, while 
they contain too large a quantity of nicotine. The preparation or manufacture of 
tobacco aims at the more or less complete destruction of the albuminous matters, the 
partial elimination of the nicotine, and the development of a peculiar aroma, while 
the leaves are formed by mechanical means into a suitable shape for smoking and 
snuffing. The leaves are moistened with water and placed together in heaps so as to 
calise a kind of fermentation, the temperature increasing to about 35 0 , the effect of 
which is that the albuminous matter of the tobacco is destroyed, while aromatic 
substances are developed. This process is assisted by the addition of what the trade 
terms “ sauce,” but nothing is known of the reactions and changes which take place. 
When the tobacco leaves are gathered from the plants they are laid one upon the other to 
the number of ten or twelve and placed in heaps in a dry shed, care being taken to cover 
the heaps with canvas. As soon as the sweating sets in, the leaves are suspended 
one by one on ropes stretched through the shed, and dried by exposure to a current 
of air; when dry the leaves are packed together to the number of thirty, so as to 
form a bundle, several hundreds of which are put together into casks. The weight 
of the casks filled with tobacco averages from 19 to 26 cwts. In some, but by no 
means in all instances, the cultivators of tobacco prepare the leaves to some extent by 
first moistening them with brine and causing them to undergo a partial fermentation. 
The leaves are then dried and packed in casks. By this means the tobacco may be 
preserved for a great many years, improving with age. 

smoking Tobacco. The tobacco leaves are first sorted; that is, those of the same colour 
and thickness are put together. They are next stripped, the thicker parts (stem or 
nerve) being cut out, because as these consist chiefly of woody fibre they would on 
burning impart an unpleasant odour to the tobacco. The leaves are next sauced or 
moistened with a liquor containing chiefly salts (common salt, saltpetre, sal-ammo¬ 
niac, nitrate of ammonia), saccharine matter, spirits, and some organic acids, such as 
tartaric and oxalic acid; the salts assist in the preservation as well as in the 
retardation of the combustion of the tobacco. The other substances impart, under 
the influence of fermentation, a peculiar aroma to the tobacco, which aroma is some¬ 
times compared to the bouquet of wine. The sauced leaves are next submitted to 
fermentation, dried at a gentle heat, and finally cut into shreds by means of 
machinery. Tobacco leaves are also twisted or spun together ; for instance, in the 
kind known as twist. Cigars are tobacco enveloped in a smooth leaf. The fact 
that cigars are improved by keeping is due to a kind of slow fermentation, during 
which the aroma is more fully developed, while noxious substances are eliminated. 

Tobacco smoke contains, in addition to carbonic acid, water, and some ammonia, 
the products of the dry distillation of tobacco, to which the peculiar flavour is due— 
among these substances are nicotine and nicotianin. Zeise found in tobacco smoke a 
peculiar empyrematical oil, butyric acid, ammonia, carbonic acid, paraffin, empyreu- 
rnatic resin, traces of acetic acid, oxide of carbon, and carburetted hydrogen. 

Curiously enough, burning tobacco does not form carbolic acid nor creosote; hence 
tobacco smoke affects the eyes less than does the smoke of smouldering wood. Zeise 
experimented on Porto Rico tobacco ; but his researches fail to convey any informa¬ 
tion as to the constitution of the essential aroma of tobacco smoke; in this respect it 
is with tobacco as with the bouquet of fine brands of wine, chemical reagents cannot 


CHEMICAL TECHNOLOGY. 


480 

detect tlie difference. But it is certain that tobacco smoke contains conjugated 
ammonias, and as* aniline has, in very dilute state, a similarity in odour with the 
smoke c f good tobacco, it may be present. Carbolic acid may also be produced by 
the dry distillation of tobacco. The combustibility of tobacco is not proportional to the 
quantity of nitric acid (nitrates) it contains, because while Kentucky tobacco, rich in 
nitrates burns badly, the Java, Maryland, Brazilian, and Hungarian tobaccos, poor 
in nitrates, burn readily. Schloesing has recently investigated the cause of the 
varying degree of the combustibility of tobacco. He found that the portion of 
tobacco ash soluble in water always contains carbonate of potash in proportion to the 
combustibility of the weed. When tobacco was carbonised by smoking, the soluble 
portion of the ash was found to contain only chloride of potassium and sulphate of 
potash. A badly burning tobacco is improved by saucing it with the solution of a 
potash salt of some organic acid (malic, citric, tartaric, or oxalic acid), and then 
drying the tobacco; on the other hand, a good burning tobacco is deteriorated by 
treating it with solutions of either sulphate of lime, chloride of calcium, or the 
corresponding magnesia and ammonia compounds. The cause of this phenomenon 
appears to be due to the fact that the potash salts of the organic acids yield on being 
carbonised a bulky, light, and very porous charcoal, which readily burns off, leaving 
only ash, while the charcoal formed by the combustion, under the same conditions, 
of the organic lime salts is very compact, hard, and burning off with difficulty. 

snuff. For the making of snuff the tobacco leaves are sorted as for smoking 
tobacco, but the sauce is chiefly composed of ammoniacal salts and aromatic 
substances. The fermented leaves are formed into carottes, thick beet-root shaped 
masses tapering from the centre to both ends, but not drawn out into a thin spindle; 
these carottes are rasped ( rappe) by means of machinery, and thus converted into 
powder. After having been sifted, this powder is again moistened and submitted to 
another fermentation. Snuff contains nicotine, partly free, partly as a neutral or 
basic (probably acetate) salt to an amount of about 2 per cent. Snuff also contains 
ammonia combined with an acid. It is to the presence of these substances that snuff 
owes its irritating action on the mucous membrane. In order to prevent snuff 
from becoming dry glycerine is frequently added. 

The aim of the fermentation of the tobacco for the purpose of snuff making appears 
to be :—1. The formation of a peculiar oil or ether which imparts aroma. 2. The 
partial destruction of the nicotine of the tobacco so as to render it better fitted for 
use as snuff. 3. The production of alkalinity by the partial destruction of the 
organic acids of the tobacco. 4. Evolution of a specific flavour by the formation of 
vapours of carbonate of ammonia (probably also of ammonia bases, such as ethyl- 
amin), and nicotine. 5. The conversion of the albuminous matters and other 
nitrogenous substances into ammonia, whereby the loss of ammonia by volatilisation 
is made up and a black substance (humus), to which snuff owes its dark colour, at 
the same time formed. 

Technology of Essential Oils and Besins. 

Essential oils and Resins. These substances almost all occur naturally. To the essen¬ 
tial oils most plants owe their odour and flowers their perfume. The essential oil in 
plants is met with enclosed in cells; hence, after bruising a plant, or the parts 
containing the essential oil, the peculiar odour is more perceptible; for instance, by 
gently rubbing between the fingers the leaves of some lands of geraniums, melissa. 


ESSENTIAL OILS. 


481 

lemon-plant, &c. Essential oils do not impart to the fingers a fatty, but a rather rough, 
harsh feeling. A large number of essential oils possess the property of precipitating 
silver from its ammoniacal solution in a metallic state; hence the use of essential 
oils in silvering glass (See p. 281). 

Preparation of Essential oils. These oils are chiefly obtained by submitting parts of 
plants, previously ground to a coarse powder, to distillation with water. Although 
the boiling-point of these oils is generally much higher than that of water, the oils 
are mechanically carried over in a minute state of division with the aqueous vapour. 
When oils, the boiling-point of which is very high, have to be extracted, some common 
salt is added to the water to heighten its boiling-point. In order to separate the oil 
from the water there is employed a peculiarly shaped vessel called a Florentine 
flask. In this way the essential oils of aniseed, chamomile, lavender, peppermint, 
cloves, cinnamon, &c., are obtained, while the most common essential oil, viz., that of 
turpentine, is obtained by the distillation of Venice turpentine with water. 

Pre mi3 a byPre f ss^ S e! ntial The essential oils largely met with enclosed in the cells of the 
skin of lemons, oranges, bergamots, and, in fact, all the fruits belonging to the Citrus 
species, are obtained by pressing the rind of these fruits. Although the greater 
number of the essential oils occur ready formed in various parts of the plants, some 
of these oils are the result of the action of water, as, for instance, the essential oil 
of bitter almonds, which is formed by the action of water upon amygdalin under the 
influence of a pecular albuminous compound called synaptase or emulsin ; the 
essential oil of mustard seed is formed in a similar manner, but may be artificially 
prepared by distilling a mixture of iodide of propyl and cyanide of potassium, &c. 

E bymeaTsof^atTyOih. 113 Some of the essential oils, more especially those present in 
flowers, are so sparingly distributed that they can only be obtained by digesting the 
fresh flowers with pure olive oil or with cotton-wool soaked in sweet olive oil, the 
fresh flowers being placed in alternate layers between the cotton saturated with oil; 
in some cases pure lard is employed. The essential oils may be recovered from the 
sweet oil by agitation with strong and highly rectified alcohol! The e ssential oils of 
jasmine, sweet violets, hyacinths, &c., are obtained in this manner. 

Pr 0 P Es3entiai oils! ° f These oils are more or less soluble in water, and the solutions 
are known in pharmacy as distilled waters. The essential oils are soluble in alcohol 
in proportion to the amount of oxygen they contain. Upon this property is based 
the use of these oils in perfumery and for the preparation of liqueurs (cordials). 

perfumery. This-branch of industry provides us with scented waters (espritsmux de 
senteur), odoriferous extracts {extraits a odeurs), perfumed fats, pomatums, oils, &c. 
Scented waters are really alcoholic solutions of one or more essential oils. The 
alcohol used for this purpose requires to be very pure and perfectly free from fusel oil 
or other impurity. The oils are dissolved in the alcohol, and in order to blend the 
mixture and render it mellow, it is kept for several months in a bottle before being 
sold. The old process of distillation is very properly discarded, because, owing to 
the high boiling-point of the oils, a portion was left in the still, while the scented 
waters thus prepared were inferior in quality. Eau de Mille Fleurs is prepared by 
dissolving in 9 litres of alcohol, 60 grms. of balsam of Peru, 120 grms. of oil of 
bergamot, 60 grms. of oil of cloves, 15 grms. of neroli oil (oil of orange 
flowers, a very expensive oil), 15 grms. of oil of thyme, adding to the mixture 
4 litres of orange-blossom water, 120 grms. of tincture of musk, obtained by 
digesting 15 grms. of civet and 75 grms. of musk with 2 litres of alcohol. Eau 
32 


CHEMICAL TECHNOLOGY. 


482 

de Cologne is obtained by dissolving in 6 litres of alcohol 32 grms. of essential 
oil of orange-peel and equal quantities of oil of bergamot, lemon, essence de 
limette, essence de petit grains, 16 grms. essence de cedro, and equal quantities of 
essence de cedrat, essence de Portugal; further, 8 grms. of neroli oil and 4 grms. of 
rosemary. 

The perfumed extracts are generally obtained by the exhaustion, by means of 
alcohol, of the scented fats and oils prepared from flowers as before described. 
Doebereiner first suggested the use of artificial perfumes; among these are an 
chemical Perfumes, alcoholic solution of acetate of amyl as pear oil, valerate of amyl as 
apple oil, buterate of amyl as pine-apple oil, pelargonate of ethyl as oil of quinces, 
suberate of ethyl as essence of mulberries, while nitrobenzol mixed with nitrotoluol 
(commercial nitrobenzol) is termed artificial oil of almonds, and, when very coarse, is 
sold as essence de Mirbane, chiefly used for the preparation of aniline. The perfumed 
fats (pomatums) of better quality are generally prepared from an infusion of the 
flowers with oil or fat at a temperature of 65°, or by a process of digestion in the 
cold by placing the flowers in layers between pure lard or cotton-wool soaked in 
very pure olive oil; enfleurage is the name given to this operation. The ordinary 
pomatums are made simply of lard or marrow-fat coloured with turmeric, annatto, or 
alkanet root, and perfumed with a few drops of some essential oil. 

preparation of Cordials. The aim of the preparation of liqueurs (cordials) is to render 
brandy a more agreeable beverage by the addition of sugar, glycerine, and aromatic 
substances. A distinction is made between finer liqueurs ( rosoglio) and ordinary 
cordials [aqua vitce) according to the quality of the materials employed for the purpose. 
When a sufficiently large quantity of sugar is used to render the liqueurs thickly fluid 
they are designated cremes, while those made with the juices of fruit obtained by 
pressure, sugar, and alcohol, are called ratafia. These liqueurs are not prepared to 
any great extent in this country; but in France, Italy, Austria, and especially Holland, 
the preparation is on a large scale. 

The basis of all liqueurs is a very highly rectified and pure alcohol. The 
vegetable materials used in the liqueurs may be classified under three heads :—In 
the first place, such vegetable substances as contain essential oils and are used 
for that reason only, carraway, aniseed, junker-berries, mint, lemon-peel, orange- 
blossom, and bitter almonds. These substances, previously bruised or cut up, are 
digested with alcohol, the mixture being next distilled, or, as is more generally the 
case, alcoholic solutions of the essential oils are employed and - the preparation 
performed in the cold. To the second class belong such vegetable substances as are 
used for the sake of their essential oil and for their aromatic bitter substances, 
chiefly roots, such as sweet calamus, gentian, ginger, orange-peel, unripe bitter 
Cura5oa apples (a peculiar kind of orange), wormwood, cloves, cinnamon, vanilla (the 
pod of an orchidaceous plant originally brought from Mexico). These substances 
having been bruised are digested with alcohol either at the ordinary temperature of 
the air or at 50° to 6o°, the result being the formation of what is termed a tincture. 
To the third class belong fruits, such as cherries, pine-apples, strawberries, rasp¬ 
berries, the juice of which is obtained by pressure, passed through a sieve, and 
mixed with alcohol and sugar or syrup, viz., a solution of 4 lbs. of refined loaf-sugar 
in 4 litres of water. The liqueurs generally contain from 46 to 50 per cent of alcohol. 
It is customary to colour the liqueurs re^ with santal-wood, cochineal, aniline red, 
or with the Coccus polonicus, as is the case until the celebrated Alkermes de Firense, 



RESINS. 


483 


a liqueur made at Florence; yellow with saffron, turmeric, or marigold flowers 
(Calendula ) ; green by mixing yellow and blue; blue with tincture of indigo ; violet 
with aniline violet; while in many cases caramel is used to impart a brown colour. 
The so-called cremes contain for every litre of liquid about 1 lb. of sugar or a corre¬ 
sponding quantity of glycerine. As an instance of the composition of a liqueur, 
Maraschino consists of 4 litres of raspberry water, if litres orange-blossom water, 
i£ litres kirschwasser (a Swiss preparation—from cherries fermented and distilled—a 
strong spirituous liquid which contains hydrocyanic acid), 18 lbs. of sugar, and 9 litres of 
alcohol at 89 to 90 per cent. Liqueurs are very similar to cremes , but contains less 
sugar. English bitter contains 5 parts of jiavedo corticum aurantiorum (outer rind 
of dried orange peel), 6 parts of cinchona bark, 6 parts of gentian, 8 parts of Carduus 
benedict , 8 parts of centaury, 8 parts of wormwood, 4 of orris root digested with 
54 litres of alcohol at 50 per cent, while after filtration 12 lbs. of sugar are added. 
Cherry ratafia:—20 litres of cherry juice, 20 litres of alcohol at 85 per cent, 30 lbs. 
sugar, and usually 4 to 8 litres of bitter almond water. Peppermint:—2 \ litres of 
essential oil of peppermint dissolved in 1 litre of alcohol at 80 per cent; this solution 
is poured into 54 litres of alcohol at 72 per cent sweetened with 60 lbs. of sugar 
previously dissolved in 26 litres of water, and coloured with either tincture of indigo 
or turmeric. 

Resins. By the action of the oxygen of the air most of the essential oils are 
gradually thickened, and at length converted into a substance termed resin. Resins 
are frequently met with in the vegetable kingdom; in some instances, as with 
coniferous trees, resin flows spontaneously from the wood in combination with an 
essential oil, so-called Venice turpentine, which hardens by exposure to air. Some 
resins are extracted from vegetable matter by means of alcohol, this solution being 
either precipitated with water or evaporated to dryness. Resins are either soft, and 
are then termed balsams, chiefly solutions of resin in essential oils, or hard. To the 
former belong Venice turpentine, Canada balsam, balsam of Peru, Copaiva balsam, 
&c.; to the latter, amber (a fossil resin), anime, copal, gum dammar, mastic, shellac, 
asphalte. The gum resins are obtained from incisions made in certain kinds 
of plants, the milky juice of which hardens by exposure to air; these substances 
are partly soluble in water, and yield with it in many instances an emulsion; for 
instance, assafoetida, gum gutti, &c. Many gum resins possess a very strong odour 
and contain essential oils. Although it is customary to treat of caoutchouc and 
gutta-percha under the head of resins, these substances are not related to resins at 
all, but belong to a separate class of bodies, among which, according to Dr. G. J. 
Mulder’s researches, the so-called drying oils must be enumerated. 

U seaL^-wax as Sealing-wax of modern time (for mediceval sealing-wax was really 
a mixture of wax with Venice turpentine and colouring matter) is prepared from 
shellac, to which some turpentine is added in order to promote fusibility and 
prevent brittleness. Red sealing-wax and bright coloured wax are made of a 
very pale, sometimes even purposely bleached, shellac, while black and dark 
coloured sealing-wax are made of more deeply coloured shellac. In addition to 
shellac and turpentine, sealing-wax contains earthy matter, added not only for the 
purpose of increasing the weight, but also for preventing the too rapid fusion 
of the mass; chalk, magnesia, plaster of Paris* zinc-white, sulphate of baryta, 
kaolin, finely-divided silica, are employed for this purpose. Red sealing-wax is 
prepared by melting together in an iron pan placed on a charcoal fire 4 parts of 


484 


CHEMICAL TECHNOLOGY. 


shellac, 1 part of Venice turpentine, and 3 parts of cinnabar (vermillion), care 
being taken to stir the mixture constantly. Ordinary red sealing-wax is often 


composed of:— 

1. 

2. 

3 * 

4 - 

5 - 

Shellac. 

. 550 

620 

550 

700 

600 

Turpentine . 

. 740 

680 

600 

540 

600 

Chalk or magnesia 

. 300 

200 

— 

— 

— 

Gypsum or zinc-white 

. 200 

— 

— 

— 

•— 

Baryta white _ . 

. — 

100 

380 

3 °° 

300 

Vermillion .. 

. 130 

220 

340 

3 °° 

30c 

Oil of turpentine. 

. — 

— 

— 

20 

. 2 5 


The cooled but still soft mass is either rolled on a slab of marble and shaped into 
sticks, or the fluid mass is run into brass moulds. Perfumed sealing-wax contains 
either benzoin resin, storax, or balsam of Peru. The various colours are imparted by 
cobalt ultramarine (cobalt.blue), chromate of lead, bone-black, &c. Marbled sealing- 
wax is made by mixing variously coloured sealing-wax together. Inferior kinds of 
sealing-wax—parcel-wax—are coloured with red oxide of iron, while instead of 
shellac ordinary resin is used with gypsum or chalk. New Zealand resin, the 
produce of the Xanthorrhcea hastilis, is now frequently used instead of shellac. 

Asphaite. This material sometimes known as bitumen, is a black, glossy, brittle 
resin, probably formed by the gradual oxidation of petroleum oil; it pccurs very 
largely on the island of Trinidad, on the northern coast of S. America, at the mouth 
of the Orinoco, on the water of the Dead Sea (anciently Lacus Asphaltites), and 
in some other localties, viz. France, Seyssel, Departement de l’Ain, a limestone con¬ 
taining 18 per cent of asphalt. By boiling this limestone, previously broken up 
into small lumps, with water, there is obtained an asphaite, 7 parts of which are 
mixed with 90 parts of native asphaite limestone. The materials are ground up 
together and are employed for paving purposes, being compressed with heavy and 
highly heated irons. Asphaite also occurs at Val de Travers, Switzerland; Limmer, 
Hanover; Lobsann, Lower Alsace; and in the Northern Tyrol. Asphaite, or 
bitumen, is somewhat soluble in alcohol, readily so in Persian naphtha, oil of turpen¬ 
tine, benzol, and benzoline. It is used in varnish making (iron varnish), in engra¬ 
ving copper and steel, as an etching ground, and as an oil paint. Asphaite mixed 
with sand, lime, or limestone, is largely used for paving purposes, being durable and 
somewhat elastic; it is employed for this purpose either in a pasty or semi-fused 
state, or in powder. Instead of native asphaite, Busse’s terresin, a mixture of coal- 
tar, lime, and sulphur is sometimes used, as well as coal-tar asphaite, obtained from 
gas works. The residue of the distillation of coal-tar is often employed instead of 
asphaite, and pebbles mingled with coal-tar are now used to form excellent footpaths 
in some parts of the metropolis. 

Caoutchouc. Elastic gum or india-rubber, is derived from the the milky juice of a 
series of plants, occurring also in opium; but the commercial article is obtained 
from the milky juice of various trees belonging to the natural orders of the TJrticea, 
EuplwrUacece , Apocynecc. Among the trees which yield caoutchouc in large quantity 
are the Siphonia cahucu, in South America, and the East Indian, XJrceola elastica. 
Ficus elastica, F. xelicjiosa , F. indica, also yield caoutchouc. It is obtained by 
making incisions in the tree and collecting the exuding juice in vessels of dried clay 







INDIA-RUBBER. 


485 


The juice is solidified by the application of fire or by exposure to the sun’s rays ; the 
variety known as lard gum is usually dried by exposure to the sun. Perfectly pure 
caoutchouc is a white, and in thin sheets semi-transparent, substance; its texture is 
not fibrous; it is perfectly elastic, becoming turbid and fibrous when strongly 
stretched. Excessive cold renders it hard but not brittle. The specific gravity of 
caoutchouc is 0^925. Although hot water and steam render caoutchouc soft, it is not 
further acted upon by them. It is insoluble in alcohol, not acted upon by dilute 
acids or strong alkalies, while for a very long time it resists the action of chlorine. 
Strong sulphuric and nitric acids decompose india-rubber, and when red fuming 
nitric acid is employed a violent combustion ensues. If when strongly stretched 
india-rubber is placed in cold water for a few minutes it temporarily loses its 
elasticity, which it regains by being immersed for a few minutes in water at 45 0 . By 
exposure to a gentle heat caoutchouc becomes supple, and finally melts at 200°, with 
partial decomposition, forming a viscous mass which does not again become solid on 
cooling. When caoutchouc is ignited in contact with air it burns with a sooty flame. 

^ Of all substances with which we are acquainted none would be better suited to gas 
manufacture than caoutchouc, which, according to experiments made many years ago 
at Utrecht, yields at red heat rather more than 30,000 cubic feet of gas to the ton, the 
gas being quite free from sulphur and ammonia compounds, and its illuminating 
power very superior to that of the best oil gas. Unfortunately caoutchouc is much 
too high priced for this application. Caoutchouc may be kneaded with sulphur 
and other substances by the aid of heat, becoming converted into what is known as 
vulcanised india-rubber, vulcanite, ebonite, &c. When caoutchouc is submitted to 
dry distillation, at much below red heat, it yields only oily fluids, consisting of 
carbon and hydrogen (caoutchen, heveen, &c.), which are par excellence solvents for 
caoutchouc. Caoutchouc itself contains only carbon and hydrogen, its formula being 
C 4 H 7 (in 100 parts: 8 ys carbon and I2'5 hydrogen) ; probably, however, caoutchouc 
is a more complex mixture of various hydrocarbons. 

solvents oi Caoutchouc. India-rubber is soluble in alcohol-free ether, in the oils 
(empyreumatic) of caoutchouc, in Persian naphtha, oil of turpentine, sulphide of 
carbon, and in chloroform. Industrially the ethereal solution of caoutchouc is 
useless, because it contains hardly more than a trace of that substance. As regards 
oil of turpentine, it dissolves caoutchouc only when the oil is very pure and with the 
application of heat; the ordinary oil of turpentine of commerce causes india-rubber 
to swell rather than to become dissolved. In order to prevent the viscosity of the 
india-rubber when evaporated from this solution, 1 part of caoutchouc is worked up 
with 11 parts of turpentine into a thin paste, to which is added i part of a hot and 
concentrated solution of sulphuret of potassium (K 2 S 5 ) in water; the yellow liquid 
formed leaves the caoutchouc perfectly elastic and without any viscosity. The solu¬ 
tions of caoutchouc in coal-tar naphtha and benzoline are most suited to unite pieces 
of caoutchouc, but the odour of the solvents is perceptible for a long tune. As 
chloroform is too expensive for common use, sulphide of carbon is the most usual 
and also the best solvent for caoutchouc. This solution, owing to the volatility of the 
menstruum, soon dries, leaving the caoutchouc in its natural state. When alcohol is 
mixed with sulphide of carbon the latter does not any longer dissolve the caoutchouc, 
but simply softens it and renders it capable of being more readily vulcanised. 
Alcohol precipitates solutions of caoutchouc and gutta-percha. 


CHEMICAL TECHNOLOGY. 


486 

Preparation and use of India-rubber is used to clean paper, rub out black-lead pencil 

India-Rubber. x x 

marks, for making waterproof fabrics (macintosh), rubber sponge, tubing, elastic webs, 
lutes, &c. 

vulcanised Caoutchouc. When caoutchouc is immersed for some time in molten sulphur 
it absorbs the latter, and becomes converted into a yellow, very elastic mass. The 
properties of vulcanised india-rubber are: elasticity even at low temperatures, while 
ordinary india-rubber hardens at 3 0 . Vulcanised india-rubber is insoluble in the sol¬ 
vents of caoutchouc. It resists compression to a very great extent; hence its use 
instead of steel springs on the tramway cars. According to the old method 
caoutchouc was vulcanised by being placed for some ten to fifteen minutes in 
thin plates in molten sulphur heated to 120°, the weight of the caoutchouc increasing 
10 to 15 per cent. The material was subsequently mechanically treated by pressure, 
and then heated to 150°. In order to prevent efflorescence of the sulphur, 
caoutchouc is sometimes heated to 120°, and then kneaded, by the aid of powerful 
machinery, with either kermes (Sb 2 S 3 ), or a mixture of sulphur and sulphuret of 
arsenic. At the present day Parkes’s method is generally adopted ; the caoutchouc is ^ 
simply immersed in a mixture of 40 parts of sulphide of carbon and 1 part of 
chloride of sulphur; it is next placed in a room heated to 21 0 , and when all the sul¬ 
phide of carbon has been volatilised, the process is in so far complete that it is only 
requisite to boil the material in a solution of 500 grms. of caustic potassa to 10 litres 
of water, the vulcanised caoutchouc being next washed to remove excess of alkali. 
Recently (1870) Humphrey has introduced the use of petroleum ether (benzoline) 
instead of sulphide of carbon, as the former fluid dissolves chloride of sulphur 
readily. H. Gaultier de Claubry (i860) vulcanises caoutchouc by the aid of 
bleaching-powder and flowers of sulphur. This mixture produces chloride of 
sulphur, and the caoutchouc treated by it contains some chloride of calcium. 
Neither this process nor that of Gerard—the use of a solution of pentasulphide of 
potassium of 25 0 to 30° B., aided by a temperature of 150°, and a pressure of 
5 atmospheres or 75 lbs. to the square inch—are practically available on the 
large scale. Articles of vulcanised india-rubber are made of ordinary caoutchouc 
and then, vulcanised. The uses of vulcanised india-rubber are so many and so 
generally known that it is hardly necessary to enumerate them. 

In the year 1852 Goodyear discovered a process by which caoutchouc is rendered 
hard and woodlike, being then termed vulcanite or ebonite. This substance exhibits 
a black or brown colour, and is largely used for making combs, imitation jet 
ornaments, stethescopes, and a variety of articles. The preparation of ebonite differs 
from that of vulcanite only in the introduction of a larger amount of sulphur 
(30 to 60 per cent), at a higher temperature, with the addition of other substances, 
shellac, gutta-percha, asphalte, chalk, sulphate of baryta, pipe-clay, sulphurets of 
zinc, antimony, or copper, &c. Ebonite is capable of taking a high polish; does 
not, as is the case with horn, become rough when cleaned with hot water, and is to 
some extent elastic. Vulcanised caoutchouc mixed with sand, emery, and quartz, 
is used for sharpening agricultural implements, scythes, sickles, &c. 

Production and Consumption The total quantity of caoutchouc produced in 1870 amounted to 
of Caoutchouc. 120,000 cwts., of which the island of Java yielded 60,000 cwts. 

The consumption is fully equal to the supply, the largest quantity being used in North 
America, 35,000 cwts. 

Gutta-Percha. Plastic gum, gutta or getah-percha, gettannia gum, tuban gum, is a 
substance in many respects similar to caoutchouc; it is the inspissated juice of the 


GUTTA-PERCPA. 4S7 

Isonandra gutta, a tree growing in Malacca, Borneo, Singapore, Java, Madura, and 
adjacent countries. 

Gutta-percha was at first obtained by felling the trees and collecting the exuding 
juice, either in suitable vessels or in shallow pits dug in the soil, or in baskets made 
from banyan leaves, the juice being left to coagulate under the action of the sun. 
More recently deep incisions are made in the trees and the exuding juice collected. 
The lumps of solid gutta-percha thus obtained are united by softening in hot water 
and by pressure. The raw gutta-percha of commerce is a dry, red, or marbled mass, 
not unlike leather cuttings which have been pressed together ; the raw material con¬ 
tains as impurities some sand, small pieces of wood and bark, and sometimes other 
inspissated vegetable juices of less value than gutta-percha. The name gutta¬ 
percha really means Sumatra gum, this island being known in Malay language as 
Pulo-percha. When perfectly pure gutta-percha is quite white, its ordinary brown 
colour being due to an acid insoluble in water, which is present, partly free, partly as 
insoluble salts (of magnesia, ammonia, potash, and protoxide of manganese), 
of apocrenic acid; but in addition there is a small quantity of organic colouring 
^matter. Gutta-percha is a mixture of several oxygen-containing resins, which 
appear to be the products of the oxidation of a hydrocarbon, the formula of which is 
C 2 oH6o- Payen found in gutta-percha the following substances :—75 to 80 per cent 
of pure gutta-percha; 14 to 16 per cent of a white crystalline resin termed alban; 
and from 4 to 6 per cent of an amorphous yellow resin named fluavil. Previously to 
being used gutta-percha is cleansed from dirt by a mechanical process of kneading 
in warm water, being then usually rolled into thick plates or sheets. The purified 
material exhibits a chocolate-brown colour, is not transparent unless first reduced to 
sheets as thin as paper, when the gutta-percha is in transparency equal to horn. At 
the ordinary temperature of the air gutta-percha is very tough, stiff, not very elastic 
nor ductile. Every square inch of a strap of gutta-percha, if of good quality and as 
homogeneous as possible, can sustain a strain of 1872 kilos, without breaking. Its 
sp. gr. = o - 979. At 50° it becomes ’ soft, and at 70° to 80° it is so soft as to be very 
readily moulded, while two pieces pressed together at this temperature become 
perfectly joined. By the aid of heat gutta-percha can be rolled into sheets, drawn 
into wire, and kneaded into a homogeneous mass with caoutchouc. 

solvents of Gutta-Percha. Gutta-percha is insoluble in water, alcohol, dilute acids, and 
alkalies ; it is soluble in warm oil of turpentine, sulphide of carbon, chloroform, coal- 
. tar oil, caoutchouc oil, and in the somewhat similar oil obtained by the dry distilla¬ 
tion of gutta-percha. Ether -and some of the essential oils render gutta-percha pasty. 
As already stated this substance becomes soft in hot water, absorbing a small quantity, 
which is only very slowly driven off. Dry gutta-percha is a very good insulating 
material for electricity. 

Uses of Gutta-Percha. The natural properties of this substance indicate its use as a sub¬ 
stitute for leather, papier mache, cardboard, wood, millboard, paper, metal, &c., in all 
cases not exposed to the action of heat, and where a substance is desired resisting water, 
alcohol, dilute acids, and alkalies. The raw material, previously to being moulded into 
shape, is purified and kneaded by means of powerful machinery and with the assistance 
of hot water (some soda or bleaching-powder solution being added), the aim being 
the removal of such impurities as are only mechanically mixed with the gutta-percha as 
well as the removal of some of the colouring matter, while a more homogeneous mass is 
produced. The purified substance is next submitted to the action of kneading machinery 
similar to that in use for working up caoutchouc, while it is rolled out into plates of pome 
3 centimetres in thickness. Gutta-percha is moulded into tubes by the aid of machinery 
similar to that employed for making lead and block-tin tubing. Many objects are made 
from gutta-percha by pressing it while soft into wooden or metal moulds. By the use of 


488 


CHEMICAL TECHNOLOGY. 


a solution of gutta-percha in benzol, it may be glued to leather and similar substances. 
It is almost impossible to enumerate the various uses of gutta-percha. It is employed 
for straps for machinery instead of leather, tubes for conveying water, pumps, pails, sur¬ 
gical instruments, ornamental objects of various kinds, for covering telegraph wires, &c. 
Unlike pure caoutchouc gutta-percha becomes gradually deteriorated by exposure to the 
atmosphere, so that it can be even readily ground to powder. 

Mixture of Gutta-Percha Frequently a mixture of i part of gutta-percha and 2 parts 
and Caoutchouc. 0 f caoutchouc is employed. Articles made of this compound 
possess the properties of both substances, and may be vulcanised equally as well as 
gutta-percha alone. A mixture of equal parts of caoutchouc, gutta-percha, and sulphur, 
heated for several hours to 120°, obtains properties similar to those of bone and horn. 
Sometimes gypsum, resin, and lead compounds are added to this mixture, which is then 
used for making knife hafts, buttons, &c. 

vamishes. By varnish we understand a liquid of an oily or resinous nature 
employed for coating various objects, the thin film becoming dry and hard, thus 
protecting the object on w r hich it is laid from the action of air and water, and 
at the same time imparting a glossy and shining surface. We distinguish oil and 

ou vamishes. spirit varnishes. Oil varnishes are usually prepared from linseed oil, 
but sometimes, especially for artist’s purposes, poppy seed and walnut oil (so-called 
drying oils) are used. Linseed oil (raw) becomes slowly converted by the action of* 
the air into a tough, elastic, semi-transparent mass ; but this property is possessed in 
a far higher degree by the so-called boiled oil, that is to say—an oil which lias been 
brought by the action of heat and of oxidising materials into a state of greater 
activity, in fact—into a state of incipient slow oxidation, the result of which is the 
formation of the substance termed by Dr. G. J. Mulder * linoxine, which in many of 
its properties corresponds to caoutchouc. The drying of oil varnishes is not there¬ 
fore due to evaporation (leaving, as is the case with alcohol varnishes, a coherent fi lm 
of resin), but to the oxidising action of the oxygen of the air, whereby a coherent 
film of linoxine is formed. Linseed oil (raw) is converted into what is termed 
varnish by heating the oil with certain substances which more or less readily give off 
oxygen, while these substances also act upon the elaine, palmitine, and myristine of 
the linseed oil. The greater part of the linseed and other drying oils is linoleine, 
3(C 3 2H270 3 ),C6H 5 03, which by slow oxidation becomes linoxine = C^BL^Ou, by 
the action of alkalies converted into linoxic acid, HO,C 3 2H 2 50 9 . The substances 
with which raw linseed oil is boiled are litharge, oxide of zinc, and peroxide of man¬ 
ganese. It is certainly preferable to carry this operation into effect upon the water 
bath, or at least with vessels provided with steam jackets. The oxides are employed 
in coarse powders, which are suspended in a linen bag in the oil. In practice 1 part 
of oxide of zinc or litharge is taken to 16 parts of raw oil; and of the manganese 
1 part to 10 of oil; the oxides become partially dissolved in the oil, while they aid 
in converting the palmitine, &c. (not linoleine), into plaster (lead or zinc soap). 
Boiled linseed oil usually contains from 2‘5 to 3 per cent of litharge dissolved. 
Neither the addition of sulphate of zinc nor such absurdly added substances as 
onions, bread crust, or beet-root have any result whatever. Linseed < 3 il intended to 
be mixed with zinc-white should not be boiled with litharge, but with peroxide 
of manganese. The lower the temperature at which linseed oil is boiled the brighter 
its colour. Mulder found that when raw linseed oil, especially if old, was kept for 
12 to 18 hours at a temperature of ioo°, it acquired the jwoperty 0 f boiled oil. 
Sometimes after boiling linseed oil is bleached by exposing it in shallow trays 

* This author published some years ago in the Dutch language a highly interesting and 
valuable work—practically as well as scientifically—on the drying-oils. 


VARNISHES. 


489 


10 centims. deep, best made of sheet lead, covered with sheets of glass, to the action 
of strong summer sunlight. Liebig’s recipe for making a bright varnish is the 
followingTo 10 kilos, of raw linseed oil are added 300 grms. of finely pulverised 
litharge, after which there is added a solution of 600 grms. of acetate of lead; the 
mixture is vigorously stirred, and after the subsidence of the materials the clear 
varnish is ready for use. Borate of manganese is, according to Barruel and Jean, 
an excellent so-called siccative (dryer) when added to raw linseed oil, 1 part to 1000 
of oil. Mulder’s experiments confirm this statement in every respect. 

Gold size. . This is used in gilding for fixing gold leaf on wood, paper, &c., and consists 
of a solution of linseed oil and lead plaster in oil of turpentine, prepared by first 
saponifying linseed oil with caustic soda or potassa, and precipitating the aqueous 
solution of the soap with a solution of acetate of lead, the lead soap thus formed being 
next dissolved in oil of turpentine. 

Printing ink. This is, when genuine and prepared from good linseed or walnut oil, 
anhydride of linoleic acid, C32H27O3, mixed with very finely divided lamp-black, and 
obtained by heating raw linseed oil for several hours, at a high temperature 
(315 0 to 360°), whereby the fatty constituents—glycerine, palmitine, &c.—are 
volatilised. Usually the oil is heated in vessels directly exposed to the action 
of fire, and as the colour of the ink is black, a deep colour of the residue of the 
heating of the oil is not of much consequence. In order to render printing ink more 
rapidly drying, some borate of manganese may be heated with it at 315 0 for some 
hours. The quantity of fine lamp-black (best re-ignited in close vessels, or exhausted 
with boiling alcohol) usually added to printing ink, amounts to about 16 per cent. 
Soap is added in order to prevent smearing and assist in obtaining sharpness 
of impression. Coloured printing inks kre obtained by adding to boiled oil red or 
blue or other pigments ; for red vermillion is used. The ink used in lithography 
and copper-plate printing is made thicker, a better black being added. 

ou varnishes. The so-called fat or oil varnishes are solutions of resins in boiled lin¬ 
seed oil mixed with oil of turpentine, benzol, or benzoline. Amber, copal, anime, 
gum dammar, and asphalte, are among the more ordinary resins employed for this pur¬ 
pose, the varnishes being made by melting, with the aid of gentle heat, the amber, 
copal, &c., to which, while liquid, boiling linseed oil is added. The cauldron in 
which this operation takes place should only be two-thirds filled; and the mixture of 
oil and resin kept boiling for ten minutes. The cauldron having been removed from 
the fire its contents are allowed to cool down to 140°, when the oil of turpentine is 
added. The quantities by weight are 10 parts copal or amber, 20 to 30 boiled 
linseed oil, 25 to 30 oil of turpentine. Black asphalte varnish is obtained in a 
similar manner by treating 3 parts of asphalte, 4 of boiled linseed oil, and 15 to 18 
parts of oil of turpentine. Dark coloured amber varnish is not prepared from 
amber but from the residue (amber colophonium) of the distillation of the empy- 
reumatic oil of amber and succinic acid left in the still from the preparation of 
succinic acid. These varnishes are the most durable, but they dry slowly and 
are more or less coloured. 

spirit varnish. The so-called spirit varnishes are solutions of certain resins, 
viz. sandarac, mastic, gumlac (shellac), anime in alcohol, aceton, wood spirit, 
benzoline, or sulphide of carbon. Good spirit varnish ought to dry rapidly, give a 
glossy surface, adhere strongly, and be neither brittle nor viscous. As shellac is 
frequently employed, the name of lac varnish is sometimes given to these varnishes. 
The spirit, usually methylated spirit, ought to be strong, about 92 per cent. The 


490 


CHEMICAL TECHNOLOGY. 


solution of the resins is promoted by the addition of one-third of their weight 
of coarsely powdered glass for the purpose of preventing the resinous matter caking 
together, and being thus to some extent withdrawn from the solvent action of 
the alcohol. In order to render the coating remaining from the evaporation of 
the spirit less brittle, Venice turpentine is usually added. Sandarac varnish 
is obtained by dissolving io parts of sandarac and i of Venice turpentine in 30 of 
spirit. Shellac varnish, more durable than the former, is obtained by dissolving 
1 part of shellac in 3 to 5 of spirits. French polish is a solution of shellac in 
a large quantity of spirits, and when this polish is to be applied to white wood, the 
varnish is bleached by filtration over animal charcoal. Copal varnish, far superior 
to the foregoing, is made by first melting the resin at as gentle a heat as possible 
so as to prevent the colouration of the substance, which is next pulverised, mixed 
with sand, treated with strong alcohol on a water bath, and filtered. A solution 
of turpentine or elemi resin is added to render the varnish softer. Colourless copal 
varnish is obtained by pouring over 6 kilos, of previously pulverised and molten 
copal, contained in a vessel which may be closed, 6 kilos, of alcohol at 98 per cent, 
4 kilos, of oil of turpentine, and 1 kilo, of ether; the vessel containing this mixture 
having been closed is gently heated. The solution is clarified by decantation. 

coloured spirit vamishes. These are used chiefly for the purpose of coating instruments, 
and other objects of brass and coloured metallic alloys, so as to prevent the action 
of the atmosphere. Such varnishes are used for imparting a gold-colour to 
base metals; for this purpose alcoholic tinctures of gummi-gutta and dragon’s blood, 
or fuchsin, picric acid, Martius yellow, and corallin, are separately prepared and 
added, in quantities found by trial, to a varnish consisting of 2 parts of seed lac, 4 of 
sandarac, 4 of elemi, and 40 of alcohol. 

Turpentine oil vamishes. These are prepared in the same manner as the preceding. 
They dry more slowly, but are less brittle and more durable. Common turpentine 
oil varnish is obtained by dissolving ordinary resin in oil of turpentine ; but this 
varnish is liable to crack. Copal is either dissolved in oil of turpentine, without or 
after having been melted; in the latter case the varnish being coloured. When non- 
melted copal is used it is broken into small lumps, and is suspended in a stout canvas 
bag over the surface of the oil of turpentine contained in a glass flask and placed on 
a sand bath, the vapours arising from the oil of turpentine gradually dissolving the 
copal. Dammar gum resin varnish made with oil of turpentine is prepared by 
drying the resin at a gentle heat and dissolving it in three to four times its weight of 
oil of tupentine. This varnish, though colourless, is not very durable. Green 
turpentine oil varnish is prepared by dissolving sandarac or mastic in concentrated 
caustic potash solution, diluting with water, and precipitating with acetate of copper, 
the dried precipitate being dissolved in oil of turpentine. 

Polishing the Dried varnish. In order to increase the gloss of varnished surfaces, especially 
on metallic objects and coaches, carriages and woodwork in theatres, concert-rooms, 
halls, &c., the dry surface is first rubbed over with soft felt, on which some very fine pumice- 
powder is laid, and is next polished with very soft woollen tissue on which some oil and 
rotten-stone is placed, the oil being rubbed off with starch-powder. Instead of varnishes, 
solutions of collodion (fulminating cotton in alcohol and ether) and solutions of water- 
glass are sometimes used; while Puscher recommends a solution of shellac in ammonia, 
largely used by hatters. 

Pettenkofer’s Process for I n order to remove the cracks often observed in old "pictures, Yon 
Restoring Pictures. Pettenkofer has suggested exposure to the vapour of alcohol at the 
ordinary temperature of the air, the picture being placed in an air-tight box, at the bottom 
of which is a tray containing alcohol. This method has been tried, but not only has it 


CEMENT. 


49 1 


failed in many cases, but some pictures have been actually spoiled. According to 
Dr. G. J. Mulder’s researches, the only effective preservative of pictures is complete 
exclusion of air. He suggests that pictures should be well varnished on the painted side 
as well as on the back, and next hermetically covered with well-fitting sheets of polished 
glass on the front, and some substance on the back impermeable to air. The real cause 
of the ultimate destruction of pictures as well as of paint is the gradual but continuous, 
yet slow, oxidation of the linoxine, resulting in the crumbling to powder of the pulverulent 
matters—pigments, used as colours. It may not here be out of place to state that one of 
the best solvents of linoxine (.dried paint) is a mixture of alcohol and chloroform, which 
may be advantageously used to remove- stains of paint, and also of waggon and carriage 
grease from silk and woollen tissues. 


Cements, Lutes, and Putty. 

cements. In a general sense we understand by cement, substances or mixtures 
which, when placed in a pasty state between the surfaces of bodies in close contact, 
cause them to adhere solidly after the drying or solidification of the pasty material. 
According to this definition, glue and paste are cements, but solder is not. As a 
universally applicable cement cannot be met with, it is clear that as regards any 
specific cement it should completely answer the purpose for which it is employed. 
The substances used for cement are very various, and are of course adapted to the 
particular objects they are intended to unite. There are numberless receipts for the 
preparation of cements, which may be best classified by stating the name of the most 
essential constituent. Thus we have:—1. Lime cements. 2. Oil cements. 3. Resin 
and sulphur cement. 4. Ron cements. 5. Starch, or paste. 6. Cements of less 
consequence, as, for instance, water-glass cement, chloride of zinc cement, &c. 

Lime Cements. Slaked-lime forms with casein, white of eggs, gum-arabic, and glue, 
mixtures which after some time become very solid, and are used to unite wood, 
stone, metal, glass, porcelain, &c. 

Casein cement may be made in various ways, but is most usually prepared by 
mixing freshly-precipitated casein, obtained by acidifying milk, previously freed from 
whey and separately reduced to powder, with freshly slaked lime. As this mass 
hardens very rapidly, it should be used immediately, and not prepared in larger 
quantity than may be required. Casein dissolved in bicarbonate of potash or soda 
solution, and gently evaporated to a thick consistency, also yields a good cement. 
A solution of casein in a concentrated aqueous solution of borax made with cold 
water yields a clear thick solution, which, as regards adhesive property, far surpasses 
a solution of gum-arabic. A solution of casein in silicate of soda or potash is an 
excellent cement for glass and porcelain. When stone, metal, wood, &c., are to be 
united, or when the cement is to be used for filling up small cavities, there is usually 
added to the mixture of casein and lime a powder made of 1 kilo, of fresh casein, 
1 kilo, of quick-lime, and 3 kilos, of hydraulic mortar orlime. According to Hannon 
partly decayed and liquefied gluten yields with lime a cement similar to that 
obtained from casein. 

oa cements. The main and essential constituent of these cements is a diying oil in 
the shape of an oil varnish (boiled linseed oil). Most of these cements resist the 
action of water. 

Boiled linseed oil and fat copal varnish may be used as cements to unite glass and 
porcelain, but are seldom so employed on account of requiring some weeks to become 
dry. Mixed with white-lead, litharge, or minium (red lead), the cement dries more 
quickly, but does not become quite hard until after some weeks. When a larger 


CHEMICAL TECHNOLOGY. 


492 

quantity of this cement or rather putty, is required, it is frequently made of boiled 
linseed oil with a mixture of 10 per cent of litharge and 90 per cent of either washed 
chalk or slaked lime. Zinc-white is sometimes used instead of litharge. This putty 
is frequently warmed before use in' order to render it softer; it is used for uniting 
stone, brick, &c. A mixture of 2 parts of litharge, 1 of slaked lime, and 1 of dry sand, 
made into a uniform paste with hot and boiled linseed oil, has been used by Stephenson 
as a putty to be placed into the sockets of steam-pipes. By precipitating a 
solution of soda-soap with alum solution an alumina soap insoluble in water is 
obtained, which, having been dissolved in warm linseed oil varnish, yields, according 
to Yarrentrap, an excellent cement for uniting stone. Glaziers’ putty is a mixture of 
chalk and boiled linseed oil, well beaten up together. When this putty is made with 
raw linseed oil it hardens very slowly; prepared with boiled linseed oil it may be 
kept soft for a considerable time by either-being placed under water, or kept in 
bladders like lard, or tied up in canvas bags previously soaked with oil. According 
to Hirzel, a mixture of litharge and glycerine forms an excellent cement and readily 
hardening lute, which, according to Pollack, may even be used to unite iron and iron, 
as well as iron and stone. 

Resin cements. Cements made with resin as the main constituent are often used, 
because, on becoming cold, they harden at once and possess the property of being 
waterproof; on the other hand, these resin cements will not endure a high tempera¬ 
ture without becoming soft, and by exposure to air and sunlight they become so 
brittle as to be easily pulverised. 

As a cement for glass and porcelain, sandarac and mastic are sometimes used, 
because these resins are readily fusible and are colourless. They are applied to the 
surfaces to be united in the form of a powder put on with a small hair-brush, after 
which the object is heated so as to melt the resins, the pieces to be joined being 
pressed together. As far back as the year 1828, Lampadius suggested as an excel¬ 
lent cement a solution of 1 part of amber in 1*5 parts of sulphide of carbon. 
When this solution is painted over the surfaces to be united and immediately 
pressed together, the joint is at once effected owing to the rapid evaporation of the 
sulphide of carbon. A solution of mastic in sulphide of carbon may be similarly 
used. Shellac alone does not form a good cement, being too brittle when cold, and 
contracting too much after having been melted; the addition of some Venice turpen¬ 
tine and earthy powders (see Sealing-wax) compensates these defects. While wood 
cannot be joined together with shellac, it is firmly and readily glued by coating the 
pieces to be joined with thick shellac-varnish, and then placing between the two 
pieces a slip of muslin. Resins are frequently used for lining water-cisterns, and for 
rendering terraces, &c., waterproof. Pitch, colophonium, asphalte, mixed with lime, 
sulphur, or turpentine, are used for this purpose, the object of the various additions 
being to obtain a greater or less degree of hardness. Jeffery’s marine glue is 
prepared by dissolving caoutchouc in twelve times its weight of coal-tar naphtha and 
adding twice the weight of either asphalte or shellac. The mixture is gently heated 
to render it uniform. There is a solid and a fluid marine glue in the trade; the 
former is used for glueing wood and for caulking, the latter, obtained simply by the 
use of a larger quantity of solvent, is used as a varnish; both kinds are insoluble in 
water, are not acted upon by change of temperature, and do not become brittle. By 
the name of zeiodelite is understood a mixture consisting of 19 parts of sulphur and 
42 of powdered glass or earthenware; this mixture having been heated to the 


PASTE. 


493 


melting-point oi sulphur, maybe used, instead of hydraulic cement, for uniting stones 
and bricks. R. Bottger prepares this cement by mixing with molten sulphur an 
equal weight of infusoria earth to which some graphite is added. Under the name 
of diatite Merrick prepares a mixture of shellac and finely divided silica. 

iron cement. Among the very many recipes given for the preparation of this cement, 
used for luting the sockets and spigots or flanges of cast-iron pipes, and for caulking 
the seams of the plates of steam-boilers, we quote the following as one of the best:— 
A mixture of 2 parts of sal-ammoniac, 1 of sulphur, and 60 of finely-pulverised cast- 
iron borings or filings. "When required for use, this mixture is made into a paste 
with water, to which some vinegar or dilute sulphuric acid is added. The parts to 
be joined by this cement should be free from fat, oil, or rust. The cement is forced 
in with the caulking-chisel and soon becomes very hard. A lute for small leaks in 
iron and fire-clay gas-retorts can be made with 4 parts of iron-filings, 2 of clay, and 
1 of pulverised porcelain saggers. This mixture is made into a paste with a solution 
of common salt. 

Paste. The material used by bookbinders, and, in fact, wherever paper is to be 
glued to paper, is obtained by boiling flour with water or by treating starch with hot 
water. 

Starch paste is best made by rubbing the dry starch up with cold water, so as to 
form a uniform magma, to which, while being constantly stirred, boiling water is 
very rapidly added; this paste should not be boiled if required for cementing paper 
together. Bye-meal boiled with water yields an excellent paste, which may be 
improved by the addition of some glue solution and preserved by alum. Partly 
decayed and liquefied gluten forms an excellent paste. Starch-paste to which, while 
hot, half its weight of turpentine is added is greatly improved and rendered water¬ 
proof by the addition. 


DIVISION V. 


iKIMAL SUBSTANCES AND THEIR INDUSTRIAL APPLICATION. 


Woollen Industry. 

origni and properUes of wool. Wool is distinguished from hair chiefly by the three fol¬ 
lowing properties ;—wool is finer; is not straight, but curled; while it generally 
contains less pigment, and hence is white in colour. The quality of wool increases 
with the increase of these three characteristics. Wool, like hair, exhibits an organised 
structure, consisting histologically of an epithelium, of a rind and of a pith or marrow. 
The epithelium of wool consists of small thin plates which overlap each other like 

Fig. 251. = 5 *- 



the tiles on a roof; in this manner the cuticular plates give to the surface a squamose 
appearance, which may be coarsely represented as the appearance exhibited by 
a fir-cone. Fig. 251 exhibits a piece of wool of an ordinary sheep; while Fig. 252, 
magnified to the same number of diameters, exhibits a piece of the very finest 
Saxony wool, thus showing the great difference of fineness of these two sorts 















WOOL. 


495 


of wool. The grooves on the surface of the wool are the cause of its rawness to the 
touch, and from the existence of these grooves wool admits of being felted. When 
the fibre which exhibits this texture is pressed together with a kind of kneading 
motion, while the fibre is at the same time softened by the action of steam, the result 
is that the fibres are joined to each other in the direction of the scales on their 
surface and, becoming entangled, form a firm, dense texture, which is termed felt. 

We obtain wool chiefly from sheep ; the quality of the wool very much depends 
upon the peculiar breed, the climate, fodder, and care taken of the animals. We 
distinguish two chief breeds of sheep—viz.:—i. The mountain sheep, having short, 
fine, and more or less curly wool. 2. The sheep of the lowlands, having coarse', 
sleek, long, liair-like wool. To the first breed of sheep belongs the sheep met with in 
the interior and more elevated parts of Germany, also the Spanish merino sheep, of 
which there are several varieties, the most remarkable being the infantado and 
electoral races. By the latter is understood the variety which in 1765 was imported 
into Saxony, being made a present to the Elector, and was the cause of the exist¬ 
ence in that country of a breed of sheep yielding excellent wool. Till comparatively 
recently the exportation of the living merino sheep from Spain was prohibited under 
pain of capital punishment. The variety of sheep designated Escurial is not 
a peculiar race or breed, but an electoral sheep with finer and fuller fleece. Sheep, 
like goats, are undoubtedly animals preferring a mountain plateau, and are very sen¬ 
sitive to a damp or moist soil. There are many varieties of the lowland sheep, 
among them the heath sheep (lowlands of Germany); the so-called Cretan goat 
( Ovisaries strepsiceros) of Southern Europe and Western Asia ; the various breeds of 
English sheep, Southdown, Leicester, Cotswold, Lincoln, &c., and the Scottisn 
varieties, Shetland and Hebrides. 

The varieties of wool obtained from other animals than sheep are :— 

a. Cashmere wool; the fine downy hair of the Cashmere goats inhabiting the eastern 
slopes of the Himalaya, 14,000 to 18,000 feet above sea level. The colour is white-grey 
or brown. In the state in which it is sent to Europe it is largely mixed with coarse hah, 
so that 100 kilos, of the raw material yield after sorting and cleansing only 20 kilos, of 
fine hair. 

b. The Vicuna wool ; the very slightly curly hair of the Llama or Vicuna goat 
(Auchenia Vicuna ), a native of the high mountains of Peru, Chili, and Mexico. This kind 
of wool, or rather woolly hair, was formerly more so than now employed for weaving fine 
tissues. Sometimes there is substituted for this wool a mixture of ordinary wool and the 
finest hair of hares and rabbits. What is now termed Viguna or Vicuna wool in 
the trade is a tissue made of a mixture of wool and cotton. 

c. Alpaca wool, or pacos hair; the long, sleek, white, black, or brown hair of the 
ALpagua or Alpaco (Pako), a kind of goat which dwells in Peru. This kind of woolly hair 
has great similarity with the Vicuna wool, but is not quite so fine.* 

d. Mohair, or so-called camel’s wool; the long, slightly curly, silky hair of the Angora 
goat ( Capra angorensis) , a native of Asia Minor. This substance is spun and woven into 
non-fulled tissues (camlet or plush), and is also mixed up with the half-silk tissues 
of which it forms the woof or weft. 

chemical composition of wool. Purified and cleansed wool consists chiefly of an albumi¬ 
noid sulphur-containing substance termed keratin (horny matter),but, as met with on 
the animals, wool contains much dirt, dust, and suint. The labours of Faist, Reich, 
Ulbricht, Hartmann, Marcher, and E. Schulze have greatly increased our know¬ 
ledge of this substance. 

* The microscopical texture and properties of this kindL of hair have b6en investigated 
and are described in Wiesner’s work, “ Einleitung in die Technische Mikroskopie.” 
Vienna, 1867, p. 172 etseq. 


CHEMICAL TECHNOLOGY. 


496 

The following results are those obtained by Faist when analysing various kinds of 
merino wool:— 

T. 2 . 



a. 

b. 

c. 

d. 

c. 

/• 

Mineral matter. 

6*3 

16*8 

094 

i *3 

1*0 

1*2 

Suint and fatty matter 

44*3 

447 

21*00 

40*0 

27*0 

16*6 

Pure wool. 

38*0 

28*5 

72*00 

560 

64*8 

77*7 

Moisture . 

ii ‘4 

7 *o 

6*06 

2*7 

7*2 

3*5 


100*0 

1000 

100*00 

IOO'Q 

100*0 

100*0 

Percentage of pure air- 







dry wool. 

49*4 

35*5 

78*06 

587 

72*0 

82*2 


1. Raw wool, air-dried.— a. Hohenheim wool, with a small quantity of readily soluble 
suint. b. Hohenheim wool (the name of a large agricultural establishment and agrono¬ 
mical school near Stiittgardt, Wurtemburg), containing a large quantity of glutinous suint. 
2. Washed wool, air-dry.’ 1 '— c. Hohenheim wool. d. Same variety, with difficultly soluble 
suint. c. Hungarian wool, very soft. /. Wurtemburg wool, less soft. 

While making researches on wool, Eisner of Gronow estimated the loss which 
wool experiences when treated with sulphide of carbon for the elimination of 
the suint. The results were :— 

Washed merino wool . 15 to 70 per cent. 

Unwashed wool ( laine en suint, raw wool) ... 50 to 80 „ 

Long carded wool. . 18 

Suint is a mixture of secreted and accidental substances, dust, &c. When raw 
wool is macerated for some time in warm water, there results a turbid liquid which 
contains suspended as well as dissolved matters. The dry substance of the aqueous 
extract of suint consists, according to Marcher and Schulze (1869), of:— 

1. 2. 3. 4. 

Organic matter ... 58*92 6r86 59*12 60 47 

Mineral matter ... 4ro8 38'i4 40*88 39*53 

1 and 2 relates to wool of mountain sheep. 3 and 4 to full-bred Rambouillet sheep. 

The soluble portion contains the potash salt of a fatty acid ( suintate de potasse). 
The fatty acids contained in suint are, according to Reich and Ulbriclit, mixtures ol 
oleic and stearic acids, probably also palmitinic acid and a small quantity of 
valerianic acid, with potasli in such quantity, that more recently this material has 
been employed to obtain therefrom carbonate of potash and chloride of potassium 
100 kilos, of raw wool may yield from 7 to 9 kilos, of potash (See p. 132) 
Potash from suint consists, according to Marcher and Schulze, of:— 

Carbonate of potash . 86*78 

Chloride of potassium . 6’18 

Sulphate of potash ... 2*83 

Silica, alumina, lime, magnesia, oxide of iron, 

phosphoric acid, &c. 4*21 

100 00 

* Washed on the sheep while alive, an operation performed by the farmers, and to be 
distinguished from the washing wool undergoes during manufacture. 











WOOL. 


407 


P. Havrez (1870) states that it is more advantageous to extract chloride of potas¬ 
sium and prepare ferrocyanide of potassium from suint than to employ it in 
preparing carbonate of potash. Suint is a valuable material in gas manufacture 
and the potash salts may afterwards be extracted from the coke. 

Properties of Wool. The value and applicability of wool for the purposes of being spun 
and woven depend upon a number of properties, of which the following are the mo3t 
important. 

Colo or and Gloss. Wool is generally white, but that of some of the common kinds 
of sheep and also of the alpaca and mohair are either brown, grey, or black. 
The gloss of some varieties of wool is a highly prized property. The gloss is not 
exactly related to the fineness of the wool, but more to the softness and suppleness of 
the fibre, which on being touched by the hand imparts a feeling similar to that 
of cotton-wool or silk. The curl or waviness of the wool is due to the fact that the 
hair or fibre is bent and more or less curved. When there are many and small 
curves the wool is termed small curled, while if the curves are large it is termed 
coarsely curled. There is also a difference between wool which exhibits high 
curves (strongly waved and curled) and wool exhibiting low curves (weakly waved 
and curled). The fineness of wool depends upon the smallness of diameter of the 
fibre; generally the finer the fibre the better the wool is suited for the uses 
commonly made of it. There are, however, some varieties of wool met with which, 
though very fine, are rather tough and straight, and therefore less suited for manu¬ 
facturing purposes. It should be observed that the diameter of the woollen 
fibre does not constantly vary with the fineness; while neither the wool-meter 
(eriometer) nor the micrometer can sufficiently determine the fineness of the wool for 
technical purposes, that property being best estimated by practical experience by the 
sense of touch. What is termed quality or uniformity in wool is that the fibre has 
through its entire length the same diameter. By softness, suppleness of the wool, 
it is understood that the fibre readily admits of being bent in all directions; this 
property is usually accompanied by extensibility and elasticity. A fibre of wool may 
therefore be somewhat more strongly stretched before breaking, after it has been first 
straightened so as to remove the curls. The elasticity of the fibre is shown, when a 
hair is broken, by the two ends becoming more or less rapidly contracted and curled 
up. By strength we mean that property of wool whereby it bears without breaking 
a certain weight, which, according to the quality and fineness of the fibre, varies from 
26 to 44 grins. By height is understood the length of the curled hair in its 
natural position; while by length we designate the measure (in centimetres) of 
a single fibre when so stretched that its curls are no longer perceptible. The length 
of the fibre is of great importance in the selection of wool, and constitutes one of the 
main distinctions between carded wool and short wool. The teasled wool is 
used more especially for the weaving of cloth—milled or fulled cloth. Generally 
this kind of wool is strongly curled, and the length of the stretched hair is less than 
15 centims. The combed wool (long wool) is used for smooth woollen tissues which 
require a middling length, 9 to 12 centims., some strength, and not too much curl. 

Preparation of Wool. Before wool is a marketable article it has to be washed, shaved 
or sheared off, and sorted. 

I. Just before shearing the wool is washed—or as the term more usually runs, the 
sheep are washed—for the purpose of cleansing the fleece and of eliminating a por¬ 
tion of the suint. By this washing wool loses from 20 to 70 per cent in weight. 

33 


CHEMICAL TECHNOLOGY. 


*93 

II. The Shearing of the Sheep. —Usually in our climate sheep are shorn only once 
a-year, about the middle of May or beginning of June, but with long-woolled sheep 
this operation is performed in September (summer wool), and about the end of March 
(winter wool). Lamb’s wool is distinguished by its great fineness. Besides the 
wool shorn from the live sheep we distinguish skinner’s wool, from the skins of sheep 
slaughtered for food, and pelt wool from sheep which have died from disease ; while 
the former kind is shorter than ordinary wool, the latter is deficient in strength and 
elasticity, and is therefore of less value. 

III. Sorting the Wool. —The different parts of the skin of the sheep yield wool of 
different quality ; among the parts which yield better kinds of wool are the shoulders, 
the flanks, and the thighs. The wool of the following parts is of inferior quality, 
viz., neck, withers, back, throat, breast, feet. The peculiar mode of sorting wool 
and the denominations given to the several varieties differ in different countries; 
generally the terms firsts, seconds, thirds, &c., are employed. While the fineness of 
the wool is the main character which distinguishes the various kinds, the sorter also 
looks.to the length, curl, strength, &c. As met with in commerce, wool contains a 
larger or smaller quantity of hygroscopic water, varying from 14 to 16 per cent; and 
even when wool is exposed to dry air for a long time, the water amounts to 7 or 10 
per cent. 

Wool spinning. The operations of spinning do not in strictness' pertain to chemical 
technology, because the material operated upon is not chemically treated, -and only 
mechanically undergoes a change of form. The machinery employed is very complicated, 
but has been brought to great perfection. 

Before being made into cloth, the wcol, as is the case with cotton, silk, flax, and hemp, 
has to be made into yarn. Before this operation can be proceeded with, the sorted wool 
is:—1. Carded for the purpose of weaving. 2. Or the wool is combed for the making of 
smooth woollen goods. Carded wool is ultimately made up into cloth, while combed wool 
is made up into such materials as thibet, mousseline de laine, merino, &c. The following 
eight operations are those to which carded wool is submitted :— 

1. Washing. —The aim of this operation is to eliminate the suint from the wool, and for 
this purpose the fibre is submitted to the action of very weakly alkaline liquids. These 
even in the carbonated state should be weak, because, when concentrated, the wool 
either is dissolved or its strength and elasticity impaired. The alkaline liquids chiefly 
used for this purpose are lant (stale urine) mixed with water, tepid soap-suds, or a very 
weak solution of soda. The washed wool is rinsed in plenty of cold water, wrung out, and 
then dried in the shade. By exposure to direct sunlight wool becomes yellow. 100 parts 
of fleece lose by washing from 17 to 40 parts, leaving 60 to 83 parts of pure wool. 

2. Dyeing. —When this operation takes place immediately after washing, it is only to 
impart to it very fixed dyes, such as indigo, or madder ; because, as regards most other 
dyes, they would be injured by the operation of milling, in which soap, lant, and other 
materials are employed. Wool by being dyed often increases considerably in weight, 
sometimes as much as 12 per cent. 

3. Willowing, or Devilling. — This operation aims at the obtaining of the flocks of wool in 
a more uniform mass, while at the same time mechanical impurities, straw, &c., are 
removed. The machinery by which this is effected is similar to that used for the same 
purpose for cotton. 

4. Oiling or Greasing. —As wool has a great tendency to become felted, and has to be 
submitted to the operation of carding, it might in this process become broken; and in 
order to prevent this and give the fibre, which has become harsh, suppleness, it is greased 
or mixed with oil. For the finer kinds of wool, olive oil or arachis oil is used, while for 
coarser kinds rape-seed and fish oil are employed. Olein, as it is termed, really oleic acid, 
a by-product of the manufacture of stearine candles, is often used for this purpose, pro¬ 
vided it be not contaminated with either sulphuric or stearic acids. 100 kilos, of wool for 
warp require 10 to 12 kilos, of oil, while 100 kilos, of wool for woof require 12 to 15 kilos, 
of oil. 

5. The carding of wool aims at the same result as the carding of cotton. The 
machinery employed is in each instance similar in construction. Wool is carded at least 
twice. The first carding is termed fleece-carding, the result being that the wool is formed 


WOOL. 


499 


into a loose fleece, which is rolled up on a cylinder ; the second carding converts the fleece 
into loose curls about 1 metre or a yard in length, which are turned over on to the-roving 
machine. Recently the carding-mill has been so constructed that it also performs the 
operation known as roving. 

6. Bovin; 7.—By means of machinery the wool is converted into wdiat is technically 
termed slnb or half-yarn , which by five following operation, viz., 

7. By spinning is made into yarn. The machinery, while working at a high speed, 
twists the fibres into a continuous thread or yarn. 

8. The finished yarn is wound on reels, the length of the skeins or hanks and the 
number of skeins to a bunch varying in different localities. The fineness of the yarn is 
abroad designated by the number of hanks which go to the half kilo.; but in Belgium and 
France the number of metres of yarn length which go to the kilo, expresses the fineness. 

Artificial Wool. Woollen rags are carefully sorted, and by means of machinery converted 
into what is termed mungo and shoddy; the former is a short-haired wool obtained from 
milled goods ; the latter (a longer hair) is prepared from woollen hosiery. The rags having 
been well sorted, and all seams, buttons, and ornaments cut off, silk and other linings 
separated, are cleansed, again sorted, and then oiled. The rags yield on an average 
30 per cent of the "weight of buttons, linings, &c., and the 70 per cent remaining yields 
some five-sevenths of mungo, prepared by means of a mill. Mungo is not carded; but 
shoddy, made by a similar process, is carded after having been again oiled. 

weaving the cioth. Cloth is a smooth woollen fabric, the woof-yarn passing alternately 
over and under chain-yarns. The peculiar felty appearance is given to cloth by the 
operation of milling or fulling. The operation of weaving cloth does not differ in any way 
from the weaving of linen or cotton fabrics; usually the chain and weft yarn are equally fine. 

Washing and Milling The cloth as it'leaves the weaver’s hands is not in the least similar to 

the Bough cioth. the finished fabric, but is very like a coarsely woven towel, the chain 
and weft being quite loose and every thread distinctly visible ; while the felty appearance of 
the cloth is entirely absent, this being obtained by the operation of milling, which is preceded 
by the burling process, whereby knots, pieces of straw, and other similar impurities are 
removed by the aid of small steel forceps. The rough cloth is next washed for the 
purpose of removing oil, dirt, and weavers’ glue ; this v r ashing is assisted by soft soap, 
potash or soda ley, and is performed by a washing machine. The operation of fulling or 
milling aims not only at a cleansing of the rough cloth (it is not always washed previously 
to being milled), but more particularly at the felting together of the fabric, so that the 
chain and weft can hardly be distinguished. It is performed by the joint action of 
moisture, high temperature, and a peculiar mechanical treatment, by which the threads 
are kneaded into each other. As the milling also aims at the complete removal of grease 
the water into which the fabric is steeped is rendered alkaline by means of lant, while 
soft-soap and fuller’s earth (see p. 295) are used to assist the action. Soft soap is only 
used for common cloth, while for the finer kinds palm oil and olive oil soaps are employed. 
The milling or fulling consists in beating the rough cloth with wooden mallets moved by 
machinery ; recently the use of cylinders is very general for this purpose. 

Teasling and shearing In order to give to the milled cloth a more pleasing appearance, it is 
the cioth. teasled and next shorn. 1. The operation of teasling aims at the 

loosening of the surface hairs of the felted cloth, and at brushing these hr one direction; 
the operation is performed by the use of teasles or weaver’s thistle (Lipsacus fullonum) 
v'hich acts by the thorns on the seed capsules. 2. The shearing of the cloth is an 
operation by which the surface hair is cut off to a uniform length. The shearing is either 
performed by hand—a very tedious operation, the cloth being stretched uniformly on a 
cushioned table, the operator using peculiarly made shears—or by cylinders, somewhat 
similar to lawn grass-cutters in principle of working. There is a distinction between 
transversal, longitudinal, and diagonal cylinders, a. The transversal cylinder is placed 
lengthwise to the cloth, the cylinder moving from one edge of the cloth to the other. 
[ 3 . In the longitudinal machine the moving cylinder is placed across the width of the 
cloth, which is moved under the shearing-knives. 7. In the diagonal machine several 
cutting cylinders are placed diagonally above the cloth. The v r ool shorn off is used in 
upholstering, and very largely for the purpose of giving a velvety appearance to some 
kinds of paper-hangings. _ . 

Dressing the cioth. Before the cloth is ready for sale, it has to be submitted to the three 
following operations:—Lustring, brushing, and pressing. . 

1. The lustring is now performed by stretching the cloth very tightly on a copper 
cylinder, the surface of which is perforated with a number of small holes. The cylinder 
is placed in a steam chest, and steam having been turned on, the cloth obtains, a 
permanent gloss and is prevented from becoming rough on being worn. 2. The brushing 
of the cloth takes place before and after the shearing, and is effected by machinery, the 


joo 


CHEMICAL TECHNOLOGY. 


brushes being fixed to cylinders, and the cloth moved over and under them, while at the 
same time either a jet of water or sometimes steam is made to play on the cloth. 
3. Finally, the cloth is pressed, having been first folded ; between each fold is placed on 
the right side of the cloth a piece of glazed millboard and a piece of coarser millboard on 
the wrong side; a plank is put between the pieces of cloths, some six to twelve of which 
are placed in the press at a time. 

other cioth Fabrics. In addition to milled cloth several other kinds of woollen goods 
are manufactured, which are cloth-like in some particular. Of these the following 
are the chief:—Flannel, either smooth or twilled, only slightly milled, once teasled 
on the right side, and either not shorn at all or only once; the chain often consists of 
carded wool, hut is sometimes cotton or silk ; the woof is carded yarn. Swan-skin 
is fine twilled flannel. Cashmere is finely twilled cloth only once teasled, but shorn as 
often as cloth. The hair is short and covers the textile yarn slightly, so that the 
twill is distinctly seen. Cashmere is often made with a cotton chain. 

Frieze is coarser, stouter, and longer-haired than cloth, is strongly fulled, but less 
teasled and also less shorn. After having been shorn, frieze is simply dressed by 
being brushed and hot-pressed; it is then brushed over with a solution of tragacanth 
in water, next calendered, and lastly slightly oiled with olive oil and again pressed. 
A non-twilled and finer kind of frieze is known as “ ladies’ mantle friezewhile a 
heavier and short shorn frieze is called castories. Kalmuk and thick frieze (Irish 
frieze) consists of a heavier yarn and is more strongly milled. Buckskin is a 
twilled non-teasled trouser material, the right side of which is shorn and quite 
smooth. Kersey is a coarse kind of undressed (neither teasled nor shorn) woollen 
fabric used for making cloaks and overcoats for military men, sailors, railway 
officials, &c. The coarser lands of railway rugs and horse-cloths are of a similar 
material. Paper-makers’ felt is a coarse, twilled, loosely woven, lightly milled 
material, neither teasled nor shorn, used for the purpose of being placed between the 
wet sheets of paper. Felted cloth, a fabric first made some twenty years ago without 
spinning and weaving at all, has not been found suitable, and is therefore now hardly 
ever seen. Wool intended for felting purposes is first cleansed, freed from suint, 
next carded and converted into a uniformly thick layer similar to cotton-wool, and is 
then felted. 

worsted wool. It has been already stated that long haired or combed wool is the 
material used for the purpose of preparing worsted-yarn—a smooth thread, the 
longitudinal fibres of which are placed parallel to each other—this yarn serving the 
purpose of weaving such fabrics as thibet, merino, Orleans, &c. There is a distinc¬ 
tion between genuine combed wool or worsted, and half-worsted or sayette-yarn, 
which is the link, as it were, between combed and carded wool, and is used for the 
purposes of knitting stockings, in carpet-making, Berlin-wool work, &c. Although 
half-worsted is always spun from long-haired wool, the fibre is not in this instance 
combed, but carded by a peculiarly constructed mill. Combed yarn or worsted 
consists either entirely of wool, or is a thread of wool mixed with mohair and 
alpaca, or of wool and cotton, or of wool and silk, such yarns being termed fancy 
yarns. 

The manufacture of smooth woollen fabrics is, as far as weaving and the mechanical 
operations are concerned, similar to the weaving and mode of manufacturing other 
textile fabrics. Some of the smooth-surfaced woollen fabrics are finished when 
woven; others require a dressing which depends upon the taste of the consumers 
and upon the peculiar requirements of the trade. The following enumeration 


SILK. 


501 


of tlie smooth-surfaced woollen fabrics, of which there is an almost endless variety, 
may give some idea of the various hinds of goods belonging to this category. 

A. Smooth Fabrics .—Barracan used to be formerly woven from camel’s hair, but is now 
woven from combed wool; it is termed moired when it is watered. Orleans consists of a 
twisted cotton thread chain and a single woollen weft; the fabric having been woven is 
singed, washed, dried, shorn, and hot-pressed. Camlet also was formerly made from 
camel’s hair, and consists of combed woollen chain and weft. Dress crape is a fabric 
made of a strongly twisted worsted yarn-chain and more loosely woven weft; when the 
cloth is woven it is dyed black or grey, next wound round a cylinder, and boiled in water 
in order to shrink it. Bolting cloth is made of a strongly twisted yarn, and employed for 
the purpose of making flour-sieves. Mousseline de laine, chaly, is a woollen muslin with 
silk chain, and this class includes a host of fabrics generally known as Bradford fabrics as 
well as mixed materials, alpaca, mohair, silk mohair, &c. 

B. Twilled Goods .—Merinos with three- or four-threaded twill and two “ right ” sides 
are, after weaving, singed, hot-pressed, and dressed or glazed. When unglazed it is called 
thibet. Serges are twilled fabrics with three, four, or five strands. So-called Atlas 
fabrics are kalmang and lasting, the latter employed for ladies’ shoes, gentlemen’s cravats, 
furniture, and upholstery work. The fabric from which the press-bags of the oil-mills 
are made is also a twilled woollen material woven from very strong and tough wool. 

C. Variegated or Patterned Fabrics, such as are used for trousers, and also woollen 
damask. Shawls belong to this class; in some of these the whole fabric is woollen 
(Cashmere shawls); in others a silk or cotton thread is mixed. The plaids and tartans 
are especially British fabrics. 

D. Velvets .—Woollen velvet, woollen plush, and velpel, are merely distinguished from 
each other by the length of the hair, which is greater in plush than in velvet, and greatest 
in velveteen. Woollen velvets are employed in various ways ; for instance, in covering 
chairs, sofas, for curtains, &c. These materials are more or less loosely woven, and are 
variously shorn and dressed, being known in the trade by such appellations as astracan, 
beaver, castorin. Utrecht velvet, &c. 


Silk. 


suk. Silk is at once distinguished from cotton, flax, hemp, and wool by being 
naturally produced as a very long and continuous thread, whereby the operation of 
spinning is dispensed with; but in its stead the operation known as silk-throwing is 
required, by which several of the natural fibres of the silk are twisted into one in 
order to obtain a stouter yarn. 

Silk is the produce of the silkworm (.Bombyx mori), an insect which undergoes 
four metamorphoses. The worm is produced, in the spring, from the egg, or ovule. 
It casts its skin from three to four times, and finally spins a thread, produced, or 
rather secreted, by two glands placed near the head, from small apertures, in which 
is a glutinous fluid which immediately coagulates under contact with air. Thus 
what is termed a cocoon is formed, which serves as a shelter for the pupa 
against injury and cold. The thread is double, but is united in one by a peculiar 
kind of glue termed serecin, which is laid as a kind of varnish over the whole 
surface of the thread, of which it forms about 35 per cent of the weight. After a 
period of fifteen to twenty-one days the pupa is metamorphosed into a butterfly, 
which, in order to leave its prison, softens a portion of the cocoon with a juice which 
it secretes, and then perforates the softened part. For the purpose, however, of 
producing silk, the pupa is not allowed to develop so far, but is killed (excepting in 
a number of cocoons intended for the full development of the butterflies so that they 
may produce eggs), and the thread of the cocoon is carefully wound on a reel. 

varieties of’siilcworms. The Bombyx mori is the main supplier of silk. Its food is the 
leaves of the white mulberry tree, Morns alba. There are, however, other silk- 
producing insects, among which the following are to be noticed :— 


502 


CHEMICAL- TECHNOLOGY. 


a. Bombyx cynthia , largely cultivated by the natives of the north-east portion of the 
interior of Bengal and also by the Japanese; the former call this worm Arrindy-arria, the 
latter Yama-mai. This worm feeds on rice leaves, Ricinus communis. The silk obtained 
from this insect, although less brilliant than that which the ordinary silkworm yields, is 
very useful, as being durable-and strong. This worm will feed on other leaves, such as 
that of the weavers’ thistle, Dipsacus fullonum, wild chicory, Chicorium Intibus, and the 
leaves of the Aylanthus glandulosa. The results of acclimatising this insect in France 
and Germany have been satisfactory. 

b. Bombyx Pemyi is a native of Mongolia and China ; it feeds on oak-leaves. Some 
years ago these worms were introduced into France, and have been fed and reared 
successfully upon European oak-leaves. 

c. Bombyx mylitta, or Tussa worm, is a native of the colder parts of Hindostan and of 
the slopes of the Himalaya. Its silk is an important article of commerce in Bengal. 
This insect feeds on oak and other leaves, casts its skin five times, and yields large 
cocoons. The fibre of this kind of silk is from six to seven times stouter than the silk of 
the ordinary worm, but unfortunately the Tussa worm only lives in its free natural state, 
and when captive does not produce silk. The following silk-producing varieties belong to 
North America:— d. Bombyxpolyphemus ; on oak and poplar trees, e. B. cecropia ; on 
elm, whitethorn, and wild mulberry trees. /. B. platensis ; on a kind of mimosa, 
Mimosa platensis. g. B. leuca deserves further attention. 

We quote the following account of the culture and rearing of silkworms :—i. The 
mulberry tree. The leaves of the variety known as the white mulberry tree, from 
the fact that its fruit is yellow or light red in colour, is the most suitable food for this 
insect, but its cultivation belongs to horticultural pursuits, and we cannot enter upon 
the subject here. 2. The production of the eggs or ova of the silkworm is effected in 
the following manner:—The largest and finest cocoons, and such as have a fine 
thread, are selected and preserved; usually the cocoon of the female insect is more 
oval than that of the male*, which is more pointed at the ends and is somewhat 
depressed in the centre. Although these characteristics do not apply in all cases, 
sericiculturists become sufficiently adepts in this matter to be able to select a 
sufficient number of cocoons of each sex. 100 to 120 pairs of well-formed cocoons 
yield about 30 grms. of eggs, about 50,000 in number, from which, however, only 
about 70 to 75 per cent of worms are obtained. The cocoons selected for breeding 
purposes are allowed to remain on a table covered with a white cotton cloth. 
After some twelve days the butterflies make their appearance, and having paired, the 
females after a lapse of some forty hours lay 300 to 400 eggs. 3. The eggs are 
properly protected from cold in winter and remain in the buildings, called magna- 
neries, being placed in a uniform layer on a cotton cloth stretched on a wooden 
frame. The eggs are covered with sheets of white paper perforated with small holes. 
Upon the sheets of paper mulberry leaves, at first cut up so as to form a kind of 
chaff, are placed.. In France a contrivance known as a couveuse, that is to say, an 
oven in which a suitable temperature is kept up, is now generally used for the 
purpose of breeding the worms, which are best hatched from the eggs at a tempera¬ 
ture of 30°, provided moisture is also present. The young brood on leaving the eggs 
creep through the holes in the paper, and seeking daylight (there is always free 
access of light in magnaneries) begin at once to feed on the mulberry leaves. 4. The 
rearing of the worms requires care and attention. They are best placed on paper 
laid on wooden frames. The worms grow rapidly and are very voracious. They 
cast their skins four times, and after thirty to thirty-two days begin to spin the 
cocoons. 5. When the period of spinning approaches, the worms are placed in 
small, somewhat conical wicker-work baskets, in which they are comfortably located. 
The first thread spun, or rather an entangled flocky mass, is afterwards separately 
collected and kept as floss silk. The insect discharges, before beginning to spin 


SILK. 


503 


further, first a solid substance, white or green in colour, and consisting, according to 
Peligot, chiefly of uric acid, next a clear, watery, very alkaline liquid, which contains 
15 per cent of carbonate of potash, this curious discharge amounting to 15 to 20 per 
cent of the weight of the worm. The formation of the cocoon is finished in about five 
days, but the cocoons are not collected for the purpose of reeling the silk until after 
seven or eight days, so as to make sure that all the worms have spun. 

As far as the chemical composition of silk is concerned, we have to distinguish 
between the fibre and its envelope. The fibre consists for about half its weight of 
fibroin, a substance which, according to Stadeler’s researches, is nearly related to 
horny matter and mucus, and is identical with these as regards chemical composi¬ 
tion. The formula of silk fibroin is C I5 H 23 N 5 06 . The gum-like envelope of the 
silk fibre, which.has been termed by Cramer and Stadeler silk glue or sericin, is 
partly soluble in water and readily so in soap-suds and other alkaline fluids. The 
formula of sericin is Ci 5 H 25 N 5 08 . P. Bolley’s researches have proved that in the 
silk-producing and secreting glands of the worm only glutinous, semi-liquid 
fibroin occurs, which, in coming into contact with air, is acted upon by the oxygen 
and then converted into sericin. Raw silk leaves on ignition a small quantity of 
ash ; Guinon found in Piedmontese raw silk, dried at ioo°, 064 per cent of ash, con¬ 
sisting of 0 526 lime and crii8 alumina and oxide of iron. Dr. G. J. Mulder found 
in 100 parts ofraw silk :— 


. Yellow silk from 

White silk from the 


Naples. 

Levant (Almasin silk). 

Fibroin . 

53-40 

54"0 

Glue-yielding matter . 

2070 

191 

Wax, resin, and fatty matter... 

1-50 

1 "4 

Colouring matter . 

005 

— 

Albumin . 

24^40 

25-5 


6. Killing of the Pupa in the Cocoon .—The pupa remains in the cocoon for from 
fifteen to twenty days, and is then metamorphosed into a butterfly, which will 
perforate the cocoon and thus obtain an exit. It is clear, however, that the cocoons 
not intended for breeding purposes should not be kept so long, because by the 
perforation of the cocoon the silk is spoiled, or at least greatly deteriorated; therefore 
the pupae in the cocoons are killed either by the application of oven-heat or of steam. 

Manipulation of the silk. Six different operations are required to render raw silk fit for 
use as an article of commerce and suited for weaving, &c. These operations are:— 
1. The sorting of the cocoons, an operation which requires great care and greater 
experience, its aim being—(a) the separation of yellow from white cocoons; {( 3 ) the 
elimination of all damaged cocoons as only fit for yielding floret silk; the damage may 
arise in various ways, as, for instance, by mouldiness, injury by other insects, and, 
lastly, fouling of the pupa, as well as perforation by the butterfly; (y) selection of 
the cocoons according to varying fineness of thread and uniformity of the silk. 

2. Winding the silk on a reel is the first operation with the cocoon. By this the 
threads of silk which the insect has wound up into a kind of ball is wound off and 
brought into the shape of a skein or strand. 

As the single fibre of silk is far too thin to be manipulated, the operator usually 
unites from 3 to 10 or even 20, making them unite by the operation of reeling; this 
is not by any means so readily performed as might be imagined, because it is 
difficult to find the end of the thread, whilst the surface of the cocoon is varnished 




504 


CHEMICAL TECHNOLOGY. 


with a gum-like mass which glues the fibres together. Partly by the aid ol 
hot water and partly by dexterity these difficulties are overcome, and by good 
management a thread of 250 to 900 metres length may be obtained from each 
cocoon, each yielding from o’16 to o - 20, at the utmost 0^25 grms., of raw silk. 1 kilo, 
of raw silk requires from 10 to 12 kilos, of cocoons. The silk thus obtained is termed 
raw silk, which should be quite uniform as regards thickness and strength of fibre. 
That portion—the interior and a portion of the outer layer of the cocoon—which does 
not admit of being reeled off is employed for making floret silk, by operations similar 
to those in use for wool and cotton—viz., cleansing, disentangling, combing, 
carding, and spinning, to produce a silk yarn. 

1. The Throwing of Silk. —As the thread obtained by reeling is too fine for 
use either for weaving, knitting, sewing, &c., it is usual to unite several threads of 
silk by means very similar to those used in rope-making, an operation termed 
throwing, known as twisting when the thread of raw silk is simply rotated on 
its axis so as to make it stronger. The following are the chief varieties of thrown 
silk 1. Organzine, used as chain for woven silk fabrics, is prepared from the best 
raw silk. The threads of 3 to 8 cocoons are united; being first strongly twisted and 
next thrown, after which two of such threads are twisted together. 2. Trame used 
for woof or weft and for silk cord is made from inferior cocoons. Single-threaded 
trame consists of one single twisted raw silk thread made up of the united threads of 
3 to 12 cocoons. The double-threaded trame-consists of two untwisted threads thrown 
to the left but less strongly than in organzine. There is also three-threaded trame, &c. 
Trame is softer and smoother than organzine, and therefore fills better than round 
threads in weaving. 3. Marabou silk is stiffly thrown and similar to whipcord; it is 
made from three threads of the whitest raw silk and thrown in the trame fashion; is 
dyed without being previously scoured (boiling the gum out in this instance), and is 
again thrown after dyeing. 4. Poil silk is a simple raw silk thread, twisted, 
and used chiefly as a basis for gold and silver wire, such as is worn on military 
uniforms. 5. Sewing silk is obtained from some 3 to 22 cocoon threads being 
twisted together. There are several other varieties of silk thread used for crochet, 
knitting, &c. 

4. Conditioning or Testing of Silk— The fineness of raw as well as of thrown 
silk is expressed by stating how many yards’ or metres’ length of the fibre are 
contained in a certain weight. The unit abroad is 400 ells or 475 metres. When the 
expression is used, that such silk is at 10 grains, it is understood that 475 metres’ 
length of that particular silk weigh 10 grains; a silk at 20 grains has the same 
length but double the weight, and consequently that silk is only half as fine as the 
former. 

Paw, as well as thrown silk, contains a large quantity of hygroscopic water, 
the quantity of which cannot be judged by the external appearance of the material. 
The silk usually met with in commerce contains 10 to 18 per cent of hygroscopic 
water; and silk may occasionally contain even 30 per cent without appearing to 
be moist. As silk is a very expensive material and often sold by weight, it is clear 
that this property of taking up water is too important to be left unnoticed ; and for 
that reason silk is conditioned as it is called, that is, the quantity of water it 
contains is duly ascertained. 

5. Scouring or Boiling the Gum out of Silk.— Excepting a few instances, such as 
for example, in the weaving, of fine silken sieve cloths, and for crape and gauze 


SILK. 


505 


fabrics, raw silk has to be deprived of its. envelope—the gummy matter already 
mentioned, in order to give softness, suppleness, gloss, and especially also to render 
the silk fit for being dyed. 

The operation of scouring is comprised in the following manipulations :— 

1. Removing the gum (degommer). 

2. Boiling. 

3. Colouring. 

The taking out of the gum is performed in the following manner :—Olive oil soap 
is first dissolved in hot water and into this solution at 85° the skeins of silk are 
placed hung on sticks. The skeins are moved about in this bath until all the gum 
has been uniformly taken out. The silk is next wrung out, rinsed in fresh water 
and then dried. Silk may by this process lose 12 to 25 per cent in weight, 
according to the quality of the raw silk and the quantity of soap employed. The 
scoured silk is ready for dyeing with dark colours, but if required to be dyed with 
bright colours it has to be first boiled. To this end it is put into coarse canvas 
bags, each containing from 12 to 16 kilos, of silk, and in these sacks the silk is 
placed in a soap bath and boiled for ih hours; the silk is next rinsed in water, wrung 
out, and dried. The operation of rosing or colouring aims at imparting to the silk a 
slight tint in order to enhance its beauty. The trade distinguishes various hues of 
white silk, such as Chinese white, azure white, pearl white, &c. The first of these 
hues, a somewhat ruddy tint, is obtained by rinsing the silk in soap-water, to which 
some Orleans has been added. The bluish hues are produced by indigo solutions. 
The bleaching of scoured silk is effected by the aid of sulphurous acid, the fibre 
either being placed in a room where this gas is evolved from burning sulphur, or by 
treating the silk with an aqueous solution of the acid. As silk loses a great deal in 
weight as well as in body by the scouring, which is, however, required, because raw 
silk does not admit of being dyed, it has become the practice to produce a material 
called souple, obtained by treating the raw silk with boiling water in which only 
a small quantity of soap, 1 kilo, to 25 kilos, of silk, is dissolved. Instead of this 
soap solution, an acidified (with dilute sulphuric acid) solution of sulphate of 
magnesia or of soda is sometimes used. The silk loses by this process only 4 to 10 per 
cent in weight. In order to bleach raw silk without depriving it of its natural 
rigidity, the skeins are digested at a temperature of 20° to 30° with a mixture of 
alcohol and hydrochloric acid; this liquor becomes green in colour, and the deeper 
the hue the whiter the silk. The silk is rinsed in water, and having been dried will 
be found to have lost only about 2*91 per cent in weight. The alcohol used in this 
process may be readily recovered by neutralising the acid with chalk and by 
subsequent distillation. 

weaving of silk. This branch of the silk industry is very similar to the weaving of 
cotton, linen, woollen, and mixed fabrics; very frequently, however, silk yarn 
is mixed and woven with other fibres. Often either the chain or woof is made 
simply of twisted, not of thrown, silk, the advantage being the production of thicker, 
but less coarse fabrics. Dark silk tissues are ready for the market as soon as 
woven; they are only folded and pressed. Lighter silk fabrics (atlas and taffetas) 
are washed over with a sponge dipped in a solution of gum tragacanth, and are next 
hot-pressed or calendered by the aid of iron cylinders either heated by steam or by 
placing a red-hot iron in them. Heavy silk fabrics are often, as it is termed, 


505 


CHEMICAL TECHNOLOGY. 


moired, that is, while partly moistened are passed between hot rollers. By the aid of 
copper cylinders bearing various designs, different patterns are en relief embossed 
upon heavy silken and silk .velvet fabrics, being gaufred, as it is termed. 

Silk fabrics are :—i. Smooth. 2. Twilled. 3. Patterned. 4. Gauze. 5. Velvet. 

a. To the first category belong:—1. Taffetas, a light, thin, smooth tissue, made 
of scoured silk, the chain being organzine single threaded, the woof trame, and 
bi- or tri-threaded. 2. Gros [Gros de Tours, Gros de Naples), a heavy taffetas-like 
fabric, woven with heavy thread, and hence having a ribbed appearance when thick 
and thin threads are mixed. 

b. Twilled fabrics are:—1. The various kinds of serges ( Groise, levantin, drap 
de soie, bombasin). This fabric has a right and a wrong side, the former being the 
chain side. 2. Atlas, or satin, in all its endless varieties, single, double, half, and 
serge atlas. 

c. Patterned fabrics. To this class belong all fabrics which either by the 
art of weaving or by other means are distinguished by some design (droguet, chagrin, 
reps, silk damask, &c.) 

d. To the velvet fabrics belong :—1. Genuine velvet; cut or uncut. 2. Plush. 

e. To the silk gauzes belong an immense variety of very light materials, as for 
instance:—1. Marie. 2. Silkstramin. 3. Crape. 4. Various qualities of silk webs. 
5. Barege. 

It is quite beyond the scope of this work to enter into further details on the 
subject of the mixed fabrics, of which indeed there is a very large and yearly 
increasing variety. Among them we mention here only poplin as made in Ireland, a 
beautiful mixed fabric of linen, wool, and silk, and often woven in what is known 
as tartan pattern. Mixed woollen silk and cotton fabrics are very largely produced 
in tliis country as well as abroad. 

Means of Distinguishing silk Owing to the manufacture of mixed fabrics, it has become 
vegetable Fibres. a necessity to be enabled to detect and distinguish silk from 
woollen as well as from cotton and linen fibres. Microscopical investigation 
aided by chemical tests are resorted to for this purpose. 

The animal fibres (silk, wool, and alpaca), are at once distinguished from 
the vegetable (flax, hemp, cotton), by the fact that the former are soluble in caustic 
potash, and the latter not. . The animal fibres on being singed give off a smell 
of burnt feathers, and when ignited in the flame of a candle are almost immediately 
extinguished, a carbonaceous residue being left. Cotton and linen fibres continue to 
burn, do not give off the smell of burnt feathers, and do not leave a carbonaceous 
mass when extinguished. Wool and silk are coloured yellow by nitric acid 
(i‘2 to 1*3 sp. gr.), cotton and linen not so. Nitrate of protoxide of mercury colours 
animal fibres intensely red, and upon the addition of a soluble alkaline sulphuret 
this colouration becomes black. Linen, or flax, and cotton are not at all acted upon 
by this reagent. An aqueous solution of picric acid dyes wool and silk intensely 
yellow, but not so vegetable fibres. The colourless liquid obtained (according to 
Liebermann) by boiling a solution of fuchsine with caustic potash does not impart 
to a mixed fabric of wool and cotton any colour at all; but when the fabric is 
thoroughly washed in water, the woollen fibre becomes intensely red-coloured, while 
the cotton fibre remains colourless. A solution of ammoniacal oxide of copper in 
excess of ammonia dissolves, first silk, next cotton, but not wool. When wool and 
floret silk are mixed the latter may be dissolved by successive treatment with 


SILK. 


3<>7 


nitric acid and ammonia, while wool is left. A solution of oxide of lead in caustic 
potash or soda may serve to distinguish wool from silk, owing to the fact that, in 
consequence of the former containing sulphur and the latter not, the mixture, when 
wool is present, becomes black. Nitro-prusside of sodium is undoubtedly the most 
delicate test for distinguishing between silk and wool in solution in caustic 
alkali, because, owing to the sulphur of the wool, this reagent produces in the solution 
a violet colouration. 

By the aid of the microscope, cotton, wool, and silk are readily distinguished 
from each other. As for cotton (see p. 343), it has been fully described, and its 
microscopical appearance illustrated by woodcuts, as also have silk and woollen 
fibres. Of the latter we may now state that, whereas cotton fibre consists of only 
one cell, wool (as also hair and alpaca), is made up of numerous juxtaposed cells; 


Fig. .452 


Fig. 255. 



the silk fibre being similar to the secreted matter of spiders and other kinds of 
caterpillars. The silk fibre (Fig. 253) is smooth, cylindrical, devoid of structure, not 
hollow inside, and equally broad. The surface is glossy and only seldom are 
any irregularities seen on it. If it is desired to detect in a woven fabric the 
genuineness of the silk, it is best to cut a sample to pieces, place it under water 
under the object-glass of a microscope magnifying 120 to 200 times, covering it with 
a thin piece of glass. The round, glazed, equally proportioned silk fibre, Fig. 254, 
is easily distinguished from the unequal and scaled wool fibre (w in Fig. 255), and 
from the flat band-like and spiral cotton fibre (b, Fig. 255). Under the microscope 
also the admixture of inferior with superior fibres of silk can be easily detected. A 
small microscope known as a “ linen-prover ” is sold for these examinations. 



CHEMICAL TECHNOLOGY. 


508 


Tanning. 

Tanning. The operation by which the sldns of various animals, more especially 
those of the larger mammalia, are converted into leather is called tanning. By 
leather we understand a substance, tough, flexible, not harsh; further, distinguished 
by resisting putrefaction and by not yielding any glue when boiled in water, 
as is the case with tanned hide, sole leather, and the so-called red-tanned leather, or 
only after a very continued boiling, as with tawed skins of calves, sheep, or goats. 
Whatever the differences which obtain in the practical processes for carrying out the 
conversion, the physical principle involved is the same in all. Knapp’s general 
definition of leather is that it is skin, in which by some means or other the aggluti¬ 
nation of the fibres after drying has been prevented. 

To a comparatively very recent period tanning was conducted on an empirical 
basis; it is only by a more accurate knowledge of the histological structure of the 
sldn and of the tannin-containing materials that the real nature of the process has 
become known, this knowledge being due chiefly to the researches of F. Knapp and 
Bollet. 

That which is converted into leather is, however, not the skin or hide, but really 
what is known anatomically as the corium, that is to say, the inner portion of 
the skins, from which by mechanical (cutting and scraping) as well as by chemical 
means (action of lime) the other integuments have been removed. In its most general 
sense tanning should:—1. Effect the prevention of putrefaction. 2. Bender the 
dry sldn a supple, fibrous, tough, non-transparent substance, and not horny as would 
be the case were the skin simply dried. A well-tanned skin or hide possessing these 
properties is termed “well finished.” The specific process of tanning is of course 
preceded by some preliminary operations, the aim of which is to “ dress” the skins or 
hides—that is, in scientific terms, to prepare the corium more or less perfectly free 
from all other integuments. Tanning in the more restricted sense of the word may be 
effected by a great many organic and inorganic substances; but in practice on the 
large scale there is employed :— 

1. Tannin as contained in oak bark, producing brown-red tanned leather. 

2. Alum and common salt—Tawing. 

3. Fatty matters—Samian or Oil Tawing. 

Anatomy of Animal skin. Leaving the hair out of the question, the sldn of the mam¬ 
malia consists of several layers. The uppermost of these in which the hair is 
growing, the epidermis, is very thin, semi-transparent, and consists of cells which 
contain nuclei. This epidermis is covered by a more or less horny layer not 
possessing any vital properties, which gradually wears off, and is as gradually replaced 
by the stratum Malpighii, or Malphigian net, a structure consisting of cells con¬ 
taining fluid and nuclei. It is tins layer in which the nerves and finer blood vessels 
are imbedded, together with the glands which provide the perspiration. In the tan- 
yards this layer is known as the bloom side, or hair side of the skin or hide. 
The real corium or derma, situated under the layer just mentioned, does not consist 
of cells, but is of a fibrous texture, and is that portion of the skin which after 
tanning constitutes the leather; in the living animal it is separated from the 
muscles by a more or less strongly developed fat-bearing tissue, the so-called 
panniculus adiposus, which is, however, removed in the dressing, the side of the sldn 


TANNING . 


509 


or hide to which it was attached being termed the flesh side. All the histological 
constituents of skin or hide possess the property of swelling up when put into hot 
water, and of becoming after more or less protracted boiling converted into glue, 
more slowly when the skin is taken from old, more rapidly when from young 
animals. By the action of acetic acid the fibrous tissue of the skin is converted into 
a jelly-like transparent mass, in which the fibres are not only not destroyed but-pre¬ 
sent with their peculiar structure. Alkaline leys dissolve this tissue but *very 
slowly; while lime- and baryta-water have no other effect on it than simply the dis¬ 
solving therefrom of the cellular binding tissue which permeates it, and which is an 
albumen compound also acted upon by dilute acids. 

The various operations of tanning, more particularly the preliminary operations . 
of steeping and dressing, are based upon the behaviour of the different histological 
elements of the skin and hide with alkaline and acid fluids ; but the real process of 
tanning is based upon the behaviour of the corium with totally different reagents. 
This latter substance has the property of combining with tannic acid, several 
metallic oxides, viz., alumina, the oxides of iron and chromium, oxidised fatty 
matter, the insoluble metallic soaps (compounds of fat acids, viz., stearic, palmitinic 
acids, &c., with oxide of lead, &c.), picric acid, pinic acid (present in rosin), and 
other organic substances, somewhat in the same way as animal and vegetable 
fibre combine with dyes and pigments. In the most extended sense of the word all 
these substances are tanning agents, because they possess the property of being 
precipitated on and in the fibres of the corium, so that when the latter is dried the 
agglutination of the fibres is prevented, and the natural suppleness and softness of 
the skin preserved. But in the case of the application of alumina compounds, the 
softness is only imparted to the tanned skins by the operations of currying and 
dressing. 

# 

I. Bed- or Baric-Tanning. 

Tanning Materials .—This branch of industry employs as raw materials hides and 
vegetable materials containing tannin. 

These vegetable materials contain essentially an astringent principle termed 
tannin or tannic acid, and which, though it differs in some of its properties as 
derived from different plants, agrees in being of an astringent taste, exhibiting 
acid reaction to test-paper, of yielding with salts of peroxide of iron a deep blue- 
black or green-black colour, of precipitating solutions of glue and cinchonine, and 
lastly of converting animal skins into leather. It has been proved that the tannin 
present in nut-galls—which, by-the-bye, are too expensive for use in tanning opera¬ 
tions—is converted by the action of acids and by fermentation into glucose and 
gallic acid, the latter, however, not being suited for tanning purposes. Under the 
conditions which obtain during the tanning of hides, the tannic acid contained 
in oak bark (tan) cannot be split up similarly to nut-galls, and this negative 
property really aids the tanning operations greatly. All kinds of tannic acid are, 
when in contact with alkaline liquids, such as lime-water, caustic potassa, ammonia 
and with the simultaneous presence of air, decomposed and converted into brown 
coloured humin substances. 

oak Bark. This substance is for the tanner the most important of all tannin- 
containing materials, and cannot be replaced by any other. It is the inner bark of 
several kinds of oak, Quercus robur , Q. pedunculata, and is stripped from the trees 
and branches when these have attained an age of from nine to fifteen years, the bark 


CHEMICAL TECHNOLOGY. 


5io 


when cut into splints being termed tan. According to E. Wolff, the quantity of 
tannin contained in oak-bark is as follows :— 


♦ 


In the crude bark covered with the rind 
„ inside layer of the old bark 

,, inside of the bark . 

„ crude bark and inside of bark ... 
„ inside layer and inside of bark 
inside of bark . 


Tannic Acid. Age 
io - 86 per cent 
I 4‘43 .. 

x 3’ 2 3 .. 

11*69 » 

13*92 » 

x 3’95 » 

15-83 ,» 


of the Trees. 
4 X to 53 
4 1 to 53 
4i to 53 
4i to 53 
4 1 to 53 
14 to 15 
2 to 7 


According to Buchner’s researches (1867) the quantity of tannic acid contained in 
the best kinds of oak bark does not exceed 6 to 7 per cent. The fir bark (produce of 
Pinus sylvestris) is one of the best tanning materials, and is frequently used for sole 
leather; this bark is stripped off the trees immediately after they have been cut down 
for timber. While J. Feser found 5 to 15 per cent of tannin in this bark, Dr. Wagner 
found only 7-3 per cent. In the United States the bark of the Abies canadensis 
is used; and an extract is in the trade, which according to Nessler’s researches 
(1867) contains i4’3 per cent of tannic acid. The extract is imported into this 
country under the erroneous appellation of hemlock extract. The bark of the elm 
with 3 to 4 per cent tannin, the bark of the horse-chestnut with about 2 per 
cent tannin, and beech-tree bark with also about 2 per cent tannin, are all employed 
for tanning purposes. The younger branches and twigs of the willow trees yield a 
bark (3 to 5 per cent tannin) which is especially suited for certain kinds of glove 
leather; while another kind of willow bark is used for the tanning of Russian 
leather. In Tasmania and New South Wales the barks of some species of acacia, 
viz., Acacia dealbata, A. melanoxylon, A, lasiophylla , and A. decurrens are used. 
Among the native European plants which might be advantageously cultivated 
for tanning purposes, the Polygonum bistorta deserves to be mentioned: this plant 
should contain according to Fraas from 17 to 21 per cent (?) of tannic acid. 

sumac. This substance is, next to oak bark, one of the most important tanning 
materials; it is the product—the leaves and stems—of a shrub, the so-called tanner’s 
sumac {Rhus coriaria and R. typhina ), which grows wild in Southern Europe and 
the Levant, and is cultivated in North America and Algeria. The shoots from the 
roots are collected and planted in June, and after some three years’ growth, the 
shrubs are large enough to admit of the branches and leaves being gathered. The 
young branches and twigs are cut off, and after drying in the sun, the leaves are 
beaten off with sticks or clubs, and next crushed under mill-stones, sifted, and packed 
into sacks, and thus sent into the market. The sumac of commerce is a coarse 
powder, exhibiting a yellow or blue-green colour, and containing 12 to 16*5 per 
cent of tannic acid. By keeping, the tannic acid of sumac is converted into 
secondary products, owing to a spontaneous fermentation. Sumac also contains a 
yellow dye-stuff which seems to be identical with quercitrin. With sumac should not 
be confused another material of the same name, but distinguished as Italian or 
Venetian sumac, and derived from the Rhuscotinus, also yielding fustic or yellow 
dye-wood. Italian suniac is the pulverised bark of the young twigs and leaves of 
this plant, which under the name of ruga growls in Southern Europe and also near 
Vienna; it is largely used in the countries where it grows for tanning purposes, 
being more particularly employed for preparing goat- and sheep-skins. 



TANNING. 


511 


DiTidivi. The material designated by this name is the seed capsule of some trees 
found native in Central America, and belonging to the Ccesalpiniaciae ; these seed 
capsules are about 6 centims. long, are bent as an S, have a brown-red colour, and 
contain olive-green coloured, egg-shaped, polished seeds. In 1768 the Spaniards 
brought this material to Europe, where it is used for tanning purposes on account of 
the tannin contained in the epidermis of the capsules (more correctly siliquce, or pods). 
The quantity of tannin was found by Muller to be 49 per cent, by Fleck 3^4 per 
cent, while Dr. Wagner found from 19 to 267 percent. Dividivi is rather an expen¬ 
sive tanning material, but is occasionally used for dyeing purposes. Among the 
tannin-containing substances which are occasionally imported from abroad may be 
mentioned the bablah, the produce of the Acacia Bablah and allied species. This 
material contains, according to Fleck, 20 - 5 per cent tannin, while Dr. Wagner found 
i4'5 per cent. Algarobilla, the seed capsules of the Prosopis pallida, a native of 
Chili, has been also occasionally employed as tanning material in this country. 
Although myrobolans, the fruits of Terminalia citra, T. Bellirica, and T. Chebula , are 
imported from Bombay, they contain too little tannin to be of any service in tan-yards. 
Nut Gaiis. We understand by this name an excrescence formed on the leaves of the 
Quercus infectoria by the puncture of the female insect of the Gynips gallce tinctorice, 
or oak wasp, effected in the leaves and young twigs in order to deposit its eggs; the 
juices of the tree collect round the egg, and on hardening form the nut-gall. This 
material is best collected before the young insect has become fully developed, 
because then the gall contains the largest quantity of tannic acid. In the market 
three varieties are met with, termed black, green, and white galls. The black and 
green variety have been gathered before the insect became fully developed inside the 
nut; these galls therefore do not exhibit outwardly any hole or opening, but on 
breaking the gall there will be observed in the centre a small cavity surrounded by a 
light brown friable substance, which contains the larva of the insect. Galls are 
generally spherical, but exhibit small irregularities of surface, and are of a black- 
green or grey colour. The white galls are gathered after the insect is fully 
developed, and has by perforating the tissue of the gall escaped. This variety is 
more spongy, its colour is a red-brown or brown-yellow. Galls of good quality are 
obtained only from warmer countries, for although galls are formed in our climate 
upon oak leaves, the quantity of tannin contained amounts to only 3 to 5 per cent. 
Fehling found in Aleppo gali§ from 60 to 66 per cent of tannic acid, while Fleck 
found 5871 per cent of this acid, and 5^9 per cent gallic acid, 
vaionia Nuts. These are the dried immature acorn cups of two species of oak, 
Quercus cegilops and Vaionia camata, both being employed in tanning as well as the 
vaionia nuts produced by the puncture of the Cynips quercus calycis. The quantity 
of tannic acid met with in these substances averages about 40 to 45 per cent. In the 
so-called vaionia flour, obtained by grinding the acorns belonging to this class, 
Dr. Wagner found 19 to 27 per cent of tannin. The acorn cups are imported under the 
name of drillot, and according to Rothe these contain 43 to 45 per cent of tannin. 

Chinese Gaiis. Under this name has been known in the trade since 1847, an( i imported 
from Japan, China, and Nepaul, the excrescence upon a kind of sumac, Bhus 
javanica and R. semialata, produced by the puncture of the Aphis sinensis. This 
gall-nut is rather oblong or bean-shaped, with an irregular surface covered with a 
yellow-grey felt; the length varies from 3 to 10 centims., and the thickness from 15 to 
4 centims.; the texture is horny; the quantity of tannin varies from 60 to 70 per cent. 


512 


CHEMICAL TECHNOLOGY. 


cutch. The substances long known in medicine under the name of catechu and 
kino have been for the last fifty years also employed as tanning materials. Theyare 
vegetable extracts, that known as cutch (trade term) being obtained by exhausting 
with boiling water the pith of the wood of the Acacia catechu, a tree met with in 
different parts of the tropical regions of Asia. The liquor obtained by boiling the 
pith-wood in water is inspissated, and on cooling forms a solid mass, which is brought 
into commerce in various shapes and named after the port of shipment. Bombay 
cutch is met with in the shape of large square blocks, through and round which the 
leaves of a kind of palm-tree are placed. The colour of the fracture of this substance 
is a brown-black with a fatty gloss ; externally the mass is dull and friable. Bengal 
cutch is prepared from the nuts of the Areca catechu, and occurs in commerce as 
large, irregularly-shaped cakes, externally brown, internally more yellow-coloured. 
Gambir is a variety of cutch prepared in Sumatra, Singapore, and Malacca, and 
especially in the Island of Biouw, from the leaves and stems of the Uncar ia Gambir. 
The dry extract occurs in commerce in small cubical blocks, which are light, of a 
cinnamon-colour, and very friable, the fracture being earthy. All these substances 
contain about 40 to 50 per cent of a peculiar kind of tannic acid or catechu-tannic 
acid, the formula of which, according to J. Lowe, is C I5 H I4 C>6, as well as a peculiar 
acid, catechutic acid, Ci 6H I4 06, not of much use in the tanning process. 

Kino. This drug is very similar to catechu, and is said to be the extract prepared 
from various plants, viz.:— 

African kino from . Pterocarpus erinaceus, 

East Indian kino from . Pterocarpus Marsupium, 

East Indian kino, according to others, from Butea frondosa, 

West Indian ldno from. Coccolaha uvifera, 

Australian kino from . Eucalyptus resinifera. 

Kino is met with in small, angular, brittle, brown-red to black-coloured masses, 
the powder of which is always brown-red. It is soluble in hot water and alcohol, 
yielding a blood-red solution of an astringent and sweet taste. Kino contains from 
30 to 40 per cent of a tannic acid similar to that contained in cutch; both of these 
materials are especially useful in so-called quick tanning. 

^h^iarming^MateriX° f The value of all the tanning materials entirely depends upon 
the quantity of tannic acid they contain. The latter is soluble in water, and more or 
less completely precipitated from that solution by various reagents, such as glue and 
animal skin, acetate of copper, acetate of oxide of iron, cinchonine and quinine, 
while a solution of permanganate of potash completely destroys the tannic acid. 
Upon these properties the following properties have been based for the approximative 
estimation of the quantity of tannic acid present in various tanning materials :— 

1. Precipitation by glue or skin:— 

a. Weighing of the skin before and after immersion in the liquor containing 

tannin, the increase of weight giving the quantity of tannic acid.—(D avy). 

b. Precipitation with gelatine solution of known strength.— (Fehling). 

c. Titration by means of an aluminated solution of glue.—(G. Muller). 

d. First determine the specific gravity of the tannin solution by means of an 

areometer, next remove the tannin by skin, and then again take specific 
gravity of liquid, the decrease being proportionate to the quantity of tannin 
in the original liquor.—(C. Hammer). 


TANNING. 


513 

2. Precipitation of tannin by acetate of copper, and estimation of the relation 
between tannin and oxide of copper in the precipitate :— 

a. Volumetrically.— (H. Fleck) ; or 

b. By the gravimetrical method.— (E. Wolff). 

3. Volumetrical estimation of tannin by acetate of iron.—(R. Handtke). 

4. Oxidation of tannic acid by permanganate of potash.— (Lowenthal). 

5. Precipitation of tannin by means of cinchonin, the solution of which is tinged 
red by means of fuchsin. 1 grm. of quercitannic acid requires 07315 grm. 
cinchonine, equal to 4^523 grms. of crystallised neutral sulphate of cinchonin.— 
(R. Wagner). 

The skins. The skins of almost all quadrupeds might be converted into leather by 
tanning; but the tanner chiefly prepares his leather from the hides of cattle, occasion¬ 
ally from the hides of horses and asses as well as of pigs. The quality of the 
hides not only depends upon the kind of animal, but also upon its fodder and mode 
of living, The hides of wild cattle yield a more compact and stronger leather than 
the hides of our domesticated beasts; among these the stall-fed have better hides 
than the meadow-fed or grazing cattle. The thickness of the hide varies consider¬ 
ably on different parts of the body, the thickest part being near the head and the 
middle of the back, while at the belly the. hide is thinnest. These differences are 
less conspicuous in sheep, goats, and calves. As regards sheep it would appear that 
their skin is generally thinnest where their wool is longest. 

The hides of bulls and oxen yield the best and stoutest leather for soles. In the 
raw—untanned—state, and with the hair still on, the hides are termed “ green ” or 
“fresh.” Fresh or green hides are supplied to the tanners by the butchers, or are 
imported either dry or salted. A hide weighing in fresh state from 25 to 30 kilos, 
loses by drying more than half its weight. South America (Bahia, Buenos Ayres, &c.) 
exports a large quantity of hides, both dry as well as salted and cured by smoking. 
The hides of cows yield generally an inferior grained leather; but South American 
cow hides may be worked for light sole leather. Calves’ hides, again, are thinner, 
but when well tanned, curried, and dressed, yield a very soft and supple upper' 
leather for boots and shoes. Horse hides are only tanned for saddlery purposes, 
while sheep- and goat-skins and the skins of lambs are tanned—or more generally 
tawed—for the purpose of making wash-leather, maraquin, glove-leather, book- 
binders’-leather. Pigs’ hides and seals’ skins are tanned for saddlery purposes. 

The several Operations. The several operations of the oak bark tanning process may be 
reduced to three, viz.:—A. The cleansing and dressing of the hide on the hair and 
flesh side; in other terms, the separation of the corium from the other integuments. 
B. The true tanning. C. The currying and dressing operation, by which the 
tanned hide becomes a saleable article. These three operations are again subdivided 
as follows:— 

A. The cleansing of the hide:— 

1. Steeping and macerating the hide. 

2. Dressing the flesh side. 

3. Dressing the hair side. 

4. The swelling of the cleansed hide. 

B. The tanning of the cleansed hide, performed either by placing it in tanks 01 
pits with oak bark and water, or in a liquor of these previously prepared, or by the 

so-called quick method. 

34 


CHEMICAL TECHNOLOGY. 


5M 

C. Tlie dressing and currying of tlie tanned hides, by which is understood all the 
operations which tend to improve the compactness of texture, or give a better grain 
and better appearance to the leather, together with softness, toughness, suppleness 
and colour. 

Cleansing the Hides. A. This operation includes:—i. The steeping or macerating of 
the hide in water for the purpose of rendering the texture uniformly soft and so 
supple that it may be bent without danger of cracking, while, on the other hand, this 
steeping also effects a cleansing of the hide by removing from it blood and dirt. The 
fresh hides of recently slaughtered animals require a maceration in water for some 
two or three days, but dried, cured, or salted hides have to be left macerating for some 
eight to ten days. This operation should, if possible, be carried on in a stream of 
water; but if there is no convenience, then the hides are placed in large tanks; in 
either case the hides are taken out twice daily and put back into the water again. 

cleansing of the Flesh side. When the hides have become quite soft, they are— 
(2) cleansed or dressed on the flesh side by being placed with the hair side down¬ 
wards on a “ tree,” a stout semi-circular plank, one end of which is placed on the 
ground while the other is supported by a trestle, so that the plank is in a sloping 
position. The workman has a so-called dressing-knife, a tool to which handles are 
fastened, and which is bent so as to form a slight curve ; with this knife he shaves, 
or, as it were, planes off, from the hide all fatty tissue and integuments which are 
situated between the hide and the muscles. At the same time the water is squeezed 
out of the hide to some extent. 

After a preliminary or first dressing, the hides are again placed for twenty-four 
hours in water; the dressing and planing is then quite finished, and the hides 
having been well washed, are left to drain on the tree ready for removing the hair. 
In some instances the hides are washed by the aid of “ possing-sticks,” and “ fulled ” 
by means of machinery, by which the operation is greatly shortened, so much so, 
that two to three days suffice, instead of, as is usual by the aid of manual labour, 
eight to ten days. 

cleansing the Hair side. 3. This operation aims at the removal from the corium of the 
epidermis and hair-containing integuments. As the hair and integuments connected 
therewith are very firmly attached to the corium, the removal can only be safely 
proceeded with, so as to leave the corium uninjured, by the employment of a 
menstruum which more or less dissolves and causes the epidermis to swell up. For 
this purpose the hides are usually placed in lime-pits, the effect of the lime being the 
partial dissociation (in an anatomical sense) of the epidermis, so that it and the 
hairs may be readily removed by mechanical means. 

The effect is usually obtained by— a. Sweating; b. Liming; c. Application of 
rusma or compounds of sulphuret of calcium. 

a. A semi-putrefactive fermentation called sweating is employed in the case of 
thick hides, such as serve for sole leather, which are not placed in lime owing to the 
fact that it cannot be completely removed, and would render the leather brittle. 
The operation of sweating consists in placing the hides one upon the other, the flesh 
side turned inward, some salt or crude wood vinegar having been first rubbed in, in 
a tank, or box, which can be closed so that the heat generated by the fermentation 
which sets in may be confined as much as possible to aid the action. As soon as the 
evolution of ammonia is perceptible, the hides are ready for the removal of the hair, 
which is shaved off, together with the epidermis, by the aid of the dressing-knife. 


TANNING. 


5i5 


Instead of causing the sweating to be done by fermentation, the hides are sometimes 
hung on laths in rooms either heated by means of steam or by fire. A temperature 
of 30° to 50° should be kept up, together with a good current of steam, by which the 
epidermis is thoroughly softened. In order to prevent any injury to the corium, the 
hides are sometimes submitted to what may be termed a cold sweating process, 
consisting essentially in placing the hides in water-tight tanks, in which there is a 
constant current of fresh water, the temperature being kept at 6° to 12°. The hides 
thus submitted to a constantly moist atmosphere become, after six to twelve days, 
without any perceptible putrefaction, fitted for the removal of the epidermis and hair. 

b. The liming of the hides not only prepares them for the removal of the hair, but 
also saponifies the fatty matter; and though the lime soap thus formed is insoluble in 
water, it is removed by subsequent mechanical and chemical operations. The 
operation of liming is carried on in juts, into which, along with milk of lime, the 
hides are placed so as to be quite covered. Usually several (three to five) pits are in 
use at once, each of which contains a different quantity of lime. That the milk ot 
lime should be frequently stirred in these pits is of course evident. The hides 
remain in the lime-pits for three to four weeks. 

c. The very thin skins of the smaller animals will neither sustain sweating nor 
liming and are therefore treated with rusma, a salve-like mixture of orpiment, 
1 part with 2 to 3 parts of slaked lime. By the rubbing in of this mixture on the 
hair side of the skins, the hairs are so softened as to make their removal an easy 
matter. Bottger states that hydrosulphuret of calcium has the same effect; hence 
the lime of the purifiers of the gas-works has been of late years frequently employed 
for treating hides as well as skins, with the additional advantage of yielding a better 
leather. 

stripping oft the Hair. As soon as the hides are sufficiently prepared to admit of the 
removal of the hair and epidermis, they are stretched out on the tree and the integu¬ 
ments peeled off by the aid of the blunt dressing-knife. In order to give to the 
dressing-knife a better grip, the workman strews some fine sand on the hide, and if 
he has to deal with very heavy and thick hides, uses a large and rather sharp knife. 
When the hair and the epidermis have been removed, the hides are again washed and 
macerated in water, and after this dressed; that is to say, reduced as much as 
possible to an equal thickness, while the waste—tail, leg, and head pieces—are cut 
off and the hide planed, thereby losing some 10 to 12 per cent in weight. 

swelling the Hides. The aim of this operation is to remove the lime, and also to 
render the corium more capable of readily absorbing the tan materials. This end is 
attained by placing the hides in a so-called sour bath, made of refuse malt and 
bran, which by acid fermentation yields as active principles propionic, lactic, and 
butyric acids. 

The lime is removed from the dressed hides when placed in this acid liquid, and 
the lime-soap present becoming decomposed, the fatty acids thus set free float on the 
surface of the liquid. The soluble lime salts are completely removed from the 
hides by a subsequent thorough washing with water. The thickness of the hides is 
doubled by the swelling action of the acid liquid, aided by the mechanical action of 
the carbonic acid evolved from the carbonate of lime deposited within the fibres of 
the hides; while the butyric acid fermentation distends the fibres of the hides by the 
gases thereby evolved. When the hides have not been treated with lime but have 
been submitted to a “ sweating,” they do not require the acid bath, but are 


CHEMICAL TECHNOLOGY. 


5i6 

simply placed in water for the purpose of swelling them. Yet the sour bath is 
preferable owing to its more regular action. 

Instead of using the preceding mixture for the purposes of removing the lime and 
of swelling the hides, they are often placed in acid tan liquor (red tan liquor), that is 
to say, a liquor containing exhausted oak bark solution which has served for 
tanning; this liquor appears to contain also large quantities of lactic and butyric 
acids. The dressed hides are first placed in a diluted red liquor and then in a 
stronger liquor, this operation taldng some 12 to 14 days. Macbride and Seguin 
have proposed to substitute very dilute sulphuric acid (1 in 1500), but although by 
the use of this acid the operation of swelling is rendered far more rapid, the quality 
of the leather is impaired. Phosphates and animal excreta which contain a 
large quantity of uric acid, such as that of dogs and of pigeons, have been, and in 
many cases are still, used for the purpose of swelling hides, especially skins of sheep, 
calves, and goats. 

The Tanning. B. The main object of the operations just described is first to obtain 
the corium as much as possible separated from the other integuments and textures 
belonging to the skin, and next to render the corium as much as possible permeable 
by the liquor in which the tannin-containing vegetable matter is dissolved. In 
practice it is taken for granted that a dry hide gains one-third in weight by being 
converted into leather, consequently it absorbs that quantity of tannin. 

The impregnation of the fibres of the hide or skin with tannin is effected by two 
different methods, viz.:— 

1. By placing the hides between layers of oak bark chips in a tank, so-called 
tanning in the bark ; or 

2. By immersing the hides, first in a dilute, and again in a concentrated aqueous 
infusion of oak bark. 

Tanning in the Bark. i. This mode of tanning is at the present time confined to heavy 
hides intended for sole leather. The tanks in which this operation is carried on are 
made of wood, either oak or fir, are of course watertight, and are usually sunk into 
the soil. Brick cisterns lined with cement are occasionally used, but are objec¬ 
tionable, at least when recently built, on account of the deteriorating action of the 
lime and cement upon the oak bark. In some parts of Germany tanks constructed 
of slabs of slate or sandstone are used. Each tank has sufficient capacity to contain 
50 to 60 hides. On the bottom of the tank is first placed a layer of exhausted (spgnt) 
tan, and upon this a layer of some 3 centimetres in thickness of fresh bark, then a 
hide with the hair side downwards, again a layer of fresh oak bark, and again a hide, 
alternately until the tank is nearly filled, care being taken to put some more bark on 
the thickest part of the hides, and to fill not only all interstices with bark, but to put 
on the top a layer of some 30 centimetres thickness of spent tan. Water is 
next poured into the tank until it stands a few centimetres above the topmost hide ; 
this having been done, a lid—in England loose planks—is placed on the tank, 
the contents of which are left undisturbed for some time. When Yalonia flour 
is employed with the oak bark only half the quantity of the latter is necessary. 

The hides are left in “ the first bark” for 8 to 10 weeks, the period being a little 
shortened if Valonia flour is also used. Before all the tannin has been absorbed, and 
as a consequence the formation of volatile and odorous acids (valerianic, butyric, &c.) 
has commenced, the hides are transferred to another tank and again placed between 
alternate layers of fresh bark, the only difference in the arrangement being that the 


TANNING. 


517 

hides which were first placed on the top are now laid at the bottom of the tank. 
The hides are now left for three to four months, so as to thoroughly absorb the 
tannin. They are next placed for some four to five months in another tank which 
contains less bark. In the case of very heavy and thick hides the process is 
repeated four or even five and six times. The quantity of bark required for 
obtaining thoroughly well-tanned leather depends partly on the quality of the bark, 
and somewhat on the condition of the hides. Usually the tanners reckon that the 
quantity of bark required amounts to four to six times the weight of the dry hides: 
and taking the weight of these at an average of 20 kilos.— 

For the first tank there will be required 40 kilos, of bark. 

„ second „ „ „ 35 

- third „ „ „ 30 

105 kilos, of bark. 

A dried and well-tanned hide weighs about 22 kilos., or 10 to 12 per cent more than 
the dry raw hide. A thoroughly tanned hide exhibits when cut with a sharp knife a 
uniform texture free from fleshy or horny portions, while the grain on the hair side 
should not on being bent slowly exhibit signs of cracking. 

Tanning in Liquor. 2. The thinner hides, and indeed most sldns (when tanned, as 
distinguished from tawing), are placed in infusions of the tannin-containing material. 
There are various methods in use for this operation, which is based mainly upon a 
thorough uniform swelling of the hides, so that when these are placed in weak 
liquors the tannin may penetrate readily and uniformly. The hides are, in fact, very 
gradually tanned. When taKen from a liquor the fluid is forced by mechanical 
means out of the hides before they are placed in a stronger liquor, this liquor 
being obtained by exhausting the tanning materials by the aid of cold water. The 
thinner kinds of hides are thoroughly tanned in seven to eight, the heavier hides in 
eleven to thirteen weeks. 

Quick Tanning. Many methods—some quite impracticable and most of them 
thoroughly irrational—have been proposed for converting hides into leather in a very 
short time. Of these different methods we briefly mention the following:—i. The 
hide is simply placed in an infusion of the tannin-containing material—Macbride’s 
process, improved by Seguin (1792). Application of hydrostatic pressure to force the 
liquor through the hides, kept from contact with each other by a stout woollen 
tissue. 2. Circulation of the tannin-containing fluid, several tanks being connected 
together by means of pipes, and the liquor being forced through the tanks by means 
of pumps (Ogereau, Sterlingue, and Turnbull’s methods. 3. The hides are sewn 
together so as to form sacks, which are filled with oak bark chips and water and then 
placed in an aqueous solution of cutch, to which, in order to increase its specific 
gravity, coarse molasses is added—Turnbull’s method by increased endosmose. 
At the time this mode of proceeding was brought forward, the diffusion of liquids 
by dialysis (discovered by Graham in 1861) was unknown. 4. Motion of the 
hides in the tannin-containing liquids, the hides being placed in a cylinder 
constructed of wooden laths so as to leave open spaces between them. This 
cylinder is immersed horizontally in the liquid to a greater or less depth, so that in 
every revolution the hides are alternately in and out of the liquid—Brown, Squire, 
and C. Knoderer’s methods. 5. Application of mechanical pressure to the hides. 



CHEMICAL TECHNOLOGY 


518 

which having been from time to time removed from the tanning tanks, are placed 
upon perforated planks, and either pressed under a heavy roller or are placed in a 
press—Jones, Nossiter, Cox, and Herapath’s method. 6. Application of hydrostatic 
pressure for the purpose of causing the tan-liquor to penetrate the hides, which are 
sewn together so as to form bags, which having been filled with oak bark liquor, are 
placed in suitably constructed vessels, so that hydraulic pressure may be applied 
without fear of bursting the bags ; or the hides are fastened by means of screws and 
bolts, placed in a framework which is immersed in a well-constructed eastern filled 
with tan-liquor, hydraulic pressure being applied—Drake, Chaplin, ar d Sautelet's 
methods. 7. Snyder’s method of punctation, consisting in perforating lac hide over 
its whole surface, the punctation being effected by sharp needles, so as co constitute 
artificial pores. The experiments of Knapp have proved the thorough irrationality 
of this plan, it having been found that the hide is so permeable to tannin-liquor that 
a piece of calf-skin when placed in a solution of tannin of the consistency of syrup 
is thoroughly well tanned in about an hour’s time. 8. Application of a vacuum 
by placing the hides in a vessel from which the air may be withdrawn by the aid ol 
air-pumps; tan-liquor having been forced into the vessel, the air is re-admitted and 
again withdrawn—Knowly and Knewsbury’s plan. Knoderer has recently found 
that by a judicious combination of the vacuum method, followed by motion and 
fulling of the hides in the tan-liquor, the operation of tanning is much shortened. 
The reader should bear in mind that the methods here alluded to are not now 
in general use. 

r>re8 theL 0 eathe 7 yins When the hides have been converted into leather by the 
processes described, they are not by any means fit for use nor ready for sale as 
a finished material, but require to be dressed, or, as it is technically termed, curried, 
an operation not necessarily performed by the tanner—at least, never so in England 
and France. The several operations are not similar for all kinds of leather, 
but depend to some extent upon the use to which it is intended to be put. For 
instance, sole leather is submitted simply to a process the object of which is 
to render it sufficiently stiff and compact, so as not to alter its shape by wear. 

sole Leather. The dressing or currying of this land of leather consists mainly in sub¬ 
mitting it to a mechanical operation of hammering, by which the material is 
rendered more compact. As soon, therefore, as the hides are taken from the tanning 
tanks, the adhering spent tan is brushed off with a broom, after which the hide 
is dried in a cool place, and when dry laid flat upon a polished stone slab, and then 
beaten with wooden or iron hammers, an operation in large establishments per¬ 
formed by hammers moved by machinery. 

upper Leather. The dressing of this kind of leather, chiefly used by sadlers and 
boot and shoe makers, is a far more complicated process, and depends in a great 
measure on the use for which the leather is intended. The first of these operations is 

The Paring, the paring or whitening, which means the cutting away, by the aid of a 
tanner’s shaving-knife, of all portions of the hide which are too thick, so that 
the whole hide may be made of uniform thickness. This operation is carried 
on upon the tanner’s “wooden leg,” the hide being placed with the hair-side 
downwards. When goat, lamb, sheep, or calf-skins are to be pared, they are 
placed on a polished slab of marble, and having been well stretched, the raw or 
projecting parts are cut off with the tanner’s shaving-knife. 


TANNING. 


5'9 

The scraping or smoothing. The aim of this operation is similar to that of the former, 
and more particularly is employed in the case of leather intended for making gloves. 
The leather is first dried and next fixed on the “ perching-stick,” one end of the skin 
remaining free, the other being taken hold of by the operator with a pair of forceps. 
The skin having been stretched, the perching-knife, a highly polished somewhat 
convex steel disc of 18 to 30 centims. diameter, and provided in the centre with an 
opening fitted with a piece of leather serving as a handle, is brought into use, 
the portions of the skin which require to be pared off being usually indicated by 
being rubbed over with chalk. 

Graining the Leather. As in consequence of the drying of the leather the grain has 
become flat, smooth, and unequal, it is raised by an operation performed by means of 
the pommel, also termed the graining- or crimping-board, a piece of hard wood 
30 centims. in length by 10 to 12 centims. breadth, flat and smooth on the top, but on 
the opposite side, in the direction of the length, somewhat curved, so that it is 
thickest in the middle, this part being provided with parallel notches, which are 
occasionally sharpened by means of a file; a leather strap is fastened to the top as a 
handle. The leather to be grained, having been placed on the dressing-table, is 
fastened to the edge of the wooden board by means of iron clamps, and those portions 
of the leather, the grain of which has to be raised, having been somewhat bent, are 
rubbed with the pommel so as to render the grain uniformly visible, 

Polishing-with Pumice-stone. Such kinds of leather as require no grain (for instance, the 
leather used in carding machines) after having been pared, are moistened and then 
rubbed over on both sides with pumice-stone, being thus rendered smooth; while 
leather which requires a higher gloss, such as the coloured leathers, are treated with 
^itoVommefs^/cork 417 a pommel made of cork, by which the leather is caused to 
assume a velvety appearance. Again, if a still higher gloss is required, the leather 
smootMng with uio Tawer's j s smoothed, or rather ironed, with iron or copper 

“ sleekers,” and next polished with glass sleekers, a stout cylindrical piece of glass, 
0 3 metre in length by 10 centims. diameter, the leather being placed on a tanner’s 
Roiling, wooden-leg. Leather intended for saddles, in order to impart to it the 
appearance natural to hog’s leather, is passed through rollers, the surfaces of which 
are provided with blunt points, which, being forced into the leather, give to it the 
desired appearance. 

Finishing os. In order to remove from the leather any creases and other inequalities 
of surface, it is damped, and then smoothed with a flattening-iron, or, if the skins are 
thin, with a piece of horn provided with blunt teeth. 

Greasing. When the upper leather is required to be very supple and soft, it is 
greased ; that is to say, it is rubbed with a mixture of fish-oil and tallow, or better, 
with the peculiar^ modified fish-oil which has been used in “ chamoising,” having 
been recovered by the aid of a solution of potash from the chamois leather skins. 
The hides to be greased are first moistened, and having been rubbed with the greasy 
matter, are dried in heated rooms, so that the fatty materials, by actually combining 
with the hides, become, as it were, tanned and tawed at the same time. The greasing 
is therefore not simply an operation of dressing, but in reality a second tanning 
(technically tawing) process. 

The black colour usually seen on the surface of leather required for saddlery and 
boot-making is imparted to the hides by rubbing them with a fresh solution of 
oak bark and then sponging them over with a solution of copperas to which some 


520 


CHEMICAL TECHNOLOGY. 


blue vitriol lias been added; the hides are then again dressed, and lastly rubbed 
with a paste made of fish-oil, tallow, lamp-black, yellow wax, soap, and copperas, the 
object of this operation being to protect the leather from the injurious effects of the 
shoe-blacking, which usually contains sulphuric acid. (For a shoe-blacking without 
acid see “ Chemical News,” vol. xxiv., p. 120). Finally, the leather is painted or 
brushed over with a mixed tallow and glue solution, and then, having been polished 
again with glass, is ready for sale. In order to keep leather supple and soft, it is best 
to rub it with a mixture of fish-oil and lard. 

Yufts, Russia Leather. Under the name of yufts is understood a peculiar kind of 
leather, usually of a red or black colour, which is very water-tight and strong. This 
kind of leather used to be made exclusively in Russia, whence it is. obtained in large 
quantity, the name being derived from the Russian Jufti, signifying a pair, and 
apparently due to the fact that in tanning the hides are sewed together in pairs. 
The hides usually prepared for Russia leather are those of young cattle; sometimes, 
however, the hides of horses and the skins of sheep, goats, and calves are employed. 
The operations for preparing yufti are :—1. The cleansing of the hides, performed in 
the usual manner with lime. 2. The swelling of the hides in an acid-bath prepared 
with malt, exhausted tan-liquor, or with kasclika (excreta of dogs rubbed up with 
water). 3. The tanning, not performed with oak bark, but with the barks of various 
kinds of willows, fir and birch bark also being used. The dressed hides are first 
placed for some days in partly exhausted bark, and are then put into the tanning 
tanks along with bark (as above described), or are sometimes placed in a warm 
infusion of the tannin-containing materials. The tanning continues for five to six 
weeks. 4. The tanned hides are placed on the planing-block for the purpose of 
draining, and are next impregnated with dig gut or elachert, oil of birch, obtained by 
a process of dry distillation from birch wood. This oil contains creosote, phenol (of 
a peculiar kind according to Louginine), and paraffin. It is rubbed into the hides on 
the flesh side, and when thoroughly impregnated they are stretched until they 
become soft and supple. The hides are next rubbed on the hair side with a solution 
of alum, and then grained and dried. The dry hides are dyed in pairs, sewn together 
so as to form a sack, into which a decoction of dye material is poured. When 
a red colour is desired, the dye is prepared from sandal wood, there being added 
to the former lime-water, to the latter some potash or soda. In more recent 
methods the hides are dyed by being brushed over five or six times with the dye 
material. The dry leather is finally dressed by the mechanical operations previously 
described. The use of yufts for book-binding and other purposes is well known. 
Owing to the empyreumatic oil with which this kind of leather is impregnated 
insects do not attack it. 

Morocco Leather. By morocco leather is understood a kind of leather which, when 
genuine, is obtained from goat or kid skins, is very soft, elastic, highly coloured, and 
not lacquered. We distinguish between genuine morocco and the imitation 
obtained by the splitting of calf, sheep, and other skins, as chiefly employed in book¬ 
binding. 

The preparing of morocco leather is undoubtedly one of the many industrial 
discoveries of the Saracensj even at the present day a great deal of morocco leather 
is made by their descendants in Northern Africa and in the Levant. The prepara¬ 
tion of good morocco leather requires very great care, and especially as regards the 
preliminary operations. The skins are deprived of the hair by the aid of lime and 


TANNING. 


52i 


sweating. Tlie tanning material in general use is sumac, the skins being sewn up 
so as to form sacks into which water is poured together with pulverised sumac ; by 
this mode of employing the tanning matter the operation is finished in three days. 
Calf and sheep skin are very generally tanned in England by the same method. 
The dyeing of morocco leather is not performed in the Oriental countries; the dry 
tanned skins are exported under the name of Meschin leather (cuir en croutes) to be 
dyed and dressed in Europe. 

Dressing Morocco Leather. The skins are dyed and next dressed. The dyeing is per¬ 
formed— (a) by means of the dye-vat (for genuine morocco), or (/ 3 ) with the 
brush (for imitation morocco), a. The operation of dyeing with the vat is performed 
in a small trough large enough to hold one skin, and filled with dye-liquor at 6o° 
from a larger tank. The workman pours in no more of the dye material than can be 
conveniently absorbed by the skin, which is continually moved to and fro. The 
dyed skins are laid out flat, and from two to four dozen placed one upon the other. 
The dyeing operation is repeated several (three to five) times, care being taken to 
turn the heap over so that the undermost skin is placed on the top of the heap 
previous to beginning the dyeing operation again. The dyed skins are washed in 
water and next dressed. ( 3 . The imitation morocco is dyed by the dye-liquor being 
uniformly brushed over the skins ; these having been first stretched on a table, the 
dye-liquor is brushed over more than once so as to produce a uniform hue. The 
effect of the dyeing is greatly enhanced by the dressing of the skins and the fine 
grain given to them. The dyed skins are first rubbed on the hair-side with linseed 
oil applied by means of a piece of flannel. The calendering or glazing by machinery 
is the next operation, after which the peculiar appearance of the surface is imparted 
by means of strong pressure or so-called platting. Yellow skins are not glazed, 
because their colour would thereby become a brown. The aniline colours are now 
largely employed in dyeing skins. 

cordwain, cordovan Leather. This differs from morocco only by being prepared from 
heavy skins, and by retaining its natural grain or not being platted. It is usually 
met with dyed red, yellow, or black. 

Lacquered Leather. This kind of leather, now largely used by coach-builders and for 
making shoes, boots, helmets and other military accoutrements, is an invention of 
the present time, its great merit being its property of resisting water, and in being 
supple and soft, while the lacquer, if well laid on, should not crack nor peel off'. 
Only black lacquered leather is generally met with. On the tanned, rarely tawed, 
hide, which has not been greased, is very uniformly laid a varnish, which is thick 
and tough while cold but thinly fluid when warm ; this having been done, the hide 
is placed in a brick-built stove kept at 50°, where the varnish dries after having 
become so fluid as to run uniformly over the surface of the leather, which is placed 
quite horizontally. The coloured lacquers are generally more thinly fluid and are 
dried at a lower temperature. The hides chiefly used for lacquering are cow-hides; 
or a thin hide is obtained by splitting thick hides and lacquering them. 

The leather in use by pianoforte-makers for covering the hammers is prepared by 
a process usually kept a trade secret. This kind of leather requires to be soft and 
very elastic. All that is known about the process of preparing this material is that 
it is obtained by tanning and tawing (chamoising) combined ; the hair having been 
removed, but not the epidermis, the hide is first fulled in oil, then washed in ley, 
bleached in the sun, and next tanned in a tepid oak bark infusion. Danish leather 


522 


CHEMICAL TECHNOLOGY . 


is prepared by tanning sheep, goat, kid, and lamb skins with willow bark; such 
leather being chiefly used for gloves. It is distinguished by its strength, suppleness, 
and bright colour. 


II. Tawing. 

Tawi whitfLeather ? 11 of This mode of preparing leather is based upon the peculiar 

action of the salts of alumina upon skins, not hides generally. 

Four modifications of tawing are known, viz.:—i. Common tawing. This 
operation extends only to thin skins, such as sheep and goat skin, &c., which are 
treated only with alum and common salt without the application of oil. 2. Hunga¬ 
rian tawing process. Heavier hides not treated with lime are tawed and next 
chamoised. Klemm’s method of preparing fatty leather is somewhat similar to this 
treatment. 3. The French or Erlanger tawing method, by which the skins are 
prepared for glove-leather. 4. Tawing by the aid of insoluble soaps, according to 
Knapp’s suggestion. 

common Tawing. i. The tawer obtains sheep skin, or occasionally goat skin, either 
with the wool off or “ in the wool,” as the term runs, in the latter case greater care 
being required, because the value of the wool, which, by careful working may be 
obtained in good condition, refunds a considerable portion of the expense of the 
operation by its sale. The various operations of tawing are in a certain measure 
similar to those of tanning. 

The steeping and planing is carried on as in the tanning process. The workman 
places ten skins on the planing-tree, and dresses each skin with the dressing-knife on 
the hair as well as on the flesh side; next the wool or hair is shaved off after the skins 
have been first treated with the lime; but when “ in the wool ” the skins are cleansed 
with thin lime-water, which is laid on the flesh side of the skin by a brush made of 
cow’s-hair, so that the wool is not brought into contact with lime. The wool is 
removed, not by a planing-iron, but by means of a piece of wood somewhat sharpened. 
The wool having been removed, the skins are brushed over with a mixture of equal 
parts of lime and sifted ashes ; next the head and leg strips of the skin areturne d 
inside. Each skin is then folded together and beaten, in order to prevent the wool 
being touched by the lime. The skins are left in this condition for eight to ten days 
until the wool is loosened. The skins are next thoroughly washed on the flesh side as 
well as on the wool side in order to remove the lime and dirt; this having been 
done the -wool is partly pulled off by the hands, partly removed by a blunt tool. 
The skins thus deprived of wool are placed in the lime-pit and further treated as 
just described. In order to remove the paste adhering to the skins they are, on 
being removed, placed in a tank, where, owing to the quantity of animal matter 
dissolved in the water, a fermentation has arisen accompanied by an evolution 
of ammonia. By the action of this alltali a large portion of the fatty matter con¬ 
tained in the skins is removed. After being taken from the lime-pit the skins are 
placed on the dressers block, and some parts, such as the ears, skin of tail, portion 
of top part of chest, cut off and thrown aside for the glue-boiler. The skins are put 
over night to soak in water, and then again placed on the dressing-block in order to 
be planed with a blunt iron on both sides of the skin; this operation is repeated 
after the skins have been placed in a tank containing water, and while there 
thoroughly beaten with a heavy wooden “ possing-stick ” in order to remove lime. 
In the subsequent planing the lime and lime-soap are forced out, and any wool that 


TANNING. 


523 


has remained shaved off. In order to dissolve the last traces of lime the skins are 
placed in an acid-tank containing bran and water, in which by fermentation lactic 
and acetic acid have been formed. These acids convert the lime of the skins into 
soluble salts, while the process causes the swelling of the skins, which thus become 
better adapted to absorb the tanning materials. The skins remain in the sour-tank 
for two to three days. The tanning material consists for 1 dicker (= 10 skins) of 
an alum ley, containing 075 kilo, of alum, 030 kilo, of common salt dissolved in 
22*5 litres of boiling water. 1 litre of this liquid is poured into a trough, and 
having become tepid, each skin is separately thoroughly washed with and soaked in 
it, and then put aside without being wrung out, the skins being placed one upon the 
other so as to form a heap. After lying thus for two or three days, the skins are 
wrung out and hung up to dry slowly by exposure to air. 

As regards the theory of the action of the alum ley in the tawing operation, it was 
formerly believed that only the chloride of aluminium—formed by double decompo- 
• sition between the constituents of the common salt and the sulphate of alumina of 
the alum (the alkaline sulphates being considered useless)—was active, and that a 
basic chloride of aluminium (aluminium oxychloride) combined with the skin, 
there being left in solution hydrochlorate of alumina. It was also known that 
acetate of alumina, if used instead of alum ley, was quite as active and yielded excel¬ 
lent results. The experiments made by Dr. Knapp, sen., with alum, acetate of 
alumina, and chloride of aluminium, have proved that no decomposition ensues 
when the aluminium salt is taken up by the skin, the quantity taken up being for the 
undermentioned salts as follows :— 

Of alum . 8 5 per cent 

Of sulphate of alumina . 27 9 „ „ 

Of chloride of aluminium. 27'3 „ „ 

Of acetate of alumina. 23*3 „ „ 

The alumina salts do not, however, combine with skin under all conditions in the 
same quantity as just mentioned, as experience proves that the skins absorb more 
when placed in concentrated than when in dilute solutions. As regards the part 
played by the common salt in the preparation of the alum ley, the salt is not there 
simply to bring about the conversion of the alumina sulphate into chloride of 
aluminium (recent experiments made by Knapp in 1866 have proved that by 
employing 1 atom of potash alum and 3 atoms of common salt = 37 per cent, no 
mutual decomposition ensues), but the salt is in this process active by itself, partly 
aiding dialytically the action of the alum, partly owing to its property—possessed 
also by alcohol—of withdrawing from animal tissues the water they contain suffi¬ 
ciently to prevent the fibres to become glued together by the drying of the substance, 
thus promoting the formation of leather. The dry and tawed skins will be found to 
have become shrunken and stiff, having lost much of their suppleness and flexibility. 
In order to remedy these defects the skins previously damped with water are sub¬ 
mitted to a mechanical operation, being placed on the convex side of a curved iron, 
and stretched by being drawm between this fixed iron and a movable steel plate, 
which is fitted closely upon the other. After having been thus softened, the skins 
are stretched on a frame for some time to become dry. When dry they are ready for 
sale, the leather thus obtained being largely used under the name of white-skins for 
the lining of boots and shoes. 


524 


CHEMICAL TECHNOLOGY. 


Hungarian Tawing Process. 2. This process is distinguished from that just described, 
inasmuch as the heavy hides of oxen, buffaloes, cows, horses, &c., are made into 
leather for saddlery and other purposes, while sometimes also the skins of wild boars 
and of other animals are thus tawed for making flail strings. The raw hides are first 
soaked in water to remove blood and impurities. Next the hair is shaved off by 
means of a sharp knife. This operation performed, the hides are put into an alum 
ley, which for a hide weighing 25 kilos., consists of 3 kilos, of alum, 3 of common salt, 
and 20 litres of hot water. This liquor when tepid is poured into an elliptical tub 
in which the hide is placed. 

One of the workmen then jumps into the tub and by moving the hide about with 
his feet soaks it thoroughly with the liquor, in which it is then left for at least eight 
days, the operation of treading with the feet being repeated. The hide is now taken 
from the tub and hung up to dry, and when dry is stretched and “fatted” in by 
the following method:—The hide is warmed by being held over a charcoal fire, and 
when warm is rubbed on the hair as well as on the flesh side with molten tallow, of 
which some 3 kilos, are used for every hide. When thirty hides have been thus 
treated, they are one by one again held and moved to and fro over the fire, and next 
hung up in the open air to dry. The tallow partly combines with the hide. 

The hides thus prepared are converted into a leather of excellent quality, especially 
suited for the harness of horses and saddlery work of a more common kind, in 
which, as in that used for artillery horses, great strength is required. This leather 
is cheap on account of its being prepared in a short time. 

Glove Leather. 3. The so-called Erlanger, or French tawing process, is employed 
only for the production of the glace, or kid leather, used for making gloves and ball¬ 
room shoes. The hair side of the skins intended to be converted into this leather 
is left unchanged, while as regards wash-leather gloves which are treated (tanned) 
with fish oil the hair side is cut off. The skins intended to be converted into kid 
leather are treated with extraordinary care, and thus acquire in a very high 
degree all the good quality of alum-tanned (or rather tawed) leather. As these 
skins are often intended to remain white or are dyed with delicate colours, the 
greatest care is taken to prevent any injury, as, for instance, contact with oak wood 
or with iron while wet. 

Two kinds of skins are employed for conversion into the better varieties of 
kid leather; one of these, the more expensive, being the skins of young goats, 
fed solely with milk, the other being lamb skin. Each of these skins yields on 
an average 2 pairs of gloves. The leather of which ladies’ ball-room shoes are 
made is obtained from the hides of young calves (so-called calf-kid). The preli¬ 
minary operations of preparing this leather are exactly similar to those already 
described for the ordinary white . leather; but the tawing operations are quite 
different, the skins being put into a peculiar mixture, by which they are not only 
tawed, but simultaneously impregnated with a sufficient quantity of oil to render 
them soft and give suppleness. The mixture consists of a paste composed of wlieaten 
flour, yolks of eggs, alum, common salt, and water. The flour by the gluten it con¬ 
tains aids the absorption of the alumina compound, and thus assists the real tawing. 
The starch does not enter into the composition of the skins, while the yolk of 
eggs acts by the oil it naturally contains in the state of emulsion, this oil giving to 
the kid leather that suppleness and softness which is so much esteemed in gloves. It 
appears that emulsions made with almond oil (the so-called sweet oil of almonds—a 


TANNING . 


525 

fixed oil), olive oil, fish oil, and even paraffin, may be advantageously substituted foi 
yolk of eggs. The skins are thoroughly soaked and kneaded in this mixture, tc 
which, in France, there is sometimes added 2 to 3 per cent of carbolic acid for the 
purpose of preventing the too strong heating of the skins when impregnated with 
the mixture and packed in heaps. The skins are next stretched by hand and dried 
as rapidly as possibly by exposure to air. Having been damped, a dozen of the skins 
are placed between linen cloths and trodden upon to render them soft. After this 
they are, one by one, planed, dried, and again planed. Either by rubbing with a 
heavy polished glass disc or by the appreteur, simultaneously with the application of 
some white of egg, or a solution of gum, or of fine soap, a gloss is given to the skins, * 
the hair side of which is the right side or dyed side. The dyes are applied either by 
immersion or by brushing over the leather; the latter, or English method of dyeing 
skins, is more ordinarily practised. 

According to Knapp’s researches very good white kid leather is obtained by tawing 
the epidermis (bloss) from lamb or goat skins in a saturated solution of stearic acid 
in alcohol. The leather thus obtained is very soft, has a whiter colour than ordinary 
glace leather, and a beautiful gloss. 

Koapp's Leather. 4. The preparation of leather with the aid of insoluble soaps, 
introduced by Knapp, would appear to have become of some importance. The pro¬ 
perty possessed by oxide of iron of acting as a tanning material has been known for 
a long time, and in 1855 Mr. Belford took out a patent in this country for a mineral 
tan method, in which oxide of iron was used; but good leather did not result. 
The hides do not become really tanned by being immersed in solutions of such 
metallic salts, as those of the protoxide and peroxide of iron, oxides of zinc 
and chromium : for though the acidity of these solutions is reduced to a minimum 
without producing a permanent precipitate, and thereby the deleterious action of the 
acid upon the fibres of the hides decreased, and though a certain combination of the 
oxide and fibres takes place, no real leather is formed because the substance 
when finished is not fitted for contact with water, for then the so-called tanning 
is washed out. Knapp’s process also is not really a tanning but a tawing operation, 
by which the skins are alternately immersed in a solution containing 3 to 5 per cent 
of soft soap, and then in a saline solution of oxide of iron, or of chromium, 
containing 5 per cent of the salt, from which. an insoluble metallic soap is precipi¬ 
tated and impregnated with the fibres. After this operation has been several times 
repeated the hides or skins are washed in water and dried. Although the exterior 
colour of good sound leather may be imitated, the real qualities of leather are 
wanting. Knapp’s process is not in use or is so entirely modified by substituting 
alum for metallic oxides that the skins are tawed by a combination of the preceding 
tawing processes and the oil-tawing process now to be described. 


III. Samian or Oil-Tailing Process. 

Samian Taking Process. By this name is understood a peculiar process by which the 
skins and hides of various animals, such as harts, deer, sheep, calves, oxen (for the 
white leather for military use as belts, &c.), are converted into so-called oil- or wash- 
leather. The tanning material is oil, fat, tallow, or fish oil, to which recently there 
has been added 4 to 7 per cent of carbolic acid. The leather thus obtained is 


526 


CHEMICAL TECHNOLOGY. 


chiefly used for making military breeches, socks, vests, gloves, braces, belts, surgical 
applications, and not in small quantity for washing glass and porcelain, owing 
to its softness. On this account wash-leather is also largely used by gold and silver¬ 
smiths for polishing trinkets with rouge (very carefully prepared oxide of iron). The 
upper or exterior layer of the corium, which owing to its greater compactness does 
not possess the ductility and suppleness of the lower or interior layer, is in the 
skins intended to be converted into wash-leather entirely cut away, so that no hair 
and flesh side are taken into consideration. The cutting away of this layer greatly 
promotes the absorption of the oil, which by the joint action of air and heat yields a 
'product which is a dry compound of fibre and oil, in which the latter physically has 
disappeared, inasmuch as the leather is not impervious to water. Wash-leather 
differs in this respect from oil or fat leather; still, on immersion in water, the skin does 
not glue together and shrink. Thin skins, such as those of goats and lambs, are 
not deprived of their hair side, because it would render them too thin for use. 

The skins intended to be made into wash-leather are, as regards the first stage of 
the operation, treated exactly as described for the skins treated with alum, the only 
difference being that the hair is removed together with the hair side portion of the 
skins, which are next placed in a bran bath in order to remove the lime. After this 
the skins are stretched and conveyed to the fulling machine in order to become 
saturated with oil, for which purpose the skins are first laid on a table or bench and 
are rubbed with oil, the hair side being placed uppermost. This having been done 
they are made into clouts and placed under the stampers of a machine so as to 
thoroughly impregnate them with oil. From time to time the skins are taken from 
the trough and exposed to the air, then again rubbed with oil and put under the 
stampers until enough oil has been absorbed. By the repeated exposure to air 
the skins become dry, and oil (fish oil is chiefly used) absorbed ; the exposure to air 
is continued until the surface of the skins appears quite dry. When the skins have 
an odour somewhat similar to that of horse-radish, and have lost their fleshy odour, 
they have absorbed a sufficient quantity of oil, while a portion of the oil has been 
somewhat changed and has entered into combination with the fibre, another portion 
only mechanically adhering to the pores of the skins. The next operation therefore 
aims at rendering the process of the combination of the oil with the skins more 
rapid by bringing about a fermentation attended with an elevation of temperature; 
this is effected by placing the skins in a warm room, heaping them together, and 
covering them with canvas to keep in the heat which is generated, care being taken 
to air the heap from time to time in order to prevent overheating and consequent 
deterioration of the skins. This operation of airing the skins is repeated until by 
the spontaneous heating they have acquired a yellow colour and the workmen 
know by experience that the oxidation of the oil is finished. A portion of the oil 
(estimated at about 50 per cent of the quantity originally employed) is left in the skins 
in uncombined state, and is removed by washing with a tepid solution of potash. 
From this liquor there separates on being left at rest a portion of fat termed clegras, 
and which, as already mentioned, is employed for the dressing of tanned hides. 
The skins having been thus deprived of the excess of oil are wrung out, dried, and next 
dressed, in order to restore to them their softness and suppleness partly lost in the 
drying. Cordovan or Turkey leather, is oil-tawed without the hair side having been 
first removed, while the flesh side is blackened in the usual way. This kind of 
leather is chiefly used for ladies’ boots and shoes. According to Knapp, skins from 


TANNING. 


527 


which the hair has been first removed may he tawed by treating them alternately 
with a solution of soap and dilute acids, so that the fatty acids are precipitated into 
the fibre. After the tawing the skins thus treated should be thoroughly washed 
in water to remove all acid. As regards the constitution of the leather, commonly 
known as wash-leather, tawed with oil, nothing is definitely known, but it would 
appear that this process of tawing has some analogy to the process of imparting oil 
to calico intended for Turkey-red dyeing. 

parchment. The substance known as parchment is not really leather, because its 
fibres are neither tanned nor tawed, as proved by the fact that boiling water readily 
converts parchment into a superior kind of glue similar to isinglass, of course too 
expensive for joiners’ use. Parchment is essentially the well-cleansed and carefully 
dried skins of hares, rabbits, and especially of calves and sheep. 

Ordinary parchment is prepared from sheep-skins, but the variety known as 
vellum, Velin or Parcliement vierge, is far finer, and is made from the skins of young 
calves, goats, and stillborn lambs. According to the use intended to be made 
of parchment, so is its preparation modified. The skins are first soaked in water 
and then placed in the lime-pits. Sheep skins are cleansed by working with cream 
of lime in order to preserve the wool. When the hair has been removed the skins 
are washed, being placed on the dresser’s block, and usually also planed with 
a sharp knife to remove the superfluous fleshy parts. This having been done, each 
skin is separately stretched in a frame, in a manner very similar to that in use for so- 
called Berlin-wool work, the skins being held in position by means of strings, and 
dried by exposure in the open air. Parchment intended for drum skins (from 
calves’ skins), for kettledrums (from asses’ skins), does not require any further 
operation. If intended for bookbinding the parchment is treated as described, 
but after drying it is planed with a tool the cutting edge of which is somewhat 
bent in order to impart a rough surface, whereby the parchment is rendered capable 
of being written on and dyed. If the parchment be intended—as it used fre¬ 
quently to be formerly before the invention of metallic paper—for memoranda, 
written with lead-pencils, to be wiped out if desired with a wet sponge, it is 
after planing painted over with a thin white-lead paint, for which a mixture of glue- 
water with baryta- or zinc-white is often substituted. The vellum of this country is 
generally obtained from sheep skins, which are split into two sheets by means of 
cutting-tools. Parchment after having been dried on the frames is dusted over with 
chalk and rubbed with pumice-stone. The sieves used in powder mills for granula¬ 
ting the powder are made of parchment obtained from hogs’ skins. 

shagreen. Genuine Oriental shagreen (saghir, sagri, sagre), is a variety of tawed 
parchment, one side of which is covered with small hard grains. This material 
is manufactured in Persia, at Astrakan, in Turkey, and in Roumania, from certain 
portions of the skins and hides of wild asses, horses, and other animals. The hides 
are soaked in water until the epidermis can be removed easily together with the 
hairs by the aid of a dressing-knife ; next the hides are again placed in water so ar*- 
to swell the material sufficiently to admit of cleansing it, and cutting away on botl 
flesh and hair side all superfluous material, so as to leave only the corium, which then 
has the appearance of a fresh bladder. In order to produce on skins thus prepared 
a grained surface, they are put into frames, as described under Parchment, while 
on the hair side, allabuta, the hard black seed of the Chenopodium album is 
stamped in, either by the feet or forced in by pressure. When the skins are dry they 


CHEMICAL TECHNOLOGY. 


528 

are removed from the frame, the seed shaken off, and the skins thoroughly planed 
with a sharp dressing-knife, then put again into water, tawed, and finally dyed. The 
tawing is effected by the aid either of alum or of oak bark. The dye of shagreen is 
generally green, and is due to salts of copper. After dyeing the skins are soaked in 
mutton tallow. 

Fish skin, or fish chagrin, is obtained from various kinds of sharks (Squalus 
canicula, S. catulus, S. cent rind) and other fishes of the same class. The skin of 
these animals is not covered with scales, but with more or less projecting hard 
points. The skins having been removed from the fish are stretched in frames and 
simply dried, being then sent to the market. Formerly sharks’ skin was in some 
countries used by joiners instead of sand- and glass-paper for preparing wood. The 
skins deprived of the projections are dyed and used for covering small boxes, tubes 
of small telescopes, &c. 


Glue-Boiling. 

General Observations. The organisms of all animals, but more especially of the higher 
classes, contain tissues which are insoluble in cold as well as in hot water, but 
which by continued boiling become dissolved, and yield on evaporation of the solu¬ 
tion a glutinous gelatinising mass, which, by further drying, exhibits, according to the 
degree of purity of the material, a more or less transparent and brittle substance, which 
in pure state is devoid of colour as well as of smell, becoming swollen in cold water and 
dissolved by boiling in that liquid. This substance, i.e., the product of the conver¬ 
sion of the so-called glue- or gelatine-yielding tissues, is what is known in the trade 
as glue, and largely Used by joiners, carpenters, tbc., for joining wood, also for 
sizing paper, for clarifying various liquids, beer and wine for instance, and as a 
cement. Among the glue-yielding tissues the following are the most important:— 
Cellular tissue, the corium, tendons or sinews, the middle membrane of the vasa 
lymphatica and veins, the osseine or organic matter of bones, hartshorn, cartilage, 
the bladders of many lands of fish, &c. Chemically we distinguish between glutin, 
that is to say, glue derived from skins, bones, &c., and chondrin, which has been 
obtained from cartilage. In a technical point of view this distinction is hardly 
required, as the cartilaginous matter is as much as possible selected from other glue¬ 
making materials, because experience has shown that glutin has a much greater 
power of adhesion than chondrin. The latter, however, is largely used as size in 
this country. 

As already observed, the glue- or gelatine-yielding tissues yield on being dissolved 
a gelatinising mass, the aqueous solution of which does not, however, possess to any 
great extent a glueing property, which is only imparted to the gelatine by a process 
of drying. In considering, therefore, the process of glue-boiling, we have to distin¬ 
guish the animal matter capable of yielding glue, the gelatinous mass obtained 
therefrom, and the glue obtained by drying the latter. The temperature required for 
obtaining gelatine differs according to the different animal tissues employed; the 
consistency of the gelatine obtained from equally strong solutions varies with the age 
of the tissues operated upon. 

Glue readily dissolves by boiling in water, forming on cooling a gelatinous mass, 
even if the quantity of glue is only 1 per cent. Repeated boiling and cooling a 
glue solution causes it to lose the property of gelatinising, and the same effect is pro¬ 
duced by acetic and dilute nitric acids. Solutions of alum precipitate glue solutions 


GLUE. 


529 


only after the addition of potash or soda, the precipitate consisting of glue mixed 
with basic sulphate of alumina. Glue enters with tannic acid into a combination of 
constant composition; hence glue or gelatine may be used for the estimation of 
tannin in vegetable matter. 

Three different kinds of glue are distinguished by the manufacturers, viz.:— 

a. So-called skin-glue, or leather-glue, prepared from refuse hides, skins, 

tendons, &c. 

b. The glue obtained from bones. 

0. The glue obtained from fish-bladders, termed isinglass. 

Very recently glue from vegetable gluten and so-called albumen glue have been 
prepared. 

Leather Glue. This substance is prepared from a large variety of animal refuse, the 
chief sources being the following:—Refuse from tan yards, tawing and leather¬ 
dressing works, old gloves, rabbit and hare skins (the hair having been used by liat- 
makers) , r skins of cats and dogs, ox feet, parchment cuttings, surons (skins which have 
served the purpose of carrying drugs, especially from America), sinews, guts, 
leather cuttings (leather tanned with oak bark cannot be readily converted into glue). 
The glue-boiler on an average obtains from the various materials about 25 per cent 
of glue, preference being given to the refuse of tawing operations and kid leather 
making, because these materials are ready for boiling without requiring any previous 
treatment. Glue-boiling involves the following operations:— 

1. Treating the glue-yielding materials with lime. 

2. Boiling these materials. 

3. Forming the gelatine. 

4. Drying the gelatine so as to form glue. 

Treating with Lime. I. The aim of this operation is the cleansing of the refuse and the 
prevention of putrefaction. It is effected by placing the cuttings in tanks or lime-pits 
and pouring in a thin milk of lime. The materials, while the milk of lime is 
frequently renewed, are thoroughly mixed with the lime-liquid and left for fifteen to 
twenty days in the pits. By the action of the lime any blood and flesh is dissolved 
and the fatty matter saponified. In order to remove the excess of lime, the 
materials are placed either in nets or in willow-baskets, and these are immersed in a 
brook or river, where a continuous stream of fresh water removes the greater part of 
the lime in a few days. The washed material is next exposed in the yard to the 
action of the air in order that it may become dry, as well as form a carbonate of 
any lime still present in the materials. "When the materials are dry they are packed 
and sent off to the glue-boilers, who, previous to proceeding with the boiling opera¬ 
tion, macerate the materials again in a weak milk of lime, the maceration being 
followed by washing. 

Fleck states that a weak alkaline ley (5 kilos, of calcined soda and 7*5 kilos, of 
quick-lime to 750 to 1000 kilos, of glue-yielding material) is preferable to the use of 
milk of lime. When the glue-boiling and tanning operations are executed on the 
same premises, the lime-treated glue materials are put for a few hours into old oak 
bark liquor, the acids (lactic, butyric, and propionic acids) of which remove the lime, 
while the animal matter is at the same time superficially tanned. This glue tannate 
rises during the boiling as scum to the surface and assists in rendering the glue 
liquor clear. According to Dullo, the Cologne glue—a very pale and strong glue 
35 




CHEMICAL TECHNOLOGY. 


is obtained from offal, which, after liming, has been treated with a solution of 
chloride of lime (hypochlorite of lime), and thereby bleached. 

Boiling the Materials. This operation is carried on either in the ordinary manner of 
boiling anything with water, or by so-called fractioned boiling, or finally by the 
application of steam. As the conversion of the glue-yielding materials into glue 
takes place slowly and gradually under the influence of the boiling water, it is clear 
that the method of boiling cannot be without influence upon the glue ultimately 
produced. The first portions of gelatine which are formed remain in contact with 
a boiling-hot mass, and are thereby further changed so as to lose the capability of 
gelatinising, while the glue at last obtained exhibits a dark colour and is often not so 
strong, although it is generally believed that deep-coloured glue is of a better 
quality. A rational mode of glue-boiling would involve the gradual removal of the 
solution obtained, while of course fresh water would have to be supplied to replace 
the liquor drawn off. The older method of glue-boiling consists in simply placing 
the materials with water in a cauldron, care being taken to prevent burning by placing 
the materials on a stout wire gauze or tying them in a net and suspending it in the 
boiling liquid. Soft water yields a better result than hard. Gradually the materials 
become dissolved, and the scum which is formed is taken from the surface with a 
large ladle. The refuse of glue of former operations is added to the boiling liquid, 
and the operation continued until the liquid is of the required strength, which is 
tested by pouring into a broken egg-shell a small portion of the liquor, and by 
placing the partly-filled shell in ice-cold water. If the solution gelatinises after a 
while, forming a hard and rather stiff gelatine, the liquor is run off by means of a 
tap, filtered through a layer of straw placed in a basket, and conveyed to a wooden 
lead-lined cistern, externally covered with mats or straw, or some bad conductor of 
heat. In some works the liquor is decanted into a deep but narrow boiler, the 
furnace of which is so arranged as to impart heat to the top of the vessel only. This 
vessel, as well as the cistern, is heated previously to the liquor being poured in. The 
liquor is clarified by stirring it with a small quantity of very finely-pulverised alum, 
075 to 1-5 per mille of the liquid. After this the liquid is left to stand all 
night. The alum precipitates any lime remaining as sulphate of lime, and also some 
organic matter which renders the liquid turbid. Alum, though it prevents the 
putrefaction of the glue while drying, impairs its strength. The lime might better 
be precipitated by oxalic acid, and the organic matter removed by adding to the 
boiling mass some astringent matter, such as oak bark decoction or hops, so that 
during the boiling the organic impurities could be taken away as scum. 

Fractioned Boiling. By this operation only a comparatively small quantity of water is 
added to the animal matter intended to be converted into glue. When the water is 
fairly boiling the cauldron is covered with a well-fitting lid, and the steam being kept 
in as much as possible, is allowed to act upon the materials so as to convert them 
into glue. When, after continued boiling for about two hours, the water has taken 
up sufficient gelatine, the liquor is run off and fresh water poured on the materials. 
This operation is repeated until the decoction no longer gelatinises, the last liquor 
being kept for use instead of water for a following operation. The liquors thus 
obtained, excepting the last, are either mixed or each is treated separately. The glue 
yielded by the first decoction is stronger than that yielded by the subsequent liquors. 
By this method of boiling the saturated liquor does not remain exposed to the action 
of heat and water too long, and consequently a better article is produced. In some 


GLUE. 


531 


instances the materials intended to be converted into glue are boiled in a vessel 
similar in construction to those in use in bleaching-works and in paper-mills, 
arranged in the following manner. At some distance from the bottom a perforated false 
bottom is placed, in the centre of which is fixed a wide tube which reaches to about two- 
thirds of the height of the cauldron. The materials intended to be converted into glue 
are placed upon the perforated bottom and water under it; as soon as the water boils, 
the steam produced, not being able to escape rapidly and readily through the materials, 
exerts a pressure upon the liquid and forces it through the tube, the consequence being 
that a constant stream of boiling liquid falls upon the glue materials, which are rapidly 
dissolved. 

A more rational mode of conducting this operation consists in employing high- 
pressure steam admitted into the mass of the animal materials to be converted into 
glue. In this manner a very concentrated solution of glue is obtained in a short 
time. In England steam is generally employed, but on the continent its use is the 
exception. It has been said that it is advantageous to allow the animal offal intended 
for glue to become somewhat decomposed and then to disinfect it with chlorine 
and sulphurous acid before boiling it for glue, because by this mode of treatment a 
brighter glue is obtained. We are unable to say whether this opinion is correct. 

Moulding. As soon as the glue solution has, by standing in the tanks into which it had 
been transferred from the boilers, become quite clear and somewhat cooled, the 
liquid is poured into moulds, and when solidified the jelly is cut into cakes of the 
shape and size met with in the trade. 

The moulds, into which the glue solution is poured through a strainer made of 
metal gauze, are of wood, and generally a little wider at the top than at the bottom, 
so as to admit of an easy removal of the solid material. At the bottom of the moulds 
a series of grooves are cut at such a distance from each other as agrees with the size 
of the intended glue-cakes. Before the liquid is poured into the moulds, these are 
thoroughly washed, and either allowed to remain damp, or if dried are oiled, so as to 
prevent the solidifying gelatine adhering to the wood. Recently moulds made of 
sheet-iron and zinc have been introduced. The moulds are filled with the lukewarm 
glue solution, and when the glue is sufficiently hard it is gently loosened from the 
sides with a sharp tool, and the mould having been turned over on a wooden or stone 
table, previously damped, is lifted off the block of gelatine, which is next cut into 
cakes or slabs. The cutting tool is simply a piano-wire, or more frequently a series 
of these stretched in a frame at sufficient distance from each other to make the 
cakes of the desired thickness, the frame being placed on small wheels so as to be 
easily moved. Glue is met with in the trade as a gelatinous mass, or is sold in 
casks under the name of size. It is said that the process of drying impairs the good 
qualities of the glue. 

Drying the Glue. This operation is performed by placing the gelatine cakes on nets 
made of twine stretched in frames and exposed in a dry airy place to the action of 
the sun. The drying is one of the most difficult operations of the glue-making 
process, because the temperature of the air and its hygrometric condition exert a 
great influence on the product, especially during the first few days. The glue will 
not bear a temperature above 20°, because at a higher temperature it becomes again 
fluid, and as a matter of course flows through the meshes of the net and adheres to 
the twine so strongly as to require the nets to be put into hot water for the removal 
of the mass. Too dry air causes an irregularity in the drying of the glue, and as 


532 


CHEMICAL TECHNOLOGY. 


a consequence the cakes become bent and cracked; while frost causes disintegration, 
so as to necessitate a re-melting of the glue; hence it follows that drying in the 
open air can only be effected in the spring and autumn. Although the glue-boilers 
have tried to dry glue by artificial heat, this plan has not been generally introduced owing 
to the fact that a slight excess of heat causes the melting of the gelatine, the more 
readily when ventilation is neglected. Drying-rooms, as recently constructed are large¬ 
sized sheds fitted with the required frame-work for receiving the gelatine cakes, and 
heated by steam-pipes placed on the floor near the latter. The Avails are provided 
with openings Avhich can be closed by means of valves, Avhile there are ventilators in 
the roof arranged to obtain a proper circulation of air. As the gelatine placed 
nearest to the floor of the room becomes most quickly dry, it is, AA r ith the frames 
upon which it placed, removed after eighteen to twenty-four hours to a higher part of 
the drying-room, which is not heated at all if the outer air has a temperature of 
15° to 20°. The drying-shed, or room, is by preference built so-as to face the north. 
When the glue has been thus dried as much as possible, it is generally quickly dried 
in a stove in order to impart hardness. It is next polished by being immersed in 
hot water, and cleaned Avith a brush, and again dried. 

Glue from Bones. The organic matter contained in bones, forming nearly one-tliird 
part (32’i7 per cent) of their weight, consists of a material which, after the bones have 
been treated with hydrochloric acid, is very readily converted by the action of high- 
pressure steam into glue. The preparation of glue from bones by the action of 
hydrochloric acid is the usual mode of proceeding, and the operation is advantage¬ 
ously combined Avith the making of sal-ammoniac and phosphorus. 

The preparation of glue from bones includes the folloAving operations :—I. Boiling 
out the Grease. —The bones are put into AA r ater and boiled in a cauldron, the fat 
floating to the surface. Frequently in order to save fuel the bones are put into an iron 
wire basket, which is removed after the boiling has been continued for some time, the 
bones throAvn out and fresh ones put in, the boiling being continued until a thick 
gelatinous liquor is obtained. The fat or grease is removed from the surface of the 
liquid by means of ladles. The gelatinous mass obtained by this process is either 
used as a manure or is given to cattle as fodder. In some works bones have been 
exhausted Avitli sulphide of carbon for the purpose of extracting the grease. 
II. Treating the Bones with Hydrochloric Acid. —The bones having been drained are 
placed in baskets, and Avith these are immersed in tanks to more than half their height, 
the tanks being filled Avith hydrochloric acid at y° B. (= 1-05 sp. gr. = io'6 per cent 
C 1 H); 10 kilos, of bones require 40 litres af acid. The bones are kept in this 
liquor until they become quite soft and transparent. They are next drained and then 
Avith the baskets immersed in a stream or brook with a good supply of running 
water to wash out the greater portion of the acid, Avliicli is fully neutralised by 
placing the bones in lime-Avater, again followed by washing with fresh water, 
the bones being then ready for boiling. Gerland has suggested the use of 
sulphurous instead of hydrochloric acid. III. Conversion of the Organic Matter 
into Glue. —The cartilaginous substance having been either partly or completely 
dried is put into a cylindrical vessel containing a false perforated bottom, and 
between that and the real bottom a pipe or tube. To the top of the vessel a lid is 
fitted, provided Avith an opening for a steam-pipe leading from a small boiler. 
Shortly after the admission of the steam a concentrated glue solution begins to run 
off from the pipe at the bottom of the cylinder ; this solution is usually so concen- 


GLUE. 


533 


trated as to admit of being at once run into the moulds, and after having become 
solid is treated as before described. After a few hours a weak liquid makes 
its appearance, and as soon as this happens the cylindrical vessel is opened, the glue 
mass removed with the weak liquid to a copper and boiled, care being taken 
to stir the magma constantly. As soon as the glue is dissolved the liquor is poured 
into moulds. Glue obtained from bones exhibits a milky appearance due to the pre¬ 
sence of a small quantity of phosphate of lime retained in the substance. Some¬ 
times there is purposely added more or less baryta-white, zinc-white, white-lead, 
chalk, or pipe-clay. The glue obtained from bones is sold under the name of patent 
glue. 

Liquid Glue. When glue is dissolved in its own weight of water and a small quantity 
of nitric acid added to the solution, it loses the property of gelatinising, while the 
adhesive property of the glue is not impaired. Dumoulin prefers to dissolve i kilo, 
of Cologne glue in i litre of boiling water, and to add to the solution o z kilo, 
of nitric acid at 36 B. = 1*31 sp. gr. After the evolution of the nitrous acid fumes 
has subsided the fluid is cooled. A better liquid glue is obtained by dissolving good 
gelatine or glue of superior quality in strong vinegar and moderately strong acetic 
acid, to which one-fourth of its bulk of alcohol is added, and some pulverised alum, 
the solution being aided by a water-bath. The action of the acetic acid is the same 
as that of the nitric acid. According to Knaffl, a very excellent liquid glue is 
obtained by heating for some 10 to 12 hours upon a water-bath, a mixture of 3 parts 
of glue in 8 parts of water, to which are added 0'5 part of hydrochloric acid, and 
075 part of sulphate of zinc, the temperature of the mixture being kept below 
8o° to 85°. This kind of liquid glue keeps for a very long time and is largely used 
for joining wood, horn, and mother-of-pearl. This glue is employed by the makers 
of artificial pearls. 

Test for the Quality of Glue. Although the quality of glue is best ascertained by practical 
use, some of the physical qualities and the external appearance of glue may be 
mentioned as indicating a superior article. Glue of good quality should exhibit a 
bright brown or brown-yellow colour, should be free from specks, glossy, perfectly 
clear, brittle, and hard, should not become damp by exposure to air; when being 
bent it should snap or break sharply, the fracture presenting a glassy, shining 
appearance. When placed in cold water glue should not even after forty-eight 
hours in this fluid swell up and increase in bulk nor dissolve. A splintery fracture 
•of glue indicates that it has not been well boiled. The adhesive property of glue is 
often increased by adding certain pulverulent earthy substances. This addition is 
regularly the case with Russian glue. Among the substances employed are white- 
lead, sulphate of lead, zinc-white, baryta-white, and even chromate of lead. As 
different kinds of glue may agree in their external aspect and yet vary as regards 
their adhesive power, methods of testing glue have been proposed, some of which 
are based upon the chemical, others upon the physical, properties of this substance. 

I. Chemical Processes of Testing Glue.—Oi these we mention the following:— 
Graeger’s Method—Premising that the quality of a glue is dependent on the 
quantity of glutin contained, irrespective of the origin of the glue and its freedom 
from foreign substances, which might weaken its adhesive property, Graeger estimates 
the quantity of gluten by precipitating the glue solution with tannin, and by calcu¬ 
lating from the amount of tannate of gelatine obtained (the composition being taken 
in 100 parts at 4274 parts of gluten and 57^26 of tannin), the quantity of pure 


534 


CHEMICAL TECHNOLOGY. 


gluten contained in the glue. Pdsler-Beunat, while employing the same principle, 
prepares two normal fluids, one of which contains io grms. of puro tannic acid 
to the litre, while the other contains in i litre io grms. of pure isinglass and 
20 grms. of alum. As equal hulk of these fluids do not saturate each other, the 
author determines by- titration the relation between them, and dilutes the tannic acid 
solution with the requisite quantity of water. In order to test a glue the author dis¬ 
solves io grms. of the sample to he tested with 20 grms. of alum in a litre of water, 
heat being applied if necessary. Next 10 c.c. of the tannic acid solution are taken, 
to which an equal bulk (10 c.c.) of the glue solution is at once added, because one 
may be sure that this is not too much, as no sample of glue met with in commerce is 
as pure as isinglass. The vessel containing the mixed liquid being well shaken and 
the precipitate having settled, another c.c. of glue solution is added to the tannin 
solution, which is next filtered through a moistened cotton filter. If one drop of the 
glue solution still produces a precipitate in the clear filtrate another c.c. is added to 
the tannin solution, and then again filtered, these operations being repeated until the 
filtrate is no longer rendered turbid by the glue solution. 

These modes of testing glue give only an approximate value of the glue, as its 
precise chemical constitution is not known, and is, in all probability, complex ; while 
it has not been proved that the substance combined with tannin corresponds to the 
adhesive power of glue. Finally, it should be observed, that gelatine and glue, though 
both precipitated by the same quantity of tannin, are altogether different substances. 

II. Mechanical Modes of Testing Glue. —Schattenmann’s Method.—The glue to be 
tested is kept immersed for a considerable time in a large quantity of water at 15 0 ; the 
substance swells up, absorbing five to sixteen times its own weight of water. The more 
consistent and elastic glue is found to be in this state the greater its adhesive power. 

The larger the quantity of water 
absorbed the more economical will 
the glue be in use. According to 
Weidenbusch’s experiments, this 
method should be employed only 
with glue obtained from bones, as 
that obtained from animal offal does 
not behave similarly. Lipowitz has 
proposed the following method:— 
5 parts of glue are dissolved in 
such a quantity of water that the 
weight of the solution is equal to 
50 parts. This solution is kept for 
twelve hours at 18 0 in order to 
cause the solution to gelatinise. 
The gelatine obtained is placed in 
a glass vessel, Fig. 256. a is a 
piece of tinned iron through which 
the iron wire b moves easily. At the 
lower end of b is soldered a saucer¬ 
like piece of tinned iron, the convex 
side of which is turned downwards. The weight of the wire b and the convex 
piece soldered to it is 5 grms., while the funnel, c, put on the top of the wire 


Fig. 256. 



1 










































GLUE. 


535 


also weighs 5 grms. The funnel is of sufficient size to contain 50 grms. of small 
6hot. According to the consistency the greater weight will it require to force the 
gelatine down into the glass, and from the weight required the adhesiveness may 
be judged. Heinze has tried this haethod (1864), and the results of his experiments 
prove the correctness of Lipowitz’s proposition. 

Weidenbusch’s method is essentially that suggested by Karmarsch, and consists 
in testing the weight required to tear asunder two pieces of wood glued together 
with the sample of glue ; but it is evident that this plan is not satisfactory, because 
it is impossible to obtain wood always of the same quality, while the adhesiveness of 
good glue is greater than that of wood itself. Weidenbusch has evidently observed 
that the method is not reliable, for he has suggested the following plan:—Small 
sticks or rods are made of gypsum, are gently dried, first by heat and next over 
chloride of calcium until the rods do not lose weight. They are then saturated 
with solutions of samples of glue; the force required to break these rods after drying 
determines the strength of the glue, because the force required to break the gypsum 
is of a constant value. An apparatus has been contrived by the aid of which the 
weight required to tear asunder the dried gypsum rods may be ascertained; the 
average weight has been found to be 219 grms. The glue to be tested is dried 
at ioo°, put over night into cold water, next dissolved in hot water, the solution 
being so arranged as to contain one-tenth of glue. This solution is coloured with 
neutral indigo tincture in order to render it more easily discernible. The gypsum 
rods are left in the solution for a couple of minutes and then dried until the weight 
does not vary. When this obtains the rods are broken by the action of mercury, 
which is gradually admitted into the apparatus. 

isinglass. The substance met in commerce under the name of isinglass is, if 
genuine, the dried interior pulpous vesicular membrane of the air-bladder of certain 
kinds of fish belonging to the order of the cartilaginous ganoids, and more 
especially of the common sturgeon {Accipenser sturio); the huso, or grand sturgeon 
(A. sturio ) ; the A. Giildenstaedti, and A. stellatus. The bladders of these and of kin¬ 
dred species of fish plentifully met with in the Caspian Sea and the estuaries of the 
rivers running into it, are cut open, cleansed, stretched, and dried by exposure to sun¬ 
light, and when sufficiently dry to admit of being handled without fear of tearing the 
outer muscular membrane, which does not on being boiled yield any glue, is torn off, 
while the interior membrane is moulded in various ways (as in rings, lyre-shaped, or 
folded as leaves of paper), and bleached by sulphurous acid, then thoroughly dried 
by exposure to sunlight. 

According to the countries from .which it is sent into the trade isinglass is 
distinguished,—as Russian (the best kind being obtained from Astrakan); North 
American (from Gadus merlucius) ; East Indian (from Polynemusplebejus) , met with in 
leaves, also as small sacks, and in the entire bladder ; Hudson Bay isinglass (derived 
from sturgeons); Brazilian is probably obtained from various kinds of Silurus and 
Pimeladus. This isinglass occurs in hollow tubes, in lumps, and in discs. German 
Isinglass is prepared at Hamburg from the air-bladder of the common sturgeon. In 
Roumania and Servia the sldn and intestines (not the liver) of cartilaginous fishes 
are boiled into a stiff jelly, which, having been cut into thin slices, is dried and sent 
into the market as isinglass. As regards the use of this material we have, to 
distinguish between fish glue and isinglass. The former, if properly prepared, is not 
at all distinguishable from ordinary glue as obtained from bones or other animal 


536 


CHEMICAL TECHNOLOGY. 


refuse; but isinglass is not glue, and is only converted into it by boiling. It consists 
of fibres or threads, which when placed in water are somewhat dissolved, but 
retain their organised structure; this being especially of importance for the use 
of this substance in clarifying wine, beer, and similar fluids, as the fibres con¬ 
stitute as it were a close network, which readily takes up the turbidity produced by 
small particles. The presence of tannin in liquids which are intended to be clari¬ 
fied by the use of isinglass is advantageous, inasmuch as it promotes the contraction 
of the isinglass fibres, whereby the suspended particles present in the fluid to be 
clarified are retained ; so that in truth the clarifying by isinglass is a kind of filtration, 
which cannot be performed either by glue or by a hot saturated solution of isinglass. 
For isinglass may, in all other instances, such as the dressing of woven silk fabrics, 
the preparation of so-called court-plaster and cements, be substituted good gelatine. 
Under the name of Iclityocolle Frangaise, Roll art some years ago introduced a substi¬ 
tute for isinglass, a compound said to be obtained from fibrin of blood and tannin. 

Substitutes for Glue, and New Recently three substitutes for glue have been introduced, 

Preparations obtained . . 

from Glue. viz. i—i. Gluten glue {colle gluten). 2. Albumen glue ( colie 

vegetale ou albuminoide. 3. Caseine glue (colle caseine ). The first is a mixture 
of gluten and fermented flour. It is a very sour mixture, endowed with but 
very slight adhesive power. Albumen glue is partially decayed gluten, the 
substance largely obtained in the manufacture of starch from wheaten flour 
thoroughly w T ashed with water, and then exposed to a temperature of 15 0 to 20°, at 
which it begins to ferment and become partly fluid, or more correctly soft, so as to 
admit of being poured into moulds which are placed in a room heated to 25 0 or 30° 
for twenty-four to forty-eight hours. The surface having become dry enough 
to admit of the cakes being handled, they are taken from the moulds and further 
dried by being placed either on canvas or on wire gauze. After four to five days the 
cakes are quite dry and fit for being kept in a dry place for any length of time. A 
solution of this substance in twice its weight of water constitutes a normal solution, 
which may be diluted according to the use desired to be made of it. This kind of 
glue may be used for the following purposes:—Glueing w r ood, cementing glass, 
porcelain, earthenware, mother-of-pearl, for pasting leather, paper, and cardboard; it 
may further serve as weaver’s glue, and as dressing for silk and other woven 
fabrics; also for a mordant instead of albumen in dyeing and printing various* 
fabrics ; and lastly, for clarifying liquids. 

Caseine glue is prepared by dissolving caseine in a strong solution of borax. The 
thick fluid thus obtained has great adhesive powers and may be advantageously 
employed by joiners and bookbinders. What is known as elastic glue is a prepara¬ 
tion of glue and glycerine, by the addition of which glue may be rendered 
permanently elastic and soft. It is prepared in the following manner:—Glue is 
melted in water by the aid of a water-bath, into a very thick paste, to which 
glycerine is added in the same quantity by weight as that of the dry glue. The 
mixture is thoroughly stirred and then further heated in order to evaporate the 
excess of water. The mass is then cast on a marble slab, and after cooling, serves 
for the purpose of making printer’s inking rollers, elastic figures, galvano-plastie 
moulds, &c. 


PHOSPHORUS. 


537 


Manufacture of Phosphorus 

Genera! Properties. Phosphorus was discovered in 1669 by Brand, at Hamburg, and 
prepared by him from urine. In 1769, Gahn, a Swedish chemist, first prepared this 
element from bones; his mode of preparation being improved in 1771 by his 
celebrated countryman, Scheele. Since the introduction of phosphorus matches, its 
manufacture has become one of the most important technical operations. Phos¬ 
phorus occurs largely in the mineral kingdom as phosphoric acid, but for the manu¬ 
facture of phosphorus in sufficient quantity only in such minerals as apatite, phos¬ 
phorite, and staffelite. 

Phosphorite is found in various localities, as, for instance, near Diez, "Weilburg, 
and Amberg and Redwitz in Bavaria. Some of this phosphorite is very rich in 
phosphoric acid, a sample of that found near Diez having yielded on analysis (by 
Petersen, 1866), 37*78 per cent of phosphoric acid, corresponding to 16 06 per cent of 
phosphorus. 

Preparation of phosphorus. Bone-ash is now the only material used by phosphorus makers, 
as the commercial preparation of phosphorus has not succeeded by using either apatite 
and other varieties of pure phosphorite which contain about 18 6 per cent of phos¬ 
phorus—as well as sombrerite (a mineral met with on the American island of Som¬ 
brero) , consisting of phosphate and carbonate of lime, and imported into England for 
the manufacture of superphosphates ; or the Navassa guano, also imported from the 
United States, containing, according to Ulex’s researches, one-third of its weight of 
phosphoric acid; or phosphate of iron, as proposed by Minary and Soudray, 
by distilling that substance with previously well-ignited coke-powder. 

Bones, as used by the manufacturers, contain :— 

In dry state, but not ignited, from 11 to i2'o per cent of phosphorus. 

As bone-black „ 16 to i8 - o „ „ „ „ 

As bone-ash (white burnt bones) „ 20 to 25*5 „ „ „ „ 

The composition of bone-ash is exhibited by the following results of analysis :— 



1. 

2. 

Carbonate of lime . 

... 1007 

9-42 

Phosphate of magnesia. 

2*98 

2*15 

Tribasic phosphate of lime ... 

... 83*07 

84-39 

Fluoride of calcium. ... 

... 3-88 

405 


The bone-ash is decomposed by means of sulphuric acid, according to a plan first 
suggested by Nicolas and Pelletier:— 

a. Bone-ash, Ca 3 (P 0 4 ) 2 1 • lrl f Acid phosphate of lime, <JaH 4 (P 0 4 ) 2 

Sulphuric acid, 2H 2 S0 4 f ^ 1 Sulphate of lime, 2CaS0 4 . 

The acid phosphate of lime is heated with charcoal, and converted by loss of water 
into metaphosphate of lime:— 

b - 5 l a l i,P 0 J 2 —2H 2 0=Ca(P0 3 ) a . 

XI4 ) 

— -r ~ t 

Acid phosphate Metaphosphate 

of lime. of lime. 




I 



538 


CHEMICAL TECHNOLOGY. 


c. Metaphosphate of lime, 3Ca(P0 3 ) 2 ) • 
Charcoal, 10C f ^ 


The metaphosphate of lime yields, when ignited to white-heat with charcoal, two- 
thirds of its weight of phosphorus, while one-third remains in the residue: 

'Tribasic phosphate of lime, Ca 3 (P04) 2 
r y Acid * Carbonic oxide, 10CO 
^ (Phosphorus, 4P. 

The ordinary mode of preparing phosphorus includes the following operations:— 
In some instances the preparation of phosphorus is cotemporary with other 
businesses, viz., glue-boiling, the preparation of sal-ammoniac, yellow prussiate of 
potash, &c., but generally in England the phosphorus makers do not even burn the 
bones to ashes, but purchase bone-ash and occasionally apatite; this salt, however, 
is very difficult to treat with sulphuric acid, and is also objected to on account of its 
hardness, for it has to be ground to a very fine powder. English makers only carry 
out these four:— 


1. Burning the bones and grinding the bone-ash to powder. 

2. Decomposition of the bone-ash by sulphuric acid, and evaporation of the acid 

phosphate previously mixed with charcoal. 

3. The distillation of the phosphorus. 

4. The refining and preservation of the phosphorus. 

Bumin^otttieBones j The bones to be used for phosphorus malting are obtained 
either from bone-boilers or from the waste bone-black of sugar-refiners. The aim 
of the ignition of the bones is the complete destruction of the organic matter. The 
operation is conducted in a kiln very similar to those in use for burning lime. A 
layer of brushwood having been put at the bottom of the kiln, bones form the next 
stratum, and so on alternately. The wood having been lighted, the combus¬ 
tion of the bones ensues. In order to carry off the fumes, the smell of which is very 
offensive, a hood made of boiler-plate is placed on the kiln, and either connected with 
a tall, chimney, or the smoke and gases are conducted into the fire of the kiln and 
burnt. The white burnt bones are withdrawn through an opening reserved in the 
wall on purpose, the kiln being kept continuously in operation, as is the case with 
some lime-kilns. 

100 kilos, of fresh bones yield from 50 to 55 kilos, of white burnt bone-ash, which 
is converted into a coarse powder by means of machinery. 

Decomposjuonouhe Bone-Ash 2 I00 ]^q 0S- 0 f the bone-ash, of which about 80 per cent 
is tribasic phosphate, require for decomposition :— 

10673 kilos, sulphuric acid of 1*52 sp. gr. 

85'68 „ „ „ „ 170 ,. „ 

7 3'63 m •• „ „ i‘8o „ „ 

Payen advises that for 100 kilos, of bone-ash 100 parts of sulphuric acid at 50 per 
cent or 1*52 sp. gr. be taken, The operation of mixing the acid and bone-ash is 
effected in lead-lined wooden tanks, or in wooden tubs internally coated with pitch or 
coal-tar asphalte. The liquor decanted from the precipitate has a sp. gr. of 1*05 to 
1*07 = 8° to io° B. The sediment is lixiviated with water, and the liquor obtained 
(— 5 0 to 6° B.) evaporated with the first liquor in leaden pans. A second lixiviation 
of the sediment yields a fluid which is used instead of water for the purpose of 
diluting the oil of vitriol. The evaporation in the leaden pans (these are smaller, but 
otherwise similar in construction to those used for evaporating sulphuric acid) is 
continued until the fluid has attained a sp. gr. of i'45 = 45 0 B., when it is mixed 



PHOSPHORUS. 


539 


with charcoal-powder, or rather granulated charcoal, of the size of small peas, in the 
proportion of 20 to 25 parts of charcoal to 100 of liquor, and quickly dried after 
having been put into cast-iron pots placed on a furnace. 

The dry mass consists of phosphate of lime, carbon, and water, to an amount of 
5 to 6 per cent. At the commencement of the manufacture of phosphorus the idea 
prevailed that in the preceding preparation the phosphoric acid was present in free 
state, while the lime had combined with sulphuric acid; but Fourcroy and Vau- 
quelin finding that the tri-basic phosphate of lime as met with in bone-ash 
(Ca 3 (P 0 4 ) 2 ) was, by the action of the sulphuric acid, converted into acid phos¬ 
phate of lime (CaH 4 (P 0 4 ) 2 ), supposed that more sulphuric acid was required, 
an opinion opposed by Javal, who proved that when pure phosphoric acid is inti¬ 
mately mixed with carbon, it yields only a small quantity of phosphorus, because the 
acid is volatilised at a temperature lower than that required for its decomposition, or 
rather reduction by carbon. Owing to the presence of water in the mixture, there is 
given off during the distillation in addition to oxide of carbon, carburetted and 
phospliuretted hydrogen. 

Distillation oi phosphorus. 3. The mixture of acid phosphate of lime and charcoal is 
distilled in fire-clay retorts similar in shape to those used for distilling Nordhausen 
sulphuric acid, while the furnace in which these retorts are placed is also similar in 
construction and holds twelve retorts on each side. The body of the retorts is 
placed on the side of the fire, while the neck passes through an opening in the wall 
of the furnace, that portion of the wall being only lightly bricked up, as the retorts, 
after the distillation is finished and the furnace cooled, have to be removed, in order to 
clear out the residue and introduce fresh mixture. Between each pair of retorts is left 
a space of some 12 to 15 centims., in order to afford room for the passage of the flame. 
As already mentioned, the heat causes the acid phosphate of lime (CaH 4 (P 0 4 ) 2 ),to be 
converted into metaphosphate of calcium (Ca(P 0 3 ) 2 ), which, with increased heat, 
gives off two-tliirds of its phosphorus, there being left in the retorts one-third in the 
shape of tri-phospliate of calcium (Ca 3 (P 0 4 ) 2 ). The receivers used in Germany are 
constructed in the following manner :—The material is clay, glazed. The receiver 
consists of two parts, one of which is a cylindrical vessel open at the top, into 
which the other part fits, and is fixed by means of a rim which is prolonged so as to 
form a neck, between which and the first part is inserted a tube fitted on the neck of 
the retort, while the other end of this tube dips for about 10 centims. into the 
receiver, the latter being filled with water. Into each retort 6 to 9 kilos, of the 
mixture intended to be operated upon are introduced; the retorts are then placed in 
the furnace and the brickwork is restored. This having been done, the fire is 
kindled and kept up very gently for some time in order to dry the fire-clay used in 
joining the bricks. The receivers are filled with water and fitted to the retorts. 
In each receiver a small iron spoon is placed fastened to an iron wire which serves 
as a stem. After six to eight hours’ firing the heat has been so much increased as to 
cause the expulsion of any moisture left in the material placed in the retorts, while 
quantities of hydrocarbon gases and oxide of carbon are formed and with 
sulphurous acid expelled. Subsequently other gases are given off, and because they 
contain some phosphuretted hydrogen are spontaneously inflammable. As soon as 
this phenomenon is observed, the joints of the receivers and apparatus connecting it 
with the retort are luted with clay, care being taken to leave by the insertion of an 
iron wire a small opening for the escape of the gases, which are a3 speedily as 


540 


CHEMICAL TECHNOLOGY. 


possible removed by well-arranged ventilators from the building in which the 
furnace is placed. The appearance of amorphous phosphorus at the small opening 
indicates the commencement of the distillation. The spoon is then placed in the 
receiver in such a direction that any phosphorus coming over may collect in it. 
During the progress of the operation, and as long as any phosphorus distils over, 
the evolution of combustible gases continues, and consequently a small blue-coloured 
flame is observed at the opening in the lute. The water in the receivers is 
kept cool during the operation. After forty-six hours, with a greatly increased firing, 
a full white-heat is reached, and the quantity of phosphorus coming over has 
decreased so much as to make a continuation of the ignition process wasteful. The 
receivers are therefore disconnected from the retorts, and the crude phosphorus, a 
mixture of silicide of phosphorus, carburet of phosphorus, amorphous phosphorus, and 
other allotropic modifications of this element, is poured into a tub containing water. 
The furnace having become cool is broken up and the retorts are removed, the con¬ 
tents taken out with an iron spatula, and the retorts replaced after having been 
re-filled with fresh mixture, ioo kilos, of the mixture yield about 14*5 kilos, of 
crude and 126 kilos, of refined phosphorus. As to Wohler’s method of preparing 
phosphorus by the ignition of a mixture of charcoal, sand, and bone-ash, the process 
is not well adapted for practical use, because it requires a very high temperature, 


Fig. 257. Fig. 258. 



which would melt, or nearly so, and at any rate soften, the retorts. Moreover, the 
proposed mixture contains only one-third the quantity of phosphoric acid met with 
in the mixture now in general use. 

Re to 1 e n rh" S pho U iS? ing 4 - As already stated, the crude phosphorus is contaminated 
with carbon, silicium, red and black phosphorus, and various other impurities, which 
in former days were eliminated by forcing the phosphorus through the pores of stout 
wash-leather by means of a machine exhibited in Fig. 257, c representing a tightly- 
tied piece of wash-leather containing the crude phosphorus, the bag being placed on 
a perforated copper support, situated in a vessel filled with water at 50° to 6o°. As 
soon as the phosphorus is molten, there is placed on the wash-leather a wooden 




















PHOSPHORUS. 


54 * 


plate, d d, wliicli by the aid of the mechanical arrangement e, and the lever, g g, can 
be forced downwards so as to cause the fluid phosphorus to pass through the pores of 
the leather, the impurities being retained. More recently French manufacturers 
have introduced another system of purifying phosphorus, viz. a. By filtration 
through coarsely-powdered charcoal, which is placed in a layer of 6 to io centims. on a 
perforated plate of the vessel a, Fig. 258, two-thirds filled with water, kept by means of 
the water-bath, b, at a temperature of 6o°. The molten phosphorus placed on a passes 
through the layer of charcoal, and is thereby purified. It flows through the open 
tap c and the tube e, being collected in the vessel r filled with water, maintained by 
means of the water-bath, g, at a temperature sufficiently high to render the phos¬ 
phorus fluid, so that it may, when aided by hydraulic pressure, pass through the 
perforated bottom, h, and the wash-leather spread over it. The filtered phosphorus 
may be run off by means of the tap j. 

According to another process of purification ( b ), porous, unglazed porcelain or 
earthenware plates are fixed in an iron cylinder connected with a steam-boiler. The 
steam yielded by the latter forces the molten phosphorus—previously mixed with 
charcoal powder for the purpose of preventing the pores of the plates becoming 
choked—through the earthenware plates. The charcoal containing some phosphorus 
is used in the distillation of the phosphorus. This method of purification 
yields from 100 kilos, of crude, 95 kilos, of refined, phosphorus. In Germany crude 
phosphorus is purified by distillation, this operation being carried on in iron retorts 
of a peculiar make and shaped like the glass retorts used in chemical laboratories. 
The neck of these retorts dips for a depth of 15 to 20 millimetres in water contained 
in a basin filled to the rim, so that any phosphorus which is discharged into this 
water causes it to overflow. The crude phosphorus having been fused under water 
is next mixed with 12 to 15 per cent of its weight of moist sand, and this mixture is 
placed in the retorts in quantities of 5 to 6 kilos., the object of the mixing with sand 
being to prevent the phosphorus becoming ignited during the filling of the retorts. 
Crude anhydrous phosphorus yields by this process of distillation about 90 per cent 
of the refined product. In a phosphorus manufactory at Paris the crude phosphorus 
is purified by chemical means, viz., by mixing with 100 kilos, of the crude substance 
3-5 kilos, of sulphuric acid and the same quantity of bichromate of potash; a slight 
effervescence ensues, but the result is that the phosphorus is rendered very pure, and 
may, after washing with water, be at once cast in the shape of sticks. The yield of 
refined phosphorus by this process is 96 per cent. 

Mo ’ i pholp t horus eflned It has long been the custom to mould phosphorus into the shape 
of sticks formed by the aid of a glass tube open at both ends, one of these being placed 
in molten phosphorus covered by a stratum of warm water. The liquid phosphorus 
is sucked by the operator into the tube until it is quite filled. The lower opening of 
the tube being kept under water is closed by the finger of the operator ; the tube is 
instantly transferred to a vessel filled with very cold water, by which the phosphorus 
is solidified. It is removed from the glass tube by pushing it out with a glass rod or 
iron wire while being held under water. Instead of suction by the mouth, a 
caoutchouc bag similar to that used in volumetric analysis for the purpose of sucking 
liquids into pipettes may be employed. In the French phosphorus works the glass 
tubes are fitted at the top with an iron suction tube provided with a stop-cock. The 
operator, who has from one to two thousand of these tubes at his disposal, sucks, 
either by mouth or with a caoutchouc bag, the molten phosphorus into the glass tube, 


542 


CHEMICAL TECHNOLOGY . 


and having turned off the stop-cock, rapidly transfers the tube to a vessel filled with 
cold water. When all the tubes are filled the phosphorus is removed by opening the 
stop-cock and pushing the stick out by the aid of a wire. A clever workman may 
mould in this way 2 cwts. of phosphorus daily. 

Another mode of performing the moulding has been introduced by Seubert. The 
apparatus contrived by him for this purpose is exhibited in Fig. 260, and consists of 
a copper boiler fitted on a furnace; to the flat bottom of this boiler is fastened by 
hard solder an open copper trough communicating with the water-tank, c. In the 
boiler is fitted a copper funnel, a, provided with a horizontal tube, n. This portion 
of the apparatus is intended for the reception of the phosphorus, of which it will 
hold 8 to 10 kilos. At the end of the horizontal tube,'B, is placed a stop-cock, h, 
while the portion of the projecting mouth of the tube beyond the cock is widened 
out and fitted by means of bolts and nuts with a flange-like copper plate, into which are 
inserted two glass tubes, a a. Into the copper trough is let a wooden partition, c c, 
which serves the purpose as well of supporting the glass tubes as of preventing 
the communication of the hot water in the boiler and a portion of the trough 
with the cold water of the tank and the portion of trough nearest to it. The 


Fig. 260. 



vessel a having been filled with refined phosphorus, the water in d is gently -warmed 
so as to cause the fusion of the phosphorus. As the warm water reaches to the 
partition, c c , it is clear that on opening and closing the tap b, some phosphorus will 
pass through and flow out of the tubes a a, but that remaining in these tubes will 
solidify, and on opening the tap b again the solid sticks of phosphorus may be 
removed from the glass tubes by taking hold of the piece of projecting phosphorus 
the phosphorus being immediately immersed under water in the tank c, and kep: 
there protected from the action of the light. While, according to Seubert, it would 
be possible for a workman to mould in an hour’s time 30 to 40 kilos, of phosphorus, 
Fleck has found, that under the most favourable conditions of temperature, it takes 
six hours to mould 50 kilos, of phosphorus. If it is desired to prepare granulated 
phosphorus with this apparatus, a stratum of 6 to 8 centims. thickness of hot water is 
so carefully poured on cold water as not to mix; next the tap b is opened sufficiently 
to cause the phosphorus to form drops, which, immediately on falling into the col 1 

























PHOSPHORUS . 


543 


water, becomes a hard solid mass. For practical purposes granulated phosphorus is 
preferable to the moulded sticks. The phosphorus is stored either in strong sheet- 
iron tanks or in wooden boxes lined with thinner (tinned) sheet-iron, these vessels 
being capable of holding 6 cwts. of phosphorus covered with a stratum of water fully 
3 centims. deep. When large quantities, say, from i to 5 cwts., of phosphorus have 
to be sent off, it is usually packed in water in small wine casks, and the casks having 
been tightly closed, are coated externally with molten pitch, then rolled through 
chaff, and lastly covered with stout canvas sewed tightly round the cask. Another 
method of packing phosphorus consists in placing it in well-made water-tight sheet- 
iron or tinned iron canisters, such as are largely used in London for the purpose 
more particularly of conveying oil paints, and which are closed by soldering on a lid 
very securely. In some cases these canisters are packed in wooden boxes to the 
number of six or twelve according to size and weight. 

°*Preparmg Phosphonfs 8 . ° f Among the many suggestions as to the preparation of phos¬ 
phorus, we may mention Donovan’s plan of obtaining this element by the calcination 
of a mixture of finely divided charcoal and phosphate of lead, prepared by 
digesting 10 kilos, of broken-up bones with 6 kilos, of nitric acid, and 40 litres 
of water ; this liquid, after having been decanted from the gelatinous material of the 
bones, is treated with a solution of 8 kilos, of acetate of lead. The washed and 
dried precipitate of phosphate of lead is next ignited, and afterwards, when cold, 
mixed with one-sixth of its weight of lamp-black or Charcoal powder. Cari-Mon- 
trand exposes a mixture of bone-ash and carbonaceous matter at red heat to the 
action of hydrochloric acid gas :— 

Calcium tri-phosphate, Ca 3 (P 0 4 ) 2 

Carbon, 8C 

Hydrochloric acid, 6 C 1 H 

Neither of these methods have been tried practically on the large scale. 

Fleck’s Process. By this method the preparation of phosphorus is allied to that of 
glue- and size-making. The process is based upon the solubility of phosphate of 
lime in hydrochloric acid, and the separation of an acid phosphate of lime on the 
evaporation of the solution, carried on in earthenware evaporating basins. Theo¬ 
retically, 156 parts of tribasic phosphate of lime (Ca 3 (P 0 4 ) 2 ) require 73 parts of 
anhydrous hydrochloric acid, whereby are formed—of chloride of calcium, 111; of 
acid phosphate, 100; and of water, 18 parts. By the ignition of 100 parts of acid 
phosphate of lime with 20 parts of carbon, are generated—of phosphorus, 21‘3 ; 
of tri-phosphate of lime, 52 ; and of oxide of carbon, 467 parts. 

By re-heating the tri-phosphate of lime remaining in the retorts with hydro¬ 
chloric acid another portion of acid phosphate of lime might be obtained ; and as far 
as experiments have been made, it is proved that it is possible to extract all the 
phosphorus contained in bones, by working with hydrochloric acid free from 
sulphuric acid, and carefully evaporating the acid solution thus obtained. Practi¬ 
cally the process includes the following operations:—1. Cleaning, breaking up, and 
exhausting the bones. 2. The evaporation of the acid liquid; crystallisation of the 
acid phosphate, and mixing of the latter with charcoal. 3. The distillation and purifi¬ 
cation of the phosphorus ; and finally,—4. The glue boiling. The bones, previously 
crushed and deprived by boiling of the fat they contain, are macerated in dilute hydro¬ 
chloric acid at y° B.=sp.gr. 1048, and then in a stronger acid at 30° B.=sp. gr. r246, 
in which the bones are left until they have become quite soft. The liquid which has 


f yield 


Phosphorus, P 2 
Chloride of calcium, 3CaCl 
Hydrogen, 3H 2 
Carbonic oxide gas, 8CO 





344 


CHEMICAL TECHNOLOGY. 


served this purpose is afterwards employed with water in preparing the first acid 
liquor for the exhausting of the bones. The first liquor, a solution of acid 
phosphate of lime (superphosphate) and chloride of calcium, obtains a sp. gr. of 
ni8 = i6° B. This acid liquid is evaporated, but this operation cannot be pro¬ 
ceeded with in leaden vessels, and there is some difficulty in finding very large 
evaporating basins made of porcelain or earthenware which will answer the 
purpose. As soon as the liquor has reached a density of 30° B = sp. gr. 1*246, it is 
sufficiently concentrated to crystallise; on cooling, the crystals, having been by 
means of pressure separated from the mother-liquor, are mixed with one-fourtli 
of their weight of charcoal powder. They are then heated to ioo° in the porcelain 
or earthenware vessels, so as to obtain a dry mass which admits of being sifted 
through a copper-wire gauze sieve, after which the material is put into peculiarly 
shaped retorts and calcined for the purpose of yielding phosphorus. The residue 
left in the retorts is afterwards calcined with access of air so as to burn off the 
charcoal, and the remaining phosphate of lime is again treated with strong hydro¬ 
chloric acid, yielding a concentrated liquor which does not require much evaporation. 
The phosphorus obtained by this process is refined as already described, the 
softened bones being treated for glue and size. 

Genteie, Geriand, Minary, According to a communication published by Gentele in 

and Soudry’s Methods of 

preparing Phosphorus. 1857, upon a plan oi phosphorus manufacture, he com¬ 
bines that industry with the preparation of sal-ammoniac. The bones are treated 
with hydrochloric acid. To the resulting solution crude carbonate of ammonia is 
added; this substance being obtained as a by-product of the manufacture of animal 
charcoal. The phosphate of lime precipitated is employed in the preparation of 
phosphorus, while the solution of chloride of ammonium is evaporated and sublimed. 
Gerland (1864) suggests the treatment of bones—first, with an aqueous solution of 
sulphurous acid, the heating of the liquor obtained with the view of expelling the 
acid, which being again absorbed by a layer of coke (a coke column such as used in 
alkali works to absorb hydrochloric acid), the phosphates first held in solution are 
precipitated by the elimination of the sulphurous acid. Minary and Soudry (1865) 
proposed to prepare phosphorus from a mixture consisting of phosphate of iron and 
well-ignited coke. 

Properties of Phosphorus. When perfectly pure and kept under distilled water, which 
previously to being employed for this purpose has been by boiling deprived of the 
air it held in solution, and has been cooled either under a layer of oil or in 
well-stoppered bottles, and in perfect darkness, phosphorus is a colourless and trans¬ 
parent substance; but usually it has a wliite-yellow colour and waxy appearance. 
Its sp. gr. is == 1*83 to 184. When the temperature of the air is not too low 
this element is as soft as wax, but becomes brittle in cold weather. Phosphorus 
cannot be pulverised ; is tough ; but when molten in a bottle under warm water and 
shaken until the fluid is quite cold, the substance is thereby reduced to a finely 
divided state; instead of water it is better to use either alcohol, urine, or a weak 
aqueous solution of urea. Phosphorus fuses at 44 0 to 45 0 , and remaihs, especially if 
kept under an alkaline solution, fluid for a considerable time though cooled far below 
its melting-point, but solidifies suddenly when touched by a solid body. At 290° 
phosphorus boils, and it evaporates sensibly at the ordinary temperature of the air. 
By slow oxidation (fumes of phosphorus are given off at the ordinary temperature of 
the air) there is formed not only phosphorous acid but nitrate of ammonia and 


PHOSPHORUS . 


545 


antozone. Phosphorus is in the state of vapour slightly soluble in water. The solid 
element itself is slightly soluble in alcohol and ether, also in linseed oil and oil of 
turpentine, the best solvents being sulphide oi carbon, chloride of sulphur, and 
chloride of phosphorus. At 75 0 phosphorus ignites in contact with air, and in order 
to ignite it by friction this temperature has to be reached. Amorphous or red 
phosphorus requires a very high temperature (300°) for ignition. Commercial 
phosphorus usually contains some impurities, such as sulphur, arsenic, and sometimes 
traces of calcium, due to the lime of the bone-ash used in the preparation. Beside 
being used in chemistry, phosphorus is chiefly employed in the making of matches; 
also for what is termed liquid fire (a solution of phosphorus in sulphide of carbon), for 
the preparation of tar colours, and for hardening some copper alloys. 

Amorphous or Rea Phosphorus. Dr. Schrotter, of Vienna, discovered in 1848 that the 
property possessed by ordinary phosphorus (first noticed in 1844 by E. Kopp) 
of becoming coloured red by the action of light, was due to the formation of an 
allotropic modification, which has been since termed red or amorphous phosphorus. 
This is best prepared by heating ordinary phosphorus, with exclusion of air and 
water, in a closed vessel and under pressure, to 250° for a length of time. On the 
large scale this operation is conducted in an apparatus invented by A. Albright, of 
Birmingham. In Fig. 261, g represents a glass or porcelain vessel, filled for 
five-sixths of its capacity with pieces of phosphorus to be heated to 230° to 250°. 
The vessel/is placed in a sand-bath, b, heated by the fire. To the vessel g is fitted 
an air-tight lid, into which is fastened the bent tube, i, provided with a tap, Jc, and 
dipping into the vessel n, which is filled with water, or preferably with mercury 
covered with a layer of water. The tap, It, is left open at the commencement of the 
operation for securing the escape of the air contained in g, and as soon as no more 
air escapes the tap is closed, and 
the heat increased so as to con¬ 
vert the ordinary into amorphous 
phosphorus. The time required for 
the operation depends upon con¬ 
ditions which can only be met by 
experience. After the thorough 
cooling of the apparatus, the vessel 
g is opened, and the red phos¬ 
phorus removed. It is then placed 
under water and crushed to a pulp 
in order to remove any uncon¬ 
verted ordinary phosphorus. Sul¬ 
phide of carbon might be used for 
this purpose, but the danger of 
ignition (by accident) of the solu¬ 
tion of ordinary phosphorus thus 
obtained is prohibitive. Nickles proposes to separate ordinary from amorphous 
phosphorus by shaking up the mixture of amorphous and ordinary phosphorus with 
a fluid, the specific gravity of which is less than that of amorphous phosphorus (2*1), 
and greater than that of ordinary phosphorus (1*84). A solution of chloride of cal¬ 
cium at 38° to 40° B. can be used for this purpose ; the ordinary phosphorus floats in 
tliis fluid and can then be readily taken up by sulphide of carbon, while the operation 
36 


Fig. 261. 











546 


CHEMICAL TECHNOLOGY. 


can be carried on in a closed vessel. When very large quantities of amorphous 
phosphorus have to be purified it is best to follow Coignet’s plan, consisting in 
treating the boiling mixture of the two varieties of phosphorus with caustic soda 
solution, whereby the ordinary phosphorus is converted into phosphuretted hydrogen 
gas and hypophosphite of soda is formed, the remaining amorphous phosphorus 
being purified by washing with water. R. Bottger suggests the use of a solution of 
sulphate of copper, which with ordinary phosphorus forms phosphuret of copper. 

properties of^Amorphous This substance occurs either in powder of a red or scarlet 
colour or in lumps of a red-brcwwn hue; fracture conchoidal, sometimes with an 
iron-black hue; sp. gr. = a*i. Amorphous phosphorus is not soluble in sulphide 
of carbon or other solvents of ordinary phosphorus. -It is unaltered by exposure to 
air; and when heated to 290° is re-converted into ordinary phosphorus. When 
mixed and rubbed with dry bichromate of potash red phosphorus does not explode, 
and when mixed with nitre it does not burn off by friction, but only by application 
of heat and then noiselessly. It explodes, however, when mixed with chlorate 
of potash. With peroxide of lead amorphous phosphorus ignites by friction with a 
slight explosion, but when heat is also applied a violent explosion ensues. 

Owing to its properties and behaviour with several oxides, moreover its non-vola¬ 
tility and non-poisonous properties, amorphous phosphorus is, as well as on account 
of its less ready ignition, an excellent material for the malting of matches; but 
amorphous phosphorus is not in general use for this purpose. It is, however, used 
for preparing iodide of phosphorus, which serves for the preparation of iodides 
of amyl, ethyl, and methyl, used in the manufacture of cyanin, ethyl violet, and 
other coal-tar colours. Sir William Armstrong’s explosive mixture for shells 
contains amorphous phosphorus and chlorate of potash. From 66,000 cwts. of bones 
there are annually prepared in Europe some 5500 cwts. of phosphorus. 


Requisites for Producing Fire. 

Generalities and History. According to the writings of the ancients, Prometheus drew 
fire from stones by their concussion. The Romans rubbed together two pieces 1 of 
hard wood for producing by friction sufficient heat to ignite dry leaves fallen from 
trees ; while Darwin and the Prince of Neuwied state that the uncivilised races of 
man obtained fire by the rapid rotation of two pieces of wood. Turners at the pre¬ 
sent day employ friction in the carbonisation of wood for ornamental purposes. 
During Titus’s reign the Romans obtained fire by rubbing decayed wood between 
two stones, along with a small thin roll of sulphur. In the fourteenth century, the 
tinder-box, with the flint and steel, became known, and also the so-called German 
tinder, a prepared cryptogamic plant. Till 1820 these remained generally the 
chief means of obtaining fire, aided, of course, by the wooden splints tipped with 
sulphur. 

In the year 1823, Dobereiner, at Jena, discovered that finely divided spongy 
platinum has the property of igniting a mixture of atmospheric air and hydrogen 
gas, and he contrived the so-called Dobereiner hydrogen lamp, which has been, and 
is still, occasionally employed to procure fire and light. About the same period 
there was invented a kind of phosphorus match of the following arrangement. 
Equal parts of sulphur and phosphorus were cautiously fused in a glass tube ; after 
the fusion was completed the tube was tightly corked. If it were desired to obtain 


PHOSPHORUS . 


547 


fire, a thin splint of wood was immersed in this mixture, and some of it having been 
fixed to the wood, the latter on being brought into the air became ignited by 
the combustion of the mixed substances, which took fire spontaneously in the air. 
It is evident that this rather clumsy contrivance never became general. Of far 
more importance as suited for j>ractical purposes were the chemical matches or dip 
splints, first manufactured at Vienna, as early as 1812. These splints were tipped 
with sulphur covered with a mixture of chlorate of potash and sugar, to which 
for the purpose of imparting colour was added some Vermillion, while a little 
glue gave a pasty and adhesive consistency. 

By touching this composition with concentrated sulphuric acid ignition ensued; 
the acid was kept in a small glass or leaden bottle into which some asbestos had 
been inserted, which acted as a sponge for the acid. The only friction matches 
known up to the year 1844 were discovered and made by M. Chancel, assistant to 
the well-known Professor Thenard of Paris, 1805. The Prometheans, first made in 
England in or about the year 1830, were contrived on the same principle, viz., the 
ignition by friction between two hard substances of a mixture of chlorate of potash 
and sugar fixed to a kind of paper cigarette, which contained also a small glass 
globule filled with sulphuric acid; however, the high price of this kind of match 
prevented its general use. Under the name of Congreves the first real friction 
matches were made in 1832. On the sulphur-tipped splints was glued a small 
quantity of a mixture of 1 part of chlorate of potash and 2 parts of black sulphuret of 
antimony, to which some gum or glue was added. By strongly pressing this compo- 
sitiop between two pieces of sand-paper the mixture became ignited, but frequently 
also on becoming detached from the wooden splint flew about in all directions with¬ 
out igniting the sulphur or the wood. It is not well known who was the first to 
substitute phosphorus for sulphuret of antimony; but according to Nickles phos¬ 
phorus matches were already in. use in Paris as early as 1805, while in 1809 Derepas 
proposed to mix magnesia with phosphorus in order to lessen its great inflammability 
-when in finely divided state. Derosne (1816) appears to have been the first who 
made phosphorus friction matches at Paris. However, it was not before the middle 
of 1833 that phosphorus matches became more generally known, when Preshel, at 
Vienna (this city is famous for the match and fusee industry in Germany), made not 
only phosphorus matches, but also fusees and German-tinder slips tipped with the 
phosphorus composition. About the same period F. Moldenhauer, at Darmstadt, 
made phosphorus lucifer matches. The South Germans attribute to Kammerer the 
invention of phosphorus lucifer matches, while in England, according to the opinion 
of the late celebrated Faraday, John Walker, of Stockton, Durham, was the inventor 
of lucifer matches, or at least the first maker. The older kind of matches, although 
very combustible, ignited with a rather sharp report, owing to the presence of chlorate 
of potash in the mixture, while, moreover, the too ready ignition by concussion 
rendered the transport of these matches so unsafe, that in Germany, the transport, 
as well as the manufacture, became prohibited. In the year 1835 Trevany substi¬ 
tuted a mixture of red-lead and manganese for a portion of the chlorate of potash, 
thereby greatly improving the composition. In 1837 Preshel altogether discarded 
this salt, substituting peroxide of lead, or, as Bottger advised, either a mixture of 
red-lead and nitrate of potash, or of peroxide of lead and nitrate of lead. From this 
period the manufacture of matches became an extensive industry, greatly aided by 
the manufacture of phosphorus on the large scale. 


54» 


CHEMICAL TECHNOLOGY . 


In the course of time other improvements were made, as, for instance, the 
substitution for sulphur of wooden splints, thoroughly dried and soaked in wax, 
paraffin, or stearic acid, the coating of the composition with a varnish to protect it 
from the action of moisture, while, at the same time, the external appearance of 
the matches was rendered more ornamental. At the present day matches are a 
product of an industry which cannot possibly be much more improved in a technical 
point of view, being also a product which, as regards its price, is within the reach 
of all. 

However useful phosphorus lucifer matches may be, it is a great drawback to their 
utility that the combustible composition is a poisonous mixture, while, moreover, the 
workpeople engaged in that department of the lucifer-match making in which the 
phosphorus is handled are often affected by a peculiar kind of caries of the jaw¬ 
bones, the real cause of which is the more difficult to ascertain as the workpeople 
engaged in the manufacture of phosphorus and exposed to its vapours to such an 
extent as to render their breath luminous in the dark are not similarly affected. 
The discovery of the red or amorphous phosphorus, which is neither poisonous nor 
very inflammable, affords a happy substitute for the ordinary phosphorus, but the 
former is by no means generally used in the preparation of matches. 

ManufactureofLucifer The operations required are :— 

1. The preparing of the splints of wood. 

2. The mixing of the combustible composition. 

3. The dipping, drying, and packing of the matches. 

1. The Preparation of the Wooden Splints .—Generally white woods are used for 
this purpose, such as white fir, pine wood, aspen, more rarely fir wood (Fohrenholz), 
sometimes beech wood, lime-tree wood, birch, willow, poplar wood, and cedar. The 
shape of the splints is usually square in section, but abroad the splints are some¬ 
times cylindrical. The square splints are readily made by hand, simply by splitting 
up a block of wood having the length required for the splint. A cutting tool, a large 
knife, similar to that which is sometimes used by chaff-cutters, is very frequently 
used for the purpose of cutting the wooden splints, while a contrivance similar to 
that in use for propelling the hay or straw forward is also employed, being so 
arranged as to propel the wood after every cutting stroke the length required for a 
splint. More generally the operation of splitting the block of wood parallel to its 
fibres and next cutting off the splints to the required length is effected by machinery 
consisting of fixed knives, against which the wood is moved with sufficient force to 
split it up into splints, which are next cut to the required length. Instead of 
splitting the wood by these means, the splints are now in Germany always made by 
a kind of plane, invented by S. Homer, of Vienna, by which the wood is cut 
up into circular splints. The cutter of this plane differs from that of the ordinary 
carpenter’s plane, by possessing, instead of the cutting edge, a slight bend, in which 
three to five holes have been bored in such a manner that one of the edges of these 
holes is sharpened; in practice three holes are preferred. When this plane is 
forced against a lath of wood, placed edge way, the cutting tool penetrates into the 
wood, splitting it up into as many small sticks or splints as the cutter contains holes. 
When a number of thin splints have been cut from the lath, it is again planed true 
with an ordinary plane and then the operation repeated. The dividing of the thin sticks 
into splints of the required length is effected by a tool consisting of a narrow trough 
about 6 centims. wide and provided with a slit in which works a knife fastened to a 


PHOSPHORUS . 


549 


lever. A clever workman can prepare 400,000 to 450,000 splints daily. In the 
south-west of Germany a plane for cutting wooden splints, the invention of Anthon, 
at Darmstadt, and similar in action and construction to that above mentioned, is in 
general use ; but throughout an extensive portion of the empire the manufacture of 
the splints has become a separate trade often carried on in woods and> forests, the 
splints being sold to the lucifer-match makers in bundles ready for dipping. 

Instead of -making the splints by hand they are occasionally made by a machine, 
such as that by Pellitier, at Paris (1820), having on a bench a plane 36 centims. long 
by 9 wide, made to move backwards and forwards, while a piece of wood is placed 
so that it is caught by the fore-cutter, which consists of a steel knife provided with 
twenty-four teeth sharpened like little knives, the second cutter removing the small 
laths from the plank of wood. Cochot’s machine (1830) consists of a large iron 
wheel 1 metre in diameter, on the periphery of which are fixed thirty wooden blocks 
lengthway of the size of the splints. When the wheel is turned round the blocks of 
wood are caught by the knives fastened to a small cylinder, and the wood is split up 
into splints, which are removed from the block by another knife. Jeunot’s machine, 
patented in 1840 in France, is of a similar construction. Neukrantz, at Berlin 
(1845), contrived a tool based upon the principle of the hand-plane, the wood intended 
to be cut being moved against a fixed steel cutter, which produced sixteen to twenty 
splints at a movement. Krutzsch, at Wiinschendorf, Saxony, has improved upon this 
plan (1848) by perforating a steel plate with about 400 holes placed as near together 
as possible ; the edges of these holes having been sharpened, a block of wood is forced 
in the direction of its fibres against the plate and thus divided into splints. A piece 
of wood 3 centims. in thickness and width by 1 metre in length yields 400 lengths, 
each of which can be cut up into fifteen splints; 6000 of the latter are made in 
two minutes. Of the several tools and machines contrived for the purpose of 
cutting splints—and the number of these contrivances is very large—we quote the 
following of German origin. The machine invented by C. Leitherer, at Bamberg 
(1851), consists of what might be termed a kind of guillotine, viz., a box at the bottom 
of wliich is placed the wood to be formed into splints, the fibre of the wood being 
vertical. In front of this box is placed a frame-work, in which a heavy block, 
provided with four cutters, each terminated by eight to ten narrow tubes (somewhat 
similar to cork-borers), can be made to move rapidly, so as to give forty-five strokes 
a minute, the wooden block intended to be cut into splints being made to move under 
the cutting tool after each stroke. Wrana’s machine is in principle the same as 
that of Neukrautz, but has been greatly improved, the plane not being fixed, but 
supported by a piece of wood. Long’s machine, again, consists of a series of 
cylinders, between which the block of wood is placed, while knives are so arranged 
as to cut the block into splints while the wood moves on by the motion imparted to 
the cylinders. 

2. The Preparation of the Combustible Composition is carried on in the following 
manner :—The glue, or gum, or any other similar substance, is first dissolved in a 
small quantity of water to the consistency of a thin syrup, with which, having been 
heated to 50°, the phosphorus is incorporated by gradually adding it and keeping the 
mixture stirred so as to form an emulsion, to which are next added the other ingre¬ 
dients after having been pulverised. In order to obtain a good composition, it is 
essential that there should be neither too much nor too little phosphorus, for an 
excess of phosphorus will not only tend to increase unnecessarily the price of the 


550 


CHEMICAL TECHNOLOGY. 



composition, but it has also the effect of rendering it unfit for igniting the sulphur 
and stearin wherewith the matches are tipped, because the phosphoric acid gene¬ 
rated by the combustion of the phosphorus is deposited as an enamel-like mass, 
which prevents further combustion. It appears that the best proportion is from one- 
tenth to one-twelfth of phosphorus. 

A much smaller quantity of phosphorus is required if this element is first dissolved 
in sulphide of carbon and the solution added to the other constituents of the compo¬ 
sition ; the sulphide of carbon while rapidly volatilising leaves the phosphorus in a 
very finely-divided state. As phosphorus is very readily soluble in sulphide of 
carbon, and as the latter is moderately cheap, the method has the advantage that the 
mixing of the materials can take place without the application of heat. It is, how¬ 
ever, evident that the greatest care is required in manipulating such a liquid as 
sulphide of carbon, and far more when phosphorus is dissolved therein. C. Puscher 
suggested (i860) the use of sulphuret of phosphorus, P 2 S, instead of pure phosphorus 
in the composition for matches. He prepared a composition containing 3*5 per cent 
of this sulphuret, and obtained excellent matches. 

Among the metallic oxides which are employed in the mixture, preference is given 
either to a mixture of peroxide of lead and nitrate of potash, or to a mixture of the 
former with nitrate of lead obtained by treating red-lead with a small quantity of 
nitric acid and leaving this mixture for a period of several weeks to dry. Glue, gum, 
and dextrine are used as excipients; the first, however, is objectionable because it 
carbonises and prevents the combustion. Perhaps a dilute collodion solution or a 
mixture of sandarac or similar resin, with benzole, might be used as an excipient 
instead of the gum. 

The mixtures actually used in the trade are kept secret, but the following recipes 
may give some idea of the composition :— 

I. 


Phosphorus . 

. 1’5 parts 

Gum Senegal . 

. 3 'o » 


Lamp-black . 

. °'5 „ 

A mixture of nitrate of 

Red-lead . 

. 5 '° * » _ 

lead and of peroxide of 

Nitric acid at 40°B. (= 

sp.gr. 1-384) 2-0 „ 

II. 

lead, technically known 
, as oxidised red-lead. 

Phosphorus . 

. 8 0 parts 1 

[Dissolved in the required 

Glue. 

.. *• 210 „ J 

quantity of sulphide of 

Peroxide of lead 

— .24-4 „ 1 

carbon. 

Nitrate of potash ... 

.240 

III. 


Phosphorus . 

. 3 0 parts 

Gum Senegal . 

. 3 'o „ 


Peroxide of lead 

. 20 „ 


Fine sand and smalt... 

. 20 „ 



No doubt there is room for great improvements in these compositions. 

3. Dipping and Drying the Splints .—In order to fix the sulphur and combustible 
composition to one end of the splints, it is clear that these should not touch each 




PHOSPHORUS. 


55i 


other, but be so arranged a 3 to leave an intermediate space. A contrivance is 
employed, consisting of small planks, o - 3 metre long by 10 centims. wide, the surface 
being provided with narrow grooves placed close together, and just large enough 
each to hold a single splint, Fig. 262. The splints are one by one placed in the 
grooves, an operation usually performed by girls. One plank having been filled 
another is placed on the top of it. The surface of the plank on one side is provided 
with a piece of coarse flannel, while the other side is grooved for holding splints. 
Each of the planks has at the end a round hole, through which pass iron 
rods, Figs. 263 and 264, in the top of which a screw thread is cut, so that as soon as 
some twenty to twenty-five planks have been filled with splints and placed one upon 
another, they are fastened so as to form a framework. A clever hand can fill during 
ten hours fifteen to twenty-five of these frames, each containing 2500 splints. 
Recently it has been attempted to perform this work by machinery, and the machine 
constructed by 0 . Walsh, at Paris (1861), enables a lad to frame 500,000 to 600,000 
splints in ten hours. 

The sulphur intended for dipping the splints is kept in a molten state over a mode¬ 
rate fire in a shallow rectangular trough, in the middle of which a stone is placed as 

Fig. 262. 



Fig. 263. Fig. 264. 



precisely level as possible. The quantity of sulphur is so regulated that it covers 
the stone to a depth of 1 centim. In the operation of dipping, the ends of the 
splints are made just to touch the stone and immediately removed, care being taken 
to cause, by shaking the frame, any superfluous sulphur to flow into the trough again. 

Instead of sulphur the better kind of matches are impregnated with stearine, 
stearic acid, or paraffin. The splints having been first thoroughly dried, are placed 
in a bath of molten paraffin, and left there for a time so as to allow the wood to 
absorb by capillarity. 

The tipping with the phosphorus composition is performed similarly to the 
sulphuring of the splints, the composition being placed in a uniform layer on a piece 
of thick ground glass or on a well-polished lithographic stone (Solenhofen lime¬ 
stone). 

The drying of the matches takes place in a room heated by steam, the frames 
being hung on ropes or put on shelves. The position of the frames is such that the 




























552 


CHEMICAL TECHNOLOGY. 


matches are in a vertical position, and the composition hangs on them as a drop. The 
composition of the saloon matches is, after drying, coated with coloured resinous 
solutions, and often with a collodion film. 

Anti-Phosphor Matches. This variety of match was invented in 1848, by Bottger, 
at Frankfort, and was prepared industrially by Fiirth, at Schiittenhofen; Lund- 
strom, at Jonkoping (Sweden); Coignet, at Paris (under the name of Allumettes 
hygieniques et cle surete au phosphors amorphe) ; De Villiers and Dalemagne, Paris 
(under the name of Allumettes androgynes) ; also by Forster and Wara. These 
matches are of two kinds:— a. Those which are free from phosphorus, the 
amorphous phosphorus being incorporated with the sand-paper. ( 3 . Those which are 
free from phosphorus both in the match and on the sand-paper. 

To the matches of the first category belong:—1. Matches, the composition 
of which is free from phosphorus, consisting simply of a pasty mass, the main con¬ 
stituents of which are sulphuret of antimony and chlorate of potash. 2. The 
amorphous phosphorus mixed with some very fine sand or other substance promoting 
friction is, with glue, put on to the box in which the matches are contained; or, as is 
the case with the androgynes, at the other end of the splint. The friction surface on 
the boxes consists of a mixture of 9 parts of amorphous phosphorus, 7 parts of pul¬ 
verised pyrites, 3 parts of glass, and 1 part of glue. The matches ignite readily by 
friction on the surface containing this composition, but do not ignite when rubbed on 
any other rough surface. These so-called safety matches are largely manufactured 
at Jonkoping, under the Swedish name of Sakerhets-Tdiulstickor (security fire 
matches). Jettel (1870) uses for the friction surface a compound consisting of equal 
parts of amorphous phosphorus, pyrites, and black sulphuret of antimony; for 
coating on the two sides of 1000 small boxes, each containing fifty matches, about 
80 grms. of this mixture are required. It need hardly be mentioned that in 
England safety matches are largely made and of excellent quality, in fact, better than 
anywhere else. 

B. Forster and F. Wara, at Vienna, have introduced a “ non-poisonous ” match. 
The amorphous phosphorus is mixed up with the combustible composition in 
the usual way, so that these matches ignite readily by being rubbed on any rough 
surface, but the ignition is accompanied by noise, owing to the chlorate of potash 
contained in the mass. 

As regards the matches belonging to the second category—viz., such as neither 
contain phosphorus nor require a phosphorus-containing surface, we may give 
the analysis by Wiederhold, of the composition of those made by hummer and 
Gunther, at Konigswalde, near Annaberg, in Saxony :— 

Chlorate of potash . 8 parts. 

Black sulphuret of antimony. 8 „ 

Oxidised red-lead . 8 „ 

Gum Senegal . 1 „ 

Oxidised red-lead is a variable mixture of peroxide of lead, nitrate of lead, and 
undecomposed red-lead. Weiderhold, at Cassel, suggested (1861) the following 
ignition mixture:— 

Chlorate of potash. 7 8 parts. 

Hyposulphite of lead . 2 6 „ 

Gum arabic . 10 ,, 



ANIMAL CHARCOAL. 


553 


This is the best anti-phosphorus mixture 
mixtures free from phosphorus:— 

Chlorate of potash . 

Sulphur . 

Bichromate of potash. 

Sulphuret of antimony . 

Sulphur auratum, SbS 5 (Stibium \ 
sulfuratum aurantiacum). 
(Antimonium sulfuratum, B.P.) . 

Nitrate of lead . 


Jettel, at Gleiwitz, gives the followinj 


a. 

b. 

C. 

d. 

4 ‘° 

70 

3‘ 00 

8'o 

ro 

1*0 

— 

— 

o *4 

20 

— 

05 

— 

— 

— 

80 

— 

— 

025 

— 

_ 

2*0 


, 


While B. Peltzer has called attention to the applicability of copper-sodium hypo¬ 
sulphite for the preparation of a phospliorus-free ignition mass, Fleck* has also 
remarked the use which might be made of sodium in this respect. 

wax or vesta Matches. Instead of the phosphorus composition being fixed to a wooden 
splint it is in the wax matches (allumettes bougies ) attached to a thin taper made of a 
few cotton threads (4 to 6), immersed in a molten mixture of 2 parts of stearine and 
1 part of wax or paraffin. The tapers, while this mixture is hot, are drawn through 
a hole perforated in an iron plate, the opening of which corresponds to the desired 
thickness of the taper. The taper is next cut by means of machinery into suitable 
lengths; afterwards the phosphorus composition is affixed and the vestas put into 
boxes. 

Zulzer’s machine for cutting the tapers and for making them into matches has the 
following arrangement. The wicks having been rolled on a drum are forced between 
two cylinders, which impart the fatty composition, and next the tapers are carried by 
the machinery across grooves in planks to holes in a movable vertical iron plate, 
which is connected with a cutting apparatus intended to divide the tapers into 
suitable lengths. As the cutters are placed at the entrance of the holes, the tapers 
after having been separated from the main wicks are left dangling in these holes, and 
by a mechanical contrivance, the plate containing the holes is lifted sufficiently 
to bring another row of holes level with the wick-producing apparatus. When a 
plate has been thus filled with tapers it is removed, another put in its place, and the 
ends of the tapers immediately immersed in the phosphorus composition, and next 
placed in a drying room. Marseilles is the great centre of the wax match industry, 
while Austria stands next. 


Animal Charcoal. 

Animal charcoal. Animal charcoal is the residue obtained by the dry distillation of 
bones. Owing to its introduction (1812) by Derosne, and afterwards re-introduction 
with improved filtering apparatus by Dumont (1828), into the sugar refining 
industry, animal charcoal, or bone-black, has become one of the most important 
substances of chemical technology. When bones are submitted to ignition in closed 
vessels with exclusion of air, the organic matter yields a tar known as crude Dippel’s 
oil, and carbonate of ammonia, while a coal-black residue remains exhibiting 
perfectly the organised structure of the bones. 

preparation of Bone-black. The bones are either boiled with water or, better, 
exhausted with sulphide of carbon to remove the fat, which being obtained in 

Jahresbericht der Chem. Technologie (Dr. Wagner), 1868, p. 220. 



CHEMICAL TECHNOLOGY. 


554 

a quantity of 5 to 6 per cent of the weight of the bones, is a valuable by-product of 
this branch of industry. The carbonisation of the bones is so conducted that the 
volatile products are either burnt or condensed. In the latter case the broken-up 
bones are put into iron retorts similar to those used for coal-gas manufacture, 
and the volatile products are collected in suitable condensing apparatus, while 
the gas after having been purified is sometimes led into a gasholder and used 
for illuminating purposes, or when not purified is burnt under the retorts. Ac¬ 
cording, however, to the experience obtained in Germany, bone-black thus made 
has a lower decolourising power than when the bones are ignited in iron pots, 
the volatile products being burnt at the same time. In Germany, therefore, the older 
plan of carbonisation in pots is usually resorted to. In England and Scotland, and also 
in Holland, Belgium, and France, retorts are generally used for this purpose. The 
carbonisation in pots is carried on in the following manner:—Cast-iron pots are 
filled with broken-up bones and placed one on the top of the other, the edges of the 
mouths of the pots being luted with clay. The pots are placed on the hearth of a 
kind of reverberatory furnace. After awhile the vapours which are forced through 
the lute become ignited, thereby enveloping the pots in a sheet of flame, so that the 
carbonisation goes on without requiring the firing of the furnace to be kept up. 
When the flame subsides the carbonisation is complete. The yield of animal char¬ 
coal amounts by this method of procedure to 55 to 60 per cent, the carbonaceous 
matter being, however, mixed with about ten times its weight of mineral matter, as 
may be inferred from the following results of analysis of a dried sample of bone- 
black, which in roo parts was found to consist of—Carbonaceous matter, 10; phosphate 
of lime, 84 ; carbonate of lime, 6 parts. By exposure to air bone-black absorbs 
7 to 10 per cent of moisture. The carbonised bones are broken up and granulated 
by machinery, the formation of dust having to be avoided as much as possible 
because it has very little value. 

Properties of Bono-biack. As far back as the year 1811, Figuier discovered that bone- 
black possesses the property of withdrawing organic and inorganic substances—viz., 
lime and potash from solutions. It appears that this property is due to surface 
attraction (capillary action), although bone-black is also capable of decomposing 
chemical compounds. Owing to the fact that bone-black can absorb inorganic 
matter, it is largely used for the purpose of withdrawing lime and saline matter from 
saccharine fluids in beet-root sugar works. According to Anthon, the property of 
bone-black to withdraw lime from solutions is partly due to the fact that carbonic 
acid is condensed in the pores of this substance. 

By treating bone-black with hydrochloric acid, and thus dissolving the mineral 
matter it contains, the residue, after having been well washed with water, dried, and 
re-ignited in a closed crucible, lias lost in a very great measure its property of with¬ 
drawing from solutions and retaining within its pores inorganic matter. When acid 
liquids are to be decolourised by bone-black, it should always be employed after having 
been treated with hydrochloric acid. Shoe-blacking manufacturers employ in their 
trade a large quantity of bone-black. 

Testing Bone-black. The greater the decolourising power of charcoal the better its 
quality, though it appears that the decolourising power is not proportionate to the 
power of withdrawing lime and saline matters from solutions. In,order to ascertain 
the decolourising power of any sample of bone-black, its quality in this respect 
is compared with that of another of known strength. Payen proposes to take equal 


ANIMAL CHARCOAL. 


555 


bulks of water coloured with caramel, to treat these with equal weights of animal 
charcoal, and to filter these mixtures; the charcoal which yields the clearest liquid 
being the best. Bussy obtained the following results by the estimation of the 
relative decolourising power of equal quantities by weight of different kinds of 


charcoal:— 

Ordinary bone-black . ro 

Bone-black treated with hydrochloric acid. i*6 

Ditto, ditto, but afterwards ignited with carbonate of potash. 20*0 

Blood ignited with carbonate of potash . 20'o 

Blood ignited with carbonate of lime . .. 20 0 

Glue ignited with carbonate of potash ... .. 15 5 


Brimmeyr’s experiments on the decolourising properties of bone-black led to the 
following results :—1. The capability of absorption of this substance does not depend 
upon the mechanical structure of the bone-black, but upon the quantity of pure 
carbon it contains. 2. The quantities of matter absorbed by bone-black of various 
kinds are—when reduced to pure carbon—really equivalent, and are probably 
independent of the varying chemical nature of the soluble absorbed substance. 
3. Bone-black saturated with any substance retains its absorptive power for other 
materials of a different chemical nature. 4. Bone-black acts the quicker and better 
the less its capillary structure has been interfered with either by mechanical or 
chemical means (action of hydrochloric acid). Schultz’s results of experiments 
agree with those just quoted. The specifically lightest bone-black which contains 
the largest amount of carbon is the most strongly decolourising material. As 
regards the sugar (especially beet-root) manufacture, the power of bone-black to 
withdraw lime from a solution comes also into consideration; this lime-absorbing 
capability is estimated by directly testing the quantity of lime which a given sample 
of charcoal can take up. 

KeTivifi o?charSai burninK) After having served the purpose of decolourising and 
absorbing lime for some time in the process of sugar refining, the bone-black 
becomes, as it is termed, foul and requires to be revived, for which purpose it is 
either first thoroughly washed with hot water or sometimes left to enter into a state 
of fermentation, or treated with steam, and finally always re-ignited. The more 
usual plan is to wash the bone-black, while still in the filters, with hot water, so as 
to remove all soluble matter, the material being next re-ignited. In this manner 
bone-black may be restored for use twenty to twenty-five times. This mode of 
reviving labours under the disadvantage that during the ignition the organic matter 
(absorbed impurities) is not quite destroyed, and by choking the pores of the bom - 
black impairs its decolourising power. It is therefore preferable to cause the bone- 
black to ferment, to treat it next with dilute hydrochloric acid, wash it well, 
and lastly ignite it. The quantity of hydrochloric acid employed for this purpose in 
sugar-producing works is very large. 

Substitutes for Bone-black Among the substances which have been tried as substitutes 
for the use of bone-black, carbonised bituminous shale takes the first place. This 
material (the coke of the Boghead coal is an excellent example) absorbs colouring 
matter, but does not touch the lime. Moreover it often happens that the coke 
is rendered unfit for this use by the presence of a considerable amount of mono- 
sulphuret of iron. The coke of sea-weed is perhaps a more suitable material. 







556 


CHEMICAL TECHNOLOGY. 


Milk. 

Milk. This fluid is secreted by glands with which all female mammalia are 
provided. It contains all the organic and inorganic substances required by the 
young animal as food, being intended to feed the young until they are sufficiently 
developed to partake of other nutriment. The main constituents of milk are:— 
Sugar (lactose), caseine, butter, inorganic salts, such as chlorides of potassium and 
sodium, phosphate of lime, and finally water. The average percentage composition 
of cow’s milk is the following :— 


Butter . 3‘288 

Lactose and soluble salts ... 5-129 

Caseine and insoluble salts ... 4'107 , 

Water . 87’476 


12-524 per cent. 


IOOOOO 

Milk is a mixture of several insoluble, very minutely divided, .emulsioned sub¬ 
stances, suspended in a watery liquid. The specific gravity of milk varies from 
1-030 to 1*045. Under the microscope it becomes evident that the white colour of 
milk is due to the so-called milk globules—small globular bodies of a yellow colour, 
with a more deeply coloured circumference, and exhibiting a pearly gloss. It was 
formerly believed that these globules consisted of an exterior envelope filled with 
butter, but the recent researches of Drs. Yon Baumliauer and F. Knapp have 
proved this opinion to be erroneous. When milk is left standing these globules rise 
to the surface and form cream, below which remains a blue transparent fluid 
containing the sugar of milk, salts, and caseine, the latter in the form of caseine-soda 
When milk is kept for some time a portion of the lactose (sugar of milk) is decom¬ 
posed and converted into lactic acid by the aid of the caseine, which acts as a 
ferment. In its turn the lactic acid decomposes the caseine-soda, whereby the 
caseine is set free and separated as an insoluble substance ; this action takes place in 
the coagulation of milk. The whole of the lactose or sugar of milk becomes 
converted into lactic acid by long keeping. 

Lactic acid (C 3 H 60 2 ) is also formed by the fermentation of starch, cane sugar, 
and glucose, under the influence of caseine and a ferment. This acid is met 
with in sauerkraut (a favourite dish of the Germans, being a well-preserved 
mixture of white and savoy cabbages cut into shreds, and packed in casks 
along with salt, coarse pepper, and some water), and in other pickles, in beer, 
and in nearly all animal liquids. Lactic acid is also present in some of the 
fluids of the tan-yard tanks; in the sour water of starch works where starch 
is prepared by the old methods; in the bran bath of dye works; and is con¬ 
stantly met with in the residual liquids of corn spirit distillation. When lactic 
acid is heated with sulphuric acid and peroxide of manganese, aldehyde is formed, 
which is used in the preparation of aniline green and of hydrate of chloral. 

The coagulation of fresh milk is effected by the use of rennet, which is pre¬ 
pared from the stomach of a calf, well washed and stretched out in a wooden frame, 
then dried either in the sun or near a fire. The substance thus prepared was for¬ 
merly soaked in vinegar, but experience has proved this to be unnecessary. When 
required a small piece is cutoff and steeped in warm water, and the liquid added to the 
milk previously heated to 30° to 35 0 . The milk is hereby coagulated, even in large 





MILK. 


557 


quantity, in about 2 hours; 1 part of rennet is sufficient for the purpose of coagula¬ 
ting 1800 parts of milk. The mode of action of rennet is not well understood, but it 
does not consist, as was formerly believed, in the instantaneous conversion of a por¬ 
tion of the lactose present in milk into lactic acid, since experiments have shown 
that rennet coagulates milk which exhibits an alkaline reaction. 

whey. By the term whey is understood the fluid in which the coagulated caseine 
of milk floats and which may be obtained either by decantation or filtration. The 
whey of sour milk contains very little lactose and a large quantity of lactic acid 
(sour whey) ; while sweet whey, obtained by coagulating milk with rennet contains 
all the lactose. Sweet whey containing 3 to 4 per mille of a proteine compound 
(termed lacto-proteine by Millon and Commaille) is evaporated to some extent 
in Switzerland, with the view of obtaining the sugar of milk in crystalline state. The 
Lactose-sugar of Miik. substance thus obtained is purified by re-crystallisation. Lactose, 
C12H22OH + H 2 0 , does not possess a very sweet taste and feels sandy in the mouth. 
It is soluble in 6 parts of cold and 2 parts of hot -water. It is not capable of alcoholic 
but only of lactic acid fermentation. By the action of dilute acids sugar of milk is 
converted into galactose, a kind of sugar similar to grape sugar, and is then capable 
of alcoholic fermentation. Industrially sugar of milk is sometimes employed for the 
purpose of reducing a silver solution to the metallic state, as in the case of looking- 
glass maldng. 100 parts of the commercial sugar of milk from Switzerland (a), and 
from Giesmannsdorf in Silesia (Z>), were found to consist (1868) of:— 


a. b. 

Salts . 003 cri6 

Insoluble matter. 0*03 005 

Foreign organic substances... 1*14 1*29 

Sugar of milk . 98’8o 9850 

IOO’OO 10000 


Mea becomTng V sour^ Iilk By boiling milk the air it has taken up is eliminated and 
thereby the conversion of the caseine into a ferment, and the consequent decomposi¬ 
tion of the sugar of milk, prevented. Milk may very readily be kept fresh by 
the addition of small quantities of carbonates of alkalies or borax. The coagulation 
of milk (not its becoming sour) may be prevented by the addition of some.nitrate of 
potash, chloride of sodium, or other alkaline salts. 

Testing Miik. In localities where milk is consumed in very large quantities—for 
instance, in large cities and towns—it is sometimes adulterated by the addition of 
rice-water, bran-water, gum-solution, and emulsion of sheep’s brain. The most 
common adulteration of milk is its dilution with more or less water. Several 
methods and instruments have been invented for the purpose of testing the quantity 
of caseine and butter present in milk, and it should be here observed that, according 
to Dr. F. Goppelroder’s excellent researches (1866), it has been found that the 
relative proportion of the quantity of these substances varies in milk from one day 
to another, and even in the milk drawn at mornings and afternoons. According to 
Jones’s plan milk is poured into a vertical graduated glass tube; the quality of the 
milk varies with the number of graduated divisions occupied by the cream separated 
from the milk. It is evident that in this way only the quantity of cream contained' 
in the sample of milk under examination is found, and nothing learnt about the 
degree of dilution of the milk with water, which somewhat influences the rapidity 




558 


CHEMICAL TECHNOLOGY. 


of tlie separation of the cream. Chevalier and Henry employ for the testing of 
milk an areometer, the degrees of which are ascertained by experiment from really 
genuine milk. Other methods are based upon the use of tincture of nut-galls or 
solution of sulphate of zinc for the purpose of precipitating caseine and butter in a 
sample of genuine milk, and next to compare the quantity of these reagents neces¬ 
sary to precipitate in an equal quantity by bulk of any other sample of milk. 
Donne’s galactoscope may be used for the purpose of testing the purity of milk, 
more especially in reference to its adulteration with water, the instrument being 
based upon the greater or less transparency of a column of milk of a certain length 
which admits through it the rays from the flame of a lighted candle; the more 
transparent—that is, the longer the column of milk—the more it is adulterated with 
water. Brunner tests milk in the following manner:—To 20 grms. of the milk to be 
tested are added 10 grms. of charcoal powder. This mixture is evaporated to 
dryness at a temperature of 70° to 8o°. The butter is then extracted by means of 
ether, and this solution evaporated and weighed. Pure milk yields 3*1 to 3*56 per 
cent of butter, cream from io*6 to ii’o6per cent. C. Reiclielt has lately tried to 
apply the hallimetrical method (see p. 422) for the purpose of determining the 
quantity of water contained in milk. 

uses of Milk. Milk is used as food and for the preparation of butter and cheese, for 
clarifying wine in order to render it less deep coloured, and, if turbid, quite clear. 
More recently milk has been largely sold in the so-called condensed state, by which is 
understood milk evaporated in vacuo after the addition of sugar to the consistency 
of thick honey. This mode of preserving milk was first employed by the Anglo- 
Swiss Condensed Milk Company at Cham, Canton Zug, Switzerland, and is now 
carried on in various parts of the Continent and in the United States, and also in 
England, in Surrey and Berkshire. The average composition of the condensed 
milk is:— 

Water. 2244 

Solid matter . 77'56 

IOOOO 

One-half of the solid matter consists of the sugar which has been added, the rest 
being butter, 9 to 12 per cent; caseine and lacto-proteine, 12 to 13 per cent; sugar 
of milk, 10 to 17 per cent; salts, 2*2 per cent. Condensed milk is soluble in cold 
water, and yields with 4-5 to 5 parts of water a liquid similar to genuine, but of 
course sweetened, milk. 

Butter. This substance is prepared as follows:—Milk of good quality is placed 
in a rather cool cellar or other locality for the purpose of causing the cream to 
separate. The cream is poured into a clean stoneware or glass vessel kept for the 
purpose, and left until by constant stirring it has become thick and sour; it is then 
put into a churn, by the action of which the solid fat globules are separated from the 
thick fluid in which the caseine with a small quantity of butter remains suspended. 
Butter being specifically lighter than water should, it might be thought, separate 
very readily from a liquid which contains in solution various substances which are 
heavier; but the fact is, that caseine renders the separation of butter from cream 
difficult even when the cream is sweet and not thick ; when, on the other hand, milk 
coagulates before the cream is separated, the butter is lost. Two methods have been 
devised for the purpose of obtaining all the butter contained in milk. Gussander, a 



MILK. 


559 


Swedish agriculturist, has proposed that the separation of cream should be rendered 
more rapid, and always completed before the milk becomes sour, while Trommer 
prevents the souring of the milk by the addition of some soda. 

The churns vary very much in construction ; the most simple, which is that most 
extensively used, consists of a tall somewhat conical wooden vessel covered with a 
wooden lid, through a round opening in which a cylindrical wooden stem passes. 
To this stem is fixed a wooden perforated disc, which is moved upwards and downwards 
by a similar motion imparted to the stem. The butter having been separated from the 
liquid is thoroughly washed and kneaded with fresh water, and next more or less 
salted, at least in most cases, although thoroughly well-washed butter may be kept 
for a very long time without becoming rancid. The liquid from which the butter is 
separated is known as churn-milk or buttermilk; it contains 0-24 per cent butter, 
3*82 per cent casein, go'8o per cent water, 5*14 per cent sugar of milk and salts. In 
the water lactic acid is present. 18 parts of milk yield on an average 1 part of 
butter, which in fresh condition consists of:— 


I. H. III. IV. 

... 944 93-0 875 785 

}... 03 03 ro 03 

5'3 6'7 ir 5 21-2 


Butter fat . 

Caseine, sugar of milk 
Extractive matter 
Water . 


Owing to the presence of water and caseine, butter after some time becomes rancid. 
It is salted in order to prevent this rancidity as much as possible, the salt being 
thoroughly mixed with the butter by kneading. To 1 kilo, of butter 30 grms. of salt 
are required. According to Dr. Wagner, butter in England is salted with a mixture 
of 4 parts of common salt, 1 part of saltpetre, and 1 part of sugar. In Scotland, 
France, Southern and Western Germany, butter is not salted at all, and therefore 
only made and sold in comparatively small quantities at a time. Salt butter is 
termed in Scotland pounded butter. 

By melting butter until the first turbid liquid has become clear and oily, water 
and caseine are eliminated, and settling to the bottom of the vessel, the supernatant 
fat may be put into another vessel, and will, after cooling, keep sweet without salt 
for any length of time. Butter is often artificially coloured either by the aid of annatto, 
turmeric, or infusion of calendula flowers. 

chemical Nature of Butter. Butter consists of a mixture of neutral fats—glycerides— 
which on being saponified yield several fatty acids, among which the non-volatile 
are :—Palmitinic acid, C I 6H 3 20 2 , and butyroleic acid (C12H30O2). The volatile are:— 
Butyric acid* (C 4 H 80 2 ), capronic acid (C6H12O2), caprylic acid (CsHjsOa), caprinic 
acid (C I0 H 20 02). The last four constitute in the shape of glycerides the butyrin or 
peculiar fat of butter, and impart to that substance its peculiar odour and flavour. 

cheese. Cheese is prepared from caseine. It is made either from skimmed or 
unskimmed milk. In the former case a lean, dry cheese is obtained; in the 
latter a fat cheese, such as Cheshire, Cheddar, American, and the bulk of 
Holland cheeses. Lean cheese is made in Germany by pouring the skimmed 
and already sour milk upon a cloth, through the pores of which the whey passes, 

* This acid is formed not only by the saponification of butter, but is also met with in 
secreted perspiration, the juices of the stomach, and results from the fermentation and 
decay of sugar (in weak solutions), starch, fibrine, caseins. &c. 


560 


CHEMICAL TECHNOLOGY . 


while the caseine remains on its surface as a pasty mass, which is put by hand into 
the cheese-moulds, these being next exposed- to air. 

Fat cheese is made of sweet milk just drawn from the cows, the milk being 
coagulated by rennet after having been heated to 30° to 40°. The gelatinous mass 
thus obtained is broken up and pressed by hand, and the whey gradually removed 
by the aid of wooden ladles. The caseine having been freed from whey is next well 
kneaded with some common salt and then put into wooden moulds with two or three 
small holes at the bottom for the purpose of allowing the whey to flow off when the 
cheese is pressed. The newly made cheese is usually every alternate day dipped in 
warmed whey, next wiped dry, put into the mould again, and pressed. When the 
crust has sufficiently formed and the cheese become so hard as to admit of being 
handled, some salt is rubbed into its surface and it is then placed in a cool well-aired 
room upon a shelf to dry, and become as it is termed ripe. The vesicular appearance 
of some kinds of cheese (the Gruyere cheese exhibits this in a high degree) is indi¬ 
rectly due to the incomplete removal of the whey, the sugar contained becoming 
during the ripening converted into alcohol and carbonic acid, which by its 
expansion while escaping produces the vesicular texture. Dutch cheese does not 
exhibit this appearance on account of being strongly pressed and containing much salt, 
by which the fermentation of the sugar of milk in the cheese is prevented. The 
quality of the cheese depends to some extent upon the temperature of the room in 
which it ripens. At Allgau 1 cwt. of Swiss cheese of the first quality is produced 
from 600 litres of milk, while for the second quality 720 to 750 litres of milk are 
taken for the same weight. The theory of cheese formation is not well known, but 
it appears that fermentation plays an important part in it. W. Hallier has proved 
that freshly made cheese is filled with ferment nuclei (Kernheje). 

Cheese cannot be formed without this ferment, and by the addition of suitable 
ferments the duration of the cheese-ripening process and the quality of the cheese 
may be to some extent regulated at will. By exposure to air cheese undergoes 
changes which maybe best observed in skimmed-milk cheese. When new or young 
its colour is white. By being kept so that it does not dry, it turns yellow and often 
becomes transparent, waxy, and then exhibits the peculiar odour of cheese. When 
cheese gets very old it becomes a soft pasty mass, this change commencing at the 
outside and progressing towards the interior. The waxiness of cheese is due either 
to an evolution of ammonia or of acid. Mild cheese usually exhibits an acid reaction, 
while strong cheese is ammoniacal. Chemically speaking, skimmed-milk cheese is 
a compound of caseine with ammonia or ammonia bases, amylamine for instance. 
The so-called dry cheeses, green Swiss cheese, consists of an infusion of herbs, 
Melilotus, &c., with volatile fatty acids, valerianic, capric, caproic acids, and indif¬ 
ferent substances, leucin, &c. The composition of sweet milk cheese (a) and of sour 
skim-milk cheese ( b ) is exhibited by the following table :— 



a. 

b. 

Water . 

. 360 

44 *o 

Caseine. 

.. 29'0 

45 0 

Fatty matter... 

. 30'5 

60 

Ash . 

••• .. 4‘5 

50 


MILK . 


5«>i 

The results of the researches of Payen on cheese are quoted below in 100 parts for 
the following kinds:—1. Brie. 2. Camembert. 3. Roquefort. 4. Double cream 
cheese. 5. Old Neufchatel cheese. 6. New Neufchatel cheese. 7. Cheshire. 
8. Gruy&re. 9. Ordinary Dutch. 10. Parmesan cheese. 


I. 



1 - 

I. 

2. 

3- 

4- 

5- 

Water . 

45-20 

5 r 9° 

34-50 

950 

34*50 

Nitrogenous matter 

18-50 

18-90 

26-50 

18-40 

13-00 

Nitrogen . 

2'93 

3 00 

4’2I 

2*92 

3-3i 

Fatty matters . 

2570 

21 00 

30-10 

59-90 

41-90 

Salts . 

5-60 

4-70 

5*oo 

650 

3-60 

Non-nitrogenous organic ! 






matter and loss > 

5*°o 

4'5o 

3-90 

570 

7~oo 




H. 




t 

6. 


8. 

9- 

- 

10. 

Water . 

36-60 

35-90 

40-00 

3610 

27-60 

Nitrogenous matter ... 

8*oo 

2000 

3I-50 

29*40 

44-10 

Nitrogen . 

1-27 

4-I3 

5*00 

4-80 

7*oo 

Fatty matters . 

40-70 

26-30 

24-00 

27-50 

16 - oo 

Salts . 

0-50 

4*20 

3*oo 

090 

5-70 

Non-nitrogenous organic! 

14-20 

760 

1-50 

6’io 

6-6o 

matter and loss I 







The varieties mentioned under I. exhibit an alkaline reaction, and contain with 
ammonia cryptogamic plants, or, as it is termed, are mouldy. The varieties under 
II., so-called boiled, strongly pressed and salted, cheese, exhibit an acid-reaction, as 
also does freshly prepared caseine. A portion of the fat contained in the cheese is 
even from the first decomposed into glycerine and fatty acids.. 

Emmenthaler (a) and Backstein (&) cheese are composed, according to Lindt’s 
researches (1868), as follows:— 

a. b. 





r - 

1 \ 

f - 



Water... 

. 

. 

37*4 

367 

45-2 

35*8 


Fatty matters ... 

.. 

30-6 

30'5 

28-2 

37*4 


Caseine 

. 

. 

28-5 

29*0 

23-2 

24-4 


Salts ... 

. 

. 

3*5 

3-8 

3*4 

2-4 

• 




100-0 

1000 

1000 

1000 


The results of E. Horni 

g’s recent 

analyses (1869) of different kinds of cheese are:— 


1. 

2. 

3- 

4- 5- 

6. 

7- 

8. 

Water . 

38-66 

56-60 

51-21 

57-64 36-72 

34-08 

59-28 

49*34 

Fatty matters ... 

20-14 

i7’05 

916 

20-31 33:69 

28-04 

10-44 

20-63 

Caseine . 

34*90 

18-76 

33-6 o 

18-51 25*67 

23*28 

24*09 

24-26 

Salts. 

6*17 

678 

601 

3-5I 371 

5-58 

6-17 

5*45 

Loss. 

0-13 

o-8i 

0*02 

0-04 0*21 

0*02 

002 

0-32 


100*00 

100*00 

100*00 

IOO'OO 100*00 

100*00 

100*00 

ioo-oo 


37 




















562 


CHEMICAL TECHNOLOGY. 


1. Dutch cheese. 2 ancl 3. Ramadoux cheese, made in Bavaria. 4. Neufcliatel 
cheese. 5. Gorgonzola cheese. 6. Bringen or Liptau cheese, from the Zyps 
Comitat, Hungary. 7. Schwarzenberg cheese. 8. Limburg cheese, made in the 
environs of Dolhain-Limburg, in Belgium. 

Freshly made caseine mixed with lime is used as a kind of cement. Caseine is 
also used in calico-printing as a mordant; and a solution of caseine in borax is used 
instead of glue. In the seeds of the leguminous plants, peas, beans, lentils, &c., is 
met with a nitrogenous substance which is soluble in water and precipitable there¬ 
from by weak acids; this material is very similar to caseine, and according to 
M. J. Itiers’s accounts, peas and beans are in China boiled with water and strained, 
and to the liquid thus obtained some solution of gypsum is added, whereby the 
vegetable caseine (legumine) is coagulated, and the coagulum thus obtained is 
treated as that of milk, obtained by the addition* of rennet to the latter. The mass 
so obtained gradually becomes like cheese in all respects. 


Meat. 

aeneraiities. That which we term butchers’ meat is the muscular substance of 
slaughtered animals, together with more or less fat and bone, so that the meat 
exhibited for sale contains on an average in 100 parts:— 

Muscular tissue . 16 

Fat and cellular tissue. 3 

Bones . 10 

Juices . 71 


100 


Muscular tissue is histologically composed of a variety of complex tissues and 
fluids, the basis of which is animal fibre or fibrin, an organised proteine compound. 
The muscular fibre held together by cellular tissue forms the muscles, fat being 
deposited in the cellular tissue and in cells peculiarly constructed for that purpose. 
Blood-vessels, lymph-vessels, nerves, and other organised tissues are dispersed 
through the muscles and serve a variety of physiological purposes. The muscular 
tissue is impregnated with a proteine fluid in which are. met with a variety of other 
substances, as kreatinin, liypoxanthin, kreatin, inosite or muscular sugar, lactic acid, 
inosinic acid, extractive matter, and inorganic salts—among these chloride of 
potassium and phosphate of magnesia. 

constituents of Meat. The average result of a great number of researches recently made 
on the large scale concerning the quantity of water contained in the meat of fattened, 
and half- or non-fattened animals, are the following:— 


In the non-fattened meat 
„ „ half-fattened meat 
„ „ fully-fattened meat 
„ „ fat meat . 


Lamb. 

Sheep. 

Bullock. 

Pig- 

62 

58 

— 

56 

— 

50 

54 

— 

49 

40 

46 

39 

.— 

33 

— 

— 


It hence appears that with an increase of fat the quantity of water present in meat 
decreases, a portion being replaced by fat. Well fed and fattened meat contains for 
equal weights about 40 per cent more dry animal matter than non-fattened meat 
while in highly fattened meat it may amount to 60 per cent. 



MEAT. 


563 


The difference in nutritive value of the meat of well-fattened bullocks as compared 
with that of non-fattened is exhibited in the following percentage results obtained by 
Breunlin:— 



Fattened. 

Non-fattened. 

Water . 

. 38*97 

5968 


Ash . 

. ... 1*51 

i *44 


Fat. 

. 23*87 

8*07 


Muscle. 

. 3665 

30*81 



100*00 

100*00 


1000 grms. contain :— 

Muscular 




Meat. Fat. 

Ash. 

Water. 

Meat from fattened bullocks ... ., 

•• 356 239 

15 

390 

Meat from non-fattened bullocks., 

,. 308 81 

14 

597 

Difference . .. 

+48 + i 58 

+ 1 

—207 


Consequently the meat of fattened bullocks contains in 1000 parts 207 more of 
solid nutritive matter than the meat of the same in unfattened condition. 

The cooking of Meat. Meat is either roasted or boiled. By boiling, meat is very essentially 
altered in composition according to the time it is boiled and the quantity of water 
used to boil it in. The fluid in which meat has been boiled contains soluble alkaline 
phosphates, salts of lactic and inosinic acids, phosphate of magnesia, and a trace of 
phosphate of lime. In order to be of the highest nutritive value, meat should retain 
all its soluble constituents; hence boiled meat loses much in nutritive power. The 
albumen contained in meat is lost by boiling according to the usual plan. Meat 
intended to be boiled should be immersed in boiling water to which some salt has 
been added, the meat being put in while the water boils violently, whereby so great 
a heat is at once imparted to the outer portions of the meat as to coagulate the 
albumen, which then acts as an impermeable layer, retaining the juices in the meat. 
Liebig’s directions for making good broth are the following:—Lean meat is minced, 
mixed with distilled water, to which a few drops of hydrochloric acid and common 
salt are added. After having been digested in the cold for about an hour, the liquid 
is strained through a sieve, ancl upon the residue some distilled water is again 
poured so as to extract all soluble matter. In this way an excellent and highly 
nutritive cold solution of extract of meat is obtained; this may be drunk without 
being heated, and contains albumen in solution, which is coagulated by heating. 
100 parts of beef yield an extract containing 2*95 parts of albumen and 3*05 parts of 
other constituents of meat not coagulable by heat. Chevreul obtained from 500 grms. 
of beef containing 77 per cent water, 27*25 grms. of extract, in which were 3*25 grms. 
fat; deducting these there remain 4*8 per cent extract. The bulk of this fluid extract 
was 1*25 litre, the weight 1013 grms., and it contained:— 


Water 


Organic matter 


( Soluble in alcohol ... 
1 Insoluble in alcohol 


Alkaline salts. . 

Earthy phosphates. 


99 r 3 ° 

9*44 

3-12 

8*67 

0*46 


1013*09 












5&4 


CHEMICAL TECHNOLOGY. 


Broth made from beef contains only 3 parts of meat substance inclusive of glue 
and fat. 

Under the best conditions, 1 kilo, of beef yields 
Soluble in cold water ... 601 


Coagulated albumen 

... 29*5 

Albumen in solution 

... 305 

Glue-yielding substance 

6*9 

Fibrous matter . 

... 164*0 


Insoluble in cold water ... ] 

Fat . 20 

Water.750 

me Boiling of Meat. We have already stated that the meat intended to be boiled 
should be immersed in boiling water and the fluid kept boiling for a few minutes, so 
much cold water being next added as will reduce the temperature of the liquid to 
y 0 °. or 74 0 . At that heat the liquid should be kept for some hours to produce a very 
savoury, sweet, succulent piece of boiled meat. If, however, it is desired to make a 
strong broth, lean meat is first minced, next well exhausted with cold water, and then 
slowly heated—best on a water-bath—and just allowed to come to the boil over a slow 
fire. The liquid is strained from the solid meat, and the latter put into a clean cloth and 
well pressed. The residue is fit only for the making of manure. The broth may be 
coloured with caramel if desired. Broth so made contains all the soluble consti¬ 
tuents of meat, and exhibits an acid reaction owing to the free lactic and inosinic 
acids. Broth does not owe its good properties to the gelatine it contains, this 
substance being present in very small quantities, while the so-called bouillon 
tdblettes obtained from bones are altogether unfit for food. These tablettes should, 
not be confused with solid meat-extract cakes of Russian make, which contain, 
according to Reichardt (1869) :—• 

Water driven off at ioo° . 3:5*13 per cent. 

Ash .; ... 475 „ „ 

Fat . o’22 ,, „ 

Nitrogen . 10*57 „ „ 

Substance soluble in alcohol at 80per cent ... 38*09 „ ,, 


When broth is boiled fcr a long time it becomes deep coloured and assumes 
the very agreeable flavour of roast meat. Evaporated upon a water-bath it yields a 
pasty deep brown-coloured mass, 18*27 g rms * of which yield, with 1 lb. of hot water 
and the addition of some salt, a very strong and excellent soup. 32 lbs. of bones 
with the adhering scraps of lean meat yield 1 lb. of this extract. Extract of meat as 
general^ met with is now made in South America by several firms, viz., at Fray- 
Bentos, Uruguay, Gualeguaycliu (Entre Rios). 1 kilo, of this extract contains all the 
soluble portion of 34 kilos, of meat without bones, or 45 kilos, of average butchers’ 
meat. Australian extract of beef (the American extract is of mutton and beef mixed, 
manufactured by. R. Tooth) is largely imported into Europe. The chief test for the 
purity of the extract of meat is its solubility in alcohol at 80 per cent, next the 
quantity of moisture it contains, and the absence of albumen and fat. 60 per cent of 
the extract at least should be soluble in alcohol. The quantity of water amounts to 
about 16 per cent, the nitrogen -to 10 per cent, and the ash to 18 to 22 per cent, 
consisting essentially of phosphate of lime and magnesia, chlorides of the alkalies, 
among which potassium chloride predominates. 

Preservation of Meat. Among the many methods employed for the preservation of meat, 
that by complete exclusion of air ranks foremost. Appert’s plan of pacldng meat in 



MEAT. 


565 

tin canisters, from which the air is completely exhausted, is generally the follow¬ 
ing:—The meat, or very concentrated soups, game, &c., is put into tin canisters, 
which are thoroughly filled. A lid is then soldered on, in which a small hole is made 
for the purpose of entirely filling any interstices with gravy. This having been 
done, the small hole is soldered over, after which the canisters are placed in a 
cauldron filled with brine and boiled therein for a half to four hours,, according to 
the size of the canisters. When any of them is not well soldered, there will 
issue from the leakage smaller or larger vesicles of air and vapour, and where 
such is the case hot solder is applied to the spot. By this boiling the albuminous 
substances are coagulated and converted into a less-readily putrescible modification. 
The oxygen of the air contained in the canisters is partly converted into carbonic 
acid, partly deozonised, and thus rendered ineffective for the production of putres¬ 
cence. After having been submitted to the action of boiling heat for some time, the 
' canisters are placed in a room heated to 30°, and left there in order to test whether 
putrefaction can set in, manifested by the bulging outward of the top cover, which, 
if the operation has been thoroughly successful, is usually somewhat concave in con¬ 
sequence of a vacuum having been formed inside the tin. After having been thus 
tested for several days, the canisters may be considered sound, and will keep for an 
indefinite period.* Dr. Redwood’s method of preserving meat under' a layer of 
paraffin, and Shaler’s plan of preserving meat in dry carbonic acid gas at o°, are in 
principle the same as Appert’s method. 

P \vahtowai of water/ Meat may be preserved by drying it or salting it, both methods 
being based upon the withdrawing of the water. Although drying is the best 
method of preserving meat, it is an operation attended with very great diffi¬ 
culty. The natives of North and South America cure meat by cutting it into 
thin strips, removing the fat, and rubbing Indian-corn meal on the surface. Thus 
prepared, the meat is exposed to the heat of the sun and dries rapidly, forming a 
flexible non-putrescent mass, which in North America is termed Pemmikan, in 
South America Tassajo, and in South Africa Biltongue. 100 parts of beef, which is, 
after drying, rolled up so as to form a compact mass, yield 26 parts of tassajo. The 
drying of meat is in Europe never effected on a large scale, partly on account of the 
low temperature, partly on account of the necessity of cutting the meat into pieces, 
rendering it in many instances unfit for culinary purposes. 

Many preparations of flour and meat extract have been introduced at different 
times under the name of meat-biscuit, first made in 1850 by Gail Bordon, at 
Galveston, in Texas, U.S., and greatly improved upon by C. Thiel, at Darmstadt. 
The latter minces fresh lean meat, next exhausts it with water, and uses the liquid 
obtained for mixing with the flour instead of water. The large biscuit manufacturing 
firms in England, especially Huntley and Palmer at Reading, prepare patent meat- 
biscuits or wafers, made with Liebig’s extract of meat and Hassall’s flour of meat. 
On the Continent, E. Jacobsen, at Berlin, prepares a similar biscuit, more especially 
with the view of preparing soup. To the mixtures of animal and vegetable matter 
prepared so as to be suitable for keeping for a length of time belong the pea- 
sausages, first made by Griineberg in Berlin, and largely used during the late war 
as an excellent food for the German armies. 

salting Meat. This method of preserving meat, based upon the principle of with¬ 
drawing water, has been used from time immemorial. The salt, while penetrating 
into the meat and thereby hardening it, displaces the water and aids the preservation 


566 


CHEMICAL TECHNOLOGY. 


of the substance. The freshly-slaughtered meat is first rubbed with coarse salt, and 
then left in a cask with salt for some days. It is next pressed and put into another 
cask, the wood of which has been previously soaked with brine. Some salt is then 
added, and lastly the brine, which had been obtained by pressing the meat, is 
poured over it, and the lid of the cask put on. Frequently some nitrate of potash 
and sugar are added, as well on account of the antiseptic property of these substances 
as for imparting a bright red colour to the meat. 

Salt, however, not only withdraws water from the meat, but also, as has been proved 
by Dr. Liebig’s researches, some of the very best and essential portion of the juices of 
the meat, including albumen, lactic and phosphoric acids, magnesia, potash, kreatin, 
and kreatinin. Hence it is clear, that unless these substances are in some way or other 
added to the salted meat, its use as food for a lengthened period cannot fail to become 
injurious to the system, and it is surmised that scurvy is due to this condition of salt 
meat. Liebig has suggested that meat, instead of being treated with dry salt, should 
be salted with a strong brine made up of common salt, Chili saltpetre, chloride of 
potassium, and extract of meat. The salt to be used for making this brine should be 
previously purified by the application of a solution of phosphate of soda, whereby 
lime and magnesia are precipitated. Cirio’s method of meat preservation, which was 
exhibited in 1867 at the Paris Exhibition, consists in placing the meat in vacuo and 
then forcing brine into it. By this process the nutritive value of meat is much 
impaired owing to the loss of the juices. 

smoking or Curing Meat. The rationale of this process and the preservative action of the 
smoke have not been scientifically elucidated. In the first place the heat of the smoke 
dries the meat, while, further, smoke contains a creosote, which, according to the 
more recent researches of Hlasiwetz, Gorup-Besanez, Marasse, and others, essentially 
consists of a mixture of C 7 H 80 2 , C 8 H io 0 2 , and C 9 H 12 0 2 . This creosote possesses 
the property of coagulating the albuminous substances of meat, and once coagulated 
and thereby rendered insoluble these substances are not capable of decay, or only 
so after a very great lapse of time. Smoke, moreover, contains some pyroligneous acid- 
and other creosote-like substances (oxyphenic and carbolic acids), which undoubtedly 
play some part in the preservative action. 

Vinegar is an excellent preservative of meat, especially in hot summer weather. 
Abroad meat is frequently put into a clean linen cloth which is thoroughly soaked 
with vinegar, some salt also being sprinkled on the cloth. Meat kept for a few days 
in this manner is very tender and readily digested. It is very probable that vinegar 
might be advantageously employed on the large scale for the preservation of meat 
together with complete exclusion of air. In order to prevent the vinegar extracting 
the juices of the meat, the latter should be exposed to the action of the vapours o* 
strong vinegar. 

Lamy more recently, and Braconnot, Robert, and De Dombaslc, nearly half a cen¬ 
tury ago, proposed to preserve meat by the aid of sulphurous acid gas, pieces of meat 
weighing some 2 to 3 kilos, being exposed to the action of this gas for ten minutes, 
while larger pieces of 10 kilos, and more, are exposed to the action of the gas for 20 to 
25 minutes. After having been exposed to fresh air for some minutes for the purpose 
of getting rid of the excess of the gas, the meat is coated with a brush with a solu¬ 
tion of albumen in a decoction of marsli-mallow root, to which some molasses have 
been added. Very recently meat has been preserved by first drying it in a current of 
hot air and next coating it with a film of caoutchouc or gutta-percha, by immersing 


MEAT. 


567 

the meat in a solution of these substances in chloroform or sulphide of carbon. It is 
very generally known that a temperature below freezing-point is a most perfect pro¬ 
tection against decay of animal matter ; hence ice is largely used for the preservation, 
of fish in summer time. Meat as well as game and poultry are best preserved in hot 
weather in ice pits. In no country of the world is so much use made of this mode 
of preserving meat and vegetables as in Russia, where the very severe winter is 
turned to good account by the preserving of all kinds of animal food; in fact, oxen, 
sheep, hogs, deer, and all kinds of game and poultry are brought to market in a frozen 
condition, and may be kept so for any length of time without impairing the goodness 
or taste after cooking. At St. Petersburg large stores of frozen animal food and 
game brought from distances of hundred of miles are kept throughout the winter. At 
the Dornburg, near Hadamar (Province of Nassau, Prussia), a natural permanent 
ice store exists wherein perishable food is kept stored in large quantity. The 
artificial production of ice by means of Carre’s machine is employed in New South 
Wales for the freezing of meat, which is next packed in ice ready for transport. 


DIVISION VI. 


DYEING AND CALICO PRINTING. 


On Dyeing and Printing in General. 

Dyeing and Printing in General. The object of the art of dyeing is to impart to textile 
fibres, chiefly in the shape of woven tissue, but in many instances as yarn, some 
colour or other. Dyeing is distinguished from painting by the fact that the 
pigments are fixed to the animal and vegetable textile fibres according to certain 
physico-chemical principles, and are not, as in painting, simply fixed by adhesion to 
the surface, although painters and artists occasionally use the same pigments. 
Printing consists in the duplication of coloured patterns, and is a very important part 
of dyeing. 

Dyes. The materials employed for the production of colours, the dyes and pigments, 
are partly of mineral, animal, and vegetable origin, partly artificially obtained—that 
is, the products of modem chemistry. Among the very large number of inorganic 
pigments few only are as such fit for use, and if employed at all it is by an indirect or 
circuitous process, that is, they are produced upon the woven fabric itself. For 
instance, chromate of lead is obtained by first impregnating the woven tissue with 
acetate of lead, after which the fabric is treated with a solution of bichromate or 
neutral chromate of potash, the result being the formation of a solid adhering 
chromate of lead. Among many other inorganic pigments may be enumerated— 
Berlin blue ; hydrated oxide of iron, for drab, nankeen, or rust colour ; bistre colour, 
hydrated oxide of manganese: chrome-green, oxide of chromium. Among the dyes 
of animal origin are—The ancient Tyrian purple, derived from a mollusc, a native of 
the Mediterranean, now not used; kermes (Coccus ilicis) ; cochineal (Coccus cacti ); lac 
dye (Coccus laccai). A much larger number of dyes are obtained from the vegetable 
kingdom. It appears from recent researches, that a large number of the so-called 
vegetable pigments are present in the plants themselves in a colourless condition, 
becoming coloured by the action of the atmosphere. It is impossible to mention any 
general properties of the vegetable pigments, because excepting the fact that they are 
all coloured, they are not possessed of any property common to all. Nearly all dyes 
fade by the combined action of sunlight and moist air. Chlorine destroys most 
colours ; while many dyes are bleached, not destroyed, by sulphurous acid. We owe 
to the researches of modern chemistry a class of pigments which surpass in beauty 
almost all the native dye materials. These chemically prepared dye materials are 
chiefly derived from coal-tar, more particularly from benzol, toluol, carbolic acid, 
anthracen, and naplithalin. The pigments derived from these substances are 



DYEING. 


569 

commonly termed aniline or coal-tar colours, fuclisin, magenta, aniline blue and violet, 
Manchester yellow, aniline orange, picric acid, aniline brown, coralline, alizarine 
(artificially prepared from anthracen), magdala red, aniline black, and aniline green. 
Among the chemically prepared colouring matters should be mentioned those 
obtained by the decomposition of the alkaloids (cinchonine, quinine, &c.), chinoline 
blue, quinine green (thalleiochine), and also murexide, a product of the decomposi¬ 
tion of uric acid. 

Lake Pigments. The so-called lakes are compounds of starch, alumina, oxide of tin, oxide 
of lead with sometimes carbonate of lime, baryta, or oxide of antimony, with the colouring 
matter of madder, cochineal, woad, logwood, tar-colours (viz. coralline, fuchsin, aniline 
'violet), but as yet these substances are not prepared in definite proportions. By paints 
we understand substances which as a rule are insoluble in water and are mixed with 
either weak glue solution, being then termed water-colours, or with linseed oil, called 
oil-paints. To these pigments belong white-lead, red-lead, ultramarine, Berlin blue, 
vermillion, chrome-yellow, bone-black, &c. The ordinary water-colours arc insoluble 
in water, being finely suspended therein by the aid of gum, white of egg, gum 
tragacanth, &c. The pastel pigments used for drawing are made up of various 
pigments, mixed with pipe-clay, soap, and some tragacanth mucilage, and moulded 
into cylindrical sticks. 

colouring Materials. Dyeing means strictly the tinging or colouring of absorbent 
substances by impregnating them with solutions of colouring matters. It is thus 
opposed to painting, which consists in laying a colour upon the surface to be 
coloured. In the art of dyeing some colouring matters are applied by immersing 
the tissue to be coloured in the decoction or solution of the pigment. Some sub¬ 
stances are applied to the surface of the woven fabric by the intervention of what 
is technically termed a mordant, which is in the case now under consideration 
only a means of obtaining adhesion, as when, for instance, ultramarine is fixed by 
the aid of white of egg. Sap-colours are substances more or less soluble in water, 
covering very slightly, and more or less translucent, as sap-green, gamboge, carmine 
solution, many of the tar-colours, &c. 

The Coal-Tar Colours. 

coai-Tar. This substance is very largely obtained as a by-product of the dry dis¬ 
tillation of coal for the purpose of gas manufacture, and is a most complex mixture 
of a very large number of substances, among which are fluid and solid hydro¬ 
carbons (benzol, toluol, cumol, cymol, anthracen, naphthalin); acids (carbolic or 
phenylic, cresylic, phlorylic, rosolic) ; bases (aniline, chinoline, odorine, picoline, 
toluidine, coridine, &c.), and asplialte-forming materials. Leaving the small quantity 
of basic substances out of the question, 100 parts of tar consists of the following 


substances:— 

Benzol . 1*5 

Naphtha . 35*o 

Naphthalin . 220 

Anthracen. i'o 

Carbolic acid . 9 ° 

Pitch. 31 '5 


1000 




















570 


CHEMICAL TECHNOLOGY. 


By fractional distillation of tar we obtain, on the one hand, light oils, from which 
benzol and its liomologues are separated; on the other hand, heavy tar oil, which is 
used for making carbolic acid ; while, lastly, antliracen is separated from the pitch. 

Approximatively, the following table shows the quantity of the various materials 
obtained by the dry distillation of coal:— 


ioo kilos 
ioo kilos 


of coal yield 300 kilos, of tar. 

of tar yield 075 to 1 kilo, of antliracen. 

3 00 kilos, of crude benzol. 

1‘50 kilos, of pure benzol. 

3 - oo kilos, of nitro-benzol. 

2'25 kilos, of crude aniline. 

3'37 kilos, of crude aniline red. 
1‘12 kilos, of pure fuchsin. 


For tne preparation of 1 kilo, of pure fuchsin 60 cwts. of coal are required. 

Benzol. Chemically speaking, benzol or benzine is a fluid hydrocarbon, dis¬ 

covered in 1825 by Faraday among the products of the dry distillation of oil, in 
the liquid resulting from the strongly compressed oil gas. In 1833 Mitscherlicli 
obtained this body by distilling benzoate of lime. Leigh, at Manchester, 1842, first 
discovered benzol in coal-tar; and to Mansfield’s researches is due the method 
of separating benzol from tar by a process available on the large scale. 

The benzol as met with in commerce is a mixture of benzol boiling at 8o'4° with 
toluol, C 7 Hs, boiling at 108°; xylol, CsHi 0 , boiling at 130°; cumol, C 9 H I0 , boiling at 
151 0 ; and cymol, Ci 0 H I2 , boiling at 175 0 ; benzol and toluol, however, predominate. 
Abroad benzol is sold to the aniline makers at a certain specified percentage 
of benzol, CgH^; for instance, benzol at 30 to 40 per cent contains by bulk or 
weight, as may be agreed upon, the above percentage of the compound CeHg, the 

rest being 60 to 70 per cent of 
toluol and xylol, forming a fluid 
which is suitable for making aniline 
red, while for aniline blue or black a 
fluid at go per cent benzol, CeHe, is 
required. The boiling-point of the 
benzols usually employed for making 
the so-called tar-colours varies from 
8o° to 120 0 , while the specific gravity 
varies from 0 85 to 0*89. 

Benzol is prepared from light tar 
oil which boils below 150°. The 
apparatus invented by Mansfield for 
this purpose is shown in Fig. 265. 
a is the still placed on a furnace, 
n; c is filled with cold water. As 
soon as the oil in the still begins to 
boil, the vapours are condensed in b and flow back into a ; this continues until 
the water in c has been heated to a certain temperature, when the vapours are 
condensed in the cooler, d, the liquid flowing at n into the carboy, s. As soon as the 
water in c begins to boil, all the substances contained in the tar-oil and volatile 


Fig. 265. 


















DYEING. 


571 


at ioo° are condensed and collected in s. A very pure benzol is prepared with this 
apparatus. By opening the tap m , the hydrocarbons which boil above ioo° can 
be rectified. The stopcock, i, is used for emptying the still. In the benzol works the 
apparatus exhibited in Fig. 266 is used, a is the still, n the condenser, c a water 

Fig. 266. 



Fig 267. 



tank. At the commencement of the operation the water in c is heated by means of 
the steam-pipe d, which communicates with the steam boiler. The tube g is attached 
to the still; i is a contrivance for filling, b for emptying it. The condensed water is 































































































572 


CHEMICAL TECHNOLOGY. 


carried off by means of h. By freezing benzol and pressing the solid substance 
obtained it may be rendered quite pure. 

In the year i860, Dr. E. Kopp, at Turin, showed that the preparation of benzol 
might be advantageously effected by the use of an apparatus similar in construction 
to that employed in spirit distilleries. Coupier has constructed an apparatus upon this 
principle, which is shown in Fig. 267. a is the still; at b the crude benzol is 
poured in; c is a steam-pipe for heating the still and its contents. The vapours 
evolved from the boiling liquid are carried into the column n, which acts as a dephleg- 
mator, by which a first fractionation is effected. The volatile vapours which are not 
condensed in n are carried to the apparatus d, which is filled with a solution of 
chloride of calcium. This apparatus is kept at a uniform temperature determined by 
the thermometer, t , and maintained by the steam-pipe m. 

The steam conveyed by the heating pipe escapes by p. When it is desired to pre¬ 
pare pure benzol the chloride of calcium solution is heated to 8o°. The vapours which 
are conveyed to g are a mixture of benzol, toluol, &c. As the temperature of the 
receiver g does not exceed 8o°, the vapours of toluol and other homologous 
compounds, as xylol, are condensed; while the vapours still uncondensed are carried 
to the receivers h, i, and k, losing or depositing there the last. traces of the less 
volatile hydrocarbons, becoming finally condensed in l, surrounded with cold water, 
and trickling down into the carboy, m. The fluid condensed in g, h, i, and k, flows 
back into the column n. As the receiver g contains the heaviest oils these are 
carried, for the purpose of dephlegmation, to the lower portion of the column, while 
the products condensed in k are conveyed by pipes into the upper portion of 
the column. When it is desired to prepare toluol instead of benzol the chloride of 
calcium apparatus is heated to 108° to 109°. 

H. Caro, A. and K. Clemm, and F. Engelhorn have suggested, instead of making 
benzol from coal-tar, it should be extracted from coal-gas by causing this to be passed 
slowly through tar-oils which have a higher boiling-point than benzol, toluol, &c., and to 
extract by distillation the benzol, &c., from these heavy oils after they have become 
saturated. The heavy oils can serve the same purpose again, while as regards the 
depreciation of the illuminating power of the gas caused by the withdrawal of the 
hydrocarbons, benzol, &c., present in the gas as vapours, the authors suggest the 
saturation of the gas with petroleum oil (benzoline). This mode of making benzol is 
not yet practised on the large scale. 

Bitro-benzoL The benzol is converted into nitro-benzol by the aid of nitric acid; the 
commercial article is a mixture of nitro-benzol, Cg f Sa nitro-toluol, C 7 j 

f IJNU2, ' 

and nitro-xylol, Csj^Q^. E. Mitscherlich discovered nitro-benzol in 1834, and 

C. Collas first prepared this substance on the large scale at Paris under the name of 
Essence de Mirbane. The apparatus employed formerly for the making of this prepara¬ 
tion was contrived by Mansfield, and consists of a convoluted glass tube, which 
towards its top or uppfer end is bifurcated so as to form two separate tubes fitted 
with funnels. Into one of these a continuous stream of benzol, and into the other 
strong nitric acid, is caused to flow; and while these liquids are carried downwards 
by gravitation through the windings of the tube the combination takes place, and 
the warm liquid is so far cooled that it can be collected at the lower end of the tube. 
The crude nitro-benzol thus obtained is rendered pure by first washing it with water 
and next with a dilute solution of carbonate of soda. 


DYEING. 


573 

Para-nitro-benzoic acid, a substance isometric with nitro-benzoic acid, is found in 
the washings of the nitro-benzol. 

It is preferable, however, to prepare nitro-benzol from a mixture of 2 parts of 
nitric acid at 40° Beaume (sp. gr. 1-384) and 1 part of concentrated sulphuric acid, 
the operation being carried on in closed vessels very similar to those in use for 
making aniline. The upper part of the apparatus is fitted with a tube for conveying 
the nitrous acid fumes to a chimney, while an S-shaped tube connects the apparatus 
with the tank containing the acid mixture. The quantity of benzol intended to be 
nitrated is introduced into the apparatus at one time; the mixed acids are gradually 
poured into the benzol, and the reaction aided by a stirring apparatus. Any benzol 
volatilised by the heat generated by the reaction is condensed by an apparatus fitted 
to the reaction vessel and is thus saved. The end of the reaction is indicated by 
the liquid becoming colourless and being separated into two distinct strata by the 
addition of water. The acid is first diluted to 50° B. (sp. gr. 1-532) and the fluids 
are separated by decantation. The nitro-benzol is purified by washing with water, 
the dilute acid mixture being used either in the making of sulphuric acid or in 
other chemical processes, such as the preparation of superphosphates. On E. Kopp’s 
suggestion nitro-benzol is now made by the aid of a mixture of nitrate of soda and 
sulphuric acid. 100 kilos, of benzol yield 135 to 140 of nitro-benzol. 

We distinguish three different kinds of nitro-benzol, viz.:—1. Light nitro-benzol, 
boiling between 205° and 210°. This is used in perfumery and soap-making in very 
large quantities under the name of artificial oil of bitter almonds, or Essence de 
Mirbane, sp. gr. = r20 (= 24 0 B.) 2. Heavy nitro-benzol, boiling between 210° and 

220°, possessing a peculiar fatty smell. It is not used in perfumery, but chiefly for 
the preparation of aniline red; sp.gr. s= rig (= 28° B.) 3. Very heavy nitro- 

benzol, boiling between 222 0 and 235 0 , sp.gr. = 1-167 (= 58° B.) Of disagreeable 
odour, this kind is chiefly used for the preparation of aniline intended for making 
aniline blue. 

Aniline. The crude aniline used for the preparation of the so-called tar or 
aniline colours is essentially a mixture of aniline, CgH 7 N, toluidine, C 7 H 9 N, and the 
pseudo-toluidine discovered by Rosenstielil, a body isomeric with toluidine. This 
kind of aniline is known in the trade as aniline oil. Pure aniline and pure toluidine 
only yield pigments under special conditions. Aniline was discovered at Dahme, in 
Saxony, by Dr. Unverdorben, in 1826, among the products of the dry distillation of 
indigo, and in 1833 Bunge, at Oranienburg, near Berlin, discovered its presence in 
coal-tar. Bunge also discovered that aniline yielded, when brought into contact 
with a solution of hypochlorite ’of lime (bleacliing-powder), a beautiful violet colour; 
hence the name kyanol [blue colouring oil). Dr. von Fritzsche, St. Petersburg, 1841, 
thoroughly investigated the substance obtained by Dr. Unverdorben from indigo, 
ascertained its composition, and called it aniline, from anil , the Portuguese term for 
indigo. In the year 1842 Zinin found that when nitro-benzol was treated with 
sulphuretted hydrogen, there was formed a base which he termed benzidam. The 
further researches of 0 . L. Erdmann and Dr. A. W. Hofmann, brought the fact to light 
that Dr. Unverdorben’s crystalline, kyanol, benzidam, and aniline were the same 
substance, to which the name aniline was then finally given. We owe to the exten¬ 
sive researches of Dr. A. W. Hofmann our present knowledge of aniline and its 
compounds. 

Coal-tar contains 0-3 to 0-5 per cent of aniline, but its extraction from tar io 


574 


CHEMICAL TECHNOLOGY. 


attended with so many difficulties that it is preferred to prepare aniline from nitro- 
benzol by a reaction discovered by Zinin ; that is to say, to bring nitro-benzol into 
contact with reducing agents, i molecule of nitro-benzol, C6H 5 N 2 0 =123, yields 
1 molecule of aniline, CgH 7 N = 93. In practice it is assumed that 100 parts of nitro- 
benzol yield 100 parts of aniline. 

Although sulphuretted hydrogen completely reduces nitro-benzol to aniline, the 
trade working on the large scale prefers to follow Bechamp’s method, the treatment of 
nitro-benzol with iron-filings and acetic acid. The apparatus in use for carrying 
out this operation was devised by Nicholson, and is exhibited in Fig. 268. It 
consists essentially of a cast-iron cylinder, a, of 10 hectolitres (220 gallons) cubic 
capacity. A stout iron tube is fitted to. this vessel reaching nearly to the bottom of 
the cylinder. The upper part of this tube is connected with the machinery g, while 

Fig. 268. 



the surface of the tube is fitted with steel projecticns. The tube serves to admit 
steam as well as acting as a stirring apparatus. Sometimes, instead of this tube, a 
solid iron axle is employed, and in this case there is a separate steam-pipe, d. ' 
Through the opening at k the materials for making aniline are put into the 
appai atus, while the volatile products are carried off through e. h serves for 
emptying and cleaning the apparatus. The S-shaped tube connected with the 
vessel b acts as a safety-valve. When it is intended to work with this apparatus, 
there is first poured into it through k 10 kilos, of acetic acid at 8° B. (= sp.gr. ro6o), 
previously diluted with six times the weight of water; next there are added 30 kilos, 
of iron-filings or cast-iron borings, and 125 kilos, of nitro-benzol, and immediately 
after the stirring apparatus is set in motion. The reaction ensues directly, and is 
attended by a considerable evolution of heat and of vapours. Gradually mere iron 

















































































































DYEING. 


575 


is added until the quantity amounts to 180 kilos. The escaping vapours are 
condensed in f, and the liquid collected in n is from time to time poured back into 
the cylinder, a. The reduction is finished after a few hours. The resulting thick 
magma exhibits a reddish-brown colour, and consists essentially of hydrated oxide of 
iron, aniline, acetate of aniline, acetate of iron, and excess of iron. Leaving the 
acetic • acid out of the question, the process may be elucidated by the following 
formula:— 

C 6 H 5 N 0 2 +H 2 0 +Fe 2 =C 6 H 7 N+Fe 2 0 3 . 

Nitro-benzol. Aniline. Peroxide 

of iron. 

This magma is either first mixed with lime or is put into cast-iron cylinders shaped 
like gas-retorts, and submitted to distillation, the source of heat being either an open 
fire or steam. The product of this operation, consisting of aceton, acetaniline, 
aniline, nitro-benzol, &c., is rectified by a second distillation, care being taken to 
collect only the product which comes over between 115 0 and 190°; but a 
product which comes over at between zio ? and 220° is • very suitable for 
the preparation of aniline blue. The aniline oil thus obtained is a somewhat 
brown-coloured liquid, heavier than water, and pure enough for the preparation of 
the aniline colours. According to Brimmeyer, acetic acid is not necessary, and a 
very good result may be obtained by mixing nitro-benzol with 60 parts of pulverised 
iron with acidified water (2 to 2*5 per cent of hydrochloric acid upon the weight of 
nitro-benzol), and leaving this mixture to stand in a retort for some three days 
before distilling off the aniline oil. In the aniline-oil works of Coblentz Freres, at 
Paris, nitro-benzol is reduced by the aid of iron-filings, a portion of which have been 
coated with copper by being immersed in a solution of the sulphate. 

The composition of the aniline oil—essentially a mixture of aniline, toluidine, and 
pseudo-toluidine—depends upon the nature of the benzol and nitro-benzol used for 
its preparation. The aniline oil boiling between 180° and 195° (sp. gr. = roi4 to 
ro2i = 2 0 to 3°B.) is prepared from nitro-benzols which boil between 210° and 220°, 
and the aniline it yields is chiefly used for aniline red ; while for aniline blue a very 
heavy nitro-benzol is employed, and for aniline violet a nitro-benzol which boils at 
210 0 to 225 0 . The following table exhibits the boiling-points of the substances which 
have been mentioned:— 


Benzol . 

... 8o° 

Nitro-toluol 

. 225 ° 

Toluol . 

... 108 0 

Aniline ... 

. 182° 

Nitro-benzol . 

... 213 0 

Toluidine 

.198° 


As regards the annual production of aniline oil it is now (1871) 3,500,000 lbs., of 
which 2,000,000 lbs. are consumed in Germany, and the remainder in Switzerland, 
England, and France 

I. Aniline Colours. 

Aniline Colours. The a nilin e oil serves for the industrial production of the so-called 
aniline or toluidine colours:—1. Aniline red. 2. Aniline violet. 3. Aniline blue 
4. Aniline green. 5. Aniline yellow and aniline orange. 6. Aniline brown. 7. Am 
line black. 

Aniline Red. i. This pigment or dye, also known as fuchsin, azaleine, mauve, 
solferino, magenta, roseine, tyraline, &c., is the combination of a base, which 
Dr. A. W. Hofmann has named rosaniline, with an acid, usually acetic or hydro- 


576 


CHEMICAL TECHNOLOGY. 


chloric. In Germany and Switzerland fuchsin is the hydroclilorate of rosaniline, 
C2oH ig N 3 ,ClH ; while in England the acetate is used, the formula being 

C 20 H ig N 3 ,C 2 H 4 0 3 . 

The base rosaniline is a colourless substance, but its readily crystallising salts are 
coloured. The composition of this base is expressed by the formula, C 20 Hi 9 N 3 ,H 2 0 ; 
and it is formed by the combination of 2 atoms of toluidine with 1 atom of aniline 
and the elimination of 4 atoms of H, which become oxidised— 

2C 7 H 9 N+C 6 H 7 N+30=2H 2 0+C 20 H I9 N 3 ,H 2 0. 

Accordingly the constitutional formula of rosaniline is:— 

C 6 H 4 ) 

2C 7 H6 • N 3 = - = 0 2 oHi 9 N 3 

According to Rosenstiehl’s researches (1869) all the different lands of fuchsin ol 
commerce contain pseudo-rosaniline, a base isomeric with rosaniline. 

Aniline red can be obtained from aniline oil by the application of various reagents, 
as, for instance:—Chloride of tin, Yerguin’s method; perchloride of carbon, Hof¬ 
mann and Natanson’s methods; pernitrate of mercury, Gerber-Keller;* perchloride 
of mercury, Schnitzer; nitric acid, Lautli and Depouilly; antimonic acid, Smith; 
arsenic acid, Medlock, Girard and de Laire; aniline oil, nitro-toluol, hydrochloric 
acid and metallic iron, Coupier. 100 parts of aniline oil yield 25 to 33 parts of 
crystalline fuchsin. 

Notwithstanding the great danger arising from the use of arsenic acid, and the 
difficulty of disposing of the very poisonous residues of this mode of preparing fuch¬ 
sin, the majority of the manufacturers of this dye prefer to use the arsenic acid 
method. According to Girard and de Laire’s method 1 cwt. of aniline oil and 2 cwts. 
of hydrate of arsenic acid at 6o° B. (=171 sp, gr.) are heated together for 4 to 5 
hours at a temperature which should not exceed 190° to 200°. The red fused mass 
.fuchsin mixture or smelting) formed by this operation is broken into small lumps 
and then boiled with water, and as soon as the mass is dissolved it is filtered through 
felt or linen bags, and the filtrate poured into tanks for the purpose of obtaining 
crystal's. After the lapse of 2 to 3 days the mother-liquor, a very poisonous liquid, 
which covers the crystals, is run off into perfectly water-tight tanks made of stone and 
coated with asphalte, and in order to precipitate the arsenic and arsenious acids 
there is added a mixture of washed chalk and lime, the ensuing precipitate being 
employed for making arsenical preparations.! The crystalline mass is purified by 
re-crystallisation. In the French fuchsin works the fused mass is dissolved in 
water and hydrochloric acid, and next neutralised with soda. The fuchsin is thus 
obtained as a crystalline cake, which is dissolved by being boiled with water, and this 
solution allowed to crystallise. The fuchsin thus obtained always contains arsenic 
and when it is desired to use a salt of rosaniline for colouring liqueurs and sweet¬ 
meats it is necessary to use a preparation made with either chloride of carbon or 
bichloride of mercury. The salts of rosaniline exhibit by reflected light a green 
golden hue ; by transmitted light the colour is red. The hydrochlorate of rosaniline 
is usually called fuchsin, the acetate, roseine, and the nitrate, azaleine. The solutions 


* The fuchsin prepared by the aid of this reagent is known as rubin, and is employed 
for dyeing silk and for colouring liqueurs and sweetmeats. 

f According to Dr. Bolley, the arsenical fluids obtained can be rendered again fit for use 
by distillation with hydrochloric acid. On being diluted with water the arsenious acid 
contained in the distillate is thrown down. 



DYEING. 


577 


of these salts in water or in alcohol exhibit a well-known and very magnificent 
carmine red. The tinctorial power is exceedingly high, since i kilo, of fuchsin 
is sufficient to dye 200 kilos, of wool. The tannate of rosaniline is very difficultly 
soluble in water. Fuchsin is the basis of nearly all other aniline colours; for 
instance, fuchsin yields violet or blue with aniline oil; fuchsin and iodide of ethyl, 
blue or violet. The action of the arsenic acid in the formation of rosaniline may be 
represented as follows :— 

2C6H9N} = ^2 o H 2 5N 3 -f- 3A s 2 05^ — C 20 H I 9 N 3 -f 3 As 2 0 3 4 - 3 H 2 0 . 

Aniline Arsenic Bosaniline. Arsenious Water 

oil. acid. acid. 


Aniline violet. 2. This pigment, also known as aniline purple, anileine, indisine, phena- 
nicine, liarmaline, violine, rosolan, mauveine, was discovered in 1856 by Dr. W. H. 
Perkin, and is prepared by the action of bichromate of potash and sulphuric acid. 
This substance has also been prepared by other reactions, for instance, by the treat¬ 
ment of a salt of aniline with a solution of bleaching-powder (Bolley, Beale, Kirk- 
ham) ; with peroxide of manganese (Kay), and peroxide of lead (Price), both in the 
presence of sulphuric acid ; by the action of permanganate of potash upon a salt of 
aniline oil (Williams) ; by treating aniline oil with chlorine (Smith); with ferri- 
cyanide of potassium (Smith); with chloride of copper (Caro and Dale). Indus¬ 
trially, only Dr. Perkin’s method with the bichromate and sulphuric acid is used. 
The base of the violet thus obtained is mauveine, C 27 H 24 N. 

The so-called Violet Imperial obtained by Girard and de Laire by the action 
of chromate of potash upon a mixture of aniline oil and hydrochlorate of rosaniline 
at 180 0 , differs from the preceding product, while another violet is obtained according 
to Nicholson by heating fuchsin to 200° to 215°. When a salt of rosaniline is heated 
with excess of aniline there are formed, before blue colours ensue, violet pigments, of 
which, according to Hofmann— 

The red-violet is monophenyl-rosaniline. 

The blue-violet is diphenyl-rosaniline. 


This latter yields on being further heated triphenyl-rosanilme or aniline blue. 
Accordingly,— 

Bosaniline red is . 0 2O H 2I N 3 O. 

Monophenyl-rosaniline (red-violet) is . C 2 oH 20 (C 6 H 5 )N 3 0. 

Diphenyl-rosaniline (blue-violet) is . C 20 H I9 (C6H 5 ) 2 N 3 0. 

Triplienyl-rosaniline (blue). c 20 h i8 (C 6 h 5 ) 3 n 3 o. 


The violet is now named the old or Nonpareil violet; and we have the new 
or iodine violet, Hofmann’s violet or dahlia colour, distinguished by the presence of 
the alcohol radicals, ethyl, methyl, and amyl, instead of phenyl. These new violets 
are obtained by heating to 100° or no 0 fuchsin with alcohol as a solvent, and 
the iodides, or more recently, the bromides, of the alcohol radicals, the mixture 
being kept in closed cylindrical vessels. According to the length of time this 
reaction is allowed to take place there are formed:— 


Monethyl-rosaniline, 
Diethyl-rosaniline, or 
Triethy 1-rosaniline. 


The most ethylised base exhibits a blue-violet colour,, while the less ethylised 
38 





CHEMICAL TECHNOLOGY. 


57 3 

exhibits a red liue. The methylated and ethylated violets are far more brilliant than 
the phenylated. The Violet de Paris , introduced by Poirrier and Chappat, is the 
product of the action of chloride of tin and similar compounds upon the methyl or 
ethyl aniline. 

Aniline Blue. 3. This colour, also known as azuline and azurine, was first obtained in 
1861 by de Laire and Girard by heating together for some hours a mixture of fuch- 
sin and aniline oil, and treating the product of this reaction with hydrochloric acid. 
The blue pigment produced is known in commerce as bleu de Paris or bleu de Lyons ; 
in dry state it is a copper-coloured shining material, not exhibiting green or yellow 
by reflection, the characteristic of fuchsin and aniline violet. In order to purify the 
aniline blue it is dissolved in strong sulphuric acid, and this mixture heated to 150° 
for i£ hours. By the addition of water to this solution the blue is precipitated in a 
modified and soluble form and is then called bleu soluble. We quote here the 
following methods for preparing this blue:—Rosaniline and aldehyde (Lauth) ; 
rosaniline and crude wood-spirit (E. Kopp) ; rosaniline and alkaline solution of 
shellac (Gros-Renaud and Schaffer), this is termed bleu de Mulliouse; also by oxida¬ 
tion of methylaniline (J. Wolff); rosaniline and bromated oil of turpentine (Perkin); 
rosaniline and isopropyl iodide (Wanklyn); rosaniline and ethylen iodide and 
bromide (M. Vogel); rosaniline and iodide and bromide of aceton (Smith and Sie- 
berg). The conversion of hydrochlorate of rosaniline (fuchsin) by heating with 
aniline oil into aniline blue is elucidated by the following formula:— 

C 20 H I9 N3,C1H+3 C 6 H 7 N = C 20 H i6 (C 6 H 5 ) 3 N 3 ,HC 1+3NH 3 . 

Rosaniline salt. Aniline. Aniline blue. Ammonia. 

c 6 h 4 ) 

The aniline blue thus prepared is rosaniline, 2C 7 Hg j-N 3 , in which 3 atoms of basic 

H3 i 

hydrogen have been substituted by 3 atoms of phenyl, CeH 5 ; or, in other words, 
this aniline blue is triphenyl-rosaniline, the hydrochlorate of which is—C 3 8H 32 N 3 C1. 
When a salt of rosaniline is heated with toluidine, the toluidine blue (tritolyl- 
rosaniline), C 4I H 37 N 3 = C 20 H I 6(C 7 H 7 ) 3 N 3 . When aniline blue is heated, the products 
of the dry distillation contain diphenylamine, C I2 HnN, a white crystalline compound, 
which when moistened with nitric acid yields a magnificent blue colour. Diphenyl¬ 
amine and its homologue phenyl-tolylamin, Ci 3 H I 3 N, which yields by dry distilla¬ 
tion bleuine, C 39 H 33 N 3 , are employed for the preparation of blue pigments. Dr. A. 
W. Hofmann found that when rosaniline is heated for a considerable length of time 
with iodide of ethyl or iodide of amyl, the result is that the most ethylated or 
amylated product (triethyl-rosaniline, or triamyl-rosaniline), yields aniline blue 
(iodine blue). Naphthyl also may be introduced into fuchsin to form, according to 
Wolff, a brilliant blue colour termed naphthyl blue. Under the names of Bleu de 
lumiere or Bleu de nuit, is known a blue dye which appears blue in daylight as well 
as in artificial light. A blue with a violet hue is known as Bleu de Parme. 

Aniline Green. 4. We are acquainted with two varieties of this colour, viz. aldehyde 
green and iodine green. The former, also called emeraldine, was discovered in 1863 
by Cherpin, chemist in M. Usebe’s Works at Saint Ouen, and is obtained by 
treating a sulphuric acid solution of sulphate of rosaniline with aldehyde. By 
cautiously heating this mixture, a deep green pigment is obtained which contains 
sulphur; the formula of this compound is, according to Dr. A. W. Hofmann, 
C 22 H 27 N 3 S 2 0. When required for use hyposulphite of soda is added and the 





DYEING. 


579 


compound boiled therewith in water; this solution is used for dyeing silk, and instead 
of the soda-salt sulphuret of ammonium or sulphuretted hydrogen may be used. 
The green-coloured material can be precipitated by a mixture of common salt and 
sodic carbonate, while a mixture of 2 parts of sulphuric acid and 50 to 70 parts of 
alcohol is a solvent for this substance. This aniline green is especially beautiful 
when seen by candle-light. The other kind of aniline green is the so-called iodine 
green, discovered (1863) by Dr. A. W. Hofmann, as a by-product of the manufacture 
of the methylated and ethylated rosaniline violets. 

Iodine green is obtained by the following process:—1 part of acetate of rosaniline, 
2 of iodide of methyl, and 2 of methylic alcohol, are heated together for several 
hours under a high pressure, or on the small scale in a sealed tube. When the 
operation is finished the result is a mixture of violet and green pigments dissolved in 
methylic alcohol. The volatile substances having been driven off by distillation the 
mixture of pigments is put into boiling water, wherein the green is completely 
dissolved, while the violet remains insoluble; the former is precipitated by a cold 
saturated solution of picric acid in water, the ensuing precipitate—picrate of iodine 
green—is collected on a filter, rapidly washed with the smallest possible quantity of 
water, and after having been partly dried, brought into commerce as a paste 
(en pate). The crystalline iodine green, free from picric acid, has the formula 
C25H33N3OI2. 

AniUne orange. 5* By the preparation of the red-coloured pigments from aniline oil, 
there is formed, as well as fuchsin, a resinous substance, from which Nicholson 
obtained a brilliant yellow-coloured pigment, the aniline yellow, aniline orange, 
aurin, or hydrochlorate of chrysaniline, which dyes wool and silk brilliantly yellow. 
Chrysaniline is a base of the formula C 20 Hi 7 N 3 . The most interesting salt of this 
base is the nitrate, which is insoluble in water. The residue of the preparation 
of fuchsin is treated with steam, and as soon as a portion of the base has been dis¬ 
solved, it is precipitated by the aid of nitric acid. Schiff obtained aniline yellow by 
the action of antimonic acid or hydrated oxide of tin upon aniline; M. Vogel 
obtained a yellow pigment by the action of nitrous acid upon an alcoholic solution of 
rosaniline. This aniline yellow has the formula, C 20 Hi 9 N 2 06 ; it is soluble in 
alcohol, not so in water. 

andSne B Browii. 6. Aniline black, C 6 H 7 N 0 6 , a deep aniline green formed by the 
action of oxidising agents upon aniline oil, was observed as early as 1843 by Dr. J. 
von Fritzsche, and was formerly prepared from the residues of the prepara¬ 
tion of aniline violet with bichromate of potash; but now we obtain aniline black by 
the action of chlorate of potash and chloride of copper upon hydrochlorate of 
aniline, as recommended by Lightfoot. As has been proved by Cordillot, these two 
chemical reagents may be replaced by ferricyanide of ammonium ; or, according to 
Lauth, by freshly precipitated sulphuret of copper. According to Bolley, the last 
substance acts by becoming oxidised to sulphate of copper, and simultaneously 
carrying' oxygen on to aniline. The black made according to this method! being 
insoluble has to be formed on the woven textile fabrics themselves, and is hence also 
called black indigo or indigo black. More recently, again, the so-called Lucas black 
(Peterson’s black) has been obtained, its most valuable property being that it is 
a ready made black, which for its full development only requires a weak oxidation. 
It is a black fluid mass consisting of hydrochlorate of aniline and acetate of copper, 
which mixed with some starch paste is printed on. the fabrics. The black becomes 


580 


CHEMICAL TECHNOLOGY. 


oxidised by exposure to air; the oxidation is rendered more rapid by ageing 
the fabrics in a room heated to 40°. Aniline black is used both in dyeing and 
printing textile fabrics. 

7. Aniline brown (Habana brown) is prepared according to de Laire by heating a 
mixture of aniline violet or aniline blue with hydrochlorate of aniline to 240°, until 
the mixture becomes brown-coloured The brown thus obtained is soluble in water, 
alcohol, and acids, and can be at once employed in dyeing. Another kind of aniline 
brown (Bismark brown) is obtained by fusing fuchsin with hydrochlorate of aniline. 


II. Carbolic Acid Colours. 

carbolic Acid Dyes. The portion of heavy coal-tar oil -which distils over at 150* to 200°, 
consists chiefly of carbolic acid (phylic acid phenol). As brought into commerce by 
C. Calvert and Co., C. Lowe and Co., and a great many other eminent firms both in 
this country and abroad, carbolic acid is a crystalline mass which becomes slightly 
reddened by exposure to air, fuses at 34 0 , and boils at 186 0 . It is prepared according 
to Laurent’s method by treating the heavy oils of tar with alkalies. There are three 
homologous phenols in this preparation:— 

Carbolic acid, CgHgO, 

Cresylic acid, CyHsO. 

Plilorylie acid, CsILoO, 

Carbolic acid is soluble in 33 parts of water. Calvert’s carbolic acid, as used in the 
colour-works, is prepared by cooling a mixture of the Laurent acid in water. At + 4° 
a hydrate of carbolic acid, C6 Hg 0+H 2 0, is separated, and by elimination of water it 
becomes pure carbolic acid, which fuses at 41 0 . While carbolic acid is very largely 
used in several degrees of purity for a variety of purposes as an antiseptic, disin¬ 
fectant, &c., more than 50 per cent of all the carbolic acid manufactured is used for 
the purpose of preparing the following pigments and dye materials :— 

1. Picric acid. 4. Coralline. 

2. Phenyl brown. 5. Azuline. 

3. Grenat soluble. 

picric Acid. Picric acid, trinitro-phenylic acid, C 6 H 3 (N 0 2 ) 3 0 , obtained by the action 
of nitric acid upon carbolic acid, or better, by treating crystallised phenyl sulphate 
of sodium with nitric acid, is a yellow substance crystallising in foliated structure, 
difficultly soluble in cold, readily in hot water, and also soluble in alcohol. It is 
used for dyeing wool and silk yellow, and with aniline green (iodine green), indigo, 
and Berlin blue, it is used for dyeing silk and wool green.* 

In France annually some 80 to 100 tons of picric acid are prepared, but the bulk is 
used for the manufacture of the picrate gunpowder (see p. 157). The ammonia salt 
of the trinitro-cresylic acid is met with in the trade as Victoria yellow as a dye 
material. When treated with cyanide of potassium, picric acid yields isopurpuric 
acid, while the trinitro-cresylic acid yields with the same cyanide cresyl-purpuric acid 
(V. Sommaruga); the potassium and ammonium salts of the respective acids yield the 
grenate brown. 

* It has of late become usual to employ, instead of pure (non-explosive) picric acid, the 
soda salt of that acid, under the name of picric acid and aniline-yellow. This has given 
rise to very serious accidents, owing to the highly explosive nature of the salt. 


DYEING. 


581 

Phenicicnne. 2. Phenyl brown was first prepared by Roth in 1865 by causing nitro- 
sulphuric acid to act upon carbolic acid; the resulting substance, phenicienne or 
phenyl brown, is an amorphous powder, a mixture of two pigments, viz., a yellow, 
according to Bolley, dinitrophenol, C 6 H 4 (N0 2 )20, and a black-brown substance 
which is similar to the humus compounds. Phenyl brown is used for dyeing wool 
and silk. 

GrenateBrown. 3. Grenat soluble, which has been very recently* introduced by 
J. Casthelaz in Paris as a substitute for orseille, is nothing more than the well- 
known isopurpurate of potash, which -was first discovered by Hlasiwetz, and is 
formed by the action of cyanide of potassium upon a solution of picric acid according 
to the following reaction, as described by Zulkowskv:— 

C 6 g3(N0 2 )39 +3KCN+2H a 0=C8H 4 KN 5 0 6 +NH3-fKC0 3 . 

Picric acid. Cyanide of Isopurpurate Am- Carbonate 

potassium. of potash. monia. of potash. 

As Grenate brown when dry is explosive with the least friction, it is kept in the 
state of a paste, to which some glycerine is added for the purpose of keeping it moist. 

coralline. 4. Coralline, or pseonine, a scarlet dye material, is formed, according to 
Kolbe and R. Schmidt, by heating a mixture of carbolic, oxalic, and sulphuric acids 
until the colour has been sufficiently developed. When the reaction is finished the 
mass is washed with boiling water for the purpose of eliminating the e'xcess of acid. 
The residue is next dried, pulverised, and submitted at 150° to the action of ammonia. 

The relation existing between the rosolic acid, discovered in tar by Runge, and 
coralline is at present not fully established, but according to Caro’s researches these 
substances are identical. Rosolic acid may be formed from carbolic and cresylic 
acids (as rosaniline is from aniline and toluidine) according to the following 
formulae:— 

C 6 H 6 0 f2C 7 H 8 0=C 2 oH l6 0 3 +3H 2 . 

Carbolic Cresylic Rosolic 

acid. acid. acid. 

Axuline. 5. Azuline (phenyl blue). When coralline is heated with aniline oil (com¬ 
mercial aniline) there is obtained, according to J. Persoz and Guinon-Marnas, a blue 
pigment, which is termed azuline, or azurine. 

Pigm Nftro^Moi from has been attempted to prepare pigments directly from nitro- 

benzol. Laurent and Casthelaz state that a red pigment is obtained by keeping a 
mixture of 12 parts of nitro-benzol, 24 parts of iron-filings, and 6 parts of hydrochloric 
acid for twenty-four hours at the ordinary temperature of the air. There is formed 
a solid resinous-like mass, which is first exhausted with water and the solution 
precipitated with common salt. The pigment thus obtained is said to be a substitute 
for fuchsin, and as such capable of being used as a dye and for calico-printing. 

III. Naphthaline Pigments. 

Naphthaline. This material. CioHs, was discovered in the year 1820 by Garden in 
coal-tar, and was afterwards the subject of researches by Faraday, A. W. Hofmann, 
M. Ballo, and others. According to Berthelot it may be synthetically prepared by 
substituting for 2 atoms of hydrogen of the benzol 2 atoms of acetylen (C 2 H 2 ):— 
C 6 H6-2H+2C 2 H 2 -FC 6 H 4 (C 2 H 2 ) 2 =C io H 8 . 

Acetylen. Naphthaline. 


Benzol. 







5 g 2 CHEMICAL TECHNOLOGY. 

Naphthaline is a crystalline substance, exhibiting rhomboids when in very tlnn 
scales. Its odour is peculiar and somewhat similar to that of storax; it has a burning 
taste. When cooled, after having been fused, it appears as a white crystalline mass 
having a sp. gr. = 1*151. It fuses between 79 0 and 8o°, and boils between 216° and 
2 18°. ° When treated with nitric acid, naphthaline yields phthalic acid, which accord¬ 
ing to circumstances and by elimination of carbonic acid may be either converted 
into benzol or into benzoic acid:*— 

a. C 8 H60 4 -2C0 2 =C 6 H6. 

Phthalic acid. Benzol. 

( 3 . C 8 H 6 0 4 -C 0 2 =C 7 H 6 0 2 . 


Phthalic acid. 

There exists between the derivatives of benzol and naphthaline a great analogy, 
which not only extends to the composition and reaction, but even to chemical and 
physical properties. The analogy of composition is exhibited by the following 
tabulated form:— 

Benzol (hydride of phenyl), CgHg. Naphthaline (hydride of naphthyl), Ci 0 H 8 . 
Nitro-benzol, C 6 H 5 (N 0 2 ). Nitro-naplithaline, C IO H 7 (N 0 2 ). 

Aniline, C 6 H 7 N. Naphthylamine, C I0 H 9 N. 

Bosaniline, C 20 Hi 9 N 3 . Base of the naphthaline red, C 30 H 2I N 3 . 


Naphthylamine, C IO H 9 N 3 , the base which corresponds to aniline, is prepared from 
naphthaline in exactly the same manner as aniline is prepared from benzol, by con¬ 
verting naphthaline by the aid of nitro-sulphuric acid into nitro-naptlithaline, which 
is next converted into napthylamine by Bechamp’s process (see p. 574). As proved 
by M. Ballo (1870) the naphthylamine may be readily eliminated from the reduced 
mass, treated with iron and acetic acid, by distilling it with the aid of steam. 
Naphthylamine crystallises in white acicular crystals, fuses at 50°, and boils at 
about 300°. Its taste is sharp and bitter. It is almost insoluble in water. 

Naphthylamine serves for the preparation of the following dyes:— 

1. Martius yellow, 3. Naphthaline violet, 

2. Magdala red, 4. Naphthaline blue. 

Martins Yellow. i. This pigment, better known in England as Manchester yellow, or 
naphthaline yellow, Jaune dor, is the calcium or sodium compound of binitro-naph- 
thalinic acid (Ci 0 H6(N0 2 ) 2 0), obtained by adding to a solution of hydrochlorate of 
naphthylamine nitrite of soda until all the napththylamine has been converted into 
diazonaplithol. The fluid which contains diazonaphthol is next mixed with nitric 


* The large quantity of benzoic acid now consumed in the preparation of some of the 
tar colours, and employed for other chemico-technical purposes, is no longer obtained 
from the benzoin resin (gum benzoin, as i* is often termed); but this acid is prepared 
either from hippuric acid present in the urine of horses, or it is a derivative from 
naphthaline. The naphthaline-benzoic acid may be prepared by two different methods, 
viz. :—1. By converting naphthaline into phthalic acid, and converting this acid, by 
heating it with lime, into benzoate of lime, from which, by the addition of hydrochloric 
acid, the benzoic acid is set free and precipitated. 2. By converting phthalic acid into 
phthalimide,C 6 HsN 0 2 , and converting this substance by distilling it with lime into benzo- 
nitrile, C 7 H 5 N, the latter by boiling with caustic soda solution being converted into 
benzoate of soda, from which solution the benzoic acid is set free and precipitated by the 
addition of hydrochloric acid. In the year 1868 Merz obtained from cyannaphthyl a new 
acid, to which the name of naphtoe acid is given (formula CuH 8 0 2 ), a substitute for 
benzoic acid. 



DYEING. 


583 


acid and then heated to the boiling point, the binitro-naphthylic acid is thrown down 
in yellow acicular crystals. The conversion of naphthylamine into binitro-naphthylic 
acid (binitro-naphthol) may be elucidated by the following formula:— 
a. C 10 H^+HN 0 2 = 2 H 2 0 +C IO H 6 N 2 . 

Naphthylamine. Diazonaphthol. 

( 3 . C IO H 6 N 2 + 2 HN 0 3 = 2 N+H 2 0 +C IO H 6 (N 0 2 ) 2 0 . • 

Diazonaphthol. Binitro-naphthylic acid. 

As proved by M. Ballo, the latter acid may be directly formed by the action of 
nitric acid upon naphthylamine. Manchester yellow imparts directly to wool and 
silk, without the intervention of any mordant, yellow hues, which may be made 
to differ in depth of colour from lemon-yellow to deep golden-yellow. 1 kilo, of the 
dry calcium or sodium compound dyes 200 kilos, of wool brilliantly yellow. While 
picric acid dye is volatilised by steam, the Manchester yellow perfectly admits of the 
operation of steaming. In this country this dye material is frequently employed 
for the purpose of modifying the hue of magenta. 

Hagdaia Red. 2. This pigment, naphthaline red, C 30 H 2I N 3 , was discovered in 1867 
by Yon Scliiendl at Vienna, and has been the subject of researches by Durand, 
Ch. Kestner, Dr. A. W. Hofmann, and others. It is generated from naphthylamine 
by the elimination of 3 molecules of hydrogen from 3 molecules of the base:— 

3C I oH 9 N-3H 2 = C 30 H 2I N 3 . 

Naphthylamine; Magdala red. 

On the large scale the preparation of Magdala red is effected in two stages. In 
the first the naphthylamine is converted into azodinaphthyl-diamine by the action of 
nitrous acid:— 

a. 2 C io H 9 N+HN 0 2 = 2 H 2 0 +C 20 H I5 N 3 . 

V-,-' v - 1 -;-' 

Naphthylamine. Azodinaphthyl-diamine. 

In the second stage the azodinaphthyl-diamine is treated with naphthylamine, the 
result being the formation of Magdala red. 

( 3 . C 20 H I5 N 3 -f C io H 9 N = C 20 H 2I N 3 +NH 3 . 

Azodi- Naphthyl- Magdala 
naphthyl-diamine, amine. red. 

The Magdala red of commerce, a black-brown, somewhat crystalline powder, is the 
chloride of a base of the composition described. As regards tinctorial powder Mag¬ 
dala red is not less valuable than fuchsin, while it surpasses the latter in being a 
very fast colour. When treated with iodide of methyl and iodide of ethyl, naphtha¬ 
line red yields violet and blue-coloured derivatives. 

N NaphthSe B vioiet nd 3 an( * 4- Violet and blue naphthaline pigments may be prepared 
in various ways; for instance, by plienylising naphthylising, methylising, or 
ethylising Magdala red; also by treating naphthylamine with mercuric nitrate 
(Wilder), by substituting for hydrogen in aniline and toluidine the radical naplithyi, 
C i 0 H 7 . J. Wolff, as early as 1867, obtained a very brilliant naphthyl blue in 
this manner; again, from rosaniline and mono-bromnaphthaline, and from rosaniline 
and naphthylamine (M. Ballo). Very recently Blumer-Zweifel as well as Kiel- 
meyer have produced naphthylamine violet on cotton and linen fabrics, by treating 










CHEMICAL TECHNOLOGY. 


5S4 

naphtliylamine while present on the woven tissues with chloride of copper, chlorate 
of potash, and, in fact, all such reagents as may be employed for the production of 
aniline black* (see p. 579). 


IY. Antliracen Pigments. 

Anthracen Pigments. Antliracen (para-naphthaline, photen), Ci 4 H io , is present in coal- 
tar to an amount of 075 to ro per cent, and was discovered by J. Dumas in 1831, 
while in 1869 it was first employed by Graebe and Liebermann for the purpose 
of obtaining anthracen red or artificial alizarin. Anthracen occurs in that portion 
of the products of the distillation of coal-tar which being rather thick are known 
in this country by the designation of green grease, and, as such, used as a 
coarse lubricating material. The green grease consists of heavy oils, some 
naphthaline, and about 20 per cent of anthracen. By means of the hydro¬ 
extractor, and by submitting the raw material to strong pressure, crude (con¬ 
taining 60 per cent pure) anthracen is obtained. This raw material is purified by 
being treated with benzoline (petroleum spirit), aided by heat, and again aided 
by the centrifugal machine, fusion, and sublimation, these operations resulting at last 
in the production of pure anthracen. This substance then appears as small foliated 
ciystals, white, void of odour, fusing at 215 0 , and subliming at a higher temperature 
without decomposition. This body is sparingly soluble in alcohol and benzol, more 
readily in sulphide of carbon. With picric acid it yields a compound exhibiting ruby- 
red crystals; while under the influence of oxidising agents it is converted into 
anthrachinon (oxanthracen, oxyphoten), C I4 H80 2 , which in its turn is converted into 
alizarine, Ci 4 Hs 0 4 , by a circuitous process. 

According to the original method of preparing alizarine, the anthrachinon, 
C I4 H80 2 , obtained from anthracen by the action of oxidising agents, such as nitric 
acid, was first converted into bibromide of anthrachinon, Ci 4 H6Br 2 0 2 , by treating 
anthrachinon with bromine, and this bromated compound was further treated either 
with caustic potash or caustic soda at a temperature of 180 0 to 200°, the bibromide of 
anthrachinon becoming converted into alizarine potassium (or alizarine sodium, 
if caustic soda has been used), from which the alizarine is set free by the addition of 
hydrochloric acid;— 

a. C I4 H 6 Br 2 0 2 +K 0 H = C I4 H 6 K 2 0 4 + 3 BrK+2H a O. 

Bibromide of Alizarine 

Anthrachinon. Potassium. 

/ 3 . C I4 H 6 K 2 0 4 +2CIH = C I4 H 8 0 4 + 2 C 1 K. 

Alizarine Alizarine. 

Potassium. 

Alizarine is now prepared from anthrachinon by treatment at a temperature of 
260° with concentrated sulphuric acid of 1*84 sp. gr., the anthrachinon being 
converted into a sulpho-acid; this acid is next neutralised with carbonate of lime, the 
fluid decanted from the deposited gypsum, and carbonate of potash added to it for the 

* It is evident that by combining suitable aniline, naphthyl, and cetyl compounds the 
greatest variety of blue and violet pigments may be prepared. The following blue 
pigments were obtained in the summer of 1867, these researches being undertaken in con¬ 
sequence of the results obtained by J. Wolff in the same direction. 1. Fuchsin and 
bromide of naphthyl. 2. Fuchsin and cetyl bromide. 3. Naphthylamine, fuchsin, and 
aniline oil. 4. Cetylamine, fuchsin, and aniline oil. 5. Naphthylamine, fuchsin and 
cetylamine. 6. Cetylamine, fuchsin, and naphthylamine. 




DYEING. 


585 


purpose of precipitating all the lime. The clear liquid is then evaporated to 
dryness, the resulting saline mass is converted into alizarine-potassium by heating it 
with caustic potash. From the alizarine-potassium thus obtained the alizarine is set 
free by the aid of hydrochloric acid. According to another method, the preparation 
of anthrachinon is avoided, and anthracen employed directly, by first converting it— 
by the aid of sulphuric acid and the application of heat—into anthracen sulpho- 
acid, C 28 H i8 SH 4 0 3 . After having been diluted with water, the solution of this acid 
is treated with oxidising agents (peroxides of manganese, lead, chromic acid, nitric 
acid), and the acid fluid is next neutralised with carbonate of lime. When peroxide 
of manganese has been used the manganese is also precipitated as oxide. The 
oxidised sulpho-acid having been previously converted into a potassium salt, the 
latter is heated with caustic potash, alizarine-potassium being obtained. 

There is no doubt that anthracen may be converted into alizarine by other means ; 
and it is very likely that from other hydrocarbons (benzol, toluol, naphthalin) present 
in coal-tar, anthracen and anthracen red may be obtained. 

The industrial manufacture of artificial alizarine, carried on in the first place by 
the inventors of this process—Graebe and Lrebermann; and taken up by J. Gessert, 
at Elberfeld; Bronner and Gutzkow, at Frankfort-on-Maine; Briining, at Hochst 
(near Wiesbaden) ; Greiff, at Cologne; and by Perkin, in London—is one of the 
brightest pages in the history of chemical technology. Although for the present 
anthracen red cannot compete with madder, it will, in all probability, become in 
a very great measure a substitute for that dye-stuff and garancine. 


V. Pigments from Cinchonine. 

cinchonine Pigments, The preparation of pigments from cinchonine—an almost waste 
by-product of the manufacture of quinine on the large scale—may be conveniently 
considered as an appendix to the coal-tar colours. Cinchonine is submitted to 
distillation with hydrate of soda in excess, the resulting product being about 
65 per cent crude chinoline (chinoline oil), a mixture of the three following homo¬ 
logous bases:— 

Chinoline . C 9 H 7 N. 

Lepidine . C I0 H 9 N. 

Rryptidine or dispoline . CnH n N. 

Lepidine is the chief constituent of this mixture. 

When chinoline oil is heated with iodide of amyl the result is the formation 
of amyl-lepidin-iodide, which on being treated with caustic soda solution, yields a 
very brilliant blue pigment—cyanine, lepidine blue, or chinoline blue, C 30 H 39 N 2 I. This 
substance is a crystalline compound, exhibiting a metallic green gloss and golden 
yellow hue ; jt is difficultly soluble in water, readily in alcohol. The formation of 
cyanine may be elucidated by the following formulae 

a. CjoHgN+CgHnI = C I5 H 20 N I. 

Lepidine. Iodide of Amyl-lepidin- 
Amyl. iodide. 

/J. 2C I5 H 20 NI-f NaOH = C 30 H 39 N 2 I+Cal+H 2 0 . 

^--r- v - r * 

Amyl-lepidin- Cyanine 

iodide. 






586 


CHEMICAL TECHNOLOGY. 


Red Dye Materials. 
Madder. 


Bed Pigments occurring in Plants and Animals. 

Madder is the root of the Bubia tinctorum*n perennial plant 
cultivated in Southern, Central, and Western Europe; while in the Levant the 
B. peregrina, and in the East Indies and Japan the B. mungista (mungeet), 
are partly cultivated, partly met with in the wild state. According to the researches 
made in England, the dye imported under the name of mungeet from India is 
not the root, hut the reedy stem of a species of Bubia , and as a dye it is inferior. The 
native country of the madder plant is the Caucasus. All these plants are perennial. 
The root varies in length from io to 25 centims.; it is not much gnarled, and is 
generally a little thicker than the quill of a pen. Externally the root is covered with 
a brown bark; internally it exhibits a yellow-red colour. Madder is met with in the 
trade in the root (technically racine if European), and in powder exhibiting a 
red-yellow colour, and possessing a peculiar odour. Avignon madder, however, has 
hardly any smell at all; but the odour is particularly marked in Zeeland, or so-called 
Holland, madder. The powdered madder is always kept in strong oaken casks, so 
as to exclude air and light. The best kind of madder is that grown in the 
Levant (Smyrna and Cyprus), and met with in the trade under the name of lizari or 
alizari, in roots which are usually rather thicker than the roots of the European 
varieties, owing partly to the fact that the Levant madder is generally of four to five 
years’ growth, while in Europe the roots are of two to three years’ growth only. 
Dutch madder, chiefly grown in the province of Zeeland, is met with decorticated 
[robe), the outer bark and sometimes the splint bark having been removed. The well 
dried roots are broken up by means of wooden stampers moved by machinery, to 
reduce the bark and splint bark to powder, while the very hard internal portion of 
the root is left untouched, this being separated from the powder by means of sieves. 
The powder is put into casks and termed beroofde. During the last ten or twelve 
years, the old madder sheds ( meestoven ) in Zeeland have been superseded by large 
manufactories, in which the madder root is treated as it is in the Yaucluse (France), 
and ground up entirely, so that the former distinct qualities of madder are no longer 
met with. When the whole root is pulverised the madder is termed onberoofde, non 
robe. Besides the Dutch madder, that from Alsace and from the Yaucluse, 
Avignon, occur very largely in the trade. "What is known as mull madder is the 
refuse and dust from the floors of the works, and is the worst quality. In addition to 
colouring matter, madder contains a large quantity of sugar, of which W. Stein (1869) 
found as much as 8 per cent. While it was formerly considered that madder 
contained no less than five different colouring substances, it appears from recent 
researches that this root in fresh state only contains two pigments, viz. rube- 
rythrinic acid (formerly termed xanthin), and purpurine. According to Dr. Bochleder, 
the former of these is converted under the influence of a peculiar nitrogenous 
substance present in the madder root into alizarine—the essential colouring matter of 
madder—and into sugar:— 

C 2 oH 22 O xi = c I4 h 8 o 4 +c 6 h I2 o 6 +h 2 o. 

Sugar. 


Kuberythrinic 

acid. 


Alizarine. 


According to the researches of Graebe and Liebermann, alizarine is a derivative 
from anthracen, C I 4 H I0 , the formula of the former being C I 4 H 8 0 4 . As already men¬ 
tioned (see p. 585b Graebe and Liebermann have succeeded in converting anthracen 



DYEING. 


587 


into alizarine (1869). Alizarine is yellow, but becomes red under the influence of 
alkalies and alkaline earths. Madder contains a red pigment, purpurine, or 
rubiacine, C I4 H80 3 , which by itself, as well as in combination with alizarine, yields 
a good dye. 

Madder Lake. We understand by this term a combination of alizarine and purpurine 
(the colouring matter of madder) with basic alumina salts. Madder lake is prepared 
by first washing madder with water, distilled or at least free from lime salts, 
and next exhausting the dye-stuff with a solution of alum, the liquor thus obtained 
being precipitated with carbonate of soda or borax. The bulky precipitate having 
been collected on a filter is thoroughly washed and dried. 

Flowers of Madder. The preparation made from madder on the large scale and known 
in the trade as flowers of madder (jleur de garance), is obtained from the pulverised 
madder by steeping it in water, inducing fermentation of the sugar contained in it, 
and next thoroughly washing the residue, first with warm, next with cold water. The 
residue after subjection to hydraulic pressure to remove the water, is dried at a gentle 
heat, and having been pulverised again is used in the same manner as madder for 
dyeing purposes. The operation of dyeing with the flowers of madder requires a 
less elevated temperature of the contents of the dye-beck. It would appear that by 
the preparation of the flowers of madder the pectine substances of the root are 
eliminated which otherwise become insoluble during the operation of dyeing. 

Azaie. When flowers of madder are treated with boiling methylic alcohol (wood- 
spirit) , the solution obtained filtered, and water added to the filtrate, a copious yellow 
precipitate is obtained, which having been washed with water and dried constitutes 
the material known as azaie (from azala , Arabian for madder), which has been 
suggested for use as a dye material in France. Probably this substance is crude 
alizarine ; as obtained from madder or garancine it is met with in the trade sometimes 
under the name of Pincoffine, having been first discovered and prepared by Mr. 
Pincoffs, at Manchester. 

Garancine.. This preparation of madder contains the colouring principles of the root 
in a more concentrated, pure, and more readily exhaustible state. In order to 
prepare garancine, madder (generally this term is given to the pulverised root) is 
first moistened uniformly with water, and next there is added k part of sulphuric 
acid diluted with 1 part of water. This mixture is heated by means of steam 
to about ioo° for one hour, and the magma then thoroughly washed with water 
for the purpose of eliminating all the acid. This having been done the garancine 
is submitted to hydraulic pressure for the purpose of getting rid of the greater part 
of the water, after which the material is dried and lastly ground to a very fine 
powder. By the action of the sulphuric acid, some of the substances contained 
in madder and more or less interfering with its application as a dye, are eliminated 
by the washing of the garancine, while the colouring matter remains mixed with the 
partly carbonised organic substances. As regards its tinctorial value 1 part of 
garancine may be taken as equal to 3 to 4 parts of madder. As madder when 
employed in dyeing does not become quite exhausted, the fluids of the dye-beck are 

Garanceux. strained from the solid residue, and this is treated with half of its weight 
of sulphuric acid. The mass is next treated as has been described under Garancine, 
and constitutes after drying what is known as garanceux, being used generally for the 
production of what are termed sad colours (black, deep brown, lilac). As a matter of 
course garanceux is of less tinctorial value than garancine. 


588 


CHEMICAL TECHNOLOGY. 


Coiorine. The substance met with in commerce under the name of colorine is the 
dry alcoholic extract of garancine, and consists essentially of alizarine, purpurine, 
fatty matter, and other substances soluble in alcohol present in garancine. E. Kopp 
commenced some years since to exhaust madder with an aqueous solution of 
sulphurous acid, thereby obtaining the pigments of madder in a (for technical pur¬ 
poses) pure condition. These preparations, which are already extensively used, are 
distinguished as:—Green alizarine ( Alizarine verte), which from Alsace madder 
is obtained to an amount of about 3 per cent, containing with the alizarine a green 
resinous material; yellow alizarine [Alizarine jaune), the former substance without 
the resinous material, this having been eliminated by suitable solvents, as purpurine 
and flowers of madder. The tinctorial value of purpurine amounts to 10 times, and 
that of the green and yellow alizarine to 32 to 36 times, that of madder. Madder of 
good quality yields on the large scale :— 

Purpurine . 1*15 per cent. 

Green alizarine . 2'50 ., 

Yellow alizarine . 0*32 „ 

Flowers of madder . 3900 „ 

Brazil or Camwood. By this name are designated several varieties of wood belonging 
to the Ccesalpinia , and used for dyeing purposes. The best kind is the so-called 
Pernambuco or Fernambuco wood, obtained from the Ccesalpinia hrasiliensis s. crista ; 
externally it is yellow-brown, internally its colour is a bright red, while the wood 
is heavy and rather hard. Its name is derived from that of the state of the Brazilian 
Empire, in which the tree grows abundantly. It is met with in commerce in chips 
and large logs. The sapan wood obtained from Japan, and derived from the 
[C. sapan) is an inferior kind, while the varieties known as Lima or Nicaragua wood, 
or Bois de Ste. Mar the [C. echinata), and the brasilet wood (G. vesicaria ), are all of 
less value. All these kinds of wood contain a colouring matter termed brasiline, 
(according to Bolley the formula is C 44 H 4 oO I4 4-3H 2 0), a colourless substance, 
crystallising in small acicular crystals, the aqueous solution of which turns gradually 
carmine-red by exposure to air, a change brought on almost instantaneously either 
by boiling the solution or by the action of alkalies. Brazil wood is used in dyeing 
for the production of a beautiful red colour, which is not fast. This wood is also used 
for the preparation of round lac, for which purpose, however, the red and violet tar- 
colours are now more often employed. Bed ink is commonly made with brazil wood 
according to the following recipe :—Brazil wood, 250 grms.; alum, 30 grms.; cream 
of tartar, 30 grms.; water, 2 litres. Boil down to 1 litre, strain the liquid, and next 
add of gum arabic and sugar candy each 30 grms. A better red ink is obtained by 
dissolving 2 decigrammes (4 grains) of carmine in i 8'27 grms. (5 drms.) of liquid 
ammonia, and adding a solution of 1 grm. (18 grains) of gum arabic in 2 fluid ounces 
of water. Bed inks are now frequently prepared from solutions of fuclisin to which 
some gum and alum are added, or by dissolving commercial aurine, a modification 
of rosolic acid, in a solution of carbonate of soda. 

sandalwood. There is a red and a yellow variety of this wood in commerce. The 
red wood is derived from Pterocarpus santalinus, a tree growing in Ceylon and other 
parts of India. The wood is imported in logs exhibiting a straight fibrous texture, 
and externally a deep red, internally a bright red. The colouring matter contained 
in this wood is of a resinous nature and is named santaline. According to the 


DYEING. 


■ 589 

researches of H. Weidel (1869), sandal wood contains a colourless body, santal, 
CsH 60 3 , which appears to be converted by oxidation into santaline. Sandal wood is 
used for the preparation of coloured lakes, coloured furniture polish, for dyeing wool 
brown, dyeing leather red, as a pigment in tooth powders, &c. The same pigment is 
found in barwood, derived from Bapliia nitidci, an African tree; this wood is said to 
contain no less than 23 per cent of santaline, while sandal wood only contains 
16 per cent of this substance. 

safflower. The drug to which this name is given consists of the dried petals of the 
flowers of the Carthamus tinctorius, a thistle-like plant belonging to the family of the 
Synantherece , a native of India, and cultivated in Egypt, the southern parts of 
Europe, and also to some extent in parts of Germany. Safflower contains a red 
matter, carthamine, insoluble in water, and also a yellow substance soluble in 
that liquid. The quality of this drug is better according to its greater purity from 
mechanical admixtures, such as seeds, leaves of the plant. Carthamine, dr 

Rouge vegetal, is prepared in the following manner:—The safflower is exhausted 
with a very weak solution of carbonate of soda, and in this fluid strips of cotton¬ 
wool are dipped, after which the strips are immersed in vinegar or very dilute 
sulphuric acid for the purpose of neutralising the alkali. The red-dyed cotton strips 
are next washed in a weak solution of carbonate of soda, and the solution thus 
obtained is precipitated with an acid ; the carthamine thrown down is first carefully 
washed, and next placed on porcelain plates for the purpose of becoming dry. 
Carthamine when seen in thin films exhibits a gold-green hue, while when seen 
against the light the colour is red. When carthamine has been repeatedly dissolved 
and precipitated it is termed safflower-carmine. Mixed with French chalk (a 
silicate of magnesia), carthamine is used as a face powder. Safflower is used for 
dyeing silk, but the red colour imparted is, although brilliant, very fugitive. 

Cochemiie, or Cochineal This substance is the female insect of the Coccus cacti, found on 
several species of cacti, more especially on the Nopal plant and the Cactus opuntia. 
This insect and the plants it feeds on are purposely cultivated in Mexico, Central 
America, Java, Algeria, the Cape, &c. The male insect, of no value as a dye 
material, is winged, the female wingless. The female insects are collected twice 
a year after they have been fecundated and have laid eggs for the reproduction 
of young, and are killed either by the aid of the vapours of boiling water or more 
usually by the heat of a baker’s oven. Two varieties of cochineal are known in 
commerce, viz., the fine cochineal or mestica, chiefly gathered in the district of 
Mestek, a province of Honduras, on the Nopal plants there cultivated; and the wild 
cochineal, gathered from cactus plants which grow in the wild state. This latter 
variety is of inferior quality. Cochineal appears as small deep brown-red grains, -at 
the lower and somewhat flattened side of which the structure of the insects is some¬ 
what discernible. Sometimes the dried insect is covered with a white dust, 
but frequently the material is met with exhibiting a glossy appearance and 
black colour. The white dust, very frequently fraudulently imparted by placing the 
grain with French chalk or white-lead in a bag, is according to the results of 
microscopical investigation, the excrement of the insect, exhibiting when seen under 
the microscope the shape of curved cylinders of very uniform diameter and a white 
colour. Cochineal contains a peculiar kind of acid—carminic acid—which, by the 
action of very dilute sulphuric acid and other reagents, is split up into carmine-red 
(carmine)—also present in the insect, together with the acid—and into dextrose:— 


590 


CHEMICAL TECHNOLOGY. 

C^HigOio-bsHaO = CnH^C^-j-CgHiaOs 


Carminic 

acid. 


Carmine- Dextrose, 
red. 


What is commonly termed carmine is prepared by exhausting the cochineal with 
boiling water; to the decanted clear fluid alum is added, after which it is left 
standing. By another method carmine is prepared by exhausting the pulverised 
cochineal with a solution of carbonate of soda, white of egg is next added to 
this solution for the purpose of clarifying it, and afterwards the solution is precipi¬ 
tated with an acid. The washed precipitate is next dried at 30°. So prepared, 
a finer and better kind of carmine is obtained, but the common carmine—carmine 
lac and round lac—is prepared by treating an aluminous solution of cochineal with 
carbonate of soda; the larger the quantity of alumina contained in these preparations, 
the coarser the quality. 

Lac Dye. This dye-stuff is obtained from a resinous substance, stick or grain lac, 
or gum resin, and is derived from a variety of the cochineal insect in the following 
manner:—The Coccus laccce , a native of India, pierces the branches of certain kinds 
of fig-trees from which a milky juice exudes, which, while becoming inspissated, 
encloses the insects and at last forms a hard resinous mass tinged with the dye-stuff 
contained in the insects. This pigment is extracted from the resinous matter by 
means of a solution of carbonate of soda, and the solution obtained is precipitated by 
alum solution. The lac dye is not very different from cochineal. The dye materials 
contained in kermes ( Coccus ilicis ), Coccus polouicus, and Coccus fab a are similar- to 
that contained in cochineal, but are now quite obsolete; even cochineal is far less 
used since the coal-tar colours have been introduced. 

orchil and Persio. By orchil, persio, and cudbear, we designate red dye-stuffs which are 
met with in commerce in pasty masses. Orchil is prepared from several kinds of 
sea-weed, Roccella tinctoria, JR. fuciformis, JR. Montagnei , TJsnea barbata, Usnea 
florida, Lecanora parella, Unceolaria scruposa, JRamalina calicaris, Gyrophora 
pustulata , and others, which having been w r ell dried, are first ground to a 
very fine powder. This is mixed with urine and left to enter into putrefactive 
fermentation. The carbonate of ammonia formed by the decay of the urine acting 
upon the peculiar acids—lecanoric, alpha and beta orcellic, erythrinic, gyroplioric, 
evernic, usninic, &c.—contained in these sea-weeds converts these non-nitrogenous 
substances into orcine, C 7 H80 2 , this reaction being accompanied by the elimination 
of water, and usually also with the elimination of carbonic acid. By taking up 
nitrogen and oxygen orcine is converted into orceine, C 7 H 7 N 0 3 , constituting the 
essential colouring matter of orchil. This substance appears as a red paste, exhi¬ 
biting a peculiar violet odour {viola odorata) and an alkaline taste. Before the coal- 
tar colours were discovered, this dye material was prepared chiefly in England and 
France, from weeds imported from the Canary Islands, or collected oh the Pyrenees 
and imported from Lima and Valparaiso. Persio, cudbear, or red indigo, is mucli 
the same kind of product as orchil; the former was formerly prepared in Scotland 
from sea-weeds found on the coast. At a later period it was made in large quantity 
in Germany, in France, and in England. Persio was a red-violet powder. Some 
ten years ago two preparations of orchil were brought into commerce under the 
names of orchil carmine and orchil purple ( pourpre Francois). These substances 
contained the orchil dyes in a very pure condition, Since the tar-colours have made 




DYEING. 


59 * 


their appearance, the dyes obtained from the sea-weeds, very beautiful but very 
perishable colours, have in a great measure become obsolete. 

Less important Ked Dyes. Among the less important red dyes and colouring matters are the 
alkanet root (Anchusa tinctoria ); dragon’s blood, a red-coloured resin from Dracaena 
draco; harmala red from the seeds of' the Peganum Harmala, a plant growing in the 
Steppes of Russia; Chica red, or carajura, from the leaves of the Bignonia chica, a tree 
growing in Venezuela ; purple-carmine, or murexide, obtained from uric acid by treating 
it with oxidising substances (nitric acid for instance) and next with ammonia. 


Blue Dye Materials. 

Blue D ind 5 o. terials ' Indigo is the chief blue dye. Although known to the Romans and 
Greeks, who used it for painting purposes, it was not used as a dye stuff in Europe 
until about the middle of the sixteenth century. Indigo is a substance which is 
widely dispersed in the vegetable kingdom. It is found in large quantity in the 
leaves of several species of the anil plants, Indig of era, belonging to the family of the 
Papilionacece. Indigo is also met with in woad, Isatis tinctoria, Nerium tinctorium, 
Marsdenia tinctoria, Polygonum tinctorium, Asclepias tingens, &c. The indigo is. not 
met within the plants ready formed, but is generated when the freshly-pressed juice 
of the plant is exposed to the action of the atmosphere. 

According to the results of a series of experiments, it appears that in the living 
plant the colourless pigment is present in combination with a base, lime or an 
alkali. Dr. Schunck states that the indigo plant contains a material which he has 
termed indican, which either by fermentation or by the action of strong acids is 
converted into indigo blue and a peculiar kind of sugar, indigo glycine, according to 
the following formula :— 

C5 2 H62^2^34 - l - 4ll2^ - l - (^i6lIioE203-|-6C6H 1 o06. 

Indican. Indigo blue. Indigo glycine. 

The indigo of commerce is prepared from the indigo plants in the East and West 
Indies, Southern and Central America, Egypt, and other parts. In Hindostan indigo 
is prepared from the Nerium tinctorium. The following five varieties of the indigo 
plant are more particularly employed for the preparation of this dye material; the 
plants are:— Indigofera tinctoria, I. anil, I. disperma, I. pseudotinctoria, and 
I. argentea. The plant requires a warm climate and a soil so situated that it is not 
liable to become inundated. When the plants have grown to maturity they are cut 
down with a sickle close to the soil and transferred to the factory, where the indigo 
is extracted from the plant by the following process:—The factory is fitted with large 
water tanks, filtering apparatus, presses, a cauldron, drying-room, and, lastly, with 
fifteen to twenty tanks of brickwork laid in hydraulic cement and plastered inside 
with the same material. Into these tanks the branches, twigs, and the leaves 
are placed, and water is run in, care being taken to force the green plants 
down under the water by the aid of stout wooden balks wedged tight against 
the sides of the tanks. At the usual high temperature of the air in the 
tropical regions fermentation soon sets in, and the liquid contained in the tanks 
assumes a bright straw-yellow or golden-yellow colour, a large quantity of gas is 
evolved, and after a lapse of nine to fourteen hours, the liquid, having become of a 
deeper yellow hue, or almost the colour of sherry wine, is run from the fermenting 
tanks into a very large tank of similar construction, into which, when as full as may 
be judged convenient, a number of workmen enter, provided with long bamboo poles. 





592 


CHEMICAL TECHNOLOGY. 


and commence stirring the fluid vigorously for the purpose of exposing it as much 
as possible to the action of the air. During this operation, continued for some two 
or three hours, the colour of. the liquid gradually changes to pale green, -and the 
indigo may then he seen suspended in the liquid in very small flocks. The liquid is 
then left to stand, and the suspended matter gradually subsiding, the water is 
gradually run off by the aid of taps or plugs fitted into the tank at different 
heights. At last the somewhat thick, yet fluid, precipitate of indigo is run into a 
cauldron, where it is boiled for about twenty minutes in order to prevent it fermenting 
a second time, for by this second fermentation it would be rendered useless. The 
magma is left in the cauldron over night and the boiling resumed next day 
and then continued for three to four hours, after which the indigo is run on to large 
filters, consisting first of a layer of bamboo, next mats, and on these stout canvas, all 
placed in a large masonry tank. Upon the canvas is left a thick, very deep blue, 
nearly black paste, which is thence taken and put into small wooden boxes, 
perforated with holes and lined with canvas ; a piece of canvas is put on the top of 
the paste, and next a piece of plank is fitted closely into the box. So arranged, a 
number of these are placed under a screw-press for the purpose of eliminating, by a 
gradually increased pressure, the greater portion of the water, and thus to solidify the 
pasty material. On being removed from these boxes the cakes of indigo are trans¬ 
ferred to the drying-room, and there, daylight and direct sunlight being carefully 
excluded, gently dried by the aid, in some cases, of artificial heat. In order to 
prevent the cracking of the cakes, the drying has to be effected very gently, and lasts 
usually for some four to six days. The dried cakes of indigo are next packed in stout 
wooden boxes and then sent into the market. The exhausted plants are used for a 
manure, for although the boughs on being planted in the soil would again grow, they 
would no.t yield either in quality or quantity enough indigo to pay the expenses of 
culture. ‘1000 parts of fluid from the fermenting tanks yield 0*5 to 075 parts of indigo. 

properties of indigo. The indigo met with in commerce exhibits a deep blue colour, 
dull earthy fracture, and when rubbed with a hard substance (the better kinds of indigo 
even when rubbed with the nail of the thumb), give a glossy purplish-red streak. In 
addition to a larger or smaller quantity of mineral substances, indigo contains a 
glue-like substance, or indigo glue; a brown substance, indigo brown; a red pigment, 
indigo red; and the indigo blue, or indigotine, Cx6H xo N a 0 3l the peculiar dye 
material for which the drug is valued. The quantity of indigo blue contained in the 
several kinds of indigo of commerce varies from 20 to 75 and 80 per cent, and 
averages from 40 to 50 per cent. Indigo may be purified according to Dumas’s 
process by digestion in aniline, whereby the indigo red and indigo brown pigments are 
dissolved and eliminated. According to Dr. Y. Warther (see “ Chemical News,” 
vol. xxiii., p. 252), Venetian turpentine, boiling paraffin, spermaceti, stearic acid, and 
chloroform, are, at high temperatures, solvents for indigo blue. (See also “ Chemical 
News,” vol. xxv., p. 58, “ On the Solubility of Indigo (Indigotine) in Phenic Acid.”) 

Testing indigo. The quality of indigo is ascertained by its deep blue colour and light¬ 
ness (see “ Chemical News,” vol. xxiv., p. 313). G. Leuchs found that in forty-nine 
samples of this material the best contained 60*5 per cent, the worst 24 per cent of 
indigotine, the specific gravity of the former being low and of the latter high. Indigo 
should float on water, and when of good quality it should not, on being broken to 
pieces, deposit at the bottom of the vessel filled with water in which it is contained 
a sandy or earthy sediment. On being ignited, indigo should leave only a compara- 


DYEING. 


593 


tively small quantity of asli. When suddenly heated, indigo should give off a 
purplish-coloured vapour, sublimed indigotine, and the drug should be perfectly 
soluble in fuming sulphuric acid, yielding a deep blue fluid. That land of indigo 
which on being rubbed with a hard body exhibits a reddish coppery hue is termed 
coppery-tinged indigo, indigo cuivre. In order to test [indigo more accurately, a 
weighed portion is dried at ioo° for the purpose of ascertaining the quantity of 
hygroscopic water contained, which should not exceed from 3 to 7 per cent. 
Next the dried indigo is ignited for the purpose of ascertaining the quantity of ash it 
yields. For good qualities of the drug this amounts to 7 to 9-5 per cent. Numerous 
methods have been proposed by practical dyers as well as by scientific men for the 
purpose of ascertaining the value of indigo; that is to say, the quantity of 
indigotine it contains. Some of these processes are either too tedious, and cause 
great loss of time, or are not sufficiently exact. A commercial sample of indigo may 
be treated first with water, next with weak acids, then with alkaline solutions and 
alcohol, and the ash and hygroscopic water having been estimated, the residue of 
the different operations will be the indigotine, the process being based upon the 
insolubility of the latter in the different solvents used for the removal of the impuri¬ 
ties met with in the sample under examination. Mittenzwei proposes to reduce the 
indigo by means of an alkali and protosulphate of iron, to pour over the surface 01 
the liquid a layer of petroleum oil for the purpose of excluding air, to take by the 
aid of a curved pipette a known bulk of the indigo-containing fluid, and to introduce 
this fluid at once into a test-jar placed over mercury, and containing a known and 
accurately measured bulk of pure oxygen. As 1 grm. of white indigotine (soluble) 
requires for its conversion into blue (insoluble) indigotine 45 c.c. of oxygen, the 
quantity of gas absorbed gives the quantity of indigotine. This method yields very 
correct results, but requires an experienced manipulator. 

Berz by Reduction Test Take 5 grms. of pure quick-lime prepared from white marble or 
from well-washed oyster-shells, put the quick-lime into a porcelain mortar, and mix 
the lime with sufficient water to form a thin milk of Time; next take 5 grms. of the 
sample of indigo very finely powdered, and add it to the milk of lime, mixing 
thoroughly, and then pouring the fluid into a flask capable of containing 1200 c.c. 
Rinse the mortar with water so as to make up a bulk of 1 litre, next add to the 
contents of the flask 10 grms. of crystallised sulphate of iron, and immediately after 
cork the flask and let it stand for several hours in a moderately warm place or on a 
sand-bath, taking care to shake the vessel frequently. After the liquid has become 
cool and the sediment deposited, a small syphon of known cubic capacity is filled 
with distilled water, and by the aid of this instrument 200 c.c. of the fluid contained 
in the flask are transferred to a beaker-glass. Some pure hydrochloric acid having 
been added to the fluid, it is left to be acted upon by the air until the reduced and 
soluble indigotine has become insoluble and blue-coloured. The precipitate is 
collected on a tared filter, well washed, dried, and next weighed. This weight cor¬ 
responds to the quantity-of pure indigo blue present in 1 grm. of the sample. 

penny's Test. This test is based upon the application of bichromate of potash and 
hydrochloric acid. 10 parts of finely-pulverised indigo are digested with twelve times 
its weight of fuming sulphuric acid at a temperature not exceeding 25 0 for a period 
of twelve hours. When the indigo has been entirely dissolved the fluid is poured 
into 1 pint (= 0-568 litre) of water, next 24 grs. of concentrated hydrochloric acid are 
added, and the fluid is then gently heated, after which it is titrated with a solution 
39 


594 


CHEMICAL TECHNOLOGY. 


of bichromate of potash in water, this solution being added as long as a drop of the 
fluid taken with a glass rod and placed on a piece of white filtering-paper exhibits a 
trace of green or blue colouring matter. The operation is finished when the liquor 
tested exhibits a bright brown or ochrey-yellow speck upon the filtering-paper. 
8£ parts of bichromate are required for decolourising io parts of pure indigo blue. 
Chloride of iron may be used for converting indigo blue into isatine. Probably the 
observation made by Stockvis at Amsterdam (1868), that indigo blue is soluble in 
chloroform, might be rendered available for the testing of indigo. 

indigo Blue. This substance, also known as indigotine, may be obtained from the 
indigo of commerce, either by carefully conducted sublimation, or, as already stated, 
by treating indigo with lime, protosulphate of iron, and water. The formula of 
indigo blue is C^HiqIS^. When indigo blue is, in the presence of alkaline substances, 
brought into contact with bodies which readily absorb oxygen—for instance, with 
protosulphate of iron, sulphites, &c.—there is formed, with simultaneous decomposition 
of water, white indigo or reduced indigo, CjeH^NaOa. The use of indigo as a dye 
material is in great measure based upon this reduction. By the action of oxidising 
substances, such as permanganic acid, chlorine, chromic acid, a mixture of 
so-called red prussiate of potash (ferricyanide of potassium) with potash, soda, oxide 
of copper, &c., indigo blue is converted into isatine, ChgHxoNaO^ Indigo blue 
dissolves in concentrated sulphuric acid, but becomes thereby radically changed and 
cannot be brought back to its primitive state, forming as it does with the acid a 
chemical compound— sulphindigotic acid, or, as it is termed by dyers, sulphate of 
indigo. When this acid solution is treated with carbonate of potash, there is formed 
indigo carmine or blue carmine, soluble indigo, a deep blue precipitate soluble in 
140 parts of cold water. This indigo-carmine is used as a water-colour pigment; 
while mixed with some starch and a little gum-water it is formed into balls or other 
suitable shapes and used as washing-blue, ultramarine being also employed for the 
same purpose. 

Logwood, or Campeachy. This dye material is the wood, freed from bark and splint, of 
the logwood tree, Hcematoxylon campechianum, a native of Central America, and 
cultivated in several of the West Indian Islands. The colouring matter contained in 
this wood is called hsematoxyline, C^II^Oe, a pale yellow, transparent, aciculated 
crystalline body. By itself it is not a pigment, but is a colourable material, which 
becomes coloured when brought into contact with strong alkalies, more especially 
with ammonia and the oxygen of the air. The solution of hsematoxyline in water is 
quite colourless, but becomes at once purple-red by the smallest addition of ammonia. 
The colouring matter thus formed is termed hsBmateine. Log-wood is used forthe pur¬ 
pose of dyeing blue and black. Extract of logwood is very frequently prepared. 
As with other similar extracts, it should be made in vacuum pans withdrawn from the 
oxidising action of the air, because the hsematoxyline contained in logwood becomes 
thereby altered. The makers of the extracts of dye-woods invariably use vacuum 
apparatus. 

Litmus. This colouring matter, also sometimes termed tournesol, is only very rarely 
used as a dye for textile fabrics, the colour imparted being very fugitive; but litmus 
is employed to impart a bluish tinge to whitewash-lime, further for colouring test- 
papers, for giving a red hue to the red champagnes, &c. Litmus is obtained from the 
seaweeds that yield archil, cudbear, and persio, potash being employed with the 
ammoniacal liquor. The difference in the preparation consists in the fermentation 


DYEING. 


59 5 


and oxidation being carried further, the result being that the red pigment (orcin) is 
thereby converted into a blue-coloured material azolitmine:— 


Orcin, C 7 H 80 2 
Ammonia, NH 3 
Oxygen, 4O 


• yield 


Azolitmine, C 7 H 7 N 0 4 
and 

Water, 2H 2 0. 


The fermented mass is mixed with gypsum and chalk, moulded into lozenges, dried, 
and sent into commerce. 

That known as litmus on rags, tournesol en drapeaux , is prepared in the southern 
parts of France (almost exclusively at Grand Gallargues, Departement du Gard) 
from the juice of the Groton tinctorium in which coarse linen rags are repeatedly 
steeped, and these having been submitted to the action of the ammonia evolved from 
stable manure or from lant, become purple-red coloured. Weak acid3 turn this 
colour to yellow-red, which is not again turned to purple-blue by alkalies, the effect 
of these being to render the colour somewhat green. The tournesol en drapeaux is 
largely used in Holland for imparting a colour to the crust of certain kinds of cheese 
made in that country, the effect being that the cheese thus externally dyed is by far 
less liable to decay and to be attacked by cheese-mites. The pigment is also used 
for colouring a peculiar kind of paper, extensively employed for the covering of 
sugar-loaves. It is also used for imparting a tinge to liqueurs, sweetmeats, &c. 


Yellow Dyes. 

Yeliow-Wood, Fustic. Yellow-wood is the hard wood of. the dyer’s mulberry tree, 
botanically termed Moms tinctoria or Maclura aurantiaca. It is imported chiefly 
from Cuba. San Domingo, and Hayti. This wood has a yellow and in some parts 
yellow-red colour, due to a colourless crystalline body, morine, C I2 H80 5 , present in 
combination with lime, and also to a peculiar kind of tannic acid, morine-tannic acid, also 
termed maclurine (formula, C I3 H io 06), both often met with deposited in the wood in 
large quantities. Morine becomes yellow by exposure to air and the simultaneous 
influence of alkalies. When treated with caustic potash maclurine is split up into 
phloroglucine and protocatechutic acid. Yellow-wood is employed for dyeing yellow 
and also black, in consequence of the large quantity of tannic acid it contains. The 
commercial extract of this wood is termed cuba extract. 

Young Fustic, French Fustet. This is a green-yellow wood, exhibiting brown-coloured 
stripes, and derived from a European shrub, the Rhus cotinus of the botanists, a plant 
belonging to the southern parts of Europe. The prefix “young” is given to it on 
account of the smallness of its branches as compared with that of the yellow-wood, 
which is distinguished as old fustic. The fustet contains a peculiar colouring 
matter termed fustine, and in addition large quantities of tannic acid. It would 
appear that fustin yields quercetine by being split up in chemical sense. 

Annatto, or Arnotto Is a yellow-red pigment, chiefly used for dyeing silk. It is met 
with in commerce as a thick paste of the consistence of putty, and is prepared in 
America, the West and East Indies, from the pulp of the fruit of the Bixa Orellana. 
According to Chevreul, annatto contains two different pigments ; one of these exhibits 
a yellow colour and is soluble in alcohol and water, while the other, a red-coloured 
matter, is readily soluble in alcohol but not in water. Piccard states that the formula 
of the latter is C 5 H 6 0 4 . Annatto is soluble in weak caustic and carbonated alkaline 
solutions. 



59& 


CHEMICAL TECHNOLOGY. 


T simpiy Berries 01 This drug is the fruit of various kinds of shrubs which are known 
by the general name of the dyer’s buckthorn, the Rhamus infectorius, R. amyg- 
dalinus, R. saxatilis of the botanists, grown in the Levant, Southern France, and 
Hungary. The size of these berries varies very much, two sizes being chiefly met 
with and distinguished in commerce, viz., the large bright olive-coloured full-sized, 
and the smaller shrivelled deep brown berry. The former are gathered before they 
are quite ripe, while the others have been left after full maturity for a considerable 
time on the twigs. These berries contain a fine golden-yellow pigment named 
chrysorhamnine and olive-yellow xanthorhamnine. According to Bolley the former 
is identical with quercetine. Berries are used in calico-printing, for the colouring of 
paper-pulp, and for the preparation of lake colours. 

Turmeric Is the dried root of the Curcuma longa and C. rotunda, a plant growing in 
India and Java, belonging to the natural order of the Scitaminece. The root is met 
with in egg-shaped tubers or flattened lumps, exhibiting a dirty yellow colour. The 
pigment contained is termed curcumine, CsH io 0 2 . As a dye turmeric is chiefly used 
in silk-printing and dyeing, also for woollen fabrics for dark and full shades of 
colour. Upon cotton it dyes without mordant, but the colour is very fugitive. 
Turmeric test-paper is used for the detection of alkalies and boracic acid, by which 
it is turned red-brown. 

weid. This dye material consists of the dried herb and stems of a plant botanically 
known as Reseda luteola, a native of the southern parts of Europe and frequently 
cultivated for the use of dyers. French weld is considered the best. The pigment 
it contains is known as luteoline. 

Quercitron Bark. This dye material, as its name indicates, is the inner bark of the 
black oak, Quercus tinctoria. It is a native tree of North America, and the drug is 
imported in the state of powder. The colour of this substance is bright yellow, and 
it contains tannic acid in addition to a yellow pigment, quercitrine, C 3 3H 3 oO I7 . 
When quercitrine is treated with dilute acids it is split up, yielding quercetine, 
C 27 H l8 0 I2 , a lemon-yellow powder met with in commerce under the name of flavine. 
According to Hlasiwetz’s opinion, quercetine contains the complex of morine. Owing 
to the beauty of the colour it yields, quercitron bark is, with picric acid, the chief 
yellow dye of the present day. Among the more or less important yellow dyes, we 
mention :—Saw-wort, Serratula tinctoria; dyer’s brown, or greenwood, Genista 
tinctoria; the wongshy, Chinese annatto, or yellow pods, the seed capsules of the 
fruit of Gardenia jiorida, a plant belonging to the family of the Ruhiacece ; purrhee, 
or Indian yellow, Jaune Indien, a dye material imported from India, the origin of 
which is not known (it is the magnesia salt of purreic or euxanthic acid, and is 
stated to be obtained from the urine of camels); Morinda yellow, from the Morinda 
citrifolia. Since the tar-colour industry has sprung up, picric acid (see p. 580) is 
frequently used as a yellow dye, and mixed with either indigo or aniline blue, as a 
green dye for silk and woollen fabrics. In order fully to exhaust the picric acid 
dye-beck, some sulphuric acid should be added to it. More recently the so-called 
Manchester yellow (see p. 582) is frequently employed instead of picric acid. The 
latter is not used upon cotton. 

Br 0 BUckDyes an(1 Brown dyes, aniline brown excepted, are mixtures of red, yellow, 
and blue, or of yellow or red with black. Frequently a brown is dyed by the use of 
oxidising agents with tannin-containing pigments, such as willow, oak, or walnut 
barks with cutch, the extract of the wood of the Areca and Acacia catechu, &c. The 


DYEING. 


597 


latter is technically termed chemick brown. Manganese, or bister brown, is obtained 
from the hydrated oxide of manganese. Black is obtained from tannate or gallate of 
protoperoxide of iron or from logwood decoction and chromate of potash* or from 
aniline black (see p. 579). Green is produced by mixing yellow and blue, or by the 
use of the Chinese green Lo-kao, obtained from Rhamnus chlorophorus and R. utilis ; 
or by the use of sap-green from the berries of the Rhamnus catharticus; finally, 
aniline green (aldehyde green and iodine green, see p. 578) is used, and yields a most 
beautiful dye. 


Bleaching. 

Bleaching. The operation of bleaching aims at more or less perfectly whitening 
or decolourising the yarns spun from flax, hemp, jute, cotton, or of the textile 
fabrics woven from the same. Vegetable fibre resists the action of most chemical 
agents in use in the bleaching, while the foreign or incrustating or colouring matters, 
occurring chiefly on the surface of the fibre, are rendered soluble or completely 
destroyed. The bleaching of the fabrics and fibres which, such as linen or cotton 
tissues, consist mainly of cellulose, is based on this principle. The method of 
bleaching wool and silk differs from that of the vegetable fibres, inasmuch as 
the chemicals used for the latter would exert upon the former a solvent action, not 
only as regards the impurities, but the substance itself. 

In the operation of bleaching, partly chemical and partly mechanical means 
are employed. On the large scale, setting aside all tlieoretieal considerations which 
do not fall within the scope of this work, the operation of bleaching cotton fabrics 
consists of the following operations :— 

1. Singeing, followed by “ rot steep” or “ wetting-out steep.” 

2. Liming—boiling with milk of lime and water for 12 to 16 hours. 

3. Washing out the lime and passing in hydrochloric acid “sours” or weak vitriol. 

4. Bowlring in soda-ash and prepared resin, 10 to 16 hours. 

5. Washing out the bowk. 

* Ordinary black ink which, if really made with galls, consists essentially of gallate of 
protoperoxide of iron kept in suspension in water by the aid of gum arabic, is indeed a 
dye liquor. A very good black ink may be made as follows:—1 kilo, of coarsely pulverised 
nut galls and 150 grms. of logwood chips are exhausted with 5 litres of hot water; 
600 grms. of gum arabic are dissolved in t.\ litres of water ; and 500 grms. of sulphate of 
iron in some litres of water; each of these solutions being made separately. This done the 
gall-logwood infusion is mixed with those of the gum and copperas; a few drops of 
essential oil of cloves or of gaultheria (winter green oil) having been added, there is added 
as much water as will bring the bulk of the liquid up to 11 litres. While this kind of ink 
attacks and corrodes steel pens, it has the additional disadvantage that after a time the 
writing becomes yellow. In 1848 Runge called attention to an ink originally invented by 
Leykauf at Niirenberg, and improved upon by C. Erdmann at Leipzig and sold by him. 
This ink is made up of 1000 parts of a logwood decoction (1 part of wood to 8 parts of 
water) and 1 part of yellow chromate of potash, some bichloride of mercury being added 
for the purpose of preventing the formation of mould. This ink is cheap and very per¬ 
manent ; the colouring principle is a combination of hamiateine and oxide of chromium. 
Leonhard’s so-called alizarine ink is made by exhausting with water, so that 120 parts of 
fluid are obtained from 42 parts of galls and 3 of madder. To this mixture is added 
1*2 parts of sulphindigotic acid, 5-2 parts of green copperas, and 2 parts of pyrolignite of 
iron solution. Rouen’s blue ink, frequently used in France, consists of a decoction of 
750 grms. of logwood, 35 grms. of alum, 31 grms. of gum arabic in 5 to 6 litres of water. 
For an excellent extemporaneous ink, see “ Chemical News,” vol. xxv., p. 45. Copying 
inks are only more concentrated ordinary inks, to which more gum and sugar are added. 
Marking ink for linen is a solution of silver (see p. 105), or aniline black produced on the 
woven fabric (see p. 579). 


598 


CHEMICAL TECHNOLOGY 


6. Passing through a solution of chloride of lime (hypochlorite of lime). 

7. Passing through weak hydrochloric acid. 

8. Washing, squeezing, and drying. 

The singeing is not a part of the bleaching process properly considered; its 
purpose is to remove the loosely adhering filaments, and improve the appearance of 
the cloth if required for printing. 

The “ rot steep ” (so-called because the flour or size with which the goods were 
impregnated was formerly allowed to enter into fermentation and putrefaction) 
is intended to thoroughly saturate the cloth. The liming takes place in kiers 
or kettles capable of holding from 500 to 1500 pieces of cloth. The lime is very 
carefully slaked and brought to a smooth milk of lime, being sifted so that no 
small lumps of quick-lime shall get into the kier. The lime is equally distributed 
upon the cloth as it enters the kier. The cloth is pressed into the liquor and 
the boiling commenced and continued for a period of 12 to 16 hours. At the end of 
that time the liquor is run off and clear water run in to cool the pieces of cloth, 
which are then taken out and washed. The utility of the liming consists in its 
action upon the greasy matters, forming with them a kind of insoluble soap, which is 
easily removed by the subsequent processes. The souring after liming removes all 
excess of lime and breaks up the insoluble lime-soap, leaving the greasy matters upon 
the cloth, but in such an altered state as to be easily dissolved in the bowking which 
follows. Hydrochloric acid is sometimes used in this souring, but more commonly 
dilute sulphuric acid is employed. The bowking or boiling with alkali and soap has 
for its object the removal of the greasy matters; it dissolves them, and all the dirt 
held by them now comes out of the cloth, leaving the cotton nearly pure. The alkali 
used in this process is soda-ash. The soap is made from resin and called prepared 
resin. The last process is that of passing the goods through a clear solution of 
bleaching-powder for the purpose of destroying the slight tinge of colour of a buff 
or cream shade still adhering to the cotton. The solution of bleaching-powder 
is very weak, so that probably a piece of calico of the ordinary size does not take up 
more than the soluble matter from \ of an ounce of bleaching-powder. The goods 
are allowed to remain some time in soaking with the chloride of lime solution, 
and are next passed through sours for the final operation. The dilute hydrochloric 
acid has th# effect of setting the chlorine free from the bleaching-powder and thus 
completing the destruction of the colour. At the same time it removes the lime and 
likewise any traces of iron (iron moulds) that may exist in the cloth. Linen is not 
so easily bleached as cotton, and it appears to suffer considerably by boiling, with 
lime and by contact with bleaching-powder. It is, therefore, generally bleached by 
continual boilings with alkali and a few sourings with bleaching-powder; or as lime 
is injurious, the hypochlorites of potash or soda are substituted. Woollen goods or 
yarns are bleached by treating them with very mild alkaline liquors, which remove 
the fatty matters, lant and soap with soda crystals being the substances usually 
employed. Sulphurous acid gas—or, as it is termed in the trade, vapour of burning 
brimstone—is used to finish wool, giving it whiteness and lustre. The following is 
an outline of the process as described by Persoz for bleaching woollen goods; it 
is for 40 pieces each 50 yards long:—1. Passed three times through a solution of 
25 lbs. of carbonate of soda and 7 lbs. of soap at a temperature of ioo° F.; add f lb. 
of soap after every four pieces. 2. Wash twice in warm water. 3. Passed three 
times through a solution of 25 lbs. of carbonate of soda at 120° F.. and add I lb. of 


DYEING . 


590 


soap again after every four pieces. 4. Sulphured in a room for twelve hours, using 
25 lbs. of sulphur for the forty pieces. 5. Passed three times through a solution of soda, 
as in No. 3. 6. Sulphured again, as in No. 4. 7. Soda liquor again, as in No. 3. 
8. Washed twice through warm water. 9. Sulphured a third time as in No. 4. 
10. Washed twice in warm and then in cold water, n. Blued with extract of 
indigo (indigo-carmine) according to taste. 

Bleaching of silk. The operation of bleaching silk is always preceded by removing 
(decorticating, degumming) the gummy substance attached to and externally 
covering the fibre. This is effected by boiling the raw silk in soap and water. 
For the purpose of bleaching silk nothing but water, soap, and sulphur (for making 
sulphurous acid) are used. Occasionally some soda crystals are employed to 
save soap but as alkalies injure, and if incautiously used destroy, the fibre, they 
must be employed with extreme care. Bran is sometimes used with soap in order to 
neutralise any excess of alkali (bran contains, or rather develops, when it becomes 
wet, lactic acid). The process is terminated by passing in an extremely diluted 
sour (solution of sulphuric acid in water) so weak as scarcely to be acid to the taste. 
Sulphuring is only required for silks intended to be left either white or to be dyed or 
printed with bright and light colours. This operation requires great care and should 
be seldom resorted to. 

This is an outline of the process of bleaching as carried on in practice on the 
large scale in this as well as in other countries. The theoretical consideration of 
the mode of action of the substances employed belongs to theoretical chemistry, and 
is treated under the heads of Chlorine, Sulphurous Acid, Oxidising Substances, &c.; 
and as far as the textile fibres are concerned, under Cellulose for flax, hemp, jute, 
cotton, and the Animal Fibres for wool and silk. The meadow bleaching of cotton 
and linen fabrics is still resorted to in some extent, but only in connection with the 
processes already referred to. None of the novelties proposed for bleaching 
purposes—among these, for instance, the use of permanganate of potash (Tessie du 
Motay’s process) as a bleaching agent—have been found by practical bleachers of 
great experience to be either better,- more manageable, or cheaper than the methods 
sanctioned by lengthy experience and daily use. 

Dyeing of Spun Yarn and Woven Textile Fabrics. 

Dyeing. Just as animal charcoal and arable soil are possessed of “he property 
to assimilate in their pores colouring matter and some inorganic substances without 
the latter being altered, so also do animal and vegetable fibres possess the property 
of absorbing from solutions, and fixing in a more or less insoluble condition, dyes 
and some of the constituents of mordants. This combination, or more correctly 
union, is often so loose that it is readily broken up by repeated treatment with 
solvents (viz. simply washing with water or soapsuds), especially if aided by heat. 
Thus, for instance, a textile fibre dyed (rather tinged, for dyeing implies fixity) with 
sulphindigotic acid, or a solution of Berlin blue in oxalic acid, may be decolourised 
a <rain by repeated washing in water. A fibre can only be called dyed in the strict 
sense when the dissolved dye material has been united in insoluble condition with 
the fibre, for which purpose often the intervention of a third substance, viz., a 
mordant , is required, the union thus formed resisting the action of solvents, that is 

t0 sa y_repeated washing with warm water and soap. The colour thus produced is 

termed fast, and resists the action of light, air, soap-water, weak alkaline solutions, 


boo 


CHEMICAL TECHNOLOGY. 


and weak acids. A dye which does not resist these agents is termed fugitive. 
Dyeing is partly based on chemical principles, but as regards the taking up or fixing 
of the dye by the fibre, it would appear to be only a physical attraction, capillarity, 
as there does not exist between a certain quantity of fibre and of dye an atomistic 
relation. Moreover, neither fibre nor dye have lost, after fixation has taken place, 
their characteristic properties. 

The insoluble condition of the union between fibre and dye may be obtained 
in various ways, viz.—i. By removal of the solvent, as, for instance, oxide of copper 
dissolved in ammonia may be fixed on the fibre by simply evaporating the latter 
fluid; chromate of zinc dissolved in ammonia may be fixed in the same manner. The 
precipitation of carthamine from its alkaline solution by the aid. of an acid, and the 
precipitation of some of the tar colours from their alcoholic solutions belong to the 
same category. The insoluble condition can be produced by—2. Oxidation, the pre¬ 
viously soluble dye being rendered insoluble by taking up oxygen (ageing process). 

The ferrous and manganous sulphates becoming converted by oxidation into 
insoluble hydrated oxides; and further, those dyes of vegetable origin which, 
in addition to tannic acid, also contain a peculiar dye material, such as quercitron, 
sumac, yellow-wood, fustet, &c., belong to this category. When any textile fabric is 
impregnated with an aqueous or alkaline infusion of these substances, and then aged 
or stoved (technical terms for exposure to action of air in what are termed ageing- 
rooms), the dye material becomes brown, and is then no longer soluble in water. This 
is more rapidly effected by treating the textile fabrics, previously impregnated with 
the solutions of the drugs, with oxidising substances—lor instance, chromic acid or 
bichromate of potash. Another instance of this kind is the process of dyeing black 
with logwood and chromate of potash, whereby the hiematoxyline of the wood 
is oxidised, and the chromic acid reduced to chromic oxide. To some extent 
the dyeing blue with indigo in the vat (blue vat), to be more fully described pre¬ 
sently, belongs to the same category; but in this case the production of the colour is 
due to the gradual absorption of oxygen, while simultaneously hydrogen is evolved 
from the white indigo, the liydogen combining with oxygen and forming water. The 
formation of aniline black upon tissues by the aid of ozone-forming substances 
(chlorate of potash, ferricyanide of ammonium, chromate of copper, freshly precipi¬ 
tated sulphide of copper) belongs to this class. In many cases the insoluble condi¬ 
tion (3) is obtained by double decomposition; as, for instance, blue is produced by 
hydroferrocyanic acid and oxide of iron; green by arsenite and sulphate of copper ; 
yellow by chromate of potash and a soluble lead salt. This mode of fixation of pig¬ 
ments is only employed with mineral colours. The most important and most 
ordinary method of fixing dyes is (4) by the aid of mordants. We understand by a 
mordant, a solution of some substance which, not being itself a dye, has an affinity as 
well for the fibre as for the dye material, and is thereby capable of effecting the 
fixation of the latter to the fibre. 

The more important mordants are Alum; sulphate, acetate and hyposulphite of 
alumina; aluminate of soda; and acetate of iron; according to lleimann [1870], 
amorphous silica may be used for fixing several dye materials; tin mordants; fatty 
substances, Gallipoli oil, in Turkey-red dyeing; tannic acid, for madder colours: 
c x hineal colours ; aniline dyes on cotton and linen fabrics; albumen, dried white of 
egg, gluten, caseine, and fatty oils (linseed oil also sometimes). The fabrics to 
be dyed are impregnated with the mordants, which are next fixed, an operation 


DYEING. 


601 


differing according to the nature of the mordant as well as the specific dye it is 
required for; but in general terms, ageing, dung-bath, bran-bath, and soaping, are 
employed, after which the woven fabric is placed in the dye solution contained in the 
dye-beck. Most of the dyes of organic origin can be fixed only by the aid of mordants. 

Bancroft considers dyes as substantive and adjective. By the former is under¬ 
stood those which without the aid of a mordant become fixed upon the textile fibres 
in an insoluble condition: to these belong all mineral pigments; and among 
the vegetable colouring substances—indigo, turmeric, annatto, safflower, also most of 
the tar-colours, although, as already mentioned, tannic acid is used for fixing 
fuchsin and similar tar-colours. By adjective colours or dyes is understood 
such as require an intermediate substance (a mordant in fact) to become fixed upon 
the fibre in an insoluble condition. These intermediate substances are termed mor- 

Mordants. dants; they not only serve for fixing the dye to the textile fibres, but also 
produce in the mordanted goods such an alteration that the parts of the tissue where 
the composition is applied appear white when the goods are taken from the dye- 
beck. The substances which produce this effect are technically termed dischargers, 
or discharge compositions; among them are phosphoric, tartaric, oxalic, arsenious 
acids, &c.; but in practice the goods are first uniformly dyed, and the discharge then 
applied so as to act only where it is desired to exhibit a pattern. What are termed 
resists are not mordants, but only compositions applied to the woven fabric at 
certain parts where it is desired that no deposition of colour or mordant shall take 
place. Mordants may modify the original colour that a dye yields ; as, for instance, 
with alumina compounds madder yields red, pink, and scarlet; with salts of iron, 
according to the degree of concentration, lilac, purple, black; and brown with cer¬ 
tain salts of copper. For the purpose of clearing and brightening (avivage), the 
dyed or printed goods are passed through solutions of either dilute acids, weak 
or strong alkalies, soap-suds, bran-bath, solutions of bleaching-powder, or also 
of some other dye material. 

Dyeing woollen Fabrics. Wool is sometimes dyed in the flock or fleece, that is to say, 
when not spun ; sometimes in yarn or worsted and as a finished woven fabric (cloth, 
broadcloth, &c.). As there is always some refuse wool in the operations of weaving, 
fulling, and dressing the woollen tissues, it is advantageous to dye wool in the condi 
tion of spun yarn. When the dye intended to be applied to wool is fast,,the textile 
fibre is first mordanted. For this purpose the woollen fibre is treated with a solution 
of alum and cream of tartar (bitartrate of potash) ; or with the latter salt and tin-salt 
(chloride of tin); or, again, cream of tartar and green vitriol; for certain colours, 
chloride of tin and pink salt (see p. 75 ) are used. 

Dyeing wool Blue. The imparting of a blue colour to wool is one of the most 
important operations of dyeing woollen goods. It is frequently effected with indigo, 
which produces the most beautiful and fast colours ; but indigo is used only for the 
better and heavier lands of woollen fabrics; lighter tissues—merinos for instance- 
are often dyed with Prussian blue (not a fast colour), while common woollen goods, 
flannels, &c., if dyed blue at all, are dyed with logwood and blue vitriol (sulphate of 
copper). In order to ascertain whether a woollen tissue has been dyed with indigo, 
Prussian blue, or copper salts, the following tests may be employed. Woollen 
tissue dyed with indigo does not change its colour by being boiled with caustic 
potash, or by being moistened with concentrated sulphuric acid. When Prussian blue 
is the dye used, the tissue becomes red-coloured by being boiled with caustic potash, 


602 


CHEMICAL TECHNOLOGY. 


and becomes discoloured by being moistened with, strong sulphuric acid. Woollen 
goods dyed with logwood and copper salts are reddened by being moistened with 
dilute sulphuric acid, and on being incinerated, the tissue leaves an ash containing 
copper. 

indigo Blue. Woollen goods are most frequently dyed blue with indigo by means of a 
solution of white indigo (reduced indigo) in an alkaline fluid, the goods being blued 
by exposure to air—that is to say, by the oxidation of the indigo taken up by the fibre, 
the dye becoming simultaneously fixed. The principle of this mode of dyeing with 
indigo (technically known as blue vat), may be elucidated by the following formula:— 
C i6 H I2 N 2 0 2 +0 = C i6 H io N 2 0 2 +H 2 0 . 

Blue vats. The greatest consumption of indigo is in forming the blue vats, in which 
woollen or cotton goods, more rarely linen, are dyed by simply immersing them in 
the solution of white indigo. The same vats are not equally adapted for wool 
and calico, there being, as will be seen in the following details, a wide difference in 
their composition. According to the general accounts, the lime and copperas vat 
(see below) is not well adapted for woollen goods; still in the most recently 
published French treatise on woollen dyeing, there is no mention made of any 
other kind of vat; the following proportions and directions being given for setting 
a vat for dark blue:—1200 gallons of water; 34 lbs. of quick-lime; 22 lbs. 
of green copperas; 12 lbs. of ground indigo; 4 quarts of caustic potash solution at 
34 0 = sp. gr. 1’288. The indigo is ground very fine by trituration in properly 
constructed mills, this being a point of the utmost importance. In the above recipe 
the potash is mixed with 5 gallons of water in an iron pan, and the indigo added. 
The mixture is gradually heated to ebullition and kept boiling for two hours 
with uninterrupted stirring; this softens and prepares the indigo for dissolving. The 
lime is well slaked so as to be very fine, and is next passed through a sieve in the 
state of milk of lime. It is then mixed with the indigo and potash; the copperas 
(protosulphate of iron), previously dissolved, is added to the vat and well stirred; 
then the mixture of lime, potash, and indigo is poured in, and the whole well stirred 
for half an hour. If the proportions are well kept, the vat will be fit for working 
in twelve hours; if, however, it looks blue under the scum, it is a sign that the 
indigo is not wholly dissolved, and more lime and copperas should be added, and the 
vat left undisturbed for another twelve hours. The vat is worked at a temperature 
of 70° to 80° F. This is the ordinary composition of a vat for dyeing cotton, but is 
not, at least in England, in use for dyeing woollen goods. 

The usual blue vats for wool contain neither copperas nor lime, or but a small 
quantity of the latter; as, for instance—Water, 500 gallons; indigo, 20 lbs.; 
potash (carbonate, pearl-ash), 30 lbs.; bran, 9 lbs.; madder, 9 lbs. The water 
is heated to just below its boiling-point; the potash, bran, and madder are first put 
into the vat, a well-made wooden tub of convenient size, and then the indigo 
previously very finely ground. Cold water is added so as to reduce the temperature 
to 90° F., and that temperature is maintained constantly by means of a steam-pipe. 
The ingredients are well stirred every twelve hours. The vat is generally ready for 
use in forty-eight hours after setting. This vat does not work longer than about 
a month, and is somewhat expensive on account of the potash. Another—the 
so-called German—vat is much more manageable, and may be worked for two 
years without emptying, being freshened up as required. It is composed of the fol¬ 
lowing ingredients:—2000 gallons of water are heated to 130° F., and there are added 


DYEING . 603 

20 lbs. of crystals of soda (common carbonate); 2! pecks of bran; and 12 lbs. 
of indigo; tlie mixture being well stirred. In twelve hours fermentation sets in ; 
bubbles of gas rise; the liquid has a sweet smell, and has assumed a green 
colour. 2 lbs. of slaked lime are now added and well stirred, the vat is again heated 
and covered up for twelve hours, when a similar quantity of bran, indigo, and soda, 
with some lime, are added. In about forty-eight hours the vat may be worked; but 
as the reducing powers of the bran are somewhat feeble, an addition of 6 pounds of 
molasses is made. If the fermentation becomes too active, it is repressed by 
the addition of lime; if too sluggish, it is stimulated by the addition of bran and 
molasses. Like all the other blue vats for wool if is worked hot. Another kind of 
vat may be called the woad vat, because a considerable quantity of woad is added to 
it, and also madder, which in this case acts simply by reason of the saccharine 
matter it contains. The proportions are :—Pulverised indigo, 1 lb.; madder, 4 lbs.; 
slaked lime, 7 lbs., boiled together with water and poured upon the woad in the vat. 
After a few hours fermentation sets in, and fresh indigo is added according to the 
depth of colour required to be dyed. The pastel vat is set with a variety of woad 
which grows in France, and which is richer in colouring matter than the common 
woad. It is possible that the colouring matter of the pastel adds to the effect; but it 
is more likely that while it furnishes fermentescible matters useful in promoting the 
solution of indigo, it is added as a remnant of ancient usage. Before indigo became 
again known in Europe (the dye was known to the Greeks and Romans), in the 17th 
century, woad was the general blue dye material. The method of dyeing the woollen 
fibre and fabrics is very simple. The wool, thoroughly wetted out, is suspended on 
frames, and dipped in the vat for an hour and a half or two hours, being agitated all 
the time to insure regularity of colouring. The pieces are then removed, washed 
in water, and treated with weak hydrochloric or sulphuric acids to remove the alkali 
retained. As regards blue vat for cotton dyeing, in some exceptional cases when 
thick and heavy goods have to be dyed, the so-called German vat is used; but 
generally all calicos are dyed blue by means of the cold lime and copperas vat. The 
materials used are lime, protosulphate of iron, ground indigo, and water. The 
chemical action consists, in the first instance, in the formation of sulphate of lime 
and protoxide of iron; the latter substance having a considerable affinity for oxygen, 
removes an atom of it from the blue indigo, converting it into white, which dissolves 
in the excess of lime, and is ready for dyeing. The proportions are. as follows:— 
900 gallons of water; 60 lbs. of green copperas ; 36 lbs. of ground indigo; 80 to 90 
lbs. of slaked lime, stirred every half hour for three or four hours, then left twelve 
hours to settle, well raked up again, and as soon as settled ready for dyeing. 

saxony Blue. As already stated, indigo dissolves in concentrated sulphuric acid, 
forming (because it is not a solution in the ordinary sense of the word) sulphindigotic 
acid, which is employed in dyeing wool in the following manner:—First, 1 part of 
indigo is treated with 4 to 5 parts of fuming sulphuric acid; next, this solution 
is poured into a vessel containing water; and into this mixture flock wool is 
immersed for twenty-four hours. After this time the wool is removed from the 
vessel and drained, and transferred to a cauldron filled with water, to which has been 
added either carbonate of ammonia, or of soda, or of potash, and boiled for 
some time. The solution thus obtained, technically known as extract of indigo 
or as indigo carmine, is used for dyeing wool which has been previously mordanted 
with alum. There is formed on the wool sulphindigotate of alumina. 


1 


604 


CHEMICAL TECHNOLOGY. 


E fromEag8 In &c igo In order to recover the indigo from scraps and rags of woollen and 
other fabrics dyed indigo blue, the materials are treated with dilute sulphuric acid, 
which is heated to ioo°. The wool is dissolved, while the indigo is left as an 
insoluble sediment. Military uniforms yield from 2 to 3 per cent of indigo. The 
acid solution is next neutralised with chalk, and a sulphate of lime is obtained 
which, owing to the nitrogenous matter intermingled, may be usefully employed as a 
manure. 

Beriin °r Pmssian Biu e Wool is dyed with the so-called Prussian blue (ferrocyanide of 
iron) by two methods, one of which consists in saturating the wool with a solution of 
a salt of peroxide of iron (generally the persulphate, or preferably the pernitrate), 
after which the wool is passed through a solution of ferrocyanide of potassium 
in water, acidulated with sulphuric acid. The other process producing so-called Bleu 
cle France is based upon the decomposing action which the atmosphere exerts on the 
ferro- and ferri-cyanliydric acids. The goods are immersed in a solution of either the 
ferro- (yellow) or ferri- (ruby red) cyanide of potassium (commonly yellow or red 
prussiate) in water, to which are added sulphuric acid and alum. Afterwards the 
goods are aged, or exposed to the air in rooms in which steam is simultaneously 
admitted to elevate the temperature and assist the action of the oxygen of the air. 
The result is that the ferro- or ferri- cyanhydric acid is decomposed, hydrocyanic 
acid being evolved, while there is deposited on the fibres of the woven fabric ferro¬ 
cyanide of iron, Prussian or Berlin blue. Meitzendorff has recently invented a 
method of dyeing this blue by which a colour is produced very similar to that 
obtained by the so-called Saxony blue. He prepares a solution containing ferro¬ 
cyanide of potassium, chloride of tin (SnCl^, tartaric and oxalic acids ; this solution 
is heated and the wool kept therein for some time. The oxalic acid dissolves 
the Prussian blue, which of course can only act as a dye when dissolved, any 
of it left undissolved being lost. The tartaric acid increases the brilliancy of the 
colour. 

Dyei an<fa u copp«saftr ood F° r this purpose logwood is boiled in the dye-beck with 
water, and to the decoction are added alum, cream of tartar, and sulphate of copper. 
The wool is boiled in this fluid, and is next cleared by being boiled in a fluid con¬ 
taining logwood, tinsalt (protochloride of tin), alum, and cream of tartar. The goods 
dyed in this manner do not, as is the case with the indigo goods, become white by 
wear. Instead of logwood, archil and cudbear are frequently used for so-called half¬ 
fast colours. 

Dyeing Yellow. On the Continent, weld, which has become quite obsolete for dyeing 
yellow on wool in the United Kingdom, having been entirely superseded by 
quercitron bark, is still used for producing a yellow dye, on account of the fact that 
weld, when brought into contact with an alkali, becomes less red-coloured than is 
the case with the other yellow dyes. 

In dyeing with weld its colouring matter is extracted by water, and the decoction 
added to the goods intended to be dyed. With alum it dyes a very fine clear yellow, 
tolerably permanent in soap, but not resisting air and light. Weld has not more thai 
one-fourth the tinctorial power of quercitron bark, and on this account, as well as or 
that of its great bulk relative to its weight, it is not used in this country. Fustic, 
yellow-wood, is very extensively employed in dyeing, and is the most suitable yellow 
matter for working with other colours in compound shades. With aluminous 
mordants it gives yellow of an orange shade; with iron mordants it gives drabs. 


DYEING. 


605 

greys, and olive. As a yellow colouring matter it is considered to be of far less 
power than quercitron bark weight for weight, while it is also inferior in purity of 
colour; but as fustic withstands the action of acids and acid salts better than bark, 
it is used in greens, blacks, and mixed colours where yellow is required. Young or 
French fustic (also known as Venice sumac) is used for imparting yellow to merinos. 
A golden yellow is produced upon wool with either picric acid or Manchester 
yellow. 

Dyeing wool Red. Madder is the chief colouring matter employed for imparting to 
wool a red or scarlet colour. The process of dyeing wool with madder consists in 
mordanting the woollen tissue, fibre, or yarn, and in immersing it in the dye-beck 
containing madder with water. The wool is mordanted by being immersed in a 
warm solution of alum and cream of tartar. The dyeing is effected by placing the 
mordanted goods in the dye-beck or madder-bath, the quantity of madder being 
equal to half the weight of the woollen goods. In practice the goods are, of course, 
slowly moved into, through, and out of the dye-beck, proper mechanism being 
provided for this purpose. After having been dyed, the goods are thoroughly 
washed, so as to remove excess of dye as well as any mechanically adhering 
particles of madder. Dyeing red with cochineal is effected upon wool in the same 
manner as with madder. Scarlet is red with a yellowish hue, while a peculiar hue of 
red is termed crimson, often produced by cochineal. Woollen fabrics are mordanted 
in a mixture of water, cochineal, cream of tartar, and tinsalt, and next dyed 
by boiling with more cochineal and tinsalt. Wool is very readily dyed with all the 
tar-colours (red, blue, green, grey, yellow, brown, violet), the affinity of wool for 
these colours being so great, that the solution of any of these pigments may be com¬ 
pletely deprived of its colouring matter by contact with wool. 

Green Dyes. Green dyes are usually obtained by combining blue and yellow. Wool 
is first dyed blue, and having then been mordanted with cream of tartar and alum, is 
dyed with fustic, or, on the Continent, with weld. The green cloth used for covering 
billiard-tables and other furniture is dyed in the following manner :—A weak decoc¬ 
tion of fustic is prepared, and into this some Saxony blue is poured, while there is 
next added alum and cream of tartar. The woollen fabric is immersed in the bath 
and boiled for two hours. It is next thoroughly washed and brightened by being 
again immersed in a dye-beck filled with a fresh fustic decoction, to which a smaller 
quantity of Saxony blue has been added. All kinds of woollen tissues, worsted, half¬ 
wool, alpacas, delaines, &c., may be dyed green by means of lo-kao (Chinese green), 
and iodine green. 

Mixed shades. Mixed shades are produced on the fabrics by means of cochineal, 
madder, French fustic, fustic, in a manner similar to that used for dyeing green. 

Black Dyes. Excepting only aniline black, all black dyes may be considered a/ combi¬ 
nations of iron with tannic or gallic acid ; but the best and fastest blacks on broadcloth 
are such as have as a first dye either madder or indigo. The woollen goods are mor¬ 
danted with sulphate of iron (green copperas) and dyed by immersion in a decoction of 
logwood, galls, sumac, &c. The so-called Sedan black (this town is celebrated for its 
cloth manufacture) is produced by dyeing the cloth blue with woad, when after 
careful washing the cloth is placed in a dye-beck containing water, sumac, and log¬ 
wood, and is boiled for some three hours, after which sulphate of iron in a solution 
of known strength is added. This operation is repeated until the cloth has assumed 
an intensely black colour. Half-fast black colours are produced on cloth by dyeing 


6o6 


CHEMICAL TECHNOLOGY. 


them blue with Prussian blue, after which the operation just described is gone 
through. Common black is produced by dyeing with logwood, sumac, some fustic, 
and a mixture of green and blue vitriol. Chromium black, invented by Leykauf at 
Nuremberg, is obtained in the following manner:—The cloth is mordanted with a 
solution of bichromate of potash and cream of tartar, after which it is dyed in a 
decoction of logwood. The so-called pyrolignite of iron (crude acetate of iron 
prepared from scraps of old iron and crude acetic acid) is now very generally used as 
a mordant instead of the green copperas. This acetate, also known as black or iron 
liquor, is prepared on the large scale and sold as a liquid at a sp. gr. of rc>9 to 1*14. 

mite cioth. This cloth, in use especially for military uniforms, is obtained by first 
thoroughly washing, fulling, and carefully sulphuring the cloth, which is next 
passed through a bath containing chalk and a small quantity of size, after which 
it is dried, beaten, and well brushed. 

snk Dyeing. Silk is usually dyed in skeins unspun, but having been first decorti¬ 
cated, that is to say, deprived of the layer of gummy matter which forms the outer 
covering of cocoon silk. It is then scoured, bleached, and sulphured; the latter only 
when the silk is to be dyed with very bright colours and delicate light hues. Silk is 
dyed in cold dye solutions. It is dyed black by any of the following processes:— 

1. Logwood and iron mordant; 

2. Logwood and bichromate of potash ; 

3. Galls and other substances containing tannic acid with iron salts as mordant; 

4. With aniline black, according to the recipes of Persoz, jun., and others, by the 

use of chromate of copper and oxalate of aniline. 

The first and second are simply known as ordinary blacks, while the third is 
known as fast black. The ordinary black is obtained by simply mordanting the silk 
with nitrate of iron, and then dyeing it in a decoction of logwood. This cheap dye 
is more particularly applied to light silken fabrics. The colour is reddened even by 
weak acids, such as lemon and orange and other fruit juices. The fast black is far 
more expensive, but it is not affected by weak acids, while it affords the additional 
advantage of largely increasing the weight of the silk (in raw state as well as in spun- 
yarn silk is sold and bought by weight), as this textile fibre absorbs from 60 to 80, 
and even 100 times its own weight, and silk used for shoe-laces even 225 per cent of 
the dye material. When desired the silk-dyer has to return for 100 lbs. of raw silk 
from 160 to 180 or 200 lbs. weighted black-dyed silk. In Germany an indigenous 
gall, locally known as Knoppern , French avelandes, containing some 30 to 50 per cent 
of tannic acid, is used in the extract to dye silk black. In England nut-galls 
imported from the Levant are employed for this purpose. Although the increase in 
weight of the silk by black dyeing is advantageous to the dealers, the deposition of 
so much foreign matter in the fibre of the silk not only injures its wearing qualities, 
but also gives rise to the disagreeableness of the dyeing coming off while the mate¬ 
rial is being worn. Microscopic research has proved that the dye adheres very 
loosely to the silk. The process of dyeing silk black with galls is very simple. The 
fibre is first steeped in a solution, or rather infusio-decoction, of galls, technically 
known as “ galling,” after which the silk is placed in a solution of nitrate of iron. 
This black is sometimes dyed on silk previously dyed with Prussian blue, but far 
more frequently a bluish shade is given to black by first dyeing the silk with log¬ 
wood, copperas, and some sulphate of copper. 

As regards the weighting of the silk, it is essentially due to the fact that silk, as 


DYEING . 


607 

an animal product, has the property of combining with tannic acicl and thereby 
becoming heavier. The larger, therefore, the quantity of tannic acid contained in 
the dye-bath, or the oftener the galling of the silk is repeated, the heavier the fibre 
will become within certain limits. It is not quite indifferent whether a per-salt or a 
proto-salt of iron be employed, the former being preferable. The previously galled 
silk becomes, when passed through a solution of a per-salt of iron, at once coloured 
black; but when it is passed through a solution of a proto-salt of the same metal, the 
silk becomes at first coloured only black-violet, and gradually deep black by exposure 
to air. Although in every case the result is the same, the use of a per-salt is advan¬ 
tageous, and becomes necessary with a small quantity of tannic acid, while for a 
heavy weighting of the silk, the proto-salt of iron only can be employed. It is stated 
that the dyeing of silk with aniline black by means of chromate of copper and oxalate 
of aniline yields excellent results. Silk is dyed blue either with indigo, Berlin blue, 
ogwood, or aniline blue. The indigo vat has not been much used for imparting a blue 
colour to silk since the discovery of fixing Prussian blue upon silk; and if indigo 
is used at all it is as indigo carmine, or the so-called distilled blue, purified sulphin- 
digotic acid. In order to dye silk with Prussian blue, it is first immersed in a 
solution of nitrate of iron. This salt is generally in use in England, while in France 
a persulphate of iron made by dissolving green copperas in nitric acid is employed, 
and known under the name of Raymond’s solution, the blue produced being termed 
Raymond’s blue; Napoleon blue is produced by the addition of a tinsalt to the iron 
bath, followed by treatment with a solution of ferrocyanide of potassium acidulated 
with sulphuric acid. The latter blue, more brilliant than the former, is usually 
prepared in England, a tinsalt being invariably added to the iron mordant. The 
mordanted silk is next passed through a boiling soap-solution, then washed, and next 
steeped in a solution of ferrocyanide of potassium acidulated with hydrochloric acid. 
The brilliancy of the dyed silk is greatly enhanced by passing it through water con¬ 
taining ammonia. Dyeing silk with aniline or naphthaline blue is a very simple 
process, it being only necessary to put the silk into a solution of the dyes, 
the solvent being alcohol or wood-spirit, or in the case of soluble aniline blue, 
water. The silk is left in the solution until it has assumed the desired hue. Until 
the discovery of fuchsin, silk was always dyed red and pink by means of cochineal, 
safflower (carthamine), and archil; but now silk is generally dyed with fuchsin, 
coralline, and Magdala red (naphthaline red). The process is as simple as that 
just described for aniline blue. Aniline red is the brightest, purest, and deepest of 
all red dyes for silk, but it is not so fast as Magdala red. Archil is still largely used, 
but aniline violet or mauve is in close competition with it. Yellow is produced upon 
silk by first mordanting with alum and dyeing in a decoction of weld, to which, if it 
be desired to impart an orange hue, some annatto is added, or, preferably, Man¬ 
chester yellow. By cautious treatment with nitric acid silk may be dyed yellow, 
some xanthroproteic acid being formed, while without any mordant picric acid pro¬ 
duces a bright lemon-yellow on silk, the colour becoming deeper by treatment with 
alkalies. Ordinary green is produced upon silk by dyeing it yellow by means 
of either weld, quercitron, fustic, or picric acid, and then dyeing it blue with indigo- 
carmine, aniline blue, or sulphindigotic acid. Fast green is obtained by dyeing the 
silk blue with Bleu Raymond , and next treating it with fustic. During the last few 
years aniline green (emeraldine) has been generally used for dyeing silk green. Lilac 
is produced upon silk by means of aniline violet, archil, or logwood and tinsalt. 


6 o8 


CHEMICAL TECHNOLOGY. 


Cauco Dyeing. Cotton is dyed either in yarn or woven fabric, but more generally as 
yarn. Cotton is far more difficult to dye than wool, and requires, especially for 
obtaining fast colours, stronger mordants. Blue is produced upon cotton (calico it 
is termed in fabric) by means of the copperas-vat (see Indigo); further by Berlin or 
Prussian blue, logwood, and green copperas; and finally by being passed through a 
solution of oxide of copper in ammonia; the fibre, yarn, or tissue exhibiting after 
drying a beautiful bright blue colour. Yellow is produced with Avignon berries, 
weld, fustic, quercitron, annatto, acetate of iron (nankeen), and chrome-yellow. 
Green is obtained by the copperas-vat followed by dyeing with fustic. Brown is 
produced with a salt of iron and with quercitron or madder, or simply by means of 
hydrated oxide of manganese. Black is either fast, aniline black, or is produced by 
dyeing blue by the aid of the copperas-vat, next mordanting with acetate of iron, and 
then dyeing in a bath consisting of galls and logwood. The aniline colours can be 
fixed upon cotton only by the aid of a specific mordant—a solution of tannin in 
alcohol; or the fibre of cotton is first animalised, as it is termed; that is to say, 
impregnated with either albumen or casein, the fibre being to a certain extent made 
similar to that of wool or silk and rendered absorbent of aniline dyes. Cotton may 
be mordanted with Gallipoli oil, or with soft-soap for certain dyes. 

As regards dyeing cotton and calicos red, madder is the chief dye material, while 
probably at no distant period artificial alizarine from anthracen will become an important 
material. We distinguish between ordinary red and Turkey, sometimes termed 
Andrinople red; the former is produced upon cotton goods mordanted with acetate 
of alumina (commonly called red liquor or red mordant); the latter is obtained by 
complicated manipulation, the rationale of which is not quite elucidated by science. 

Turkey Red. This beautiful and very fast red, improved by washing, is produced by 
the following distinct operations:—The well-bleached cotton goods are first padded 
in a mixture of Gallipoli oil and pearl-ash containing about 200 lbs. of oil, 40 lbs. of 
pearl-ash, and 100 gallons of water, a quantity sufficient for about 4000 yards of 
calico. The pieces are next exposed to air in summer and to the heat of a stove in 
cold weather for twenty-four hours ; then padded again in a mixture of oil, potash, 
and water, and again dried and exposed, and so on for as many as eight different 
treatments for dark colours. The excess of oil, or rather that which has not suffered 
change by oxidation, and the alkali are now removed by steeping in an alkaline fluid, 
and the pieces well washed. The next process is the galling and aluming; 60 lbs. 
of ground nut-galls are exhausted with hot water, and to this liquor are next added 
120 lbs. of alum and 10 lbs. of acetate of lead, after which the liquor is made up to 
120 gallons. The pieces are padded in this liquor, dried, and aged three days, then 
fixed by passing in warm water containing ground chalk, being next washed and 
dyed in madder mixed with a little sumac and with blood. For dark shades of 
colour the fabrics undergo another galling and aluming after dyeing; and are then 
aged, fixed, and dyed a second time. After this last operation the goods exhibit a 
very heavy brown-red colour, and they are brightened by two or three soapings or a 
passage in dilute nitric acid. In other processes sheeps’ and cows’ dung are mixed 
with the oil and other modifications introduced. Garancine is largely used in Turkey- 
red dyeing. By its use the operations of clearing and brightening ( avivage) have 
been much shortened. All that has been suggested as regards the rationale of the 
Turkey-red dyeing process, and more especially as regards the action of the Gallipoli 
oil (liuile tournante , an inferior kind of olive oil which, when mixed with a weak 


PRINTING OF WOVEN FABRICS. 609 

solution of pearl-ash, should, if of proper quality, form a perfect emulsion, which, after 
twenty-four hours’ standing, should not exhibit any globules of oil floating on the 
surface), is not sufficiently substantiated to afford a secure basis for further reasoning. 

Dyeing Linen. Linen is dyed by processes similar to those in use for cotton, but owing 
to the peculiar structure of the flax fibre, its affinity for dyes is much lower than that 
of cotton. 


The Printing of Woven Fabrics. 

Pnntl F n u g bir oven This very important branch of the dyer’s art aims at producing 
coloured patterns upon calico, linen, and woollen and silk tissues. Calico printing is 
the most important portion of this industry, which is based upon the same principles 
as dyeing, but is in the practical execution far more difficult, partly because the 
colours have to be applied to certain portions only of the fabric, while others either 
remain colourless or are discharged, partly also because it frequently happens that 
many colours have to be applied close to each other. The colours employed in calico 
printing are of two' different kinds; first, such as are directly applied to the cloth by 
the aid of blocks or plates upon which the patterns and designs to be produced upon 
the calico are engraved—to the colours thus applicable belong, also, the ochres, 
Berlin blue, madder-lake, indigo, cochineal, and most of the tar colours; secondly, 
die other kind of colours are such as are produced by immersing the calico printed 
with various mordants in dye-baths—madder, cochineal, logwood, weld, sumac, cutch, 
&c., belong to this category. 

There exist various methods of printing, of which the following are the chief:— 

1. From the thickened and mordanted colours. 

2. The thickened mordant only is applied by means of engraved copper cylin¬ 

ders to the cloth, which, after the mordant has been thoroughly fixed, is put 
into the dye-beck. 

3. The entire piece of cloth is either mordanted or a colour is printed, while to 

such portions of the cloth as are to remain white or are intended to be 
afterwards of another colour or colours, or pattern, a resist is applied, 
sometimes printed from blocks, or more frequently from cylinders, the effect 
being that on the portions of the cloth thus protected the dye does not 
become fixed. 

4. Coloured patterns may be, and in practice are, largely produced by first 

dyeing the mordanted cloth (calico nearly always requires a mordant) 
uniformly with one colour, and removing this colour in certain portions 
of the cloth by what are technically termed discharges, that is to say, 
chemicals which destroy the dye. 

In order to fix certain kinds of colours they have to be submitted to the action of 
steam (steam colours); while such inorganic substances as ultramarine, emerald 
green, &c., or among the semi-organic, the lakes of madder for instance—which are 
applied mechanically by the aid of albumen, caseine, gluten, and also require for 
fixing the aid of steam—are technically termed surface-printed colours. 

Mordants. The mordants employed in calico printing are chiefly such salts as are 
comparatively loose combinations of acid and base, so that the latter can readily unite 
with the fibre. Among the mordants chiefly used the acetates of alumina (see p. 263) 
and iron occupy a first place, while alum or a solution of aluminate of soda is more 
rarely used. Acetate of lead is the mordant for producing chromate of lead; various 
40 


• 6io 


CHEMICAL TECHNOLOGY. 


combinations of tin (see p. 75) are also employed as mordants. The application of a 
mixture of caseine and lime lias been recently proposed as a mordant; for this 
purpose caseine, technically known in England as lactarine, and prepared from milk 
(of which it is the curd}, is dissolved in dilute caustic ammonia, and the solution thus 
obtained is mixed with freshly prepared milk of lime. The caseine-lime mixture is 
used for steeping the cloth intended to be dyed; the caseine-lime becomes insoluble 
by the application of heat, after which the fabric is so thoroughly mordanted that it 
resists washing with alkaline fluids. In order to prevent the stiffness of the cloth 
when the caseine-lime is used as a mordant, it has been suggested to mix the fluid, 
previous to its application to the woven fabric, with some Gallipoli oil; the calicos 
to which this mordant is applied behave as regards the dyes like wool, and readily 
take the same colours. Cheese, which does not contain too much fat, or skim-milk 
cheese, when digested with ammonia, produces a solution which can be used instead 
of caseine. Tannic acid, albumen, dried white of eggs re-dissolved in water, and 
vegetable gluten are used as mordants in calico printing. 

Thickenings. In order to give the colours or mordants used in printing, either by 
block or cylinder, a sufficient consistency, they are mixed with what are technically 
known as thickenings. As such are used:—Senegal gum, tragacanth, leiocome, 
British gum, dextrine, salep, flour, gluten, pipe-clay with gum, glue and size, sulphate 
of lead, sugar, molasses, glycerine, starch, sometimes chloride and nitrate of zinc. 
The purity of the colours and mordants depends in a great measure upon the quality 
of the thickenings. British gum, prepared from starch, is most frequently used. As 
regards the selection of the thickening, it should be borne in mind that very acid 
mordants cannot be mixed with starch, because it loses its consistency with acids ; 
while again, some metallic preparations—for instance, basic or sub-acetate of lead, 
solutions of tin, nitrate of iron, and of copper—cause gum to coagulate, and hence gum 
should not be used as a thickening with these substances. 

Resists, or Reserves. As already stated, there is used in calico printing a composition 
which, on being applied to the cloth, prevents the deposition or fixing of colour to 
the portions of the cloth where the resist composition is placed, the result being 
that these portions are left white. Most frequently the resist is employed w r ith the 
view of preventing the fixation of indigo to certain portions of the cloth, so that it 
remains white where the resist has been applied. The resists are composed of pasty 
excipients, such as pipe-clay, fat, oil, sulphate of lead, to which are added and with 
which are incorporated substances which readily yield oxygen, for instance, sulphate, 
nitrate, and acetate of copper, or a mixture of red prussiate of potash (ferricyanide of 
potassium), and caustic soda solution. In some instances resists are composed so 
that they act as a mordant (alumina or iron mordants') for other dyes, the portions of 
the cloth protected by the resist from contact with indigo, and left white, being dyed 
by immersion in a dye-beck containing another dye-stuff, which may be madder or 
quercitron bark. This kind of printing is sometimes termed lapis , in consequence of 
the remote similarity which some of these patterns bear to lapis lazuli. The so- 
called white resist for cylinder printing consists, as an example, of acetate or 
sulphate of copper, acetate of lead thickened with gum, or dextrine solution. This 
composition having been printed by means of the cylinders, the pieces are the next 
day put into the indigo-vat and kept there until the desired depth of colour has been 
, obtained, after which they are passed through a bath containing dilute sulphuric 
acid until the places where the resist has been applied have become white. The 


PRINTING OF WOVEN FABRICS. 


611 


rationale of this process is the following:—As soon as the reduced indigo (white 
indigo) in the vat comes in contact with the oxide of copper, it is converted at the 
expense of the oxygen of the oxide into blue indigo, which is precipitated in insoluble 
state on the resist. By the treatment with dilute sulphuric acid the hydrated sub¬ 
oxide (red oxide) of copper is dissolved, and with it the indigo blue washed out. 

Instead of the salts of copper white resists are used, and composed of bichloride oi 
mercury and sulphate of zinc; the former acts in a manner similar to the salts of 
copper, while the latter enters into an insoluble combination with the reduced (white) 
indigo, which is precipitated where the resist has been applied. 

Discharges. Discharges are for the purpose of producing by chemical means white 
patterns on certain parts of the dyed cloth. This end may be attained by dissolving 
a previously applied mordant or—as is the most usual method—by destroying or 
discharging the dye which has been distributed over the whole surface of the cloth. 
As regards the first method, certain acids—phosphoric, arsenic, lactic, oxalic, hydro- 
fluosilicic acids—are made to combine with the base contained in the mordant; 
while for the purpose of discharging the previously applied colour, there are 
used such substances as bleaching-powder, chromic acid, a mixture of red prus- 
siate of potash and caustic soda-ley, permanganate of potash, a paste composed 
of bromine mixed with water <and pipe-clay, nitric acid, &c. All these agents have 
an oxidising effect, whereas protochloride of tin and protosulphate of iron, also used 
for this purpose, acting by absorbing oxygen, are reducing substances. Among the 

Acid Discharges, acids, tartaric acid is generally used for the purpose of discharging 
alumina and oxide of iron employed as mordants ; sometimes this acid is mixed with 
bisulphate of soda. A piece of cloth dyed red or blue, to which is in certain parts 
applied a mixture of tartaric acid, pipe-clay, and gum (the latter as thickening 
to give consistency), becomes immediately bleached when the cloth so prepared is 
immersed in a solution of bleaching-powder. 

Oxidising ^Agents as Of i a t e fluoride of potassium has been used as a discharge for 
Berlin blue. The discharging of indigo blue by oxidising agents is due to the for¬ 
mation of isatine from the indigo blue, the former being soluble, the latter insoluble 
in water, so that the soluble substance can be removed by washing :— 
C i6 H io N 2 0 2 +20 = C i6 H io N 2 0 4 . 

Indigo blue. Isatine. 

Indigo is discharged by chromic acid, employed in practice as bichromate of 
potash, the acid being reduced while giving off oxygen to chromic oxide. More 
recently Mercer has proposed to bleach goods dyed with indigo by the application of 
a mixture of potash and ferricyanide of potassium; for this purpose the indigo-dyed 
cloth is soaked in a solution of red prussiate of potash, and then caustic 
potash thickened with British gum is printed on. The potash converts the 
ferricyanide into ferrocyanide, and by the oxygen thus set free the indigo blue is 
coverted into isatine :— 

Ferricyanide of potassium, 4K 3 FeCy6 
Caustic potash, 4KOH 
Indigo blue, Ci 6 H io N 2 0 2 

Ked Dis n ^arge3 t8as Protochloride of tin, known as crystals of tin and as tinsalt, is the 
most important of the reducing agents applied to goods dyed with oxide of iron. 
When the protochloride is placed in contact with oxide of iron, the result is the for¬ 
mation of readily soluble protochloride, which is removed by washing, while 


yield 


Ferrocyanide of potassium. 4K 4 b eCy 6 . 
Isatine, Ci6H I0 N 2 0 4 2H 2 0r 





5 l 2 


CHEMICAL TECHNOLOGY. 


simultaneously there is deposited on the fibres of the cloth stannic acid (more cor¬ 
rectly proto-peroxide of tin), which may serve as a mordant for red and yellow dyes. 

Calico Printing. Calicos may be printed by :— 

1. Dyeing in the dye-beck. 

2. By block or cylinder printing (topical colour-printing). 

3. By resist or discharge printing. 

In the process of dyeing in the dye-beck (madder style) the thickened mor¬ 
dant, to which usually some faint colouring matter is added for the purpose of 
recognition (the reader should bear in mind that the mordants are colourless, 
or at least nearly so), the pattern produced on the white calico is imprinted 
by the aid either of blocks or cylinders, upon which the desired pattern is 
engraved. 

The process of block printing takes place upon a table over which a piece of thick 
woollen cloth is stretched. The calico to be printed is laid on this cloth, and by the 
aid of blocks the mordant is transferred to the calico. The blocks, made of pear-tree 
wood, box-wood, or fir-wood, have the pattern engraved en relief, or wrought by means 
of brass wires fastened in the wood in such a manner as to form a certain figure. The 
former blocks are called engraved, the latter dotted or stippled blocks, while in some 
cases the two methods are used simultaneously. In order to distribute the mordant 
uniformly a frame or chase is employed, on which, by means of nails, a stout piece of 
canvas is stretched, the frame being made to float on the top of a thick solution 
of gum or linseed mucilage, placed in a suitably constructed vessel. On a frame a 
piece of oil-cloth is fastened to prevent percolation of the fluid; next the mordant is 
brushed over the cloth of the frame quite uniformly. The printer puts his block on 
the cloth thoroughly moistened with mordant, so that the projecting engraved 
portions of the block become uniformly moistened, and the block having been trans¬ 
ferred to the calico is pressed thereon, the pressure aided either by a smart blow 
given by the printer’s fist or by a wooden mallet, care being taken to print every 
portion of the engraving equally on to the woven fabric. When several mordants 
are placed on to the frame by the aid of separate brushes and thence printed on to 
the cloth, the result is the production of the so-called iris or fondu prints. In order 
to accelerate the operation of printing, machinery is now usual—for instance, the 
Perrotine, invented by Perrot, at Rouen, in 1833. This machine works with 
three to four wooden formes (Perrotine formes upon which the patterns are fastened by 
nails), these patterns being cast in a manner similar to stereotype plates, consisting 
of a readily fusible metallic alloy. The arrangement of this machine is of course 
such, that the formes are as wide as the cloth intended to be printed. Instead of this 
machine cylinder printing has become general. The cylinders are made of copper, 
and on these the pattern is engraved. The cylinders are revolved in a framework by 
means of machinery. By the aid of a wooden cylinder covered with cloth which 
dips into the vessel containing the mordant, the copper cylinder is fed with mordant, 
while a kind of blunt knife, known technically as the doctor, scrapes off from the non- 
engraved portion of the copper cylinders any superfluous colour, which is thus con¬ 
fined to the engraved portion forming the design. 

Before the mordanted cloth can be dyed it has to be kept for some time in 
order that the alumina and iron mordants may combine intimately with the fibre of 
the cloth. Moreover, the cloth, before being immersed in the dye-beck, has to 
undergo the operation technically known as cleansing ; that is to say, after the mor- 


PRINTING OF WOVEN FABRICS. 613 

uant has become dry, the thickening and faint colouring matter have to be removed, 
together with any mordant uncombined with the fibre. For goods intended to 
be madder dyed the cow-dung bath is required. Usually some chalk is added for the 
purpose of saturating the acetic acid or the mordant. Although all calico printers 
agree that the cow-dung bath is necessary, the rationale of the action of this bath has 
not as yet been explained. According to Mercer and Blyth, for cow-dung may be 
substituted ceitain phosphates and arseniates, and these chemists propose the use of 
phosphate of soda and phosphate of lime. More recently silicate of soda has 
been used instead of cow-dung. In England cow-dung is no longer, or at least only 
very rarely, used. After the goods have been treated with cow-dung or its substitutes, 
they are washed and then dyed. In the case of dyes the colouring matter of which 
is readily soluble in water, infusions or decoctions are used; cochineal, quercitron 
baik, weld, safiiower, &c., are thus used. But other dyes, the colouring principle 
of which is less readily soluble, such as madder and garancine, are put with 
hot water into the dye-beck in which the mordanted goods are immersed. It 
is clear that when several different mordants have been printed on to the cloth, 
several different colours can be obtained by the same dye material. With madder, 
for instance, all shades of pink and red, black, brown, violet, and lilac can be pro¬ 
duced when alumina and iron mordants and mixtures of these have been used 
as mordants. As the dye only takes where the mordant has been applied, it can 
be readily removed from the other portions of the cloth; this removal of superfluous 
dye is effected by washing, treating with bran and soap, and grass bleaching opera¬ 
tions, technically termed clearing. In some cases madder-dyed goods are cleared 
with the aid of solutions of bleaching-powder or Javelle ley (see p. 223). Some dyes 
require in order to become bright and brilliant the operation known as avivage or 
clearing, but of a special nature; this is more particularly applicable to Turkey-red 
dyed goods, which after removal from the dye-beck are submitted to a boiling under 
pressure with soap-suds and chloride of tin. 

Topical or surface colours. The process of applying thickened colours and mordants 
simultaneously is known as topical or surface printing, the colours, pigments, being 
termed topical or surface colours. Of these two varieties are known, one of which 
is printed in the state of solution, becoming gradually fixed and insoluble on the fibre 
itself; the other is applied in the insoluble state with thickening and plastic 
substances, by the aid of which the colours adhere to the fibre, so that by simple 
washing they are not removed—ultramarine is applied in this manner. Many of these 
styles of printing require for fixing as well as for clearing the application of steam, 
from which they derive their name of steam colours, now very extensively used. 
The printed goods are dried for two or three days, and next stretched on frames, and 
thus arranged exposed to the action of steam at ioo°, in properly constructed rooms. 
The length of time this operation is continued depends in practice upon several con¬ 
ditions, and varies in different establishments, but is generally twenty to forty-five 
minutes at a time. The precise action of the steam is not well known. China blue, 
deriving its name from a resemblance to the colour of old china ware, is produced by 
a very complex process, of which the following is a brief- outline. The indigo in its 
natural state is very finely ground and mixed with deoxidising bodies, such as 
sulphate of iron, acetate of iron, orpiment, or protochloride of tin, and thus applied to • 
the cloth; the goods thus printed are aged and afterwards dipped into clear lime- 
water ; this serves to “ wet out ” and to form an insoluble, or at least difficultly 


5i4 


CHEMICAL TECHNOLOGY. 


soluble, compound of the gum paste or starch of the thickening with the lime. The 
piece is next placed in the copperas vat for ten minutes, the lime-water which 
adheres to the cloth precipitating a little oxide of iron over its whole surface, but it 
does not appear that the slightest dissolution or deoxidation takes place. The piece 
is now taken to the lime vat again, in which it is gently moved about; by this opera¬ 
tion the indigo is deoxidised and dissolved, but does not spread beyond the design, 
for the reason that it is surrounded with fibres saturated with water and coagulated 
gum, while by the excess of lime present, the solubility of the deoxidised indigo is 
greatly lessened. The piece is again dipped into the copperas vat and again into the 
lime vat several tunes, the last dip being in lime for a long time. The goods, thickly 
coated with a cream of lime, are put into clean water, and afterwards into a dilute 
acid, then washed and cleared in weak soap and warm weak acid. China blue is a 
fast colour, but very dark shades cannot be obtained by this process, which is rather 
costly on account of the time and labour it requires. Steam blue is obtained by 
printing with a solution of ferrocyanide of potassium thickened with starch, 
acidulated with tartaric acid and a small quantity of sulphuric acid, after which the 
calico is dried, aged, and lastly steamed. Yellow is produced by first treating 
the goods with acetate of lead, and next passing them through a solution of bichromate 
of potash. Green is produced with a mixture of chromate of lead and Berlin blue. 

Discharge style. As employed in practice on the large scale, the term discharge is 
given to a composition which has the power of bleaching or discharging the dye 
already communicated to a fabric. The discharging of mordants by the aid of 
agents—chiefly acids—which dissolve or otherwise render ineffective the constituents 
of the mordants, seldom occurs in practice, and only then a few special styles. As 
a rule, discharge is effected with uniformly dyed goods, more especially indigo and 
Turkey-red dyed fabrics, upon which it is desired to produce white patterns; while 
sometimes upon a portion of the white ground thus obtained other colours are produced. 
The agents used to produce the discharge vary with the dye which has been applied as 
well as with the colour afterwards desired to be produced on the white ground, 
while, moreover, the discharge ought not to injure the fibre of the cloth. Oxalic, 
tartaric, citric, more or less dilute sulphuric and hydrochloric acids, bisulphate 
of potash, nitrate of lead, solutions of bleaching-powder, weak chlorine water, and 
bichloride of tin are used, being properly thickened with suitable materials, while 
some are so contrived as to serve as mordants for colours to be subsequently applied; 
for instance, for blue, a mixture of tartaric acid, Berlin blue, tinsalt, farina, and 
water, is used; for yellowy, nitrate of lead with tartaric acid, starch, and water; for 
green, a mixture of yellow and blue; for black, a logwood decoction to which 
nitrate of iron has been added. The pieces thus prepared (these discharges having 
been printed on) having been put into and passed through a solution of chloride 
of lime, the dye previously applied is destroyed where the discharge is printed, and 
in its stead the new colour is produced according to the pattern. Chromic acid, or an 
acidulated solution of bicromate of potash, is sometimes used as a discharge, 
the oxide of chromium produced yielding a brown colour. 

Aniline Printing. As regards the application of these colours to calico printing they 
may be termed steam colours. The printing and fixing is effected by the following 
methods:—i. The thickened mordant is printed on, and next fixed either by drying 
or by ageing and steaming after drying, the fabric being dyed in a solution of the 
aniline colour (red, violet, blue), the colour becoming fixed to the mordanted portions 


PRINTING OF WOVEN FABRICS. 


6 i 5 

only of the calico. 2. The thickened mordant is mixed with the aniline dye, and 
thus printed, and the fixing effected by steaming. The mordants for these colours 
are:—Dried albumen, blood albumen, viz., that bleached by the action of ozone 
obtained by means of oil of turpentine; vegetable gluten in various forms, for 
instance, that dissolved according to W. Crum’s plan in weak caustic soda ley, or 
according to Sclieurer-Rott in a weak acid, or gluten dissolved in saccharate of lime 
according to Lies-Bodard, or finally gluten dissolved by incipient putrefaction, as 
suggested by Hanon. Instead of gluten caseine may be used dissolved either in 
caustic ley or in acetic acid; glue and tannate of glue are also used (Kulilmann and 
Lightfoot). Other mordants for these colours are tannin, fat oils, and preparations 
thereof) as oleo-sulphuric acid, palmatino- and glycerin-sulphuric acid. Further, 
certain resins, among which shellac dissolved in borax is one. 

Gluten is largely obtained as a by-product of the preparation of starch from 
wheaten or other flour. When required for use as a mordant, the gluten is allowed 
to remain in moist state, and by incipient putrefaction becomes sour, and hence fluid. 
The mass is purified by first treating it with carbonate of soda; 5 kilos, of the sour 
gluten require for saturation about 560 grms. of a carbonate of soda solution at 
1-15 sp. gr., whereby the gluten is again rendered insoluble, and after having been 
washed is re-dissolved in caustic soda ley, 5 kilos, of the gluten requiring 435 grms. 
of a caustic soda solution at ro8o sp.gr. This solutionis next diluted with 3-5 litres 
of water. The fluid is printed on the calico, which is next dried, aged, and steamed, 
after which it is rinsed in water and dyed in a solution of the aniline colour. The 
gluten is sometimes mixed with the aniline colour and printed on with it, after which 
the calico is steamed a first time, then washed, and steamed a second time. Gluten 
may be used without the preparation with carbonate of soda by leaving it to putrefy 
until it has become very fluid; it is then mixed with about one-third of its weight of 
caustic soda solution of the above ro8o sp. gr. When caseine (lactarine, it is tech¬ 
nically termed in England) is used for mordanting calico previous to the application 
of aniline dyes, it is dissolved in caustic soda, and after the calico has been printed 
with this mixture the aniline colour is printed on. 

The method of printing with aniline colours as devised by (3) Gratrix and Javal, 
differs considerably from ihe preceding, and consists (a) in preparing an insoluble 
compound of the aniline colour with tannic acid, which, having been thickened with 
Senegal gum, is printed on to the cloth which has been previously mordanted with 
tinsalt or any other suitable mordant; or (/ 3 ) there is printed on the previously 
animalised cotton, that is to say, cotton mordanted with albumen, lactarine, or 
gluten, or cotton mordanted with tinsalt, a thickened decoction of galls, by which in 
the first place a tannate of albumen, &c., in the second one of tin, both insoluble in 
water, are formed. The calico having been dried is then passed through an 
acidulated aniline solution. The aniline-tannin compound mentioned under (a) is 
prepared by adding to an aniline solution as much decoction of galls (better still 
solution of tannin) as is required for the complete precipitation of the dye material. 
This precipitate is collected on a filter, washed, and dissolved in alcohol or acetic 
acid, and having been thickened with gum, the solution is used for printing. When 
printed the goods are steamed and washed either with or without soap, according to 
the shade which it is desired to give to the colour. A red colour requires a soap- 
wash. According to the second method the calico is treated With a solution of stan- 
nate of soda, after which a thickened solution of tannin, or a tannin-containing 


6 i6 


CHEMICAL TECHNOLOGY. 


material is printed on to the cloth, which is steamed and the mordant further fixed. 
The dyeing operation is carried on in a dye-beck used as for madder, the beck being 
filled with water, acidulated with acetic acid, and heated to 50°. The cloth is put 
into this liquid, and gradually the dye dissolved in acetic acid is added. When the 
requisite quantity of the dye has been added, the contents of the dye-beck are heated 
to the boiling-point. Aniline black is produced (see p. 579) upon the cloth by means 
of chlorate of potash, chloride of copper, ferricyanide of ammonium, or freshly pre¬ 
cipitated sulphuret of copper. Naphthylamin violet (see p. 583) is now produced by 
a similar process. 

Hotpressing, Finishing. The printed, washed, and rough-dried cotton goods are next 
and Dressing. finished, that is to say, starched, dried, often calendered, hot-pressed, 
folded, and again pressed. In England these operations form a distinct branch of the 
dyeing art usually not performed by the printers. For chintz white wax is added to the 
hot starch in order to impart a better gloss. In order to give muslins a somewhat velvety 
appearance spermaceti is added to the starch while being boiled with water. 

Printing Linen Goods. Linen goods are, as a rule, neither dyed nor printed, and only a few 
indigo-dyed articles on which white patterns are produced are in the trade. As regards the 

Printing Woollen Goods, printing of woollen goods, flannels more particularly, block-printing 
is most frequent. The goods are mordanted with chloride of tin. The fixing of many of 
the colours imparted to woollen goods is effected by steaming. We distinguish, moreover, 
in the printing of woollen goods—1. Golgas printing ; and (2) Berill printing. As regards 
the former method, now almost obsolete, the golgas, a very thin and light flannel fabric, is 
first mordanted with alum and cream of tartar, and next placed between wooden or 
leaden plates partly perforated with a pattern, and strongly pressed in a peculiarly 
constructed hydraulic press, where it is possible to force dye solutions through the goods, 
which are only wetted by these solutions and consequently dyed where the dye liquor can 
pass through, the strong pressure preventing the liquid running over the flannel in 
any other direction. By the berill printing process the surface colours, thickened with 
starch, are printed on to the flannel with hot brass formes ; the starch not being removed, 
the result is the formation of relieved and coloured patterns. The processes and methods 

Printing silk Goods, of printing silk goods are generally the same as for calicos ; either sur¬ 
face printing is resorted to with fixing by steam, or various mordants are printed on to 
the silk, which is next dyed in the dye-beck. A peculiar kind of printing on silk is based 
upon the property of nitric acid producing upon silk a permanent yellow colour, as well as 
of destroying most other dyes, and yet acting on resins and fatty substances only slowly. 

Mandarin Printing, This mode of printing on silk is termed mandarin printing, and the 
tissue, chiefly silk handkerchiefs, to which it is applied, mandarins. In order to etch with 
nitric acid on the indigo-dyed silk, there is printed on to it a resist, composed of resin and 
fat, after which the tissue is kept for 2 to 3 minutes in a mixture of 1 part of water and 
2 parts of nitric acid heated to 50°. The goods are then thoroughly rinsed in fresh water 
and boiled in a soap solution, to which carbonate of potash is added. The portions of the 
silk where no resist has been placed are thus made beautifully yellow. 

Bandanas. On genuine madder-red dyed silk white patterns are etched by a process 
similar to that just described for golgas printing. The goods are placed between leaden 
plates in which the pattern is cut out, and then submitted to strong hydraulic pressure ; 
next a solution of bleaching-powder acidulated with some sulphuric acid is forced through 
the goods, by which the madder dye is destroyed. The pattern thus etched may be after 
washing, the pressure remaining and water being forced through, dyed yellow by first 
forcing a solution of acetate of lead and next one of chromate of potash through the 
woven fabrics, kept of course in the press. 


DIVISION VII. 


THE MATERIALS A.ND APPARATUS FOR PRODUCING ARTIFICIAL L7<3H1. 


ArtifiC iL a Smi nation Very f ew among the large number of bodies which at a high tem¬ 
perature, either by combustion or at a red heat, evolve a permanent light are suited 
for use as materials for artificial illumination. The number of bodies which comply 
with the conditions demanded in artificial illumination is very small. These condi¬ 
tions are the following:— 

i. That by the combustion of the body a sufficient degree of heat be evolved to 
maintain the combustion. 2. That when the burning body happens to be solid, it be 
previous to the combustion converted into gas or vapour, as otherwise no flame is 
generated, which is absolutely required for the purpose of illumination. 3. That the 
burning body evolve in the flame solid bodies or very dense vapours as an essential 
condition of the illuminating property of the flame. 4. That either the body itself or 
the raw material from which it is obtainable be present in large quantity and be 
readily obtainable. 5. That the products of combustion be gaseous and harmless to 
the health. 

It is a generally known fact that any great accumulation of heat imparts to bodies 
the property of emitting light. This is more conspicuous in solid and fluid bodies, 
because their molecules are placed more closely together than happens to be the case 
with gases and vapours. At a temperature of 500° to 6oo° a solid body becomes 
red-hot, while at about iooo° white heat occurs. A gaseous body heated to these 
degrees of temperature emits only a very feeble light. In order to render a gaseous 
body (and as already mentioned only gaseous bodies are suited for illuminating 
purposes) luminous during its combustion, it should contain the vapours of some of 
the higher hydrocarbons (for instance, benzol, acetylen, naphthaline, &c.), and that 
these by becoming white-hot should yield light, or that there be present in the flame, 
by itself non-luminous, a solid body which is thus rendered white-hot; for instance, a 
spiral platinum wire in a hj'drogen flame, a piece of caustic lime in the oxy-hydrogen 
flame, a cylindrical piece of zircona or magnesia in a hydrogen or coal-gas flame 
fed by oxygen, oxide of magnesium in the flame of burning magnesium (magnesium 
light), solid phosphoric acid in the flame of burning phosphorus, &c. Leaving out of 
the question for the present such lights as are not generally available, as those just 
alluded to, and also the electric light, it is clear that for all practical purposes we 
can avail ourselves of only such materials for illuminating purposes as yield a flame 



6 i8 


CHEMICAL TECHNOLOGY. 


which emits light in consequence of the vapours of heavy hydrocarbons present 
therein. These hydrocarbons are indeed contained in all the substances which are 
either used for illuminating purposes or from which illuminating materials are 
prepared, as, for instance, tallow, palm oil, and the fatty acids, viz., stearic and 
palmitic, wax, spermaceti, paraffin, rape-seed oil, the various paraffin and petroleum 
oils, camphine (highly rectified oil of turpentine), coals, bituminous schists, boghead 
coal, wood, fats, and resins. 

name. Every solid and fluid body which becomes either volatilised, or decom¬ 
posed into gaseous matter at a temperature below that required for its combustion, 
can burn only in the shape of gas. The ensuing light is what we call flame. 

The well-known shape of flame is due to the pressure of the ambient air, because 
the latter, becoming heated and being rendered specifically lighter, ascends. When 
the illuminating material consists of molten paraffin, stearic acid, or oil (colza, rape- 
seed, or petroleum), it is sucked upwards in the interstices of the wicks acting as 
capillary tubes, and in the immediate, neighbourhood of the flame these substances are 
converted into gases and vapours, the nature of which closely agrees to that of purified 
illuminating gas. 

Sir Humphry Davy was the first to elucidate the nature of flame and the 
cause of its luminosity as well as of the unequal luminosity of different kinds of 
flames. In our day the researches of Hilgard, H. Landolt, Pitschke, Blochmann, 
Kersten, and more particularly of H. Deville, Yolger, Lunge, Dr. Frankland, and 
others, have greatly contributed to our knowledge of flame. When closely observed 
we can distinguish in flame three distinct portions, viz.:—(i) an outer luminous layer, 
or so-called veil; (2) a central nucleus, which is red-hot; and (3) an inner and lower 
portion, in which the gaseous substances about to become ignited are heated. The 
opinion formerly held about the cause of the emission of light by flame was that by 
the combined action of a very high temperature and the oxygen of the atmosphere, 
which first combines with the hydrogen, carbonaceous matter is separated, which, 
being heated to a bright white heat emits light. By the researches made by Hilgard 
on the flame of burning candles, and of Landolt and H. Deville, who experimented 
with a gas-flame, we have been taught that a very quick and rapid diffusion of air 
and the products of combustion takes place, and that in the interior of the flame a 
decrease of the quantity of the combustible gases and an increase of the products of 
combustion occurs. But all these researches do not enable us to explain many of 
the most ordinary phenomena observed in luminous flames. We do not, for example, 
know what relation there exists between the chemical composition of an illuminating 
substance and its illuminating power; consequently, gas analyses made for the 
purpose of testing gas are in that respect of very little value. According to the 
researches of O. Kersten, confirming those of 0 . L. Erdmann, the atmospheric oxygen 
combines, at least in gas flames, first with the suspended particles of free carbon and 
next with the hydrogen. The combustion, Kersten states, does not take place in the 
centre of the flame, but only at the veil and that portion of the luminous mantle 
which is nearest to the veil, because we cannot admit that any trace of oxvgen can 
pass through a layer of red-hot hydrogen and carbon. The products of combustion 
observed in the centre of the flame are not formed there, but have been carried there 
by diffusion. The total heat of the flame is consequently derived from the limit of 
the zone of combustion. The temperature of the centre of the flame and of the 
mantle increases of course towards the top, and hence the most luminous portion of 


ARTIFICIAL LIGHT. 


619 

the flame is that where the carbon is separated by the intense beat, below the thin 
layer of the dark central cone. Higher, where the heat which decomposes the 
hydrocarbons into their constituents reaches upwards to the middle, the entire 
centre is luminous, and hence a solid flame is exhibited. As, then, the free carbon 
comes nearer to the layer rich in oxygen, it is converted into carbonic acid, and is 
the more luminous the more energetic this combustion. In the veil oxide of carbon 
and hydrogen burn simultaneously. The reason why this veil does not exhibit at 
its lower part a luminous mantle is because the mass of the gases in the interior is 
too cold for admitting a separation of hydrocarbons. 

The non-luminosity of a flame, even that of pure olefiant gas, due to the too 
contracted space occupied by the temperature of the veil, may be observed when a 
gas flame is turned down as low as possible; in this case a complete combustion 
takes place before any decomposition can ensue, just as happens in the lower blue 
portion of a luminous flame. The luminosity, therefore, depends upon the composi¬ 
tion of the gas before it is burnt, and not upon a subsequent combustion of the 
carbon. It has been assumed that the luminosity of gas flames is due to the 
momentarily eliminated particles of solid carbon becoming wliite-hot; but 
according to Dr. Frankland’s researches, made in 1867, it is not the particles of solid 
carbon, but rather the dense vapours of the higher hydrocarbons, those having 
a high boiling-point, which, while ignited at an elevated temperature, cause the 
luminosity of the gas flame. There are present in illuminating gas compounds of 
great density, which in the state of vapour, similar to what may be observed of the 
vapour of arsenic, may render flame luminous; among these are the vapours of 
benzol, naphthaline, and probably of many other of the constituents of coal-tar. These 
vapours remain in the flame in undecomposed state up to the moment that they reach 
the outer layer or envelope of the flame, where they become consumed when coming 
in contact with the oxygen of the air. It has been customary to adduce as a proof 
that the luminosity of the flame is due to eliminated particles of carbon, the fact that 
when a piece of porcelain is held in the flame carbon is deposited thereon; but it has 
not been proved that this substance is pure carbon; on the contrary, when the 
deposit is submitted to analysis, it is always found to contain hydrogen, and any 
chemist who desires to obtain pure carbon from lamp-black knows well enough that 
this substance has to be strongly ignited in close vessels before all the hydrogen it 
contains has been eliminated. In order to accelerate this process of purification, 
chlorine gas is passed over the lamp-black placed in a combustion-tube, or better, a 
porcelain tube, and raised to nearly a white heat. Lamp-black is probably nothing 
more than a conglomerate of the densest light-emitting hydrocarbons, the vapours of 
which become condensed upon the surface of the cold porcelain. How could a flame 
be so transparent as it really is were it filled with solid particles of carbon? How 
could it be the same for photometrical assays if the flame be placed with its broad or 
narrow edge towards the photometer if the light of the flame were due to solid 
particles of carbon ? It is possible that in a slight degree an elimination of carbon 
actually takes place as a consequence of the decomposition of hydrocarbons, but the 
main source and cause of the luminosity of a gas-flame is the combustion of the heavy 
hydrocarbons. It is clear that the temperature of the flame has some influence on 
its luminosity. According to H. Deville’s experiments (1869) the degree of 
the luminosity of a flame is intimately connected with the density of the vapours 
present therein, while the dissociation does not appear to be without some influence 


620 


CHEMICAL TECHNOLOGY. 


upon the condition of the flame. Under ordinary conditions an illuminating material 
to be burnt in air free from draughts, and so that no smoky flame be produced, 
should contain upon 6 parts by weight of carbon i part by weight of hydrogen, 
as nearly obtains in olefiant gas, paraffin, wax, and stearic acid. Oil of turpentine, 
which contains upon i part by weight of hydrogen 7 5 parts by weight of carbon, 
burns with a sooty flame. This is the case in a higher degree with benzol, which 
upon 1 part of hydrogen contains 12 of carbon, or with naphthaline, in which the 
proportion is 1: 15. In order to burn the excess of carbon (as already stated, 
according to Ur. Frankland’s researches, this is not pure carbon, but a conglome¬ 
ration of dense hydrocarbons) which becomes eliminated, an increased supply of 
air is required, such as is created by a lamp-glass. Such flames as do not eliminate 
carbon, as, for instance, those of marsh-gas and alcohol, yield only a faint light 
when burning. The luminosity of gas is at once destroyed when atmospheric air 
is mixed with the gas, as may be observed in the Bunsen burner; the same effect 
obtains when the gas is mixed with other indifferent gases or vapours. 

Artificial light is procured:— 

I. From substances solid at ordinary temperatures, and prepared in the shape. of 
candles made of such materials as tallow, palm oil, stearic, palmitic and elaidic acids, 
wax, spermaceti, and paraffin. 

II. By employing fluid substances, chiefly in lamps, and which may be brought *to 
the following categories :— 

а. Non-volatile oils, such as rape-seed, olive oil, fish oil. 

б . Yolatile oils which are either— 

a. Essential oils, as, for instance, camphine (refined oil of turpentine); or 

/3. Mineral oils, obtained from tar, from peat, lignite, bituminous slate, boghead coal, 
and consisting of mixtures of fluid hydrocarbons, met with in commerce under a 
variety of names, such as solar oil,. photogen, ligroine, kerosen, paraffin 
oil, &c.; or 

y. Native earth-oil or petroleum, which, after having been refined, is sold in England, 
commonly under the name of petroleum oil, to distinguish it especially from 
Young’s patent paraffin oil. 

III. By means of gaseous substances obtained by the dry distillation of coals, 
bituminous slate, peat, wood, petroleum residues, resins, and fatty substances, all of 
which when submitted to a high temperature above a cherry-red heat, become decom¬ 
posed, yielding a solid residue rich in carbon (coke), tar, and gases ; or again, by other modes 
of treatment, as with the so-called water-gas, obtained by passing steam over red-hot 
charcoal. 

In the gaseous illuminating substances the luminous body is either :— 

a. Yielded by the flame itself, as is the case in the ordinary gas flame; or, 

b. Introduced externally, as in the so-called platinum light, by the aid of platinum 

wire; in the lime-light by means of lime; in the magnesium- and zirconium- 
light from cylindrical pieces of these substances ; or by the so-called carburation 
of the gas with the vapours of fluid hydrocarbons. 

I. Artificial Light obtained by Means of Candles. 

Light from candies. Leaving out of the question the use in some very poor districts of 
splints of resinous wood for the purpose of procuring artificial light, candles are the 
only shape in which solid materials are employed for illuminating purposes. A 
candle consists of the solid illuminating material, palmitic and stearic acids, paraffin, 
tallow, or wax, cast in the well-known cylindrical shape, and provided in the 
direction of its longitudinal axis with a cotton-wick, the thickness and plaiting of 
which should be arranged in proper relation to the diameter of the candle. We 
describe in the following pages the manufacture of:— 

1. Stearine candles. 3. Tallow candles. 

2. Paraffin candles. 4. Wax candles. 


ARTIFICIAL LIGHT. 


621 


Manufacture of Stearine 
Candles. 


i. Palm-oil and tallow are now in Europe the raw materials 
for the manufacture of these candles, while lard is used for this purpose in the 
United States (Cincinnati). The researches of W. Heintz, which complete those 
made by Chevreul, have taught us that these fats consist of palmitic, stearic, and 
oleic acids, and glycerine. The acid which Chevreul has designated as margaric 
acid has been proved to be a mixture of palmitic and stearic acids. The so-called 
“stearine candles” are frequently made of a mixture of stearine (viz., .a mixture of 
palmitic and stearic acids) and soft paraffin. Candles of this description are known 
abroad as Apollo and. Melanyl candles. The manufacture of stearine candles 
consists in two .chief operations, viz.:— 


A. The preparation of the fatty acids; 

B. The conversion of these acids into candles. 


A. The preparation of the fatty acids can be effected by saponification with lime, 
by means of sulphuric acid and subsequent distillation, by means of water and high- 
pressure steam, and by means of steam and subsequent distillation. 

Kep bTMeTn?oF^e Aci(l8 Saponification of the Fats biy Means of Lime .-The raw 
fats employed in this operation are beef or mutton tallow, and palm oil. The 
mutton tallow contains a larger quantity of solid fatty acids, and is more readily 
saponified, but beef tallow is cheaper. The Russian tallow, of which large quantities 
are met with in commerce, is usually a mixture of beef and mutton tallow. As palm 
oil is imported into Europe in large quantities and is comparatively low in price, it 
has become in many stearine candle manufactories the fat chiefly used. 


Stearine yields 957 parts of stearic acid (melting at 70°] ChsH^Oa. 

Palmitine „ 94 8 „ palmitic acid „ 62° CxqH. Z 2 0 2 . 

Oleine „ 90 3 „ oleic acid „ —12 0 CbsH^Oa. 

Stearine, palmitine, and oleine, are glycerides. The stearine is tri-stearine, 
C 57 H iio 06 ; palmitine is tri-palmitine, C 5I H 9 806 ; and oleine is tri-oleine, C 37 H I04 06 . 
By the saponification with milk of lime, the calcium salts of the three fatty 
acids, stearic, palmitic, and oleic, are formed, and glycerine is separated. The 
operation of saponification is conducted in the following manner:-—Of tallow or 
of palm oil about 500 kilos, with 800 litres of water are put into wooden lead-lined 
vats or tuns, of 20 hectolitres cubic capacity, and next by the aid of steam conveyed 
into the vessel by a leaden pipe coiled spirally. When all the tallow has been 
melted there are gradually added to it some 600 litres of milk of lime, containing 
70 kilos, of lime = 14 per cent of the weight of the tallow, care being taken to stir 
the mixture continuously. After heating for some six to eight hours the formation 
of the lime-soap is complete. The somewhat yellow glycerine solution is run off 
from the solid granular lime-soap and used for preparing glycerine. According to 
theory, starting from the supposition that upon 3 molecules of fatty acids found com¬ 
bined in the neutral fat there is 1 molecule of glycerine, 100 parts of fat would 
require only 87 parts of caustic lime, but in practice 14 per cent of lime is generally 
used because it has been found that the saponification is rendered easier, but a larger 
quantity of sulphuric acid is also required. 

The lime-soap thus obtained is decomposed by means of sulphuric acid, either con¬ 
centrated, or as so-called brown or chamber acid. This operation is carried on either 
in the vessel in which the saponification took place, or in a similarly constructed vessel 


622 


CHEMICAL TECHNOLOGY. 


or in stoneware basins, also fitted with a steam-pipe. The quantity of sulphuric acid 
required for the decomposition of a mixture composed of 500 kilos, of tallow and 
70 kilos, of lime amounts to 137 kilos. The acid is first diluted with water to 12 0 B. 
= sp. gr. 1 086 (in this condition the acid contains 30 per cent, H 2 S0 4 ), and is next 
poured on to the lime-soap, with which it is thoroughly stirred, while steam heat 
is applied simultaneously. When the fatty acids have been set free the supply of 
steam is shut off, and the fluid mixture left for some time, the melted fatty acids 
rising to the surface, while the gypsum settles at the bottom of the liquid. The 
melted fatty acids are transferred to a lead-lined tank, and in order to remove the 
last traces of lime and sulphate of lime, first washed with dilute sulphuric acid, and 
next with water, the steam heat being kept up to maintain the acids in a fluid state. 
The quantity of purified fatty acids thus obtained is the following :— 

500 kilos, of tallow 459*5 kilos, of fatty acids. 


500 

*> 4 6 3° 


500 

47 8 ’° 

>> 

500 „ 

„ 487*5 » 

99 


2000 kilos, of tallow i888*o kilos, of fatty a,cids, 

equal to 94*8 per cent. The yield depends on the kind of tallow used, on its purity, 
and the mode of operating for its saponification. 

100 parts of the fatty acids give:— 

a . 43*3 parts of solid fatty acids \ 

b. 45*8 „ „ „ „ I On an average 45 9 parts of a mixture of stearic 

c. 46^2 „ „ „ „ and palmitic acid. 

d. 48*4 „ „ „ „ ) 

When the fatty acids have been as much as possible freed from lime, gypsum, and 
sulphuric acid, by means of repeated washing with water, they are kept in molten 
condition for some time in order that the water may be thoroughly eliminated. 
Next, the fatty acids are cooled and become solidified, after which they are 
submitted to strong hydraulic pressure in order to remove the oleic acid, this opera¬ 
tion being repeated and then performed with the aid of heat. The acids are then cast 
into large square blocks, or cooled in moulds similar in shape to those used for large 
cakes of chocolate, and capable of containing 2 kilos, of the fatty acids. In some 
works moulds made of enamelled iron are used for this purpose. The fatty acids are 
left in these moulds for the purpose of crystallising slowly ; in winter twelve hours, 
in summer twenty-four hours, are required for attaining this end. The more slowly 
the crystallisation proceeds the better, because the more readily the fluid portion can 
be separated by pressure from the solid mass. The solidified mass is next 
submitted to hydraulic pressure, in order to eliminate the fluid fatty acids retained 
between the crystals of the solid mass. The first operation of pressing is performed 
at the ordinary temperature. The solid cake of the fatty acids is for this purpose 
put into a press-bag, which may be made of any strongly woven fabric, horsehair 
cloth being often employed. The press-bag having been filled is placed between 
plates of iron or zinc, and then transferred to the table of a hydraulic press, capable 
of exerting a pressure of 200,000 kilos. The oleic acid which runs off is collected in 
channels and thence conveyed by a pipe to a cistern. This material is used in soap¬ 
making, also for lubricating wool, and more recently as oleic acid ether mixed 
with alumina for the purpose of softening leather. When the hydraulic press does 




ARTIFICIAL LIGHT. 


623 


not remove any more fluid from the solidified crystalline acids, hot-pressure is 
resorted to. For this purpose hydraulic presses of a peculiar construction and 
placed in a horizontal position are employed ; the arrangement of these presses, the 
plates of which are heated by means of steam is, however, too complicated to be use¬ 
fully described. The pressed fatty acids are next purified. This is effected by 
treating them in a molten state with very dilute sulphuric acid (3 0 B. = 1*020 sp. gr.), 
and washing them with water, an operation repeated two to three times, the fatty acids 
being of course kept molten all the time. The wash-water to be employed for this 
purpose ought to be free from lime, and if such water is not obtainable, the lime 
should be removed by means of oxalic acid. The purified fatty acids are next main¬ 
tained in a molten state for some time, in order to eliminate the water mechanically 
adhering to them. Sometimes the fatty acids are clarified by the aid of white of 
eggs beaten to a froth, and added to the water of the last operation, in the proportion 
of 2 eggs to 100 kilos, of fatty acids; or the stearic acid is re-molten in water 
containing oxalic acid. The fatty acids thus obtained are either cast into thick 
slabs and thus sent to the candle factory, or the molten acids are directly converted 
into candles. 

It is evident that annually a large quantity of worthless gypsum must result as a by¬ 
product of the decomposition of the lime-soap by the use of sulphuric acid. It may 
therefore be worth while to suggest that caustic baryta should be substituted for lime, 
because by the decomposition of the baryta-soapf with sulphuric acid, there would be 
formed baryta white (sulphate of baryta), the value of which will cover the expense of the 
sulphuric acid ; but, on the other hand, caustic baryta is a great deal more expensive than 
caustic lime. It is true that the sulphate of baryta separates more readily and completely 
from the liquor, and a purer glycerine can be obtained from it. Cambacere’s suggestion 
(1855) to saponify with alumina was made with the view of obtaining a more valuable by¬ 
product. Alumina does not saponify fats, but aluminate of soda (employed for the purposes 
of saponification for some years in the United States under the name of natrona refined 
saponifier) does so, the result being the formation of an alumina-soap, while the soda is set 
free and may be used again for the purpose of re-dissolving fresh portions of alumina. As 
in the operations made with the native minerals cryolite and bauxite, aluminate of soda is 
obtained as an intermediate product, which may be further treated for sulphate of 
alumina and soda; the proposal to use an alumina-soap instead of a lime-soap deserves 
every consideration, the more so as the fluid obtained by the decomposition of the 
alumina-soap with sulphuric acid may be directly employed for the preparation either of 
sulphate of alumina or of alum. The alumina-soap may be decomposed at the ordinary 
temperature by acetic acid, and acetate of alumina obtained (see p. 263). The lime 
saponification process has been in a great measure thrown into the background since the 
invention of the far more profitable saponification process with sulphuric acid and super¬ 
heated steam. 

Sap °Tufic ation with jj Saponification Process with a Smaller Quantity of Lime and 
the Application of Superheated Steam. —De Milly has essentially changed the pro¬ 
cess of the saponification of the neutral fats; he found that the quantity of lime 
used in the saponification, which in his works at Paris had been already diminished 
from 14 to 8 or 9 per cent of the quantity of the fats, could be decreased even to 
4 or to 2 per cent, provided the mixture of lime-water and fatty matter was heated to 
a higher temperature than that usually employed. De Milly put into a steam boiler 
2300 kilos, of tallow and 20 hectolitres of milk of lime, which contained either 
50 kilos, of lime = 2 per cent, or 69 kilos. = 3 per cent, after which this mixture was 
heated to 172 0 by means of steam, having a temperature of 182° = 10 atmospheres, or 
150 lbs. pressure per square inch. The result was, that after seven hours the saponi¬ 
fication was complete, the contents of the boiler consisting partly of an aqueous 
solution of glycerine, partly of a mixture of free fatty acids, and a small quantity of 
a lime-soap. The boiler having been emptied was again filled, and the operatior 


624 


CHEMICAL TECHNOLOGY. 


repeated, so that in twenty-four hours 6900 kilos, of tallow could be operated upon. 
It is evident that this method of saponification is very profitable, in consequence of 
requiring much less sulphuric acid for decomposing the lime-soap. 

Several opinions have been enunciated explanatory of this process ; but if we bear 
in mind (1) that kind of action which Berzelius designated as catalytic, where a 
comparatively very small quantity of any substance may call forth a decomposition 
under favourable conditions of a very large quantity of another substance; and 
(2) recollect that Wright and Fouclie have more recently (De Milly’s experiments 
were made about twenty-five years ago) found that water at a high temperature 
causes the dissociation of fats and oils into glycerine and fatty acids, it is clear that 
while the small quantity of lime may have facilitated the saponification, the result 
obtained by De Milly is mainly due to the very high temperature of the water 
employed in the operation. This is clearer from the fact that a process of saponifi¬ 
cation is successfully in use based solely upon the application of water at a high 
temperature. 

Sfipomflcationbyjvr^ns of jjj Saponification by Means of Sulphuric Acid and Subse¬ 
quent Distillation by Means of Steam .—It was known to Achard, in the year 1777, 
that the neutral fats are decomposed by concentrated sulphuric acid in a manner 
similar to the decomposition effected by caustic alkalies. This fact was again 
brought forward in 1821 by Caventon, and 1824 by Chevreul, but was not scientifi¬ 
cally investigated until 1836 by Fremy, and not industrially applied until the year 
1841, when Dubrunfaut introduced the distillation of the fatty acids on the large 
scale. The crude fatty matter usually submitted to this process of saponification is 
of the kind that cannot be saponified by the lime process by reason of its impurities; 
thus, for instance, palm and cocoa-nut oil, bone and marrow fat, fat of slaughter¬ 
houses, kitchen-stuff, the products of the decomposition, by means of sulphuric acid, 
of the soap-water obtained from wool-spinning and cloth-making works, residues of 
the refining of fish and other oils, residues of tallow-melting, &c. 

This process of saponification by means of sulphuric acid as carried on in the large 
establishment for stearine candle-making of Leroy and Durand, at Gentilly, near Paris, 
consists of three operations, viz.:— 

a. Saponification with sulphuric acid. 

( 3 . Decomposition of the products of saponification. 

y. Distillation of the fatty acids. 

a. In order to eliminate the greatest impurities first, the crude fatty matters are 
molten and kept in theTiquid state for some time, so that the coarser impurities may sub¬ 
side. . The fatty matters are then transferred to a kind of boiler made of iron boiler-plates 
lined inside with lead, and fitted with a stirring apparatus and a steam-jacket, connected 
by means of pipes with a steam-boiler, so that the apparatus may be heated. Into this 
vessel sulphuric acid at 66° B. = i-8 sp. gr., is poured, the quantity of this fluid being 
regulated according to the nature of the fatty matters operated upon. Kitchen-stuff, fat. 
from slaughter-houses, and the like require 12 per cent of their weight of acid ; palm oil 
requires from 6 to 9 per cent according to quality. The fatty substances having been put 
into the vessel, the stirring apparatus es set in motion, and the steam turned on for the 
purpose of supplying heat to the vessel. The temperature to which the vessel is heated 
varies, in Price’s Works, Battersea, being 177 0 , while at Gentilly, the heat is seldom higher 
than from 1 io° to 115 0 . During the operation the mass foams, becomes brown, and evolves 
sulphurous acid, partly due to the action of a portion of the concentrated sulphuric acid 
upon the glycerine, partly to its action upon the impurities present among the fattj 
matters. The neutral fat is converted into a mixture of sulpho-fatty acids and sulpho- 
glyceric acid. The saponification is complete after some fifteen to twenty hours’ appli¬ 
cation of heat. According to De Milly’s new process (1867) the tallow is heated to 120°, 
along with 6 per cent of sulphuric acid, and the action of the latter is limited to two to three 


ARTIFICIAL LIGHT. 


625 


minutes; it is thereby possible to obtain 80 per cent of the solid fatty acids in a condition 
at once fit for making candles without re-distillation, only 20 per cent having to be 
distilled. 

{ 3 . Decomposition of the products of the sulphuric acid saponification. The mass is 
left to cool for three to four hours and is next transferred to large wooden tanks 
lined with lead, and previously filled one-third with water. At the bottom of these tanks 
steam pipes are fitted, by means of which the fluid contents of the vessel are soon heated 
to ioo°. The sulphuric acid and the fatty acids are dissociated, and these bodies, partly 
combined with a larger quantity of hydrogen and oxygen than was present in the fatty 
acids from which they were formed, partly also in an unaltered condition, are found 
floating on the surface. After having been repeatedly triturated with boiling water, the 
fatty acids are tapped or poured over into a vessel filled with water heated to 40° to 50°, 
for the purpose of allowing the impurities to become deposited. The clarified fatty acids 
are next heated in a vessel placed on an open fire in order to evaporate all the water, after 
which they are submitted to distillation. 

y. The distillation requires several precautions. Distillation with an open fire would 
convert the fatty acids into oil, gas-tar, and a carbonaceous residue, if the heat were 
sufficiently high. But when the temperature is properly regulated, the fatty acids 
are protected from the direct action of the fire. Air should be completely excluded from 
the distilling apparatus. With these precautions the fatty acids distil over without 
undergoing any essential alteration. These conditions are complied with by the use of 
superheated steam at a temperature of 250° to 350°. The fatty acids are put into a roomy 
retort supported by brickwork, and fitted with a steam tube as well as a condensing tube 
connected with a receiver, in which the fatty acids are collected. 

When the several fatty acids qre fractionally collected from the beginning to the end of 
the distillation their melting-points are 


From Pahn Oil. 

From Kitchen-stuff 
and Bone Fat. 

1st product 

54 * 5 ° 

44 "°° 

2nd „ 

52*0° 

41*0° 

3 rd „ 

48-0° 

41*0° 

4th „ 

46’o° 

42 - 5 ° 

5 th „ 

44-0° 

44 *o° 

6th ,, 

4i'o° 

45 *o° 

7th „ 

39 * 5 ° 

4ro° 


The water condensed with the fatty acids runs off from the receiver through a tap.' At 
the beginning of the operation the water constitutes half of the produce ; towards the end 
only about one-third. With a retort capable of containing 1000 to 1100 kilos, of material 
the distillation takes some twelve hours. The end of the operation is indicated by the 
coming over of coloured products. There remains in the retort a black tarry matter, the 
quantity of which amounts in the case of palm oil distillation to 2 to 5 per cent, and for 
kitchen-stuff to 5 to 7 per cent. This residue is not removed after each distillation ffiit 
left in the retort until it has accumulated to such an extent as to render its removal 
necessary. The first products of the distillation of palm oil saponified by means of fatty 
acids are so solid, that by pressure they do not yield any fluid acid, and are at once fit for 
the manufacture of candles. The products which come over afterwards are further 
purified by hydraulic pressure, re-melting, and washing with water. The substance 
obtained by pressure, more or less pure oleic acid, is used for soap-making only in this 
country, although abroad it is burnt in some kinds of lamps. The oleic acid obtained by this 
process is essentially different from that obtained by the lime saponification process. The 
quantities of fatty acids obtained by this process of saponification are the following :— 


From Suint. 47 to 55 per cent. 

,, Olive oil residues . 47 to 50 ,, 

,, Palm oil .. .. .. 75 to 80 ,, 

,, Fat from slaughter-houses .. .. 60 to 66 * ,, 

,, Oleic acid.'. 251030 ,, 


Chloride of zinc, which in many respects (see p. 81) is similar in its action to sulphuric 
acid, has been proposed as a substitute for the latter. For countries into which sulphuric 
acid has to be imported chloride of zinc might be of greater advantage, being capable 
of recovery and less dangerous and difficult in transport. When, according to the 
researches of L. Kraft and Tessie du Motay, a neutral fat is heated with anhydrous 
chloride of zinc, a complete incorporation of these substances takes place between 150' 

41 








526 


CHEMICAL TECHNOLOGY. 


and 2oo°; and by continuing the heating for some time, and washing the materials with 
warm water, or better with water acidulated with hydrochloric acid, there is obtained 
a fatty matter, which on being submitted to distillation, yields the corresponding fatty 
acid, while only a small quantity of acroleine is formed. The chloride of zinc, becoming 
soluble in the water used for washing, may be recovered by evaporating the fluid. The 
yield of fatty acids by this process is the same as that obtained by the use of sulphuric 
acid, while the fatty acids also agree as to their physical properties. The quantity 
of chloride of zinc required amounts to 8 to 12 per cent of the fat. 


Sftp a£d fi mgh p«ss t sure atcr IV. Some sixteen years ago another agent, capable of bringing 
about, in a manner similar to alkalies and acids, the dissociation of fatty matters intc 
glycerine and fatty acids, was introduced, this agent being simply superheated steam 
at high pressure:— 


3%Xo) 1 = C n^ + 

Tripalmitine. Water. Glycerine. Palmitic acid. 


The idea of submitting fatty matters to a similar method of treatment is not a neAv 
one, for in the researches of Appert (1823) and Manicler (1826) some hints are given 
on the decomposition of fats by means of superheated water; but the aim of these 
technologists was different, for in their experiments they employed steam to separate 
the tallow from the cellular tissue it is contained in, and for that purpose a tempera¬ 
ture of ii5°to 121 0 was quite sufficient, while at a temperature of 180° and a pressure 
of 10 to 15 atmospheres (= 150 lbs. to 225 lbs. pressure to the square inch) water 
can exert a far more energetic action upon the neutral fats, dissociating them and 
thus setting free their constituents. The knowledge of this interesting fact is due to 
the researches of Tilglimann and Berthelot, who almost simultaneously made this 
discovery in the year 1854, while shortly after Melsens, at Brussels, obtained the 
same result. As regards the industrial application of this discovery, Tilghmann and 
Melsens made further researches; their modes of operating are very similar. 

Tilghmann adds to the neutral fat about to be decomposed one-third to one-half 
cf its bulk of water, and pours this mixture into a sufficiently strong vessel in which 
the fluids can be submitted to the action of heat, viz., a degree nearly as high as the 
melting-point of lead, 320°. This vessel is so arranged that during the operation it 
can be closed so as to prevent on the one hand the evaporation of water, and on the 
other admit of a sufficiently strong pressure. The process is carried on continuously 
by causing the fluids to circulate through a tube heated to the required temperature. 
Melsens uses a Papin’s digester, in which the fat to be decomposed is heated to 180 0 to 
200°, with 10 to 20 per cent water, to which 1 to 10 per cent of sulphuric acid has been 
added. Wright’s and Fouche’s apparatus consists of two hermetically closed copper 
vessels placed one above the other and connected together by means of two tubes, one 
of which reaches nearly to the bottom of the lower vessel, and ends in the upper one 
just above the bottom. 

The second tube is fixed into the lid of the lower vessel and passes through the 
upper vessel reaching nearly to its .cover. The upper vessel is the steam-generator, 
while the decomposition goes on in the lower vessel. When it is intended to work 
with this apparatus, the steam-generator is filled with water nearly to the point at 
which the first tube ends in it. The second vessel is then filled with molten fat so 
that this material reaches the top of the second tube. There remains thus a free 
space between the fat and the lid of the second vessel, which space is termed by the 
patentees chambre d'expansion, expansion room. Heat being applied to the generator. 




ARTIFICIAL LIGHT. 


627 

the steam formed is carried by the second tube into the expansion room, and 
becoming condensed forces it way downwards through the specifically lighter fat 
and flows through the first tube again into the generator. In this manner the 
neutral fat is intimately mixed at a high temperature and under high pressure with 
water, and completely dissociated in a short time into fatty acid and glycerine. 

Manufacture of Fatty Acids Y. Allied to the process just described is the operation carried 
stcanTand Subsequent on I’Y the well-known Price’s Candle Company, Limited, at 
Distillation. Battersea. Gay-Lussac and Dubrunfaut have already tried to 

apply to industrial purposes the fact that neutral fats are dissociated by distillation, 
yielding fatty acids ; but notwithstanding that these savants employed steam, the results 
obtained did not answer the expectation, because a portion of the fatty matter was 
decomposed, yielding acroleine and leaving a carbonaceous residue. Wilson and Gwynne 
were more successful with their experiments, and by using a distilling apparatus similar 
to that described on p. 625, they obtained by means of superheated steam the complete 
dissociation of the neutral fats into fatty acids and glycerine ; while by closely watching 
and regulating the temperature, they not only could completely saponify the neutral fats, 
but also distil the fatty acids and glycerine over without undergoing any decomposition. 

The retorts have a cubic capacity of 60 hectolitres, and are heated by direct fire to a 
temperature of 290° to 315°. A malleable iron steam-pipe conveys steam at a tempe¬ 
rature of 315 0 into the molten fatty matter. The admission of steam is continued for 
twenty-four to thirty-six hours according to the land of fat. The saponification proceeds 
regularly and the products distil over and are collected at the lower aperture of the 
cooling apparatus. The fatty acids are at once fit for candle making purposes, while the 
glycerine is purified by a subsequent distillation with steam. As already mentioned, the 
proper temperature has to be scrupulously maintained, for if the temperature falls below 
310°, the saponification proceeds very slowly; but if the temperature rises much above 
that degree, a portion of the fatty substance is decomposed and acroleine is formed in 
large quantity. 

candle Making. B. The wick is a very important portion of stearine candles, and, 
indeed, of all kinds of candles, because in the interstices of the wick the molten fatty 
matter of the candle is drawn upwards to the flame. The wick ought therefore to 
consist of porous substances, and in the case of candles—for lamps it is not so requi¬ 
site—it should be combustible. 

It is essential that the wick be of uniform thickness through its entire length and 
free from knots or loose threads. The yarn ordinarily used for making wicks is the 
lightly-twisted cotton thread known in the trade as No. 16 to 20 for tallow candles, 
and No. 30 to 40 for stearine candles. It is evident that the more uniform the wicks 
the better fitted they are for capillary action, and hence, provided the illuminating 
material be pure enough, a uniform combustion. Formerly the wicks were always 
twisted, and for tallow and wax candles this is still frequently the case, the single 
threads being placed next to each other and then turned so as to form a very elon¬ 
gated spiral. In order to obviate the snuffing of the burning candles, Cam- 
baceres introduced the plaited wicks, which, while burning, become so twisted that 
the end of the portion of the wick which protrudes from the tallow or stearine is kept 
just outside the flame, so that it may be consumed to ash by the ambient air. 
Before the wick can be used in candles it has to be prepared, because unprepared 
wick leaves by its incomplete combustion a considerable quantity of a carbonaceous 
residue which greatly impairs the capillary action. When stearine candles were 
first made it became necessary to impregnate wicks with substances which should 
promote the combustion, and Be Milly found (1830) that boracic and phosphoric 
acids would answer this purpose, because these acids, while combining with the 
constituents of the ash of the wick, caused the ash to form at the top of the burning 
wick a glass bead, which by its weight turned the wick out of the flame, thereby 
increasing the combustibility. In the French candle factories the wicks to be 


CHEMICAL TECHNOLOGY. 


52 S 

prepared are put for three consecutive hours into a solution of i kilo, of boracic acid 
in 50 litres of water. The previously plaited wicks are next either wrung out or put 
into a centrifugal machine to get rid of the first excess of moisture, after which they 
are dried by being placed in a acketted tinned-iron box, which is heated by means ol 
steam. Some alcohol should be added to the aqueous solution for the purpose oi 
wetting the wicks more perfectly. Payen recommends a pickling liquor for wicks, 
composed of a solution of 5 to 8 grms. of boracic acid in 1 litre of water, to which 
3 to 5 per mille of sulphuric acid is added. In some Austrian stearine candle factories 
phosphate of ammonia is used to impregnate the wicks ; while Dr. Bolley calls 
attention to the use of a solution of sal-ammoniac at 2 0 to 3 0 B. as a cheap pickling 
for wicks. 

Moulding the Candies. The blocks or cakes of stearic acid obtained as described are not 
sufficiently pure for moulding. The edges of the blocks are often more or less coloured 
and soft, owing to some oleic acid not having been pressed out, while the surface of the 
blocks is contaminated with oxide of iron and the hair of the press-bags. In order to 
purify the blocks or cakes (in this country they frequently weigh from 1 i to 3 cwts.) the 
edges are pared off and the surface is scraped, the refuse so obtained being again sub¬ 
mitted to hot-pressing. The blocks thus treated are next put into tubs lined with lead, 
and dilute sulphuric acid of 3 0 B. = 1-020 sp. gr. having been poured over them, the fluid 
is heated by means of steam, the aim of this operation being to remove oxide of iron and 
destroy the fibres of the press-bag, and not, as is sometimes stated, to decompose the last 
traces of stearate of lime, which of course cannot be present. When the action of the 
sulphuric acid has been continued for a sufficient time, it is run off and the last trace of 
the acid removed by washing the stearic acid, of course again molten, with boiling water. 
The molten stearic acid is then clarified by means of a certain quantity of white of egg, 
which is thoroughly stirred through the molten mass heated to the boiling-point of the water 
mixed with it. The impurities which become mixed and incorporated with the white of 
egg settle at the bottom of the vessel. The great tendency of the stearic acid to crystal¬ 
lise in large foliated crystals caused at the commencement of the stearine-candle making 
business a difficulty, candles of unequal transparency as well as of great brittleness being 
obtained. The defect was remedied by the addition of a small quantity of arsenious acid, 
but as this proved detrimental to health (arseniuretted hydrogen as well as some arsenious 
acid being evolved during the burning of such candles), the use of this acid was abroad 
prohibited by law, and in England condemned by public opinion. Instead of the use of 
arsenious acid, some 2 to 6 per cent of white wax has been added to the stearic acid 
while molten, continually stirring until nearly solidified previous to pouring the stearic 
acid into the candle-moulds previously heated to the melting-point of the stearine. 
By the cooling and stirring a kind of fluid-fat paste was obtained which does not crys¬ 
tallise. Now some 20 per cent of paraffin is added to the stearic acid, and its tendency to 
crystallise altogether suspended. 

The candle-moulds are made of an alloy of tin and lead, usually consisting of 20 parts 
of tin to 10 of lead. The moulds are narrow, somewhat conical tubes, highly polished 
internally in order to impart a smooth surface to the candles. The wick is fixed in the 
longitudinal axis of the moulds, being fastened at one end (the top of the finished candle) 
in a small hole at the bottom of the mould, and at the other end fastened to a funnel, through 
which the fatty acid is poured into the mould. The shape of the moulds used in the 
French stearine candle works is exhibited in Fig. 269. a is a mould consisting of two 
parts, viz., the mould proper and tfie funnel, b exhibits these two parts fitted together, 
and c a longitudinal section with the wick inserted, while d is the wire hook with which 
the wick is passed through the mould. For the moulds now generally used one moulding- 
basin or box is employed to contain thirty moulds. This basin or moulding-box is 
exhibited in Fig. 270. a d is a large sheet-iron or tinned box in which the moulds are 
placed. This box is fitted into another of similar shape, b b, which by means of steam is 
kept at a temperature of ioo°’ As soon as the moulds are heated to 45 0 , the box a d is 
removed from b b, and the molten stearic acid is poured into the moulds. ‘When the 
moulds and the candles contained have become quite cold, the latter are removed. Now 
moulding machines are generally employed, so that this operation is performed uninter¬ 
ruptedly, the construction of these machines being such that the reeled wick is drawn 
through the moulds while the candles remain joined together by a short piece of wick 
until after the moulding is complete, the candles when cold being taken from the moulds 
and the wicks cut through to separate them. Cahouet’s and Morgane’s. machines arc 
chiefly used. 


ARTIFICIAL LIGHT. 


629 


Before the stearine candles are pared and polished they are in some works bleached by 
oeing exposed to the action of the sun’s rays and to dew in open air. The candles 
are carried to the bleaching-ground by mechanical self-acting means, consisting of a cloth 
without end, and which is connected with a slightly sloping table, upon which the candles 
are placed, and caught by the cloth, which is fitted with a series of rounded wooden laths 
fastened across the cloth, whereby the candles are held in position. For the purpose of 
exposing the candles to the action of the air they are placed on a frame-work similar to 
that of a table, instead of the top of which are stretched two textures of lead-wire, each of 
these textures in a horizontal plane distant from each other about half the height of a 
candle. The meshes of the upper wire net are so wide that a candle can be passed through 
it, while the meshes of the lower wire net are narrower. The candles are one by one put 
into the meshes, the pointed portions of the candles being placed upwards, while the base 
rests on the lower wire net. In this position the candles are left for some time according 
to the season of the year. When bleached the candles are pared and polished by 
machinery. 

TaUow Candies. 2. Refined, purified tallow is used for making the dip as well as the 
moulded tallow candles. The dips are made by the repeated immersion of the wicks in 
molten tallow. On the small scale this operation is performed in the following manner:— 
The tallow trough having been filled with molten tallow, the wicks looped on a wooden or 


Fig. 269. 



thin iron rod are immersed in the tallow. According to the weight it is desired to give to 
the candles, from sixteen to eighteen wicks are looped on to the dipping-rod, care being 
taken to place them as much as possible equidistant from each other; this done the wicks 
are dipped vertically into the molten tallow. At the first dip, when the wicks are to be 
soaked, the molten tallow sho uld be hot, because hot tallow penetrates more readily into 
the insterstices of the cotton. After the first dip the dip-rods are placed on the edge of 
the tallow trough, and next alternately hung over the dripping frame after the somewhat 
twisted wicks have been put straight again. The dripping frame is. simply a wooden 
frame-work, on the edges of which the clipping-rods rest, while the wicks are suspended 
over the tallow trough or another suitable vessel. When all the wicks looped on to the 
dipping-rods have received their first dip, and the tallow in the trough has been so far 
cooled as to begin to exhibit at the sides of the vessel signs of solidification, the second 
dip is proceeded with and the operation continued until the candles have assumed the 
desired thickness. As the lower portion of the candles would become frequently thicker 
than the upper, this defect is obviated by keeping the lower end of the candle for a 
moment in the molten tallow, so that the excess adhering to the candle may be molten off 


































































































630 


CHEMICAL TECHNOLOGY. 


again. In order to keep the tallow in the trough at a uniform degree of fluidity it is 
now and then stirred with a wooden rod. At the last dip the candles are put into the 
trough at a somewhat greater depth in order to form the upper conical portion. The 
lower end of the candles exhibits a non-symmetrical cone, which is either cut away or 
removed by placing the candles for a moment on a copper plate heated by steam and 
provided with a channel for running off the molten tallow. 

Moulded tallow candles are made in a similar manner to stearine candles. The tallow 
used for the moulded candles is usually of better quality than that used for dip candles, 
at least on the continent of Europe ; not so in England and America, where very highly 
refined tallow is used for dips by the better class of makers, the thus refined tallow being 
harder owing to the mode of purifying. What are termed composite candles (unknown 
on the Continent) are made by precisely the same method as the moulded stearine 
candles, the wicks also being plaited. Moulded tallow candles have been entirely super¬ 
seded by composites, excepting that in some of the central parts of Europe, locally 
moulded tallow candles are here and there made. One of the largest London firms states 
that the manufacture of candles (almost all moulded, viz., composites, stearine, 
paraffin, ozokerite, spermaceti), for exportation from this country to all parts of 
the world, is increasing to such an extent that the candle making business in Eussia, 
Turkey, Greece, Italy, Spain, Portugal, Sweden, and Norway, is becoming rapidly 
extinct, not being capable to compete on the small scale with the large makers in this 
country and in France, where, however, the late lamentable events have very seriously 
interfered with this branch of industry. 


Paraffin candies. Paraffin is obtained from native petroleum ^Rangoon oil) or from 
among the products of the dry distillation of peat, brown coal, lignite, bituminous 
slates, boghead mineral or ozokerite (a peculiar mineral, wax-like, and yielding 
paraffin—it occurs in Galicia and Bohemia in large quantities) It is, after having 
been purified, the substance from which the beautiful paraffin candles are made by 
precisely the same methods and apparatus as are used and have been described for 
stearine candles. The paraffin employed for making candles is a mixture of 
paraffins having different melting-points. 


Paraffin obtained from boghead coal fuses at 
„ „ „ brown coal ,, 

>> »* >> peat ,, 

„ „ Rangoon oil or tar „ 

„ „ „ ozokerite „ 


45'5° to 52 0 . 
560° 

46 * 7 ° 

6ro° 

65 - 5 ° 


As the German paraffin candle makers use almost exclusively a paraffin from 
brown coal (lignite), and peat, and of a comparatively low melting-point (45 0 to 53°), 
stearic acid is added for the purpose of raising the temperature at which the 
paraffin melts. The quantity of stearic acid (technically stearine) added, depends as 
much upon the point of fusion of the paraffin as upon the season of the year, 
summer candles being made with a larger quantity of stearine than winter candles. 
The quantity of stearine thus added to paraffin amounts to 3 to 15 per cent, while as 
already mentioned, paraffin to an amount of 15 to 20 per cent is added to stearine 
candles. A small quantity of stearine is always added to paraffin candles for the 
purpose of preventing these candles becoming bent while standing in a candlestick. 

The first paraffin candles ever made were manufactured by Messrs. Field, of Lam¬ 
beth, from paraffin extracted from Irish peat, now very many years ago, lono 
before paraffin was seen or known elsewhere than as small specimens in chemical 
laboratories. Paraffin candles are always moulded, and the moulds are heated 
to above the melting-point of the paraffin (6o°, or better even 70°), in order to pre¬ 
vent the paraffin crystallising. The molten paraffin is heated to about 6o° when it is 
cast into the moulds; these when well filled are left standing for a moment and then 
cooled by immersion in cold water, whereby the candles suddenly solidify, and are 


ARTIFICIAL LIGHT. 


631 

thus prevented becoming crystalline and opaque, instead of transparent as desired. 
Plaited wicks are used in the paraffin candles, and these wicks are treated with 
boracic acid. For black paraffin candles the paraffin is heated to nearly its boiling- 
point with anacardium shells, the resin of which is dissolved by the paraffin, 
the latter becoming very dark brown, and exhibiting after cooling a black colour, 
similar to that of coals. These black candles burn without smoke or smell, provided 
the wick be thin; this is a requisite in all paraffin candles. 

Candies irom Fatty Acids. We must not neglect to call attention here to a fatty acid, 
sebacylic acid, Ci 0 H80 4 , which might perhaps be used to impart to paraffin and other 
kinds of candles a higher melting-point. This acid may be obtained by the dry distilla¬ 
tion of oleic acid, or better by treating castor oil with a highly concentrated caustic soda 
solution. In the latter instance, the sebacylic acid is derived from the rieinoleic acid 
(castor oil is in Latin termed Oleum Ricini ):— 

r Sebacylate of soda, C IO H I 6 Na 2 0 4 = 246 
Rieinoleic acid, Ci 8 H 34 0 3 = 298' . I ( = 184 fatty acid.) 

Caustic soda solution, 2NaOH = 80) ^ 1 Caprylic alcohol, CsH^O = 130 

l Hydrogen, H 2 =2 

378 378 

According to these formulas, 100 parts of castor oil will yield rather more than 81 parts 
of fatty acid. This fatty acid is no doubt also contained in the products of the distillation 
of the fatty substances formed by sulphuric acid, the sebacylic acid being then derived from 
oleic acid. The high melting-point (127 0 ) of sebacylic acid and its ready combustibility 
render this body a very fit material for being mixed with readily fusible candle materials, 
and especially with paraffin of low fusion-point (45 0 ). Moreover, this acid will impart to 
the candles hardness and gloss. As this acid further also prevents the crystallisation of 
stearic acid, it might be usefully added to such fatty substances as have a great tendency 
to crystallise; an addition of 1 to 5 per cent of sebacylic acid to the candle materials, 
renders them as hard as wax. The simultaneous formation of caprylic alcohol, which 
can be used for varnish and lacquer making, enhances the industrial value of sebacylic 
acid; still castor oil is too expensive for this purpose, but the purification of sebacylic 
acid, obtained no matter from what source, is not easy, requiring manipulations which on 
the large scale would become expensive. 

wax candies. 4. Wax, or more particularly bees’-wax, is a fatty substance secreted 
by the bees, and employed by them for the purpose of building the cells in which 
they preserve the honey. According to the researches of J. Hunter and F. Hubner, 
it is now generally admitted that the wax-containing particles gathered by the bees 
from flowers are used exclusively as food for the young brood, while the wax is a 
product of the animal organism of the bees, and a conversion product of sugar. In 
order to obtain the wax the bees are either killed or forced from their dwelling by 
smoke, after which the honey-containing cells or honeycombs are taken from the 
hive, and the honey eliminated by pressure, or by being allowed to flow out sponta¬ 
neously. By washing in hot water the wax is purified, and on cooling, the cakes of 
yellow wax are obtained, the outer dirty crust having been removed by scraping. The 
crude wax thus obtained exhibits a more or less yellow colour, is soft and readily 
kneaded at the ordinary temperature of the air, but becomes brittle at a lower tem¬ 
perature ; its fracture is granular; specific gravity varies between 0*962 and 0*967 ; 
fusion-point between 6o° and 62°. While the granular texture of the yellow wax is 
due to the impurities it contains, it is for that reason as well as for its unsightly 
colour, not suited for candle-making, and has therefore to undergo bleaching. This 
is performed in the following manner;—First, the yellow wax is put into a tinned 
copper cauldron filled with boiling water, to which is added 0*25 per cent of alum, or 
cream of tartar, or sulphuric acid, and this mixture thoroughly stirred. After a few 
minutes the liquid is run off into a tub or cask, the impurities are left to settle, while 


CHEMICAL TECHNOLOGY. 


532 

the wax is prevented from solidifying by covering the tub with a lid, and wrapping 
it up in a woollen blanket. Next the wax is converted into thin ribbon by means of 
machinery, in order to increase the surface and facilitate the bleaching action of the 
air and light. The ribbons are placed on pieces of canvas stretched in frames, and 
these are placed on meadows or grass-plots exposed to the action of the sun and air, 
and left until the colour has disappeared. In order to bleach the interior, the 
ribbons are again molten and again converted into ribbons, and this operation 
repeated until the wax is thoroughly bleached. The bleaching takes, according tc 
circumstances, the state of the weather and the land of the wax operated upon, from 
twenty to thirty-five days, for completion. The loss of weight of wax incurred 
amounts to 2 to 10 per cent. The bleached wax is molten again, passed through 
strainers, and then moulded into large square cakes or thin circular tablets. As 
regards the bleaching of wax by artificial means (chemical bleaching) many 
suggestions have been made, but in practice these leave much to be desired. The 
application of chlorine and bleaching-powder has the disadvantage that solid and 
very brittle chlorinated products are formed, and by remaining mixed with the wax 
impair its combustive quality, and cause candles made of such wax to give off hydro¬ 
chloric acid. The process of bleaching wax, patented in 1859 by Arthur Smith, by 
the use of bichromate of potash and moderately dilute sulphuric acid, answers very 
well in practice; the bleaching is performed in a few hours, and wax by this plan is 
bleached and purified as perfectly as by exposure to air and light; but the toughness 
of the wax is somewhat impaired, so that it is not suitable for such purposes as 
modelling, flower-making, &c. In reference to the chemical properties of wax, John 
first found wax to be a mixture of two substances differing from each other by their 
solubility in alcohol; one of these substances, soluble in boiling alcohol, is cerotic 
acid, C 27 H 54 0 2 (formerly known as cerin); the other sparingly soluble in alcohol is 
known as myricin, and consists, according to Brodie, of palmitate of myricile, 
C 46 H 92 0 2 = Ci6H3 I (C 3 oH 6 I )0 2 . In addition to these bodies wax contains 4 to 5 per 
cent of a substance fusing at 28° and named cerolein, to which is due the solidity 
of wax. The relative proportions of cerotic acid and myricin present in bees’-wax 
vary considerably, and this variation is the cause of the alteration of the fusion- 
point observed in different kinds of wax. 

other kinds of wax. i . Among the more or less wax-like substances are the following:— 
Chinese wax, imported in large quantity from China, is derived from a peculiar kind 
of coccus insect, known entomologically as the Coccus ceriferus, which dwells on 
certain trees, more especially the Rhus succedanca , upon which it deposits a wax-like 
substance, in its physical appearance very similar to spermaceti. This quasi-wax 
is snow-white, crystalline, brittle, fibrous, and fuses at 82°. When submitted to dry 
distillation it yields cerotic acid and ceroten, a paraffin-like body. According 
to Brodie, Chinese wax consists of cerotate of ceryl, C 54 H io s 0 2 = C 27 H 53 (C 27 H 55 ) 0 2 . 
2. Andaquies wax, the product of an insect met with in the regions watered by the 
Orinoko and Amazon rivers, fuses at 77 0 , has a sp. gr. of 0 917, and appears to be 
similar in composition to bees’-wax. 3. Japanese or American wax, met within the 
trade in round concavo-convex cakes, covered with a whitish dust. This soft brittle 
material fuses at 42 0 , is soluble in boiling alcohol, and is said to consist of palmitine. 
4. Camauba wax, imported from Rio de Janeiro, is said to be the outer coating of 
the leaves of a kind of palm tree named the Kopernicia cenfera; it fuses at 83-5°, 
and is used on account of its high fusion-point to improve candle-making materials 


ARTIFICIAL LIGHT. 


633 

of low fusion-point. 5. Palm wax, obtained from the bark of the Ceroxylon 
andicola, a palm-tree met with on the higher peaks of the Cordilleras. The wax is 
scraped from the bark, and the scrapings are boiled with water, and the wax thus 
molten is collected fiom the surface of the liquid, in which the impurities remain 
this kind of wax fuses at 83° 86°, and is very likely identical with the Carnauba 

wax. 6. The Myiica wax, from the JMyrica ccrif&rci, is obtained by boiling the 
iiuit of the plant with water. It is imported from some of the Southern States of 
the Union. The variety of this wax known as Ocuba wax is obtained from the 
same plant and in the same manner, in the district of Para, Brazil, along the banks 
of the Amazon river. This wax has an olive-green colour, and fuses at 36° to 48°. 
It is used in America for making candles. We may add here that of all countries in 
Europe, if not in the world, Corsica produces the largest quantity of wax. In 
ancient as well as medieval times, the inhabitants paid their taxes in wax, and 
supplied 200,000 lbs. annually. Since wax is to honey in quantity as 1 to 15, 
the Corsicans must have gathered 3,000,000 lbs. of honey. 

The Making of Wax Candies. Wax candles are most frequently made by pouring the molten 
wax on to the wicks. For this purpose the wicks are hung upon frames and covered with 
metal tags at the ends to keep the wax from covering the cotton in those places • these 
frames are carried to a heater, where the wax is melted. The frames can turn round and 
as they turn a man takes a vessel of wax and pours it first down one, and then the next 
and so on. When he has gone once round, if the wax is sufficiently cooled he gives 
„ the first wick a second coat, then the third, &c., until they are all of the required thick¬ 
ness. The candles are now rolled on a marble slab or wooden board for the purpose of 
imparting the proper shape. The conical top is moulded by properly shaped tubes, and 
the bottoms are cut off and trimmed. The moulding of wax candles is now rarely if'ever 
performed, but if executed, it is done in precisely the same manner as described for 
stearine and paraffin candles. "Wax, however, is not a very suitable material for moulding, 
in consequence of its shrinking on cooling, as well as its pertinacious adherence to 
the moulds. The wick for moulded wax candles must be previously soaked with wax in 
order to prevent the candles becoming as it is termed honey-combed. The wax is molten 
on a water-bath, and glass moulds are used in preference to metal ones, as well for 
the smooth surface glass imparts as for the more ready removal of the candles when cold. 
In order to prevent the breaking of the glass moulds, they are covered with gutta-percha. 
The large sized altar candles, which often weigh from 15 to 20 kilos., are not made 
by either of the two methods described, but by hand. The wick, partly made of linen 
partly of cotton yarn, is first soaked with wax, or covered with that material cut into long 
strips, rendered soft and lmeadable by the aid of warm water, and next made up to the 
required thickness by rolling on more wax; or a quantity of wax is rolled by hand into 
the required shape, and the wick inserted by cutting a longitudinal channel in the mass of 
wax into which the wick is placed. The channel is filled up with wax and the candle 
finished by rolling. Very recently (1870) Messrs. Eiess have constructed a press for 
making w*ax candles. The arrangement of this machine seems to be somewhat similar to 
the press used for making continuous lengths of lead and block-tin pipes. This wax 
candle press is heated by steam so as to render the wax soft. The wick is inserted into 
the wax in such a manner that it is concentrically surrounded with wax when ejected 
from the spout of the cylinder of the press, thus forming a continuous candle, which is 
cut up into lengths. 

The wax tapers of various thickness are made by a method of which the following is 
tn outline:—In the first place, these tapers are not made of pure wax, but of wax and 
tallow mixed, in order to impart flexibility; while for coloured wax resin and turpentine 
are added to the tallow. The wick of the tapers should be very uniform, ard the strands 
of yarn intended for this purpose are reeled on a cylinder or drum placed at one end of the 
workshop, while at the other end is placed a similar drum. Between these drums is placed a 
shallow copper pan, which can be kept warm by means either of steam or a charcoal fire. 
This vessel is filled with the molten wax, and provided with a hook at the bottom, below 
or through the opening of which the wick is drawn. At the edge of the pan a draw-iron 
is fixed, provided with circular, somewhat conical, apertures of different size, arranged 
in the same way as those described (see p. 25) for wire-drawing. The wick is drawn 
through the wax, put under the hook, and through the aperture of the drawing-iron, and 


534 


CHEMICAL TECHNOLOG Y. 


next reeled on the other cylinder or drum, which is very slowly turned round in order tc 
give the wax time to solidify. When all the wick has been thus coated with wax, 
the taper is, when required to be rendered thicker, drawn a second, and even a third and 
fourth, time through the wax, and a larger-sized aperture of the drawing-iron. The end¬ 
less taper thus formed is cut up into the requisite lengths. 

Bees’-wax is used for many minor purposes, as is well known. Amongst them, as of 
interest, may be noted its selection by the British Government for a lubricating material 
for small-arm cartridges and also for breech-loading cannon. This is due partly to its 
power of resisting oxidation, and its consequent freedom from corrosive action upon 
metal surfaces (lead, &c.), and partly to its peculiar action as a lubricating material, by 
producing an extremely smooth surface upon the bore of the arm as it is swept through 
upon the discharge. It also prevents particles of paper or powder residue from attaching 
themselves to the metal, and thus is the best anti-fouling agent known. 


s perm ^or^spen naceti Spermaceti is the solid portion of the oil of the sperm whale, 
Physeter macrocephalus , a cetacean belonging to the mammalia, and living in some of 
the seas of the southern hemisphere of our globe. The spermaceti is obtained from 
the oil by filtration, and is subsequently hardened and whitened by pressure, and 
refining with a weak alkaline ley. In some cases a very large and full-grown sperm 
whale may yield ioo cw T ts. of sperm oil, containing from 30 to 60 cwts. of spermaceti. 
This material as anet with in commerce is a white, mother-of-pearl like, glossy, 
foliated, crystalline, semi-transparent substance, fatty, and lubricating to the touch, 
of sp. gr. = o - 943, fusing at 43°, and distilling unaltered at 360°. It is soluble in 
about 30 parts of boiling alcohol, becomes yellow by exposure to air, and may be 
pulverised. According to Mr. Smith and Dr. Stenhouse, spermaceti consists of pal- 
mitate of cetyl, C 34 H 6 4 0 2 = C I 6H3i(C'i6H 33 )0 2 ; but according to Heintz (1851), sper¬ 
maceti is a combination of cetyl with stearic, palmitic, myristic, cocinic, and 
cetinic acids. Spermaceti candles are made extensively, if not exclusively, in 
England, where they were first manufactured about 1770. These candles have 
always been greatly prized for their transparent whiteness, high illuminating power, 
and regular burning; and notwithstanding their costliness, are largely used and 
exported to British India. In order to check the great tendency of spermaceti 
to crystallise, 5 to 10 per cent of white wax or a little paraffin is added to the fused 
mass intended to be moulded into candles, by a process exactly similar to that 
already described for stearine candles. 

C H 1 

Glycerine. Glycerine, C3H8O3 (as triatomic alcohol, 3 tt 5 [ 0 3 , or C 3 H 5 1OH), 

3) l OH'' 


is present in the shape of glycerides in combination with solid and fluid fatty acid 
to an amount of 8 to 9 per cent, and may be separated by treatment with bases 
(potash, soda, lime, baryta, oxide of lead), or with acids (sulphuric acid), and certain 
chlorides (chloride of zinc), also by means of superheated steam, or very hot w , -ater 
without the formation of steam, in closed vessels. Glycerine is also formed as a con¬ 
stant product by the alcoholic fermentation of dextrose, levulose, and lactose. Accord¬ 
ing to Pasteur’s researches, the quantity of glycerine thus formed amounts to about 
3 per cent of the weight of the sugar. Glycerine w^as first discovered by Scheele 
whilst engaged in preparing lead plaster. Industrially, glycerine has been used for 
only tw r enty-five years, in consequence of the large quantity of glycerine obtained as 
a by-product in the manufacture of soap as well as of stearine candles. The vinasse 
of the potato, and molasses from beet-root sugar distillation, and likewise the 
residue of the distillation of wine, vinasse proper, as carried on in the South oi 
France, contain large quantities of glycerine. 

As regards the preparation of glycerine on the large scale, it is mainly a question 


ARTIFICIAL LIGHT . 


635 


t>f purification of the glycerine obtained in the industrial preparation of the stearic 
acid from neutral fats above described. When the lime saponification process is 
used, the glycerine remains dissolved in the water after the separation of the in¬ 
soluble lime-soap. The lime also dissolved having been eliminated by either sulphuric 
or preferably oxalic acid, the evaporation of the liquid to the consistency of a syrup 
will yield a glycerine pure enough for many technical purposes. When the decom¬ 
position, or rather dissociation, of the neutral fats is effected by means of superheated 
steam, the glycerine and fatty acids (see p. 634) are both obtained in pure state, pro¬ 
vided the heat be kept at or below 310°, because otherwise a portion of the glycerine 
is decomposed with evolution of vapours of acroleine. The fact that, when fats are 
saponified with sulphuric acid, the sulplio-glyceric acid in aqueous solution yields 
readily by evaporation glycerine and sulphuric acid, may be applied for the prepara¬ 
tion of glycerine. The soap boiler’s mother-liquor, now the most important source 
of crude glycerine, may be made available for its production, according to Reynold’s 
patent, in the following manner:—The mother-liquor is first concentrated by evapo¬ 
ration ; the saline matter which is thereby gradually separated being removed from 
time to time. When the fluid is sufficiently concentrated—ascertained by the boiling- 
point having risen to 116 0 —it is transferred to a still, and the glycerine distilled off 
by means of superheated steam carried into the still. The distillate is next concen¬ 
trated and brought to the consistency of a syrup in a vacuum pan. 

According to the researches of A. Metz (1870) :— 

A sp. gr. (at 17-5°) of 1*261 corresponds to 100 per cent of anhydrous glycerine. 


99 


1*240 „ 

>> 

94 

99 

99 

99 

99 

1-232 

„ 

90 

99 

99 

99 

99 

1*206 ., 

„ 

80 

99 

99 

99 

99 

1*179 


70 

99 

99 

99 

99 

1153 

' >* 

60 

99 

99 

99 

99 

1*125 

, 

50 

99 

f 

99 

99 

1*117 

, 

45 

99 

99 

99 

99 

1-099 

• 

40 

99 

99 

99 

99 

i*'073 

1 

30 

99 

99 


99 

1*048 

, >• 

20 „ 

99 

99 

99 

99 

1-024 »: 

t »» 

10 „ 

99 

99 


Glycerine has become largely employed owing to its oily consistency, also to the 
fact that at ordinary temperatures it is fluid, and does not freeze when quite concen¬ 
trated even at — 40 0 ;* further to its stability, its pleasant sweet taste when quite 
pure, its harmlessness, its great solvent power for many substances, and, lastly, to 
its low price. 

Among the many applications of glycerine are the following:—For keeping clay moist 
for modelling purposes; for preventing mustard from drying up; for keeping snuff 
damp ; preserving fruit; sweetening liqueurs ; and for the same purpose for wine, beer, 
and malt extracts. Glycerine is also useful as a lubricating material for some kinds of 
machinery, more especially watch and chronometer works, because it is not altered by 
contact with air, does not become thick at a low temperature, and does not attack such 
metals as copper, brass, &c. Glycerine is used in the making of copying inks, and of a 


* The freezing of glycerine, observed in 1867, by Mr. W. Crookes, in London; by Sarg, at 
Vienna ; and Dr. Wohler, at Gottingen, proves, however, that under certain conditions, 
and while being transported from one place to another, glycerine may become solid even 
at a temperature not so low as the freezing-point of mercury. 










636 CHEMICAL TECHNOLOGY. 

great many cosmetics. In order to render printing ink soluble in water—its insolubility 
is, however, its greatest advantage—it has been proposed to use glycerine for its prepara¬ 
tion instead of linseed oil. Glycerine is an excellent solvent for many substances, including 
the tar-colours (aniline blue, cyanine, aniline violet) and alizarine, Di order to render 
paper soft and pliable glycerine is added to the pulp. To the quantity of pulp required for 
making ioo kilos, of dry paper, 5 kilos, of glycerine, sp. gr. 1*18, are sufficient. It is not 
out of place here to mention the following useful weavers’ glue or dressing, composed of— 
Dextrine, 5 parts ; glycerine, 12 parts; sulphate of alumina, 1 part; and water, 30 parts'. 
By the use of this mixture the weaving of muslins need not be—as was formerly the case— 
carried on in damp darkened cellars, but may be performed in well-aired and well-lighted 
rooms. It is said that leather driving belts, made as usual of weakly tanned leather, 
when kept in glycerine for twenty-four hours, are not so liable to fray. A glycerine solu¬ 
tion is now largely used instead of water for the purpose of filling gas-meters, as such a 
solution does not freeze in winter nor evaporate in summer. Santi uses glycerine for the 
compasses on board screw-steamers, in order to protect the inner compass box against the 
vibrations caused by the motion of the propeller. It is impossible to enter here into 
minute details on the use of glycerine ; suffice it to observe further that it is employed for 
preserving anatomical preparations, for rendering wooden casks impervious to petroleum 
and other oils ; for the preparation of artificial oil of mustard or sulpho-cyan-allyl, made 
by treating glycerine with iodide of phosphorus, whereby iodide of allyl is formed, which 
on being dissolved in alcohol, and next distilled with sulphocyanide of potassium, yields 
sulpho-cyan-allyl. When glycerine is treated with very concentrated nitric acid or with a 
mixture of strong sulphuric and nitric acids, it is converted into nitro-glycerine (trinitrine 
or glyceryl nitrate) (see p. 158), largely used for various purposes, the preparation of 
dualine and dynamite, &c. A mixture of finely powdered litharge and very concentrated 
glycerine made into a paste forms a rapidly hardening cement, especially useful as a cover 
for the corks or bungs of vessels containing such fluids as benzol, essential oils, benzoline, 
petroleum, &c., the cement being impermeable to these liquids. 


II. Illumination by Means of Lamps. 

illumination^with Fluid The fluid substances in use as illuminating materials are 
either:— a. Fixed, or fatty oils. b. Volatile oils, which again are either essential 
oils, as, for instance, camphine ; or products obtained from tar, as photogen and 
solar oil; or, finally, native, as petroleum. Among the fixed or fatty oils, rape-seed 
oil, colza oil, olive oil, fish oil, and the dry papaver-seed or poppy-seed oil, are 
chiefly used. 

purifyingorRefining j n or d e r to refine these oils so as to render them more suitable 
for combustion in lamps, they are treated with about 2 per cent of their weight of 
strong sulphuric acid, or with a concentrated solution of chloride of zinc. These 
substances do not act upon the oil, but destroy or coagulate any impurities, as muci¬ 
laginous and colouring matters, present. The acid or chloride of zinc is removed by 
washing with water, after which the oil is filtered, and in order to remove any 
mechanically adhering water, it is kept for a considerable time at a temperature of 
about ioo 0 , being heated by means of steam circulating in pipes fitted in the tanks. 
Now oil is frequently extracted from the seeds by means of sulphide of carbon (see 
p. 199). The oils which serve for the purposes of illumination are termed lamp-oils 
The introduction of paraffin and petroleum oils has caused a very considerably 
decreased consumption of the fixed fatty oils. 

Lamps. Lamps were known and used even in remote antiquity, and were invented, 
it is believed, by the Egyptians. While it cannot be denied that as regards outward 
form the lamps of the ancients were graceful, their technical construction was rude, 
and remained so—not taking into account some minor improvements made in the 
seventeenth and eighteenth centuries, among which improvements are the introduc¬ 
tion of the glass cylinders by the Parisian apothecary Quinquet, and the invention 
of the hollow and circular burner by Argand, 1786—until chemistry discovered a 


ARTIFICIAL LIGHT . 


637 


sound theory of combustion and illumination, and until pliysicial science ascertained the 
principles of the supply of oil and means of estimating the illuminating power of the 
flame of lamps, and further until the refining of oil supplied a purer and more fluid 
illuminating material. A still greater step to improvement in light obtained from 
lamps was the discovery of the petroleum and paraffin oils and the construction of 
lamps suitable for their combustion. These oils have now become of general use 
wherever gas is not obtainable. In passing, it may be observed that in no country is 
gas so extensively made on the small scale as in Scotland, where farm-houses, 
country seats, and other dwellings, not conveniently situated near to public gas-works, 
are very generally provided with small gas-works, in which the excellent Cannel 
coal of the country is employed, yielding a very pure and highly illuminating gas at 
a reasonable cost, and with the advantage that gas is allowed by the insurance com¬ 
panies as light in stables and other places where readily inflammable materials are 
kept, while lamp and candle lights are absolutely prohibited in such places, for 
fear of causing fire. Some of the many inventions and improvements of oil lamps 
made during the last forty-five to thirty years are quite forgotten; the moderator 
colza lamp has been nearly superseded by improved paraffin and petroleum oil lamps, 
and as we do not treat in this work on the history of technology, but on technology 
as now developed, we cannot enter into any further historical details, but proceed 
with our subject. 

Viewing lamps generally, we observe the same parts as in a candle, viz., the 
illuminating material and the wick. As regards the illuminating material, it is in 
lamps as well as in candles fluid, the difference consisting in that with candles the 
fatty material is molten near the end of the. wick, a cup of molten fat being formed, 
while with lamps the illuminating material is fluid at the ordinary temperature, and 
therefore kept in a vessel or reservoir from which the wick is uninterruptedly and as 
uniformly as possible supplied. The differences observed in the construction of the 
various kinds of lamps depend partly upon the illuminating material employed 
(colza oil, petroleum oil, sperm oil, &c.); partly upon the shape of the wick and upon 
the mode of supplying air to the flame, either with or without a glass chimney; 
further, upon the shape of the oil reservoir and its position in reference to the wick; 
and finally and chiefly, upon the method and means by which the illuminating 
material is carried to that portion of the wick where the combustion is intended to 
take place ; that is to say, whether the illuminating material is only absorbed by the 
capillary action of the cotton wick, or whether this action is aided by hydrostatic or 
mechanical means. 

Colza oil and mineral oil—be the latter obtained from the tar yielded by the dry 
distillation of certain kinds of coal or peat, or be it derived from native petroleum 
differ from each other as regards their properties as illuminating materials in the 
following particulars :—1. Colza oil is not volatile at the ordinary temperature, and 
not even when heated to above igo°. It is hence devoid of smell, and is not by itself 
ignitable unless it be first heated to a such a high temperature (about 200°) as to 
give off products of dry distillation—in fact, become decomposed and converted into 
oil-gas. The mineral oil, even that kind which is termed odourless, possesses some 
odour, and loses in weight or is gradually volatilised by exposure to air. At a 
higher temperature it is volatilised and can be distilled over unaltered, while at a 
still more elevated temperature it is nearly all converted into illuminating gas. 
2. Colza oil consists of carbon, hydrogen, and oxygen, according to the formula 


CHEMICAL TECHNOLOGY. 


538 


Ci 8 H I2 0 2 . I11 llic dry distillation which this oil undergoes in the wick just below 
the flame it is converted into elayl gas and carbonic acid:— 


Colza oil, 2 Ci 0 H I 80 2 =340, yield 


j9 molecules of elayl gas, 9C 2 H 4 
12 ,, „ carbonic acid, 2C0 2 


= 252 

= 88 


340 

consequently 25*8 per cent of the colza oil becoming carbonic acid does not con¬ 
tribute anything to the illuminating power of the flame, but deprives the half of the 
volume of the elayl gas of its illuminating power. Refined colza oil burns in 
well-constructed lamps very completely, yielding only the odourless products of 
combustion, viz., carbonic acid and water. 3. Petroleum oils are mixtures of 
different hydrocarbons, very probably of the higher members of that homologous 
series of which marsh gas is the primary. Petroleum oil begins to boil at 250°, and 
is at a higher temperature decomposed, yielding gaseous products, marsh gas and 
elayl gas, and soot, or unburned carbonaceous matter. The quantity of carbon 
contained in petroleum oil is far larger than that contained in colza oil; hence the 
former when burning in contact with air and without a glass chimney exhibits a sooty 
flame, but this changes at once into a very bright flame when by the addition of a 
glass chimney the increased draught of air causes the complete combustion of the 
excess of carbon. While colza oil only reaches the flame in the state of gas, the 
petroleum oils come into the flame as vapour, and the construction of the petroleum 
oil lamps ought to be so contrived that the combustion be as complete as possible in 
order to prevent any disagreeably odorous vapours or gaseous matters escaping un¬ 
consumed. As regards accidents from fire, petroleum or paraffin oil lamps are, with 
proper precautions and good quality of oil, not attended with greater danger than 
that of the use of colza oil. 4. As is well known, colza oil is a fatty lubricating oil, 
while paraffin or petroleum is not so ; in consequence of this difference the former 
may be used in lamps in which the oil is carried to the wick by mechanical means— 
either by clockwork or spiral springs acting upon one or more more pistons, as in the 
Carcel and moderator lamps. Because the fatty nature of colza oil as well as its 
lubricating property keeps the packing of the pistons oil-tight as well as lubricated, 
it is clear that the paraffin oils cannot be used in such lamps. 

Independently of the illuminating material, the construction of a normal lamp 
should be such, that (1) it yields a maximum of light uniformly for a definite time 
(three to eight hours). This condition, a consequence of the complete and equal 
combustion of the illuminating material, can only result from (a) the use of a 
purified illuminating material; (J 3 ) the use of a wick of uniform thickness and 
structure; (7) the uniform supply of illuminating material to the flame ; (d) by suffi¬ 
ciently strong heat at the point where the combustion takes place, so that the 
conversion of the illuminating material into gases may be complete; (e) by the 
regulation of the supply and access of air. Too small a supjdy of air often gives 
rise to a sooty flame, while too large a supply causes a lowering of the temperature 
of the flame, and hence also separation of soot and formation of odorous product.' 
of incomplete combustion; and even if these results do not occur and a complete 
combustion obtains, too large a supply of air impairs considerably the illuminating 
power of the flame; (£) the means of regulating the size of the flame must be 
perfect. 2. The lamps ought to be so constructed that the light evolved be not 
wasted. The well-known reflectors and lamp caps aid the illumination greatly 



ARTIFICIAL LIGHT. 


639 


The reservoir for the oil should be in the first place so situated that its shadow falls 
on some unimportant part of the field to be illuminated; and secondly, so arranged 
that the point of gravitation of the lamp be maintained. 

various Kinds of Lamps. Taking the manner of conveying the illuminating material by 
means of the wick to the flame as a basis for the division of lamps into various kinds, 
we distinguish the following :— 

1. Suction lamps, in which the oil is simply sucked up by the capillary action of the 
cotton wick from the reservoir. According to the situation of the oil reservoir with 
reference to the wick, suction lamps can be subdivided into :— a. Those in which the 
oil reservoir is placed at about equal height with the flame of the burning wick. 
( 3 . Lamps in which the oil reservoir is placed higher than the burner. These lamps have 
a detachable oil reservoir, which, having been filled, is inverted into a fixed vessel, 
an arrangement common in reading-lamps for burning colza oil. 2. Pressure lamps, in 
which in addition to the capillarity of the wick, mechanical or physical means are 
employed for the purpose of forcing the illuminating material to the wick. In this variety 
the oil reservoir is placed at the foot of the lamp. According to the method of forcing 
the oil to the wick, pressure lamps are:— a. Aerostatic, in which the principle is that of 
Hero’s fountain ; into the closed oil reservoir air is forced, and this while trying to make 
equilibrium with the outer air, presses upon the oil and forces it upwards through a 
tube to the burner. ( 3 . Hydrostatic lamps, based upon the principle of the communicating 
tubes, in which the heights of fluids of different specific gravity making equilibrium 
together stands in the inverse relation to their specific gravity. The fluid which has to 
make equilibrium with the oil and force it up towards the cotton wick should be specific¬ 
ally heavier than the oil. 7 . Statical lamps, in which the oil is forced from the reservoir 
at the foot of the lamp to the burner by the pressure either of the weight of a solid body 
(for instance, a leaden weight), or by the direct weight-pressure of a piston moving down¬ 
wards in the oil reservoir, d. Mechanical lamps, in which the oil contained in the 
reservoir is forced upwards to the burner either (a) by means of pumps set in motion by 
wheelwork similar to that of a large watch (Carcel lamps with clockwork), or (ft) by the 
pressure of a spiral spring acting upon a solid piston (moderateur lamps). In the mechanical 
lamps the oil is carried to the wicks in larger quantity than is required for the momentary 
consumption; this excess of oil returns continually to the oil reservoir. The lamps here 
alluded to are only suited to burn colza oil, and we ought to observe that those mentioned 
under a, ( 3 , and 7, are obsolete, for the very good reason that they have been superseded 
by better and more simple contrivances; this applies also to the clockwork lamps which 
were, even when well made, very liable to get out of order and required very pure oil to 
work well. 3. The lamps for burning the paraffin and petroleum oils are all simple 
suction lamps, the reservoir being placed under the wick and in its axial prolongation. 
The lower specific gravity and the greater fluidity of the oils greatly aid the capillary 
action of the wick, and renders all pressure apparatus superfluous. The so-called 
benzoline sponge-lamps also belong to the category of suction lamps, the very volatile and 
highly combustible benzoline (obtained from the crude petroleum) being absorbed by the 
sponge, more commonly cotton waste or tow, and thence slowly carried by capillary action 
into the wick. 

Suction Lamps. i. To this kind belong all the lamps in which the oil is simply carried to 
the flame by the capillary action of the cotton wick, the oil reservoir being placed somewhat 
below the burning end of the wick. According to the situation of the oil reservoir in 
reference to the wick, suction lamps can be divided into (a), those in which the oil 
reservoir is placed nearly at the same height as the burning wick. Here we have to 
observe the two following conditions, viz. (a) the burning wick is placed in the oil 
reservoir itself, as may be observed in the kitchen lamp and antique lamp ; or (6), the oil 
reservoir and burner are separated from each other, the reservoir being placed by the side 
of the burner, or, as is the case in the ring lamps, at the circumference of the burner,, 
which is in the centre. ( 3 . Those lamps, the oil reservoir of which is placed higher than 
the burner, as, for instance, in the so-called reading lamp. 

Among the suction lamps are the following :—In the antique lamp, Fig. 271, the wick, a 
skein of cotton, is placed in an open or closed oil vessel, the burning end of the wick 
simply protruding from the spout. This kind of lamp is technically very imperfect, 
because, in the first place, the wick has to suck up the oil, when the level of that fluid 
gradually sinks by the burning of the lamp, to a height far too great for its capillary 
power ; hence the flame will by lack of sufficient oil become gradually more and more 
lurid, and at last extinguished altogether before all the oil is consumed. In consequence 
of the thickness of the wick the combustion is incomplete, owing to want of sufficient 


640 


CHEMICAL TECHNOLOGY. 


access of air, the lamp thus burning with a sooty flame; while the body of the lamp 
throws a great shadow. This last defect is less marked in a kind of kitchen lamp, exhi¬ 
bited in lateral projection in Fig. 272, and viewed in plan in Fig. 273, as by means of the 
spout the distance between the oil reservoir and the flame is increased, or, in other words, 
the angle, cab, rendered more acute. The so-called Worm’s lamp, Figs. 274 and 275, in 
former days much used in the Rhine provinces, should be noted on account of the shape of 
the wick, t, which is composed of a flat woven cotton hand, instead of a skein of cotton yarn, 
and thus the access of air to all parts of the wick is so regulated that complete combustion 


Fig. 271. 



Fig. 272. 


Fig. 273. 



of the oil takes place. The wick is put into the wick-holder, c, which is soldered to the ring, 
d, loosely fixed on the rim of the glass globe, which serves as an oil reservoir. By means 
of the rackwork and pinion, e and e ', the wick can he turned upwards and downwards, and 
the flame thus regulated. The part a is placed in a candlestick or in any other suitable 
stand. A glass and globe may be placed over and around the flame. Although this 
lamp is an improvement on the old-fashioned kitchen lamp, it has many defects. 



The Lamp with Constant In order to obviate the constant decrease in the intensity of the 
on Level. light as the level of the oil sinks by its consumption, as happens in 

the lamps already described, it is simply necessary to keep the oil in the burner as much 
as possible at the same height. This can be effected in suction lamps by placing the oil 
reservoir higher than the burner, but in doing this it becomes necessary so to arrange the 
construction of the lamp that the oil be gradually carried to the wick in such quantity as 
is required for its proper burning. This is practically carried into effect as exhibited in 
Fig. 276, which shows in vertical section a kind of lamp in England known as a 
reading lamp. The oil reservoir of this lamp is a movable vessel, a, of tinned 
iron, and closed by means of a valve, which when the vessel is placed vertically, 
as exhibited in the cut, leaves the neck or mouth of the oil flask open in a downward 



























ARTIFICIAL LIGHT. 


041 

direction, so as to admit of the oil running into the space bb ; but as soon as the oil has 
risen to the level, ee', the fluid acts as a hydraulic valve, and no more oil can flow out of 
a until by the burning of the lamp the level has been lowered. The tube d carries the oil 
to the wick-holder; while at c a small hole is made for the purpose of giving free access 
of air to the space between the sides of the vessel a and the cylindrical box in which it 
is placed. When more oil might flow to the wick of this kind of lamp than can be burnt 
in a given time the flame is extinguished, but, as usually constructed, these lamps, unless 
they be tilted, or exposed to a very warm atmosphere (in which case owing to the expan¬ 
sion of the air in the vessel a the oil 


Fig. 276. 


is forced out of it) answer the purpose 
very well, giving when burnt with 
suitable wicks and well-refined colza 
oil a good light, but less intense than 
that obtainable from the better kinds 
of paraffin oil lamps. 

Pressure Lamps. 2. These are distin¬ 
guished from suction lamps by the 
mode in which the oil reservoir is 
situated in reference to the burner, 
the former being not placed on a 
level with or higher than the latter 
but below it, the place assigned to 
the reservoir being the foot of the 
lamp; and as the capillary action of 
the wick is not sufficient to enable 
it to suck the oil upwards to so great 
a height, an arrangement is required 
to lift the oil towards the wick, while 
any excess of oil above that which the 
flame at the wick is capable of con¬ 
suming trickles downwards, and is 
either conducted into the oil reservoir 
or collected in a separate vessel. The 
pressure lamps are certainly, as far as 
colza oil lamps are concerned, the 
best in every respect; but the dif¬ 
ferent varieties of these lamps to be 
here noticed have been superseded by 
the moderateur. 

According to the contrivance by 
means of which the oil in pressure 
lamps is forced up to the wick, we 
distinguish:— 

a. Aerostatical Lamps .—In these 
lamps the principle of Hero’s foun¬ 
tain is employed. Air is forced into 
the closed oil reservoir, and this air 
while trying to gain its equilibrium 
with the outer air, forces the oil 
through a very narrow tube upwards 
to the burner. These lamps have, 
owing to great complicity of con¬ 
struction, difficulty of management, 
and of filling with oil, never been of any real practical use. 

( 3 . In the hydrostatic lamps, also now obsolete, though in use in France in the earlier 
part of this century, the oil is forced to the burner by the pressure of a column of liquid 
upon the oil. The physical principle involved is, that of the two vessels or tubes com¬ 
municating with each other, and filled with liquids of different specific gravity, the 
height of these fluids is inversely as the specific gravities of the fluids. The fluid which 
has to make equilibrium with the oil ought of course to be specifically heavier than 
the oil, and ought neither to act injuriously upon the metal of which the lamp is made 
nor upon the oil; while the liquid should not freeze very readily. Mercury, solution of 
common salt, molasses, solutions of chloride of calcium, and similar liquids, have 
been proposed as fluids to act in the manner alluded to. 



















































CHEMICAL TECHNOLOGY. 


5 t 3 


y. Statical Lamps. —In these lamps the oil contained in the reservoir at the foot of the 
lamp is either forced up to the burner by the pressure of a solid body exerted upon the 
oil, or by the pressure of a piston, acting directly and by its own weight, forcing the oil 
upwards through a narrow tube. In the first instance the oil is put into a bag made of any 
impermeable and sufficiently jdiable material—leather, caoutchouc, or waxed silk, for 
instance—and this bag is placed in a reservoir, and next a weight is made to press upon the 
bag, to which is fitted a small tube communicating with the burner. The second arrange¬ 
ment with the piston was the forerunner of the mechanical lamps ; but as statical 
lamps are no longer made further details are unnecessary. 

Mechanical Lamps. t>. These lamps are fitted with a mechanical contrivance by the aid of 
which the oil is forced from the reservoir in the foot of the lamp to the burner, the quan¬ 
tity of oil thus supplied to the latter exceeding the requirements at any given moment of 
the burning flame. While in all the lamps mentioned the contents of the burner is a 
constant column of oil, which decreases steadily from the top downwards, or is renewed 
from time to time, the oil in the mechanical lamps is a constantly flowing stream, which 
yields the wick the requisite quantity for combustion, while the excess flows downwards 
into the reservoir. 

Two kinds of mechanical lamps are especially noteworthy, viz.:— 

Clockwork Lamp. i. The clockwork lamp, pump lamp, Carcel lamp, invented in 1800, by 
the lamp maker Carcel, at Paris, and afterwards improved upon. The pump or pumps—for 
in the better kinds there are two, unless the single pump is double acting—which forces, 
the oil from the reservoir in the foot of the lamp is moved by clockwork, provided with a 
strong spring which is wound up. The pump is a combination of suction- and force- 
pump ; in some lamps of this kind, instead of a pump an Archimedean screw is employed 
for the same purpose. In the socket of the clockwork the oil reservoir and pump are placed. 
The tube through which the oil is forced upwards to the burner is carried through 
the shaft of the lamp. The oil reservoir and the clockwork are separated from each 
other by a horizontal metallic plate. 

An apparatus of simple construction often employed in the Carcel lamp is shown 
in section in Fig. 277. The body of the lamp forms the cylinder, in which the horizontal 
piston m is moved to and fro, while the space n above it is connected with the oil pipe 

leading to the burner. The space below the body or 
cylinder of the pump is connected with the oil reservoir, 
and divided into two compartments by means of a par¬ 
tition, and further provided with two valves, made either of 
oiled silk or of gold-beaters’ skin. When the piston 
moves in the direction from cl to c, oil enters from the 
reservoir through b, while the oil then present in the 
space between c a and m, is forced through c into the space 
n, and thence into the oil pipe. The space n serves also 
the purpose of an air vessel, for the compressed air acts as 
a regulator to the constant flow of the oil. When the 
piston moves in the direction from c to b, oil enters through 
a, and through cl into n. The clockwork which moves the 
piston rod of m is placed below the oil reservoir. The 
arrangement of the pump is such that the burner of 
the lamp is supplied with a larger quantity of oil than 
is required for the immediate consumption of the flame, the result being that the 
wick and the burner are kept cool, and the carbonisation of the wick at the flame is pre¬ 
vented, and thereby the capillary action of the cotton left unimpaired. The excess of oil 
flows again into the reservoir. The clockwork of these lamps requires winding up 
about once in twelve to fifteen hours ; and for burning seven to eight hours, the action is 
so very uniform that a light of equal intensity is maintained for that time. Some 
of these lamps are fitted with an external knob, which can be used for the purpose of 
stopping the clockw T ork by arresting the motion of the regulating wings. 

Moderateur, or Moderator 2. This lamp was invented in 1837 ky Franchot, and as it is more 
Lamp. simple, less liable to get out of order, and is cheaper than the clock¬ 

work lamp, it has in a great measure superseded the use of the latter. The essential part 
of this lamp is a large, well-packed piston, which resting on the oil contained in the 
reservoir, is forced downwards by means of a spiral spring, the oil finding no outlet but 
through a small opening, into which is inserted a narrow tube leading to the burner. A 
moderateur lamp is exhibited in -Fig. 278, the upper part of the cut being a front, 
the lower a sectional view. The oil reservoir is placed in the hollow body of the 
lamp, made of metal; this reservoir serves also as pump body or cylinder for the 
piston a, made of a metallic disc, fitted with a leather rim as packing, and also acting as a 


Fig. 277. 

















ARTIFICIAL LIGHT . 


643 


valve. To the piston is fitted the rod b, which through nearly its entire length is 
provided with teeth, biting in those of the small wheel, d, forming a rack and wheel-work 
contrivance, which admits of drawing the piston upwards by turning the handle of d. 
When thus wound up the expansion of the spiral spring which is held at e forces 
the piston downwards. When the reservoir is not filled with oil, the piston rests on 
the bottom of the vessel; and when oil is poured into the cup of the lamp, it flows 
downwards into the reservoir and on to the upper surface of the piston: if this is 
next moved upwards or wound up, there is a vacuum formed below it, and the 



atmospheric air pressing upon the oil forces it downwards by reason of the flexibility of 
the leather packing acting as a valve, until all the oil is below the piston and the latter 
fully wound up, when the oil forces the leather packing so tightly against the sides of the 
reservoir that there is no way of escape but by the tube c, which communicates with the 
burner. The spring is very accurately adjusted, and its expansion regulated to the bulk of 
oil which is consumed, so that the wick is properly supplied. After the lapse of some 
hours the lamp has to be wound up again. In order to prevent the oil passing through 
the tube c in too large a quantity at once and being forced out of the burner as a jet, there 



















































































544 


CHEMICAL TECHNOLOGY. 


is brought into play a contrivance which is technically termed the moderateur, consisting 
of (Figs. 279 and 280) a peculiarly bent wire, g, which is placed in the tube c, and is sol¬ 
dered to the inner tube of the lower part of the burner. The lower and movable portion 
of the tube c is, when the piston is fully wound up, so placed that g fits and dips into c, 
while, when the piston moves downwards, c is also lowered, and not partly plugged by o. 
By this arrangement the flow of the oil is rendered uniform and independent of the 
greater force of expansion exerted by the spiral spring when the lamp has been fully 
wound up. To some of these lamps an arrangement has been fitted, consisting of a dial 
and hand, exhibiting externally the position of the piston, so that it may be seen 
when the lamp again requires to be wound up, and in some cases an alarum has been 
added for the purpose of giving audible warning when the operation is required. With 
good colza or sperm oil an excellent light is obtainable, while the machinery is not very 
liable to get out of order. 


Fig. 281. 


Petroleum on and Paraffin 3 * The fluids commonly termed paraffin or petroleum oils, and 
on Lamps. also known as kerosen, photogen, pyrogen, &c., are always burnt in 

suction lamps, the oil reservoir being placed either below or by the side of the wick. 
Mechanical lamps, such as the moderateur lamp, for instance, cannot be used for petroleum 

oils, because these oils do not lubricate the leather 
of the piston. As the mineral oils are not viscous, 
the capillary tubes of the wick can more readily 
suck up the oil from the reservoir, so that by the 
lowering of the level of the fluid a loss of intensity 
in the light is hardly perceptible. Owing to the 
large quantity of carbon contained in these oils, 
a smokeless flame is produced only by a powerful 
current of air, which is obtained partly by the glass 
chimney and partly by the adjustment of the wick, 
which should project very slightly above the rim 
of the burner; while in the paraffin oil lamps 
provided with flat wicks the object is promoted by 
the brass cap put over the flame and provided with 
an opening, below which the admixture of air and 
vapours of the oil takes place, and also a strong 
current of air called forth to aid the combustion. 
In reality the petroleum and paraffin oil lamps are 
vapour lamps ; that is to say, the vapours of these 
liquids yield the luminous flame, not the gases 
resulting from the decomposition of the oil, as 
obtains in the case of colza oil and candles. In 
order to guard against the possibility of an 
explosion, the paraffin oil lamps are all so con¬ 
trived that the fluid contained in the reservoir 
does not become heated, and for this purpose the 
current of air which sustains the combustion is 
made to cool the burner. 

Among the many paraffin oil lamps one of the 
best is that of Pitmar, at Vienna. This lamp, 
Fig. 281, consists of a metal oil reservoir, b, which 
surrounds the wick tube and is connected with 
that tube by means of a horizontal tube, through 
which the oil is conveyed to the wick, a is an 
aperture for filling b with oil, and closed by a 
metallic screw-plug. The wick is a circular argand 
burner with double currents of air and with glass 
chimney, c. The metallic bearer or gallery, /, of 
tne chimney can be made, as in moderateur oil lamps, to slide upwards and downwards 
for the purpose of adjusting the height of the bent narrowed portion of the glass 
so as to produce the best flame. This narrowed part of the glass should stand about 
three-eighths of an inch above the wick, as indicated by the dotted lines cl and e, 
so that the greater part of the flame, which should be about 6 to 8 centims. high, 
is above the narrowed portion of the glass. If the glass is too high the flame either 
smokes or is ruddy, and when too low the flame is small and hardly emits any light. 
The oil reservoir of this lamp does not become heated, since it is kept cool by the strong 
current of air drawn in by the combustion. In one of the recently published numbers of 
the “Journal of the Society of Arts,” the petroleum lamps of Silber are very highly 































































ARTIFICIAL LIGHT. 


645 

commended. These lamps yield a light equal to that of twelve to forty wax-candles, 
while the construction is such that they can be used with either mineral or fatty 
oils alternately, and without the necessity of tr im ming the wicks. We have already 
alluded to the so-called benzoline or sponge lamps (see p. 639). 

III. Gas. 

Gen Hi8toricaiN C otes. and For many hundreds of years it lias been known that fossil coals 
yield a combustible gas, and even in very ancient times the observation. lias been 
made that large quantities of combustible gases were sometimes evolved from coal 
and other mineral seams, also from salt-mines, &c. The soil contains in many 
localities such a quantity of gas that by boring a hole the escaping gas may be 
employed for the purposes of illumination. In the neighbourhood of Fredonia, 
State of New York, a native permanent source of gas exists, which having been 
accidentally discovered by the pulling down of a mill situated on the banks of the 
river Canadaway, has been, by boring into the bituminous limestone, enlarged, and a 
gasholder constructed. The native gas now serves for the purpose of illuminating 
the locality. The quantity of gas collected in twelve hours amounts to about 
800 cubic feet, and consists, according to Fouque’s researches, of a mixture of marsh- 
gas (CH 4 ) and hydride of ethyl (C 2 H6). In the Szlatina salt-mine, situated in the 
Marmaro Comitate (Hungary), illuminating gas is constantly evolved at a depth of 
90 metres below bank from a marly clay which is interspersed between the layers of 
rock-salt. This phenomenon was known in 1770, and the gas is now collected in a 
gas-holder and used for lighting up the mine. A small quantity of gas is also 
evolved in the Stassfurt rock-salt mines. The Rev. Mr. Imbert, who as a 
missionary has travelled through China, states that in the Province of Szu Tchhouan, 
where many bore-holes for rock-salt have been made to a depth of about 1500 to 
1600 feet, gas is permanently emitted and conveyed in bamboo tubes to places where 
it is used for lighting as well as heating purposes, more especially the heating of 
salt-pans in which the brine is evaporated. In Central Asia and near the Caspian 
Sea there are at several localities so-called eternal fires, which are due to the 
constant evolution of gas from the soil. Similar phenomena are observed at Arbela 
in Central Asia, at Chitta-Gong in Bengal, and elsewhere, while now and then large 
volumes of gas emitted in the coal-pits and conveyed to bank by means of iron pipes 
are suffered to burn for several days. 

As regards the artificial production of gas from coals, Clayton and Hales, 1727 to 
1739, made the first observations on this subject; while the Bishop of Llandaff, 
1767, exhibited how the gas evolved from coal might be conveyed in tubes. Dr. 
Pickel, Professor of Chemistry at Wurzburg, lighted his laboratory, 1786, with the 
gas obtained by the dry distillation of bones. At about the same period Earl Dun- 
donald made experiments on gas-lighting at Culross Abbey; but it should be 
observed as regards these experiments that they were made more with the view to 
obtain tar, and the gas evolved by the distillation of the coals was considered a 
curiosity. The real inventor of practical gas-lighting is William Murdoch, who in 
1792 lit his workshops at Redruth, Cornwall, with gas obtained from coals. His 
operations remained unknown abroad for some ten years, and hence the French 
consider Lebon as the inventor of gas-lighting, since he lit (1801) his house and 
garden with gas obtained from wood. The first more extensive gas-work was 
established in 1802 by Murdoch, at the Soho Foundry, near Birmingham, the 
property of the celebrated Boulton and Watt; and in 1804 a spinning-mill at 


5 4 6 CHEMICAL TECHNOLOGY. 

Manchester was lighted with gas. From that period gas-lighting became more and 
more generally adopted in factories and workshops, hut not before the year 1812 did 
this mode of lighting become introduced into dwelling-houses and streets, a few of 
which in London were lit with gas in this year; while in Paris gas was first 
introduced in 1820. From that year gas-lighting may be said to have become of 
general importance in Europe, and now there is hardly any important place on the 
Continent where it is not in use, while as regards the United Kingdom in no portion 
is gas-making and lighting so general over town and country as in Scotland. 
Among the more recent improvements in this direction are Pettenkofer’s wood and 
peat gas manufacture, and Hirzel’s gas from petroleum residues. The principle of 
gas-lighting is, as has been already stated, the same as that of candles and oil lamps, 
but the raw materials in use for gas-making are not by themselves suited for 
illumination, and it is therein that the great improvement is to be found. 

B Glsufighting° f These are coals, wood, resin, fatty substances, oil, petroleum, and 
water, and according to the material employed the gas obtained is designated as coal 
wood, resin, oil, petroleum, and water gas. 

coal Gas.* I. Coals consist of carbon, hydrogen, oxygen, and small quantities of 
nitrogen, mineral matter, or ash, and contain, further, a larger or smaller quantity 
of iron pyrites. Technically we distinguish in England gas coals, steam coals, and 
household coals. As regards the first—the so-called cannel coals usually excepted— 
they belong to the class termed caking coal, for the reason that this kind of coal 
when submitted to heat softens and becomes agglutinated. According to H. Fleck, 
the best kinds of gas-coals contain upon ico parts of carbon 2 parts of fixed 
( gebundenen ) and 4 parts of disposable ( disponiblen ) hydrogen. Among the best gas- 
coals are the so-called cannel coals, the term cannel being a corruption of candle, as 
in former times pieces of these coals were in some parts of Scotland and Lancashire 
used by the poorer people to burn instead of candles. Cannel coal is chiefly found 
in Scotland and Lancashire, although there exist seams of cannel coal in some of the 
pits of Durham and Northumberland. The Boghead coal, or Torbane Hill mineral, 
is not properly speaking a cannel coal, and will—excepting as specimens in 
museums—soon have disappeared altogether; for gas manufacture it has already 
become quite obsolete. In France and Belgium—in addition to large quantities of 
imported English gas-coals and Scotch cannel—the coals of Mons and Commentry 
are used, while in Germany the Saxony, Silesian, Westphalian, and Bhenish coal¬ 
pits yield excellent gas-coals. Gas-coal should be as much as possible free from 
sulphur, and should further contain only a small quantit} 7- of ash ; but in practice 
these points are less attended to, because the defects of one kind of coal are by good 
gas-makers counterbalanced by the better properties of other kinds. 

1 cwt. (=50 kilos.) of German coals yields on an average 14 cubic metres, or 
500 English cubic feet of gas, and 35 kilos, or 150 parts by bulk of coke. In 
England it is usual to compute the quantity of gas yielded per ton of coals : on an 

* 1 cubic metre = 35*31 English cubic feet. 

40*22 Bavarian ,, ,, 

32*34 Rhenish ,. ,, 

31*65 Vienna ,, ,, 

1000 cubic feet English = 28*31 cubic metres. 

1138 Bavarian cubic feet. 

915 Bhenish ,, ,, 

896 Vienna ,, „ 


ARTIFICIAL LIGHT . 


647 


average the Newcastle coals yield about 9000 to 9500 cubic feet of gas per ton of 
coals ; cannel coals vary in yield-from 10,000 to 12,000; as regards the Boghead variety 
it gave about 15,000 cubic feet of gas, but much depends upon the mode of distilla¬ 
tion and the length of time this operation is continued. It should be borne in mind 
that the best illuminating gas is given off during the first hours of the distillatory 
process; the latter products, though adding greatly to the bulk of the mixture, contain 
much of the comparatively useless gases and diluents. The mode of decomposition 
of the gas-coals may be elucidated by the following diagram, 100 parts of coal con ¬ 
sisting of:— 


Carbon . 

Hydrogen. 

Nitrogen . 

Sulphur .>. 

Chemically combined water 

Hygroscopic water . 

Ash . 


7 8 ‘°1 
• 4-0 

1 ’5 

08 h yield - 
57 
5'0 I 
5 *°j 


Coke . 

Illuminating gas ... 

Tar . 

, Ammoniacal water 


70—75 

30-25 


Products of the Distillation. 

[ Carbon 


IOOO IOO’O 

These may be classified into four chief products :— 
90—95 


. .y^—yo 

I. Coke, j Sulphuret of iron (Fe 7 Ss) ...1 _ 

l Ash . ) 5 


100 


H. 


Ammoniacal 
liquor. 


[ Main constituents, j 


Carbonate of ammonia, 2(NH 4 ) 2 C0 3 +C0 S 
Sulphide of ammonium, (NH 4 ) 2 S 
Chloride of ammonium, NH 4 C 1 
Cyanide of ammonium, NH 4 CN 
Sulphocyanide of am¬ 
monium, NH 4 CNS 


IH. Tar. 


( 

f Fluid. 


Hydro- I 
carbons. 


H 


[ Solid. 


Acids. # 


f Benzol, 

c 6 h 6 

I Toluol, 

c 7 h 8 

I Xylol, 

c 8 h io 

{ Cumol, 

c 9 h I2 

Cymol, 

c io h I4 

1 Propyl, 


l Butyl, 

C 4 H 9 , &c. 

fNaphthaline, 

C io H 8 

I Acetylnaphthaline, 

c I2 h I0 

Fluoren, 

1 ?) 

1 Anthracen, 

c I4 h I0 * 

' Methylanthracen, 

c I5 h I2 

Beten, 

Ci6 H I2 

Chrysen, 

c i8 h I2 

^Pyren, 

Ci6H I0 

^ Carbolic, 

c 6 h 6 o 

Cresylic (cresolj, 

c 7 h 8 o 

Phlorylic (phlorol), 

C 8 H io O 

Rosolic, 

C 2 oHx60 3 

- Oxyphenie, 

C^H.e 0 2 

Creosote, consisting of 

(C 7 h 8 o 2 

three homologous 

j C 8 H io 0 2 

substances, 

Ic 9 h I2 oJ 


\ 


Combinations 
of oxyphenie 
acid and acids 
of methyl 
homologous 
therewith. 


* Has become important as a source of alizarine, in consequence of the discovery of 
Graebe and Liebermann, 1869. 













548 


CHEMICAL TECHNOLOGY. 


III. Tar. 


/'Pyridine, CsH 5 N Leucoline, C 9 H 7 N Coridine, 

Aniline, C 6 H 7 N Iridoline. C I0 H g N Bubidine, 

- Bases, j Picoline, CeHsN Cr} T ptidine, CuHnN Viridine, 
Lutidinc, C 7 H g N Acridine, C I2 H g N 
„ lCollidine, CsHnN 


Asphalte forming compounds 


Antliracen 

Empyreumatic resins 
Carbon. 


Ci 0 H I5 N 

c„h I7 n 

Ci 2 H ig N 


IY. Illuminating 
gas. 


a. Illuminating 
or light-yield¬ 
ing constitu¬ 
ents. 


Gases. 


Vapours. 


( 3 . Diluents, or light- 
bearers. 


y. Impurities. 


I 


Acetylen, C 2 H 2 

Elayl, C 2 H 4 

Trityl, C 3 Hg 

Ditetryl, C 4 H8 

.Benzol, CeHi 6 

Styrolen, CsHs 

Naphthaline, C I0 Hs 


- Acetylnaphthaline, C I2 H I0 
Fluoren, (?) 

Propyl, C 3 H 7 

v Butyl, C 4 H g 

j Hydrogen, 

1 Methylhydrogen, 

^Carbonic oxide, 

Carbonic acid, 

Ammonia, 

Cyanogen, 

Sulphocyanogen 
Sulphuretted hydrogen, 
Sulphide of carbon, 
Sulphuretted hydrocarbons 
^•Nitrogen, 


H 2 

ch 4 

CO 

C 0 2 

nh 3 

CN 

CNS 

sh 2 

S 2 C 

N 


Manufacture of coal Gas. Whether coals, resin, wood, peat, or other materials are 
employed, the manufacture of gas involves the three following chief operations, 
viz.:— a. The obtaining of crude gas by the process of distillation, b. The separa¬ 
tion of tarry and other condensable matters, c . The purifying of the crude gas so 
as to render it fit for use. 

a. The distillatory process or making of crude gas is effected by the application of 
a high temperature—above red-heat—and exclusion of air, and is carried on in 
vessels which are technically termed gas retorts or simply retorts. 

Retorts. The retorts were in the earlier days of gas-lighting always made of cast- 
iron and of cylindrical shape, but for the last twenty years fire-clay retorts have 
become very generally used, though they have not altogether superseded the use of 
cast-iron retorts, which were found inconvenient for only two reasons, Viz., for 
wearing out too rapidly, and for not admitting of being raised to the very high 
orange-heat, which has been adopted for the distillation of some kinds of cannel 
coals. As regards the size of the retorts, this varies according to the requirements 
of the works, but generally the retorts are sufficiently large to hold ioo kilos, of coal, 
leaving from 0 5 to o*6 of the interior space unfilled f<y the purpose of affording 
room for the expansion of the coals. The diameter of such a retort is about 
54 centimetres in the larger axis, and 43 to 45 centimetres in the smaller axis, by a 
length of 2 - 5 to 3 metres. One end of the retort is usually closed, although in some 
large gas-works, as at Edinburgh, Glasgow, Paisley, fire-clay retorts of very great 
length and open at both ends are in use, being fired by two furnaces situated at each 
end. In some of the London gas-works, retorts are in use not made of fire-clay, in 












ARTIFICIAL LIGHT. 


649 

one or more pieces, but built up with fire-bricks or slabs of fire-clay, of a peculiar 
shape, and made for the purpose in Wales; these slabs are put together with a 
cement of pure quartz sand and about 1 per cent of lime, or a clay which becomes 
pasty and adhesive in very great heat. Retorts of this kind are cheaper and stand 
five years wear. Retorts made of heavy boiler-plate rivetted together, as well as 
forged iron retorts, welded together like the iron mercury bottles, are also in use, but 
of course aie, in the furnaces, protected from the direct action of the fire by properly 
built arches and coverings of fire-bricks. 

Mou Me?orts. d Lid The retorts are always fitted with a separate mouth-piece, to which 
during the process of distillation the lid is fastened; this mouth-piece is always 
made of cast-iron, even in the fire-clay retorts, to which it is fitted by a flange on the 
retort, the flange of fire-clay being provided with six to eight holes for putting in the 
screw bolts for the purpose of making a good joint. In order to get a gas-tight joint 
a mixture of iron filings and gypsum is used, which is made into a paste with an 
aqueous solution of sal-ammoniac. The mouth-piece is fitted with a short tube for 

Fig. 283. Fig. 284. Fig. 285. 



the purpose of giving vent to the gases and vapours evolved during the distillation 
As the mouth-piece is placed outside the furnace, it is generally of longer duration 
than the retorts, and these are moulded to suit the mouth-piece. 

Fig. 282 exhibits the front view of a mouth-piece of a Q-shaped retort. Fig. 283 
exhibits a section, b is the opening at the retort end ; n is the lid for closing 
the retort during the distillation. At ss, Fig. 282, are seen the cast-iron eyes 
intended to support the malleable iron bars for the support of the lid. 00, Fig. 283, 
is the flange wherewith the mouth-piece is fitted to the retort, d is the short piece 
of tube. Fig. 284 is a front view of the cast-iron lid of the retort; and Fig. 285, a 
view of the side of the lid turned towards the retort. As will be observed, the lid fits 
accurately into the opening of the retort. The method of closing or rather tightly 
fastening the lids of gas retorts is exhibited in Fig. 286, being a side view of 
the mouth-piece, mm are the malleable iron bars on which the lid is supported by 
means of the projections, nn , Fig. 284. Through the bars mm are cut openings, 
through which the cross-b[y 7? is put, and in its centre a hole with screw thread, into 
which is made to fit a screw-bar and handle, a. By turning the screw, the lid is 
forced tightty against the rim of the mouth-piece ; but in order to secure a gas-tight 
joint, a lute is used consisting of some clay or spent purifier lime and clay mixed. 

Another mode of fastening the lid is exhibited in Fig. 287, being also a side view. 
The bars mm are in this instance bent at one end where the cross-bar a is 
to be placed. To that cross-bar is fitted at right angles another bar, h, provided 



















CHE MIC A L TE CHNOL 0 G Y. 


550 

at one end with a heavy iron ball, and at the other with a knee-bend, so that by 
pulling the ball downwards the lid, n, is tightly fastened. 

Retort Furnaces. The retorts are placed in a furnace in the manner exhibited in 
Fig. 288, that is to say they are placed horizontally and supported by brickwork— 
technically benches. The mouth-piece projects from the furnace, each of which may 
contain two to three, five to seven, or even twelve to sixteen retorts, as in large gas¬ 
works, in which case the lower rows are of fire-clay, the higher of iron.. 


Fig. 286. Fig. 287. 



chargin^the Retorts, and The retorts are in some works charged by means of a large 
scoop, which being filled with the quantity of coals the re'tort is intended to be 
charged with, is carried by four men and then lifted into the retort, and being over¬ 
turned fills the retort, after which the scoop is withdrawn and the lid of the retort 
fastened on. But in many gas-works the coals are thrown into the retorts with shovels. 
As soon as the retorts, which previously to being filled are alwaj^s heated to red- 
heat or higher, are charged, and the lids closed, the evolution of gas is very strong, 
and continues so for some time, until after some four to five hours the distillation is 
finished, or at least the gas then given off is not worth collecting. In Scotland the 
distillation is not continued so long, three or three and a half hours being deemed, 
with good firing, quite- sufficient, cannel coals giving off their gas more freely than 
caking coals. The lids are now loosened and the gas at the mouth of the retorts 
kindled in order to prevent explosion by its becoming, as would be the case if 
the lids were at once removed, mixed with air. The red-hot coke left in the retort is 
raked out and at once used for firing the furnaces, or put into iron wheelbarrows 
and wheeled out of the retort-house into the yard, there to be quenched with water 
and kept for sale. Cannel coals do not as a rule yield a good coke, but only broken-up 
black shaly breeze, which, however, along with some dead oil, is used in the Scotch 
gas-works for heating the retorts. On an average one-third of the coke obtained is 
required for firing the retorts. 

The Hydraulic Main. We understand by the hydraulic main a vessel with which are 
connected the ascending tubes leading from the retorts. As a rule the hydraulic 
main is placed on the top of the furnace in which the retorts are ignited. The 
diameter of the ascending tubes varies of course with the size of the retorts, but is on 
an average 12 to 18 centimetres. The hydraulic main, of which b, Fig. 288, is 
a section at right angles to the longitudinal axis, is a wide pipe of cast-iron or 
of boiler-plates rivetted together, and having an average diameter of 30 to 60 
centims. It is either cylindrical or Q-shaped, and extends over the entire length of 
the row of furnaces. The hydraulic main is intended to act as a receiver for all the 









ARTIFICIAL LIGHT, 


651 







Fig. 288. 






































































































































CHEMICAL TECHNOLOGY. 


65.2 

volatile products of the distillation, while at the same time it affords to every single 
retort a hydraulic valve, shutting it off from the other retorts, and preventing 
effectually any gas finding its way back to the retorts when opened at the mouth. 
The mode of connection between the retorts and the hydraulic main is shown in 
Fig. 289. a is the ascending tube; b the saddle-pipe; c the dip-tube carried down¬ 
wards into the hydraulic main; d is the main ; and m the liquid—viz. tar, or at the 
first starting of a gas-work, water. Fig. 290 exhibits a somewhat different mode of 
connecting the retorts and hydraulic main. There is fitted to this main a syphon 
tube for running off the excess of tar to the tar cistern, and on the top of the main 
is, as exhibited in Fig. 288, a wide iron tube for carrying off the gas to the 
condensing apparatus. 


Fig. 289. Fig. 2go. 



c°°iii^or condeiising ^ The volatile products of the distillation which are not con¬ 
densed in the hydraulic main are carried off with the permanent gases. The reader 
should observe that a comparatively very high temperature prevails in the ascending 
tubes and hydraulic main. These volatile products are gas, steam vapours of tar, 
the steam containing in solution and suspension various ammoniacal compounds. 
Before the gas can be purified it has to be cooled and deprived of a number of sub¬ 
stances which are in fact impurities, inasmuch as they would impede the flow of gas 
through the pipes if they were not got rid of. The condensing process may be carried 
on in various ways, but on the large scale the most efficient is the very simple 
expedient of causing the gas to pass through a series of cast-iron pipes, as exhibited 
in Fig. 291, in vertical section; also in d. Fig. 288. These tubes, placed in the open 
air—in warm climates or in hot summer weather arrangements being made to cool 
the pipes externally by a stream of water—are connected with each other at 
the top, and rest in a large cast-iron tank, p, which by means of partitions is 
divided into compartments not communicating with each other, being hydraulically 
















ARTIFICIAL LIGHT. 


653 

locked. Each compartment is fitted with an inlet, m, and an outlet, n. In this tank 
the gas-water or ammoniacal liquor and tar are collected, while the height these 
fluids should occupy in the tank is regulated by a tube, d, or as seen in Fig. 288, at m 
by a syphon tube. The condensed liquids flow to the brickwork tank, q, and thence 
to the tar cistern. The inlet tubes dip to some depth into the fluid so as to force the 
gas to pass through it. The size, number, and height of these condensing tules 
depends on the quantity of gas which has to be cooled in a given time; on an 
average 50 to go square feet of surface of tubes is allowed for 1000 cubic feet of gas 
to be cooled per hour. 

The Scrubber. In many of the larger gas-works the gas, after it has issued from the 
tube condenser, is passed through an apparatus termed the scrubber, for the purpose 
of more completely depriving it of tarry matter before sending it on to the purifiers, 


Fig 2gi. 



and also for getting rid of the ammonia and sulphur compounds. The rationale of 
the mode of action of the scrubber is similar to that often employed on a minute 
scale in practical chemistry, when a gas or vapour is passed through a glass tube 
filled with pumice-stone, so that in a limited space a great surface is provided. 
The scrubber consists of cylindrical cast or malleable iron chambers of sufficient 
size, and filled with lumps of coke or fire-brick, which are constantly moistened with 
water. Fig. 292 exhibits a sectional view of a scrubber, also seen in Fig. 288 at 00. 
The cylinder has a diameter of ik to i§ metres, by a height of 3 to 4 metres; 
the vessel is filled with coke, which is kept moist by means of water introduced by 
the rotating perforated tube, h. The inlet of the gas is at i; it proceeds upwards 
through the column of coke and on reaching the top passes off downwards through 
m to the second scrubber. At the lowest bend of the exit or outlet tubes a 
syphon pipe is fitted for the purpose of draining off water and tarry matters whidh 















































CHEMICAL TECHNOLOGY. 


C>54 

collect 111 the reservoir, m. The use of the scrubber—the gas hardly requires any 
additional pressure to be carried through it—effects a saving of the purifying 
materials, lime, &c„ by causing the gas to be thoroughly washed and cooled; 
in other terms—mechanically purified. 

Exhauster. This apparatus, also termed the aspirator, is placed between the 

hydraulic main, being connected with the gas leading pipe, or between the 
condensers and the purifiers. It is intended 
to suck or pump the gas from the retorts so as 
to diminish their internal pressure. This 
pressure amounts in some cases to nearly 
15 lbs. to the square inch, and it was found 
that under that pressure a great deal of gas 
was lost through the pores of the fire-clay 
retorts, especially when new, being then not 
coated with a film of graphite which after¬ 
wards acts as an impermeable layer. The aspi¬ 
rators also serve to remove the gaseous 
mixture as rapidly as possible from the red- 
hot retorts and coke, and thus prevent the 
partial decomposition of valuable illuminating 
constituents of the gas, by which decompo¬ 
sition, moreover, the retorts, iron as well as 
fire-clay, become lined with a graphite-like 
coke, which impairs the conducting power for 
heat, as well as decreases the internal cubic capacity of the retorts. The intro¬ 
duction of exhausters dates from 1839, when Grafton made and tried the first. His 
arrangement was—a box filled with water for about three-fourths of its capacity, 
while in the box, on an axis projecting outside, through gas- and water-tight stuffing 
boxes, four circularly-bent scoops were fixed, so that on a rotating motion being 
imparted to the axis, and thereby to the scoops, a partial vacuum was formed, and the 
gas inspired into the apparatus, and thence carried off by side tubes. This apparatus 
has never been of any practical use in gas-works. Next, the so-called bell 
exhauster was used; the principle of this apparatus—similar in construction to 
that in use in paper mills—being in reality nothing else than a hydraulic air- 
pump, consisting of two or three large bell-shaped iron vessels, connected together 
and placed in tanks filled with water, and moved slowly upwards and downwards by 
mechanical power. Under each of these bell-shaped vessels an inlet and outlet 
pipe is fitted provided with valves. There have been a great many variously 
constructed exhausters proposed; some of these, Anderson’s for instance, are 
similar to the cylinder blowing machines in use with blast furnaces; others 
again are similar in construction to the double-acting air-pumps of low-pressure 
marine steam-engines; some to centrifugal pumps. With the fire-clay retorts, 
now very generally adopted in gas-works, the use of exhausters is almost a 
necessity, and the apparatus is always fitted up with new gas-works. Of course an 
accessory of the exhauster is a small steam-engine and boiler. 

Purifying Gas. C. The crude gas having been passed through the apparatus just 
described, and mechanically purified, is sent on, as it is technically termed, to the 
purifiers, in order to eliminate by chemical means such substances as sulphuretted 


Fig. 292. 



















ARTIFICIAL LIGHT. 


655 

hydrogen, carbonic acid, and various ammoniacal compounds, carbonate of ammonia, 
sulphuret of ammonium, cyanide of ammonium, &c.; and also some of the compound 
ammonias, as, for instance, aniline, iridoline, &c. At the outset of the gas-lighting 
industry, quick-lime was the only material employed for purifying purposes, this sub¬ 
stance being at first employed in the form of a thick milk of lime, the purifier being 
so constructed that the crude gas was brought into intimate contact with the fluid, 
which, in order to prevent the lime from forming a sediment, was kept in constant 
motion by a stirring apparatus; while the purifier, made of cast-iron, was provided 
with inlet and outlet pipes for the gas, a pressure gauge, and the necessary syphon 
pipes and valves for letting out the waste milk of lime and re-filling the vessel. 
Variously arranged wet lime purifiers have been devised, and among them some 
which act also as exhausters; but notwithstanding the very satisfactory results 
obtained by the use of wet lime purifiers, the gas being very effectually freed from 
carbonic acid, sulphuretted hydrogen, and ammonia, there is the defect—first, of 
the back pressure on the retorts and other apparatus; and secondly, a difficulty 
in the mode of so disposing of the very foetid waste lime liquor as not to create a 
nuisance; hence it is that the wet lime purifiers have been almost entirely super¬ 
seded by the so-called dry lime purifiers. These are large square iron boxes fitted 
inside with movable trays resting on ledges and provided with sieve-like perforations, 
and either made of iron gratings or iron plates, or even wooden boards, on which the 
previously slaked and somewhat moist lime is carefully placed in layers of uniform 
thickness to a height of 20 centimetres, there being in every purifier box from five to 
eight frames. The purifier is usually divided into two compartments by a partition, 
so that the gas which enters from the bottom of one compartment has to ascend 
through the layers of lime of the inlet compartment, and to descend through those of 
the outlet compartment. The gas passes through the layers of dry lime readily 
enough and almost without producing any back pressure, and there is no hecessity 
to render the lime more porous by the addition to it of either moss, sawdust, chopped 
straw, &c. As to the quantity of lime required for the purpose of purifying a cer¬ 
tain volume of gas, it is stated that for 1000 cubic feet of crude gas from 
Newcastle coals, 2‘6 kilos, of unslaked quick-lime are required. With careful 
selection of the gas-coals to be carbonised, and a well-conducted distillation and 
mechanical purification of the crude gas, the lime purifying process, especially 
if wet and dry purifiers both are used, as is the case in some of the largest gas¬ 
works in Scotland, yields excellent results, and there is no need for any other 
purifying materials; while the spent lime, as is the case in Scotland, is found useful as 
a manure, as well as for building purposes with some fresh lime and sand. It is, how¬ 
ever, true that in many places the gas thus made is too impure for use in dwelling 
houses, and a more complete elimination of the ammonia and some of the sulphur 
compounds is found to be absolutely necessary. Since 1840 an immense number of 
gas-purifying materials and contrivances have been brought forward and tried but 
again abandoned. It is entirely beyond the scope of this work to enter into more 
than a very slight sketch of the various gas purifying processes; but we give the 
following particulars on this subject. 

It cannot create any surprise when we find that acids and metallic salts should have 
been called in to aid the absorbing of the ammonia and sulphuretted hydrogen from coal- 
gas. Protosulphate of iron has been here and there resorted to, of course in aqueous 
solution. Mallet (1840) commenced the use of the residue of the chlorine manufacture, 
crude chloride of manganese, for the same purpose. Far more important is the method 


CHEMICAL TECHNOLOGY. 


656 

first suggested in 1847 by R. Laming, and now generally known as the Laming puri¬ 
fying process. As originally patented, the mixture was composed of protochloride of iron 
with quick-lime or chalk, and in order to keep the mass porous sawdust was added. 
Instead of protochloride of iron, sulphate of iron is now more generally used, and mixed 
with previously sifted and slaked lime, and one-fifth to one-fourth of its bulk of sawdust. 
The mass is then placed in beds or layers exposed to open air, moistened with water, and 
is, after twenty-four hours, fit for use in the same apparatus as is employed in the dry lime 
purifying process. According to the results of the scientific researches of A. Wagner 
(1867), Gelis (1862), of Brescius, Deicke, and others, the peroxide of iron of the Laming 
mixture becomes converted by the sulphuretted hydrogen into sesquisulphuret of iron 
(Fe 2 S 3 ), and by exposure to air—revivifying process, for which purpose old purifiers are 
used, air being forced through—the sulphur is separated again, and oxide of iron 
mechanically mixed with sulphur is left. This mixture may be used several times, and 
as mentioned in the earlier pages of this work, the sulphur may be advantageously 
extracted from this mixture. Gauthier-Bouchard, at Paris, has proved that the spent 
Laming mixture may be used on the large scale for manufacturing Berlin blue and yellow 
prussiate of potash ; while Menier, at Marseilles, prepares annually 12 to 15 tons of sulpho- 
cyanide of ammonium from the spent gas-purifying materials. Very recently (1869) the 
proposition has been made to withdraw the benzol contained in illuminating gas by 
passing the gas through heavy oils of tar, from which the benzol, to be used for aniline 
making, is to be separated by fractioned distillation, and the gas again rendered luminous 
by passing it through benzoline, light petroleum spirit. It is evident that considering the 
great bulk of gas to be operated upon, this proposal or suggestion will be difficult to carry 
out in practice, and also costly in consequence of the apparatus required. 

Gas-hoiders, These apparatus, sometimes but less correctly termed gasometers, 
serve as well for the purpose of storage of the great bulk of the gas as for causing a 
sufficient pressure, so as to regulate its flow through the street mains and burners. 
The gas-holder consists of three parts, viz.:—1. The tank, a cylindrical water-tight, 
more or less deep vessel, with vertical sides, filled with water as a hydraulic lute. 
2. The bell, or rather inverted cylinder, which can move freely between the stand- 
pillars by the aid of grooved rollers or pulleys, which work on iron bars fitted 
against the stand-pillars. 3. The large inlet-pipe which communicates with the 
purifiers, and the outlet-pipe which communicates with the street mains, each being 
supplied with valves and syphon-boxes for the purpose of collecting any water 
which might condense or otherwise find its way into these pipes. 

The tank was in former days made of wood, then, when the size of the gas-holders 
was increased, of cast-iron plates fitted with flanges provided with holes for 
screw-bolts, the joints being filled with cement so as to make a water-tight vessel. 
Now the tanks are constructed by digging to a greater or less depth into the soil, the 
bottom and sides being laid in brickwork with a water-tight cement backed by a 
puddling of clay. I11 some few cases the tank is constructed as exhibited in Fig. 293, 
where a cone remains covered by brickwork, but as water is generally plentiful, and 
is less costly than the expense attending this arrangement, it is not usual. The 
bell or holder is always made of sheet-iron plates rivetted together, care being taken 
either to put red-lead putty, or brown paper soaked with red-lead paint or thick 
boiled tar between the overlappings of the plates so as to obtain good joints. The 
plates are inside and outside painted with iron-paint or coated with boiled coal-tar. 
Formerly, with gas-holders of a capacity varying from 30,000 to 80,000 cubic feet 
the bell was suspended by means of iron chains led over pulleys fastened to the 
stand-columns and provided with heavy weights for the purpose of counterbalancing 
the too great weight of the iron-holder and to regulate the pressure exerted upon the 
gas; but with the very large holders now in use. and the practice of building them 
of thinner iron plates, the holders are simply made to move freely between the 
stand-columns as exhibited in Fig. 293. In order to gain space with the same depth 


ARTIFICIAL LIGHT. 


657 




a hydraulic lute. The inlet and outlet mains are of cast-iron, and open just a few 
inches above the level of the water in the tank (Figs. 288 and 293). A peculiar 
construction of gas-holder, invented by Pauwels, at Paris, and in use in some of the 
gas-works of that city, is exhibited in Fig. 294. The inlet and outlet pipes, a and b y 

Fig. 294. 


are in this gas-holder connected with the roof, and consist of several pieces with 
joints fitted with gas-tight stuffing-boxes, the arrangement being readily understood 
from the engraving. The advantage is that all chance of flooding of the inlet and 
outlet pipes is prevented, but the arrangement is expensive and not compatible with 
telescopic gas-holders ; moreover, the level of the water in the tanks of gas-holders 
43 


of tank, the so-called telescopic gas-holders are constructed, being, in fact, one or more 
cylinders fitting into each other and capable of sliding upwards and downwards, the 
topmost cylinder only being fitted with a roof, while a gas-tight joint is obtained by 


Fig. 293. 














































CHEMICAL TECHNOLOGY. 


658 


is rarely, if ever, subject to any great increase in height, because a drain-pipe i? 
fitted to the upper rim of the tank for carrying off rain-water. Gas-engineers well 
enough know that it is difficult in many cases to prevent leakage from tanks so 
effectually that there should be much risk of the sudden flooding of the inlet and 
outlet pipes by a rush of water. Small gas-holders are often provided with a scale, 
the divisions of which correspond to certain quantities of cubic measure; but large 
gas-works are nearly all fitted with a station-meter, through which all the gas made 
has to pass previous to entering the gas-holders, and by means of this meter a 
control is kept over the quantity of gas made. The cubic capacity of every gas-holder 
is of course accurately known. The size of the gas-holders varies; some at very 
small works, for villages, railway-stations, county-seats, &c., are only 1000 to 3000 
cubic feet capacity, while there exist gas-holders of enormous size, 45 metres diameter 
by 20 in height, which contain 1 million cubic feet. According.to Riedinger’s rule, the 
cubic capacity of a gas-holder should be equal to 2 to 2I times the average daily 
quantity required. 

The filling of a gas-holder is proceeded with in the following manner:—The outlet 
main-pipe having been shut off by the closing of the valve fitted to it, gas is admitted 
through the inlet-main into the holder ; the gas accumulating in the latter exerts a 
pressure upon the water in the tank, which consequently is depressed inside the 
holder and rises higher outside it, while gradually the holder is lifted by the force of 
the gas, the inlet valve being shut off as soon as the holder is filled to within about 
20 centimetres of its height. When the outlet valve is then opened the gas flows into 
the street mains, the pressure being obtained from the weight of the holder. In 
order to ascertain the quantity of the gas made, it is measured by a large gaso¬ 
meter, technically termed a station-meter, and placed between the purifiers and 
the inlet to the gas-holders. The construction of these station-meters is very similar 
to that of the ordinary wet gas-meters. 

Very little is known as to the composition of the gas at the different stages of its 
manufacture from the moment it enters the hydraulic main to the moment it enters 
the street mains. The experiments of Firle, made at Breslau in i860, are very 
valuable, but only relate to a special inquiry. 

Firle tested coal-gas:— [a] after it left the condenser; (b) after it left the scrubber: 
(c) as taken from the washing-machine; (d) as taken from the purifier containing 
Laming s mixture; ( e ) as taken from the lime-purifier, consequently thoroughly 
purified gas as sent into the holder :— 


Hydrogen. 

Marsh-gas. 

Carbonic oxide. 

Heavy carburetted hydrogens 

Nitrogen . 

Oxygen . 

Carbonic acid . 

Sulphuretted hydrogen ... 
Ammonia. 


a. 

6 . 

c. 

d. 

e. 

37'97 

37*97 

37*97 

37*97 

37*97 

3978 

38-81 

38-48 

40-29 

39*37 

7'2I 

7 *i 5 

7 *n 

3*93 

3*97 

4-19 

466 

4*46 

466 

4-29 

4 ’8 i 

4*99 

6’89 

7-86 

9*99 

031 

°*47 

0*15 

0*48 

061 

372 

3*87 

3*39 

3*33 

0-41 

ro6 

r 47 

0-56 

036 

— 

°'95 

o *54 

— 

— 

— 

taking 1000 cubic feet of crude gas as the unit 




ARTIFICIAL LIGHT. 


659 


Cubic feet. 


-- 1 -, 


Hydrogen . 

a. 

... 380 

6. 

380 

c. 

380 

d. 

380 

e. 

380 

Marsh-gas . 

... 390 

388 

384 

403 

394 

Carbonic oxide . 

... 72 

71 


39 

30 

Heavy carburetted hydrogens 

... 42 

46 

45 

46 

43 

Nitrogen . 

... 48 

50 

69 

79 

100 

Oxygen. 

3 

5 

2 

5 

6 

Carbonic acid . 

... 40 

39 

34 

33 

4 

Sulphuretted hydrogen 

... 15 

15 

5 

3 

— 

Ammonia . 

... 10 

5 

— 

— 

— 


1000 

999 

990 

988 

9 66 


The above results exhibit the changes which the composition of the gas undergoes 
during the purifying process as well as the action of the different apparatus. When 
1000 cubic feet of gas composed as stated in (a) enter the purifying apparatus, in 
each of these there is taken up of the absorbable gases, chiefly carbonic acid, 
sulphuretted hydrogen, and ammonia, the under-mentioned quantities :— 

For 1000 cubic feet in cubic foot measure:— 


Washing- Laming’s 
Scrubber, machine, purifier. 


Lime- 

purifier. 


Carbonic acid . 1 

Sulphuretted hydrogen ... — 

Ammonia . 5 

Carbonic oxide. — 

Oxygen . — 


5 

10 

5 

3 


1 

2 

32 


29 

3 


The original bulk of the gas decreases consequently steadily, and there remain of 
1000 cubic feet of crude gas after leaving:— 


The scrubber . 994 cubic feet. 

The washing-machine . 971 „ „ 

The Laming’s purifier . 936 „ „ 

The lime-purifier . 914 „ „ 


This is correct, premising that the other constituents of the gas are unabsorbed, 
which really is so, as we may neglect the very small quantities of marsh-gas and 
heavy hydrocarbons, which are kept mechanically arrested in each purifying appa¬ 
ratus. The bulk of the gas is, however, slightly increased by an addition of 
atmospheric air. 1000 cubic feet of the crude gas (a) contain 51 cubic feet of oxygen 
and nitrogen; this quantity is increased:— 


In the scrubber by . 

. 4 

In the washing-machine by ... 

. 20 

In the Laming’s purifier by ... 

. 33 

In the lime-purifier by . 

. 55 


4 cubic feet. 


By this addition the total bulk of the gas in each apparatus is again increased, and 
amounts (taking account of the variable quantity of marsh-gas and heavy carbu- 
retted hydrogen compounds) for 1000 cubic feet unit quantity:— 







66 o 


CHEMICAL TECHNOLOGY. 


After leaving the scrubber, to . 999 cubic feet. 

„ „ „ washing-machine, to . 990. „ „ 

„ „ „ Laming’s purifier, to . 988 „ „ 

„ „ „ lime-purifier, to. 966 „ „ 

It is understood that temperature and pressure remain constant during the puri¬ 
fying process. 


Distribution of Gas. Generally, in the United Kingdom, and as regards coal-gas also 
abroad, the gas is conveyed to the localities where it is to be burnt by means of cast- 
iron pipes laid underground. But so-called portable gas [gas portatif) is still 
made abroad and conveyed to the consumers in large gas-tight bags placed in cars, 
the bags being emptied at the houses of the consumers into small gas-holders. The 
materials from which this kind of gas is made are generally such (refuse of oil, oil of 
bones, very crude olive oil, resins, &c.) as yield a gas of far higher illuminating power 
bulk for bulk than coal-gas, so that a comparatively small bulk of gas will suffice for 
even a large number of burners. The pressure exerted upon the gas in the holders 
causes it to move through the pipes. The amount of this pressure is, however, 
usually regulated at the works by a peculiar mechanical contrivance, so as to make 
it as uniform as possible over the total length of the mains and service-pipes. Coal- 
gas being lighter than air has a tendency to rise, and for this reason it is considered 
preferable to build gas-works at the lowest level of the locality it is intended to 
supply, because a less pressure is sufficient for moving the gas through the mains. 
The pressure at the burners should be. from 0*05 to o'15 of an inch’, water-gauge 
pressure, while at the gas-works a pressure of 2! to 5 inches (water-gauge) is quite 
sufficient to force gas to any distance within a circuit of several miles. 

The street mains are made of cast-iron, and laid under the pavement at a suitable 
depth, varying from o '6 to i*6 metre. The service-pipes in England and on the Con¬ 
tinent are of malleable-iron or of lead, but in Scotland cast-iron pipes (even quarter 
and half-inch) are preferred and in general use. The large mains are put together 
by placing the spigot into the socket-end of each pipe alternately, and caulking in 
greased or tarred tow and pouring in molten lead. In Scotland the mains are now 
generally put on the lathe, and the spigot and socket ends turned true, so as to give 
a gas-tight joint simply by the aid of some red-led paint and putty and a collar of 
soft greased tow. Although carefully laid, the gas-mains give rise to more or 
less loss by leakage, which is stated to amount in some instances to 15 or 20, and 
even 25 per cent of the gas made and sent into the mains; but if street mains are 
cast vertically and the iron be of good quality, each pipe properly tested by hydraulic 
pressure for its soundness before being laid, and, moreover, first immersed in hot 
coal-tar and the joints well secured, leakage may be very much reduced, if not 
altogether prevented. The mains should have a sufficiently large bore for the 
quantity of gas to be conveyed through them, so as to reduce friction. They are not 
laid quite level even in level streets, but slope gently; while at the lowest level 

so-called syphon-pots are placed for the purpose of collecting any condensed water_ 

the gas is almost saturated with water by being in contact with it in the gas-holders, 
although after some time a thin layer of empyreumatic matter covers the surface of 
the water, thereby preventing the gas becoming excessively saturated. These 
syphon-pots are fitted with a narrow iron tube reaching nearly to the surface of the 
pavement, being closed by a screw-cap, which, being unscrewed, a hand-pump may be 
screwed on, and any condensed water pumped out of the syphon-pot or box. For tho 


ARTIFICIAL LIGHT. 


661 


purpose of connecting the burners with the service-pipes narrower tubes are used, 
made either of pure block-tin or of an alloy of lead and tin or of lead and copper ; 
the latter are, however, not so readily bent, and have the disadvantage that there 
may be formed in them acetylen-copper, "which, as proved by Crova, is a very explo¬ 
sive compound. • 


Fig. 295. 


Hydraulic Valve. The valve represented in Fig. 295 is now almost superseded by valves 
of a totally different description, termed slide-valves, and worked s im ilarly to 
those in use for the water-mains common in London 
streets. The valve represented in the engraving 
is placed near the gas-holders, and may serve either 
for shutting off the inlet-pipe to the holder or for 
the same purpose at the outlet-pipe. The valve con¬ 
sists of an iron vessel, iklm, filled with water. The 
pipe a communicates with the gas-holder and b 
with the street main. The drum-like vessel, cefd, is 
suspended over the pipes and is counterbalanced by the 
weights x and y. When the latter are removed the drum 
sinks, and the partition h, dipping in the water, cuts off 
the communication between a and b. 

Pressure Keguiator. This contrivance, acting automati¬ 
cally, is arranged for the purpose of regulating the 
supply of gas from the gas-holders to the mains. It 
consists essentially of a small gas-holder connected with 
a conical valve placed in the outlet-pipe, while the small 
gas-holder to which it is fastened is very accurately 
adjusted, or provided with counterweights, by means of which its position may be set at a 
certain supply either per hour or evening, as the case may be. If from some cause or 
other the consumption of gas increases the gas-holder will sink, and the opening in 
which the conical valve plays becomes larger, and consequently more gas passes through; if, 
on the other hand, the supply decreases, the consequence will be that too much gas enters 
the small holder from the large ones, and the former rising draws the conical valve with it 
upwards, thus more or less completely plugging the outlet-pipe. • 



Testing illuminating Gas. The cause of the luminosity of the flame of gas is the ignited 
carbonaceous matter. Everything, therefore, which impairs the separation of the 
carbonaceous matter or chemically affects their proper ignition, decreases the 
luminosity of the flame; among these deteriorating causes are:—1. Excessive 
admission of air or of oxygen. A coal-gas flame burning in oxygen will be found to 
have lost its luminosity, and the same occurs, as is well known and exhibited in the 
Bunsen gas-burner, when gas is mixed with air previous to being ignited. 2. Car¬ 
bonic acid. When red-hot or white-hot carbonaceous matter comes into contact 
with carbonic acid, there is formed carbonic oxide (C0 2 -f-C=2C0), which burns 
with a blue, non-luminous flame. As elayl-gas (C 2 H 4 ) becomes decomposed by red 
heat into methyl-hydrogen (marsh-gas, CH 4 ) and carbon (C), and as the latter 
reduces an equivalent quantity of carbonic acid to carbonic oxide, it is evident that 
the carbonic acid deprives half its bulk of elayl-gas of its illuminating power. Sup¬ 
pose an illuminating gas to contain 6 per cent of elayl-gas, and also 6 per cent of 
carbonic acid gas, the result will be the elimination of the luminosity of 3 per cent 
of elayl-gas. This proves the great importance of. the complete removal of carbonic 
acid from gas by the lime-purifier. 

Very little has been experimentally proved as to the relation existing between the 
illuminating power of a flame and the quantity of the separated carbonaceous 
particles ; it is probable, however, that this relation is a direct one, and that there¬ 
fore the luminosity of a flame is the stronger the larger the quantity of carbonaceous 
particles separated, provided, however, that the temperature of the flame be very 
high, because otherwise the flame will be either ruddy or smoky. Although by an 
























662 


CHEMICAL TECHNOLOGY. 


increased access of air (as in the case of petroleum lamps provided with a glass 
chimney) the combustion may be increased so as to create a very high temperature 
of the flame and thereby a very white light, it is probable that this expedient (espe¬ 
cially if applied to ordinary coal-gas) would cause a too sudden combustion of the 
carbon/rendering it useless for illuminating purposes. Supposing the illuminating 
power of a flame to be proportional to the quantity of carbonaceous particles sepa¬ 
rated, and applying this principle to some of the carburetted hydrogens occurring in 
purified illuminating gas, taking account more particularly of the gases (CH 2 ) so 
composed that by ignition they become decomposed into methyl-hydrogen and 
carbon, we have:— 

Yol. Vol. Yols. 

i elayl, C 2 H 4 , which yields ro of metliyl-liydrogen and 2 of vapour of carbon. 

1 trityl, C 5 H 6 , „ „ 1*5 „ „ „ „ 3 » » 

1 ditetryl, C 4 H 8 , „ „ ro „ „ „ „ 4 „ „ 

and may assume the illuminating power of these three gases to be as 2:3 : 4. Taking 
the illuminating power of elayl-gas to be 100, the illuminating powers of the gases and 
vapours contained in purified coal-gas may be represented by the under-mentioned 
figures, the vapours having been calculated at a sp. gr. = o°:—Elayl, 100; trityl, 150; 
ditetryl, 200; propyl, 250; butyl, 350; acetylen, 450; vapour of benzol, 450; 
vapour of naphthaline, 800. 

The following figures exhibit the quantity of elayl-gas, for which can be substituted 
a combustible gas (hydrogen or marsh-gas) impregnated with the vapours of hydro¬ 
carbons at o° and 15 0 for yielding an equal amount of light. Impregnation with— 

At o° 

‘Vapour of propyl, is equivalent to 
,, ,, benzol, ,, ,, ,, 

„ „ naphthaline, ,, „ „ 

When, therefore, 100 litres of hydrogen at o° or at 15 0 are saturated with vapours 
of benzol, the illuminating power of the resulting mixture is equal to that which 
would ensue by mixing 100 litres of hydrogen with g 6 or 23*5 litres of elayl-gas. 

In order to saturate 100 English cubic feet of hydrogen- or marsh-gas with vapours 
of hjrdrocarbons, there are required of 


11-500 

9630 

o’ii6 


At 15 0 
25-700 vols. elayl. 
237 °° » » 

00016 „ „ 



At o°. 

At 15 0 . 

Vapours of propyl ... 

. 500-00 

112800 

„ „ butyl 

. 1700 

58-00 

„ „ benzol 

. 214-50 

52200 

„ „ naphthaline 

. 0-32 

0-32 


For the purpose of carburetting hydrogen-gas with vapours of benzol to saturation, 
2145 grms. of benzol at o°, and 5220 grms. of the same at 15 0 , would be required 
for 1000 cubic feet of gas. 

rnumtoafmYaSf In order to ascertain the relative value of illuminating gas four 
different modes of testing are now in practical use, viz.:—1. Gasometrical test. 
2. Specific gravity test. 3. Photometrical tests. 4. Erdmann’s gas-testing apparatus. 

1. The gasometrical test requires for its proper management an accurate know¬ 
ledge of Bunsen’s method of gas analysis.* Be it sufficient for our purpose here to 

Anleitzung zu einer technischen Leuchtgasanalyse giebt Adolf Richter; Dingier’a 
polyt. Journal (1867), Bd. clxxxvi., p. 394. 


ARTIFICIAL LIGHT. 


663 

mention that a mixture of anhydrous sulphuric acid and ordinary concentrated oil of 
vitriol has the property of absorbing the heavy hydrocarbons contained in illumina¬ 
ting gas, which absorption is best effected by bringing into an eudiometer containing 
the gas to be tested, a piece of coke moistened with the acid, and fixed on a piece of 
platinum wire. In order to ascertain the quantity of carbon of these compounds, 
the test, in which the decrease of bulk of the gas indicates the relative quantity 
of the hydrocarbons, is combined with two separate eudiometrical tests, the gas 
being first ignited by itself with an excess of oxygen, and the operation repeated 
with the gas after it has been acted upon by the sulphuric acid. The quantity of 
C 0 2 obtained in the last instance is then deducted from that obtained by the first 
operation. Chlorine and bromine are very frequently employed to absorb the 
heavier hydrocarbons present in gas, these haloids combining with the hydrocarbons 
as a fluid residue. According to a method of gas analysis originally devised by 
O. L. Erdmann, and described by C. O. Grasse,* the gas first freed from any carbonic 
acid it may happen to contain is burnt from a burner connected with a small 
gas-holder, by the aid of oxygen; the water and carbonic acid formed are collected 
and weighed. 2. The estimation of the value of an illuminating gas by specific 
gravity is frequently employed in practice, as experience has proved.that as a rule a 
higher illuminating power of gas (provided it be well purified and freed from 
carbonic acid), is intimately connected with its higher specific gravity; but it does 
not follow that a light gas is useless, while there ought to be taken into account the 
durability of the gas, by which is understood the length of time a cubic foot of the 
gas will burn under a certain pressure (as low as possible) from a given burner, 
and yield a certain light to be tested either by comparison with another kind of coal- 
gas or standard sperm candles by the photometer. In Scotland, the gas engineers 
when testing cannel and other coals always take into consideration and minutely esti¬ 
mate by means of very accurate apparatus these particulars, care being taken to manu¬ 
facture the gas on the large as well as on the small scale, taking say i cwt. of coals, and 
to compare both. In most of the large Scotch gas-works, a separate experimental gas- 
work, with two or three retorts, and all the necessary apparatus, is to be met with, as 
it has been found that only by the use of judiciously selected mixtures of different 
cannel coals, a gas of high illuminating power, great purity, and average durability, 
can be supplied at the price now generally adopted per 1000 cubic feet. 

Illuminating gas consists of a mixture of various gases and vapours, having 
different specific gravities, viz., elayl-gas, 0-976 ; methyl-hydrogen, 0-555 > hydrogen, 
0*069; carbonic oxide, 0-967; carbonic acid, 1*520. The specific gravity of the 
vapours present in coal-gas varies of course according to the bodies which are met 
with in the gas in the state of vapour; among these benzol is one of the most 
important for illuminating purposes. The estimation of the specific gravity of illu¬ 
minating gas as a test of its quality is only of value if taken in connexion with other 
tests applied to the same gas. Dr. Schilling has constructed an apparatus for the 
purpose of taking the specific gravity of illuminating gas. This apparatus is based 
upon the fact that the specific gravities of two gases issuing from narrow apertures 
in a thin plate under equal pressure are to each other as the squares of their time of 
efflux. There are several more readily managed apparatus for estimating the 
specific gravity of illuminating gas, and among them those made by Mr. Wright, of 
Westminster. 3. Photometrical tests and apparatus, Bunsen’s, Wight’s. Desaga’s 
* Journal fur Prakt. Chemie (1867), cii., p. 257. 


56 4 


CHE MIC A L TE CHNOL OGY. 


(Bothe’s tangental photometer), and others are frequently employed for testing 
the value of gas and comparing its illuminating power with that of lamps oi 
candles. As the kind of burner employed in these experiments has very great 
influence on the results, photometricaf estimations of the value of gases require great, 
care. 4. Erdmann’s gas tester, introduced on the Continent in many gas-worki 
since i860, is a very useful and readily manageable instrument, based upon the fact 
that, as the value of an illuminating gas depends mainly upon the quantity of lieavj 
hydrocarbons contained, that quantity may be measured by estimating the amoun 
of atmospheric air required to deprive the flame of the burning gas of a given size, 
of all illuminating power. 

Gas-meters. At first, in the early days of gas-lighting, the bargain between consumer and 
seller was to pay a certain sum per burner per hour, or to contract for a certain sum pej 
annum for a given number of burners kept lighted from dusk till a certain hour of the 
night, at which time it was customary to have the turncocks of the gas-works at hand or 
their respective beats, to turn off the supply of the house, by shutting a tap placed 
on purpose in the service pipes; but although here and there in small towns in Italy 
France, Spain, and Germany, this arrangement still exists, it is the exception and not tho 
rule; the latter being that the gas is sold by cubic measure as registered by instrument? 
termed gas-meters, the construction of which is—especially in the United Kingdom— 
brought to such a high standard, that Mr. Rutter’s remark is perfectly true—that gas 
is measured with greater accuracy than anything else either measured or weighed in 
commerce. 

We distinguish between dry and wet meters ; the construction of the former is briefly 
the following :—In a gas-tight metallic box are placed two or three bellows-like vessels, 
which instead of being inflated by air, are inflated by the gas entering from the service 
pipe. When inflated to some extent an arrangement of springs and levers forces the ga< 



out oi the bellows again into the exit-pipe leading to the burners. The cubic capacity of 
the chambers (as the bellows-like arrangements are called) having been accurately 
adjusted, the movement of their 'walls is communicated to wheel-work, which being con¬ 
nected with dials, indicates in tens, hundreds, and thousands, the consumption of gas in 
cubic feet. 

Dry meters are preferred on account as well of not being liable to be affected by 
frost as of not causing the sudden extinguishing of the gas-lights for want of water, as may 
occur with wet meters. Wet meters are constructed upon a plan devised in 1817 by 
Clegg, and improved by Crossley and others. Figs. 296, 297, 298, and 299, are 
drawings of this kind of meter, which consists in the first place of an outer cylindrical 
box of cast-iron, closed on all sides. In this box is placed a drum of pure block-tin, 
divided into four compartments, bearing upon a bell-metal axis, and immersed for rather 
more than half its circumference in water. By the pressure of the gas and the ensuing 























































































ARTIFICIAL LIGHT. 


665 


depression of the water the drum revolves, each of its compartments becoming alternately 
filled with and emptied of gas. On the axis of the drum is an endless screw, which 
by mechanical means is connected with the wheel-work of the dials. The drum is very 
accurately adjusted, so that at every complete revolution a certain cubic quantity of gas 
passes through and is registered. Tig. 296 exhibits the apparatus with the front plate 
removed ; Fig. 297 shows the side of the meter ; Fig. 298 is sectional plan ; and Fig. 2gg 
is a section through the box. a is the box ; a' the drum ; b its axis ; c the endless screw, 


Fig. 298. 



Fig. 299. 



bearing in the wheel, d, and carrying by means of e the movement of the drum on to the 
wheelwork of the dials,/, g is the inlet-pipe for the gas, which flows into the valve box, 
h, and passing by the valve, i (kept open as long as the meter contains sufficient water for 
its action), flaws through the bent tube, l, into the bulged cover of the drum, or 
technically antechamber, m, and thence into the several compartments of the drum. 
Thence the gas enters the space, n, to which is fitted the outlet pipe, 0. i is the valve ; 
p the float; q the funnel tube for filling the meter with water; r the waste water cistern ; 
s the plug by the removal of which the waste water may be run off. As long as no gas- 
burners are in use the meter connected with them is inactive, but when the gas is burnt 
the drum rotates, and by its communication with the wheelwork registers the quantity of 
gas. consumed. Instead of filling wet meters with water they may be filled with glycerine, 
which does not freeze nor evaporate. Wet meters should be placed perfectly level. 
As regards their size they are made to supply from three lights up to many thousands if 
required. By an Act of Parliament gas-meters are tested in order to ascertain that they 
register properly within the limits of the Act. The inspectors of gas-meters have 
been provided with very accurate sets of apparatus made according to four sets of standard 
apparatus, of which one each is in the hands of the Corporations of London, Edinburgh, 
and Dublin; W'hile the fourth is in the custody of the Comptroller of the Exchequer, 
at Westminster. These apparatus are masterpieces of highly finished workmanship. 

Elmers. These are made so as to produce all shapes of flame, and are of different 
materials, iron, steel, porcelain, steatite, brass, platinum-lined, &c. The bore from which 
the flame of the burning gas issues should be arranged, as regards its width, for the 
quality of the gas consumed—cannel coal gas-burners, for instance, being provided with 
narrower openings than those for common coal-gas. We have single jet burners, double 
jet burners, bats’-wing, fish-tail, cockspur, and other varieties; also Argand burners of 
various sizes, bored with six to thirty or forty-eight holes, or as in the Dumas burner, a slit 
instead of the holes. The quantity of gas consumed by different kinds of burners varies, 
of course, greatly for the same kind of gas under the same pressure. Much gas is wasted 
because sufficient care is not taken by the consumers to have really good burners. 

Gas Lamps. Of these there is an almost endless variety, from the most simple and unpre¬ 
tentious to the highly ornamented and expensive chandeliers. 

By ' pr MaSlfacture al 8as Among these such as are of important commercial advantage to 
coal-gas works are :—1. Coke. 2. Ammoniacal liquor. 3. Tar. 4. Spent gas-lime. 
5. Sulphur obtained from the Laming mixture. In some localities Berlin blue 
is made from the cyanide of calcium of the Laming mixture (see p. 656). 

1. Coke, of which we shall speak more particularly under the heading of Fuel, 
















































































666 


CHEMICAL TECHNOLOGY. 


as gas-coke is more porous and spongy than the oven-coke and hence better adapted 
for use in stoves. In Germany the gas-works have now very generally adopted the 
plan of selling the coke broken up into small nut-sized lumps, this operation being 
performed by means of machinery; the breeze is mixed with some tar and burnt 
under the retorts at the works. 2. The ammoniacal liquor is essentially an aqueous 
solution of carbonate of ammonia, 2 (NH 4 ) 2 C 0 3 -f-C 0 2 . The quantity of ammonia 
contained in this liquid must of necessity vary according to certain conditions, as 
the quantity of water contained in the coals, the larger or smaller amount of 
nitrogen they contain, the degree of temperature and duration of the process of dis¬ 
tillation. The higher the temperature the more nitrogen will be converted into 
ammonia, while otherwise a portion of it is converted into aniline, lepidine, cliinoline, 
&c., and also into cyanogen. Estimating gas-coals to contain on an average 5 per 
cent of hygroscopic water and 075 per cent of nitrogen, 100 kilos, of such coal will 
yield under the most favourable conditions 910 grms. of ammonia (NH 3 ). It 
has been found that 1 cubic metre of ammoniacal water yields on an average 
(see p. 230) 50 kilos, of dry sulphate of ammonia ([NH 4 ] 2 S 0 4 ), so that 20 hecto¬ 
litres yield 100 kilos, of this' salt. 1 ton of Newcastle gas-coal yields 45 litres 
of ammoniacal liquor, 1 litre of which yields from 74 to 81 grms. sulphate of 
ammonia. 3. Coal-tar, formerly a source of inconvenience to many gas-works, and 
at any rate a substance of very little commercial value, has become since 1858, of 
great importance as the raw material for the coal-tar colours. ' As already stated, tar 
consists of fluid hydrocarbons—benzol, toluol, propyl; solid hydrocarbons—naph¬ 
thaline and antliracen; of acids—carbolic, cresylic, phlorylic; of bases—aniline, 
chinoline, lepidine, &c.; and lastly, of resinous, empyreumatic, and asphalte-forming 
matters. The quantity as well as the quality of the tar obtained by the distillation 
of coals for gas-making depends partly upon the kind of coal used and partly upon 
the heat applied to the retorts; as at a very high temperature, for instance with the 
fire-clay retorts, the quantity of tar is less than at a lower temperature. Owing as 
well to the carbolic acid contained in tar as to the empyreumatic substances, it 
has antiseptic properties, and is hence used for preventing the decay of w r ood 
exposed to wind and weather, for coating iron, &c. Coal-tar is also used for the pur¬ 
pose of mixing with small coal, saw-dust, peat dust, &c., f< 5 r making artificial fuel, 
and recently, when mixed with sifted pebbles, as a substitute for asphalte 
to form excellent footpaths. In order to separate the constituents of tar from 
each other, it is poured into a large iron still, and heated to 8o° to ioo°, for 
the purpose of distilling off the light hydrocarbons along with any ammoniacal water 
the tar may contain. After thirty-six hours the distillation is further proceeded 
with, and as the latent heat of the volatile products to be obtained is very small, the 
still ought to be made as low as possible, and the helm ought to be well protected 
against any cooling influence. At the bottom of the still a tap is fitted for the pur¬ 
pose of removing, at the end of the distillation, the molten pitch which remains. In 
some cases, however, the distillation is pushed further so as to leave only a 
carbonaceous residue, the still being made red-hot at the bottom; the residue 
is removed after the cooling of the still by opening the man-hole. The distillation 
of 750 to 800 kilos, of tar takes twelve to fifteen hours. At first the heat should not 
be too strong, and in many tar distilleries liigh-pressure steam is passed through a 
coil of pipes placed in the still, in order to assist, together with open fire, the first 


ARTIFICIAL LIGHT. 


667 


stage of the distillation. The light tar-oils obtained exhibit first a sp. gr. of 0780, 
but on an average 0 830. The heavy tar-oil comes over at 200°. 

The light tar-oil is again distilled, and the distillate treated with strong sulphuric 
acid, next with caustic soda solution, and then again distilled. The treatment with 
sulphuric acid aims at the removal as well of basic substances (ammonia, aniline), as 
of naphthaline, while, by means of the caustic soda, the carbolic acid is fixed. The 
quantity of sulphuric acid to be used for this purpose amounts to 5 per cent of the 
weight of the tar-oil; while the soda solution of 1*382 sp. gr. ( = 4o°B.) amounts to 
2 per cent of that weight. The liquid thus obtained is the benzol of trade; 
it remains colourless on exposure to air, and is a mixture of various substances with 
benzol, toluol, and xylol as chief constituents. It is easily converted into nitro- 
benzol (see p. 572), the starting-point for many of the coal-tar colours. The coal-tar 
naphtha, now usually sold after the benzol has been completely removed by 
fractional distillation, is used as a solvent for caoutchouc resins, fixed oils, gutta¬ 
percha, and for burning in lamps peculiarly constructed for the purpose, and 
only used in open air. Coal-tar naphtha is also used for carburetting gas of low 
quality. When the crude oil of tar is cooled down to — io°, naphthaline is 
deposited from it, which, as already mentioned (see p. 581), is used for the prepa¬ 
ration of some dyes, and also for the manufacture of benzoic acid. The heavy oil of 
tar is purified with concentrated sulphuric acid and caustic soda ley, and freed from 
foetid sulphur compounds by distillation over a mixture of sulphate of iron and 
lime. By fractional distillation between 150° and 200° creosote is obtained, 
being a mixture of carbolic or phenylic, cresylic, and phlorylic acids. This is 
the raw material used for the preparation of carbolic acid and picric acid (see p. 580), 
also for certain blue and red pigments, for creosoting wood, for preserving anatomical 
preparations, &c. Lunge obtained from a ton of tar:— 


Benzol at 50 per cent . 2*88 gallons — 

Best naphtha. 2*69 „ = 

Burning naphtha . 3*51 ,, = 

Creosote. 83*25 „ = 

Ammoniacal liquor . 3*00 „ = 

And ii| cwts. of pitch. 


13*00 litres. 

12*00 „ 
i5'°8 » 

3*74 hectolitres. 
13*5 litres. 


The heavy oils of coal-tar and the pitch are now largely used for the preparation 
of antliracen, from which artificial alizarine is made. The pitch is further usefully 
employed in lacquer and varnish making, and also for asphalting pavements. 

4. The gas-lime is used abroad for the purpose of removing the hair from 
hides and skins intended to be tanned, the sulphuret of calcium contained in the 
lime acting as a depillatory. In some localities the spent lime is employed for making 
Berlin blue from the cyanide of calcium contained in the lime, and for the prepara¬ 
tion of sulphocyanogen compounds, owing to the §ulphocyanide of calcium it 
contains. As already mentioned, spent gas-lime is largely used in Scotland as a 
manure, which at" the same time destroys a great many injurious insects. 

5. Sulphur is prepared from the Laming mixture (see p. 198), and used for making 
sulphuric acid; it might, perhaps, be better to extract the sulphur from the mixture 
by means of steam at 130°. The Laming mixture is occasionally treated with 
heavy tar-oils for the purpose of eliminating the sulphur. 





568 


CHEMICAL TECHNOLOGY. 


composition of Coai-ga The following figures exhibit the composition of purified coal- 
gas in ioo parts by bulk :— 



I. 

II. 

III. 

IV. 

V. 

VI. 

YH. 

Hydrogen . 

... 44*00 

4 i 77 

39*80 

51*29 

50*08 

460 

27*7 

Marsh-gas (methyl-hydro, 

gen) 38*40 

38*30 

43 ’ 12 

36'45 

35 ‘ 9 2 

39’5 

500 

Carbonic oxide . 

— 573 

5-56 

4*66 

4'45 

5*02 

7*5 

6*8 

Elayl . 

... 4*13 

5 * 0 ° I 

475 

4 ’ 9 I 

533 

3*8 

130 

Ditetryl . 

... 3-14 

4 ‘ 34 ' 






Nitrogen . 

... 4' 2 3 

5'43 

4’65 

1*41 

1*89 

05 

0*4 

Oxygen . 

... — 

— 

— 

0*41 

054 

— 

— 

Carbonic acid . 

... o '37 

— 

3*02 

1*08 

1*22 

07 

0*1 

Aqueous vapour. 

— 

— 

— 

— 

— 

2*0. 

2*0 


I. and II. Heidelberg coal-gas. III. Bonn coal-gas, analysed by H. Landolt. IV. and 
V. Chemnitz, Saxony, coal-gas analysed by "VVunder. YI. London coal-gas (1867). 
YH. London cannel gas (1867). 


Wood-gas. II. As already mentioned (p. 645) the French engineer Lebon was 
engaged in 1799 with the making of gas from wood, and brought out an apparatus 
termed by him a thermolamp, which, however, was neither found to answer for 
heating nor for illuminating purposes, as the illuminating power of the gas 
obtained by his process from wood was very inferior and could not compete with the 
coal-gas which became known soon after. The reason why wood, as converted into 
gas by Lebon’s apparatus, did not give satisfactory results is explained by Dumas, 
by proving that under the conditions of the distillation of wood employed by 
Lebon, the gas evolved consists chiefly of marsh-gas and carbonic oxide, both of 
which can scarcely be considered luminous gases. In the year 1849, Dr. M. von 
Pettenkofer, at Munich, resolved to experiment on the manufacture of gas from 
wood, and he found that, as stated by Dumas, when wood is submitted to distillation 
in a manner similar to coal, the gas produced is entirely unfit for illumination, 
as in acklition to carbonic acid, there are only formed carbonic oxide and marsh-gas. 
But Dr. Pettenkofer also found that when the vapours of tar and empyreumatic oils 
given off by the carbonisation of wood at a comparatively low temperature are 
further heated by passing through a red-hot retort, a very large quantity of heavy 
hydrocarbon gas remains among the products, so that then wood yields a better gas 
than coal. 

While coals are not perceptibly acted upon by a temperature as high as 200°, wood 
gives off combustible vapours at 150°; and in order to understand the process of 
wood-gas manufacture, we must distinguish between the temperature at which wood 
is carbonised or converted into charcoal and empyreumatic vapours, and the tem¬ 
perature at which these vapours are converted into permanent gas suited for illumi¬ 
nation. Coals, resin, and oils yield an illuminating gas at once, when submitted to dry 
distillation in gas retorts, because the temperature of carbonisation and of formation of 
gas are nearly the same ; consequently the vapours formed by the dry distillation of 
these substances are far higher in illumination power than obtains in the case of wood. 
Therefore the apparatus in use for coal- and oil-gas preparation are not suited for making 
wood-gas. Some of the substances rich in carbon and hydrogen met with in wood-tar 
(Stockholm tar) boil, by themselves, at a higher temperature (200° to 250°) than that 
at which they are formed from wood; and the illuminating power of wood-gas is in 
a great measure due to their conversion, by a higher temperature, into permanent 




ARTIFICIAL LIGHT. 


669 


gases. The manufacture of wood-gas, therefore, requires in the first place a retort 
in which the wood is converted into vapour, and another retort or generator 
in which the vapours are rendered gaseous. At first the carbonising retort, oi 
the same shape as the ordinary coal-gas retorts, was connected with a series of iron 
tubes, which were made red-hot, and through which the vapours given off by the car¬ 
bonisation of the wood, at a temperature of 250° to 300°, were passed to be 
converted into gas; but now large retorts are used for this purpose, about three 
times as large as the carbonisation retort, which holds 60 kilos, of wood, and there 
is, therefore, ample space for the conversion of the vapours into gas. As regards the 
quality and quantity of gas obtained from different kinds of wood, there is no very 
great difference, as may be inferred from the under-mentioned results of the 
researches made by W. Reissig, who operated upon aspen wood (1); linden wood (2); 
larch wood (3); willow wood (4); fir-tree wood (5); and white wood or Memel 
timber (6). 


50 kilos. 

(1) gave of purified gas 592 cubic feet, 

and g'g kilos, of charcoal. 

50 » 

(2) 

„ 620—640 „ 

„ 9—11 „ 

50 *> 

( 3 ) 

„ 550 

v 12-5 

50 V 

( 4 ) 

„ 660 

„ 90 

50 „ 

( 5 ) „ 

,, 648 ,, 

„ 9'5 

50 » 

(6) 

„ 564 

„ 9'2 


That the crude wood-gas contains a large quantity of carbonic acid may be 
inferred from the following results of analysis by Pettenkofer, the gas having been 
made of wood as much as possible free from resin :— 


Heavy hydrocarbons . 

6-91 

Marsh-gas (methyl-hydrogen) 

ii*o6 

Hydrogen . 

I 5'°7 

Carbonic acid. 

2572 

Carbonic oxide . 

40*59 


One volume of the heavy hydrocarbons contained 2"82 volumes of vapour 
of carbon. The carbonic acid is removed from the crude gas by means of- hydrate 
of lime. According to Reissig’s researches, the composition of purified wood-gas is 
the following:— 



1. 

2. 

3 - 

4 - 

Heavy hydrocarbons . 

7-24 

7*86 

900 

7*34 

Hydrogen. 

3 x *84 

48*67 

29*76 

29*60 

Light hydrocarbon gas (marsh-gas) ... 

35*30 

21-17 

20*96 

24-02 

Carbonic oxide. 

25-62 

22*30 

40*28 

39*04 


100*00 

IOO'OO 

100*00 

100*00 


Method or Wood-Gas qq ie wood cliieflv fir-wood, is first dried for twenty-four hours in 
a drying room, generally brick-built, and heated by the waste heat of the retort 
furnaces. The carbonising retort is filled with 50 to 6q kilos, of wood and the lici 
screwed on; the distillation is finished in 11 hours, and after the removal cf the 
carbonic acid there is obtained about 16 cubic metres (nearly 600 cubic feet) of good 
illuminating gas. In some places, where wood-gas is regularly made, it is preferred 










670 chemical technology. 

to distil with the wood some Scotch boghead coal or Bohemian foliated coal (. Mattel 
kohle ). 

Wood-Gas Burners. The construction of the burners is of great importance with regard 
to wood-gas illumination. The sp. gr. of this gas amounts on an average to 07, 
while that of ordinary coal-gas scarcely every reaches 0*5 ; the lighter the gas the 
more readily and rapidly it flows out and expands in the air, and the heavier the 
gas the more slowly and difficultly it issues and expands. A light gas will not on 
issuing into the air separate its particles, while, on the other hand, a heavy gas will, 
by exerting greater friction, mix with the air; in order that this effort shall not 
injure the luminosity or the gas, the openings in wood-gas burners must be con¬ 
siderably larger than in coal-gas burners. When wood-gas is burnt with rather 
strong pressure from coal-gas burners calculated to consume 70 to 100 litres 
(3 to 4 cubic feet) per hour, the flame is scarcely luminous, while when burnt from 
burners with large openings, wood-gas yields a light exceeding that of coal-gas. 
According to the experiments made in 1855 by Drs. Liebig and Steinhill, the illu¬ 
minating power of coal-gas and wood-gas used each at 4! cubic feet per hour was 
found to be:— 

For coal-gas = 10*84 normal wax-candles. 

„ wood-gas = 12*92 „ „ 

so that the average illuminating power of coal-gas stands to that of wood-gas as 6 : 5. 
The advantage of wood-gas manufacture over that of coal-gas (only of course in locali¬ 
ties where wood is very abundant and coal either not to be had or at great cost) is 
evident enough, because, in addition to less complicated apparatus than required for 
coal-gas, the manufacture of wood-gas yields far more valuable by-products, wood char¬ 
coal being the chief of these. Wood, moreover, yields weight for weight more gas 
than coal in a shorter time and of higher illuminating power, while the gas is abso¬ 
lutely free from sulphur and ammoniacal compounds, so that by the burning of wood- 
gas no sulphurous acid can be formed. As the distillation of wood-gas proceeds 
rapidly, one retort kept continuously in action for twenty-four hours will yield 
10,000 cubic feet, while for coal-gas only 4000 cubic feet are obtained with one retort 
in the same time. On the other hand, wood-gas requires for purifying purposes a 
very large quantity of quick-lime. The wood-tar, about 2 per cent of the weight of 
the dry wood, and the wood-vinegar—100 parts of wood yield 0 5 to 075 parts of dry 
acetate of lime—are usefully applied; the tar, however, is in some localities burnt 
under the retorts. 

Peat-Gas. III. When peat is submitted to dry distillation, there is obtained, as with 
coals, an aqueous distillate, tar, and carbonised peat or peat-coke. Vohl obtained by 
the dry distillation of an air-dried peat, taken from a high moorland in the canton 
Zurich, Switzerland, from 100 parts:— 

17*625 

5’375 
52*000 
25*000 


0 885 sp. gr. 


■ Gas.. . 

Tar. 

Aqueous distillate. 

Peat-coke. 

The products of the dry distillation of peat are:— 

Fluid and solidly sp ' ... 

hydrocarbons. fej ( lubl ™ atin g- 011 ). 



ARTIFICIAL LIGHT. 


673 


Bases. ~ 


/Ammonia. 

Ethylamine. 

Picoline. 

Lutidine. 

Aniline. 

'Caespitine. 


Acids. 


f Carbonic. 

I Sulphuretted hydrogen. 
I Cyanhydric. 

Acetic. 


Propionic. 
Butyric. 
Valerianic. 
I Carbolic. 


Gaseous products. 


/Heavy hydrocarbons. 
J Light hydrocarbons. 

1 Hydrogen. 

I Carbonic oxide. 


The apparatus in use for making wood-gas answers the purpose of making peat- 
gas. W. Reissig, who has for a long time been engaged in experimenting on 
peat-gas manufacture, used a fat peat from the neighbourhood of Munich,, con¬ 
taining very little ash and 14 to 15 per cent of water. On an average 1 Bavarian 
cwt. of this peat yields 426 Bavarian cubic feet of gas; 134 lbs. of this peat yield 
337 English cubic feet of gas. The gas is evolved at first very rapidly, as 
is also the case with wood, but the evolution of gas from peat decreases more 
uniformly and steadily than it does from wood. Reissig’s experiments prove that 
peat-gas may be prepared of very good quality; he found the purified peat-gas to 


consist of:— 

I. Heavy hydrocarbons . 9*52 

Light hydrocarbon gas. 42*65 

Hydrogen. 2750 

Carbonic oxide. 20*33 

Carbonic acid and sulphuretted hydrogen . traces 


IOO'OO 


The analysis of another gas, made with a very excellent peat, gave the following 
result:— 


Heavy hydrocarbons { = } = - 

... 1316 

Light hydrocarbons. 

... 3300 

Hydrogen. 

... 35 -i 8 

Carbonic oxide. 

... 18*34 

Carbonic acid and sulphuretted hydrogen ... 

... 0*00 

Nitrogen . 

... 0*32 


100*00 

Water-Gas. IV. The manufacture of water-gas essentially consists in forcing steam 
through iron or fire-clay retorts filled with red-hot charcoal or coke. The steam is 
decomposed, yielding a mixture of hydrogen, carbonic oxide, and carbonic acid gases, 
with a small quantity of marsh-gas. The purified gas, consisting essentially of 
carbonic oxide and hydrogen, is, although not luminous when burnt by itself, suitable 
for illuminating purposes under the following conditions :—i. By placing on the 
burners small platinum cylinders which, by becoming white-hot, yield a strong light 
—Gengembre’s and Gillard’s plan. 2. By impregnating the gas with vapours of 
hydrocarbons, a more common plan, the original idea being due to Jobard (1832) of 
Brussels. 
















CHEMICAL TECHNOLOGY. 


672 

The determinations of the compositions of water-gas vary very much. Jacquelain 
and Gillard state that the crude gas obtained by them is a mixture of hydrogen and 
carbonic acid, which, after having been purified by means of lime, consists essentially 
of hydrogen. But it is stated by others, and not without good reason, that the 
purified gas contains carbonic oxide and hydrogen; and Langlois’s results agree 
with this account. The formation of 1 molecule of carbonic oxide requires 1 mole¬ 
cule of steam, the hydrogen of which is set free, C-f H 2 0 =C 0 +H 2 . When the 
carbonic oxide meets again with steam at a higher temperature, it, as has been 
experimentally shown by Dr. Yerver, withdraws oxygen from the steam, forming 
carbonic acid, while some hydrogen is again set free : C 0 +H 2 0 =C 0 2 +H 2 . Only 
when the carbonic acid is not withdrawn rapidly enough from the retorts is its 
re-conversion into carbonic oxide by contact with the red-hot charcoal possible. 

piatinumG a as I* 1 the y ear 1846, Gillard established at Passy, near Paris, a gas- 
work for the purpose of manufacturing hydrogen by the decomposition of water. 
At first the steam was decomposed by passing it through retorts filled with 
ret-hot iron wire, the idea being to re-convert the oxidised iron to the metallic state ; 
but as this process did not answer, Gillard commenced decomposing the steam by 
passing it through a retort filled with red-hot charcoal. The crude gas thus 
obtained is readily freed from the large quantity of carbonic acid it contains, by 
crystallised carbonate of soda, which is converted into bicarbonate of soda. The gas 
is burnt from an Argand burner provided with numerous small holes, and the 
flame, not luminous by itself, is surrounded by a net-work of moderately fine 
platinum wire, which on becoming white-hot is luminous. In Paris this gas is 
known as platinum-gas (gaz-platine). It is free from smell, burns without smoke or 
soot, and for this reason is preferred by gold and silversmiths and electro-gilders. 
The illuminating power of this gas exceeds that of coal-gas in the proportion, 
according to Girardin, of 130 : 127. The flame is quite steady, because the light- 
producing substance is a solid body at a white heat.* According to Dr. Verver’s 
researches there are used atNarbonne, France, for the production of 1 cubic metre of 
this gas o - 32 kilo, of wood-charcoal, and for heating the retorts i:\41 kilos, of coals. 

carburetted Water-Gas. 'While engaged in his experiments on the oil obtained by the 
strong compression of oil-gas, Faraday proved that if marsh-gas, which burns 
with a scarcely luminous flame, is impregnated jvith this oil, it becomes a very 
luminous gas. Lowe proposed, in the year 1832, that common coal gas should 
be rendered more luminous by impregnating it with vapours of tar-oil or petroleum. 
He also showed that with the aid of steam and red-hot coke a mixture of carbonic 
oxide and hydrogen might be obtained and rendered luminous by impregnation with 
these vapours. Afterwards Jobard, at Brussels, took up the subject and communi¬ 
cated his researches to the French gas-engineer Selligue, who having at an earlier 
period (1833) been engaged with similar researches, entered upon the subject with 
great energy, and employed carburetted water-gas for illuminating purposes on the 
large scale. Selligue used the oil obtained from a bituminous shale for the purpose 
of carburetting the water-gas, the oil being obtained in the same manner as such oil 
is now made from various kinds of cannel coal and bituminous shales. Selligue’s gas- 
making apparatus consisted of a battery of three vertical retorts kept continuously 

* Schinz has lately published an essay on this gas; see Dr. Wagner’s “ Jahresbericht 
der chem. Technologie,” 1869, p. 731. 


ARTIFICIAL LIGHT. 


e 73 

red-hot, two of these retorts being filled with charcoal or coke of good quality 
and very free from sulphur. Into the first of these retorts, which are connected 
together, steam is introduced, forming with the red-hot charcoal carbonic oxide and 
hydrogen. This gaseous mixture passing through the second retort, also, filled with 
charcoal, is there deprived of any carbonic acid, which is converted into carbonic 
oxide. This is the reverse of the method of water-gas making now employed, 
where the carbonic oxide is converted into carbonic acid, to be next removed from 
the gaseous mixture by means of lime. The very hot mixture of hydrogen and 
carbonic oxide is next passed into the third retort, which is filled for two-thirds of its 
height with iron chains kept red-hot, while a continuous stream of the oil of the 
bituminous shale flows from a reservoir through a syphon-pipe into this retort (tc 
every 10,000 litres of gas 5 kilos, of oil are admitted), and upon becoming decomposed, 
mixes with the carbonic oxide and hydrogen, forming a gaseous mixture, which, 
notwithstanding the large quantity of carbonic oxide contained, burns with a highly 
luminous flame, the gas being at the same time of great durability. A gas-furnace 
upon Selligue’s plan and containing six retorts in two batteries, together of 6 cubic 
metres capacity, yielded in twenty-four hours 24,000 to 28,000 hectolitres (=84,768 
to 98,896 English cubic feet) of excellent gas, with a consumption of 1231 kilos, of 
oil of bituminous shale, 400 kilos, of wood-charcoal, and 16 hectolitres of coal for 
firing the retorts. 

Selligue’s process has given rise to the following methods:—1. White’s hydrocarbon 
process, in which steam and gas are made from coals (originally resin was employed, but 
cannel coals have been substituted) under the influence of a jet of superheated steam 
passed through a red-hot retort. 2. Leprince’s process, Gas mixte Leprince, is an 
improved hydrocarbon process, the products of the decomposition of steam and coke 
being carried at a suitable temperature and in the same retort (provided with a partition 
and thus divided into two compartments) over coals in process of carbonisation. 
3. Isoard’s process, with superheated steam and coal-tar mixed. 4. According to 
Baldamus and Griine’s plan, steam and a fluid hydrocarbon are decomposed simul¬ 
taneously in the same retort. 5. Ki rkham’s plan and that of others, the impregnation of 
water-gas with fluid hydrocarbons, benzol, photogen, petroleum, naphtha, &c. 6. Long- 

bottom’s proposal to carburet air by impregnating it with vapours of benzol, or, according 
to WTederholt’splan, with petroleum naphtha, the benzoline as used in sponge-lamps, 
white's Hydrocarbon White in so far modified Selligue’s plan in causing water-gas and 
Process. steam to he forced through a retort in which cannel coal, boghead, or 
resin are submitted to distillation. W r hite’s process, as yet rarely employed, came under 
notice through the researches which Dr. Frankland instituted at Clarke and Co.’s gas¬ 
works at Ancoats, near Manchester. 

Dr. Frankland found the gas made by White’s process to contain about 15 per cent of 
carbonic oxide, no carbonic acid, and some 45 per cent of hydrogen. This increase of 
hydrogen, without an equivalent increase of carbonic oxide, can only be explained by the 
action of the steam upon the marsh-gas evolved in the retort filled with cannel coal, 
probably according to the following formulae :— 

Marsh-gas, CH. 1 . n (Carbonic oxide, CO. 

Steam, H ,0 \ y ield | Hydrogen, 3 H 2 . 

The composition of the gas, made with and without water-gas, -was as follows:— 


Gas from Boghead coal:— 

Without 

water-gas. 

W 7 ith 

water-gas. 

Heavy hydrocarbons 

.. .. 24-50 

14-12 

Marsh -gas. 

.. .. 58-38 

22-25 

Hydrogen. 

.. .. 10-54 

45 ‘ 5 1 

Carbonic oxide. 

.. .. 6-58 

IF 34 

Carbonic acid. 

— 

3-78 

Oxygen and nitrogen 

100-00 

IOO’OO 


44 









CHEMICAL TECHNOLOGY. 


P74 

The advantages of White’s hydrocarbon process are not only the increase of hydrogen 
and decrease of carbonic oxide and marsh-gas as met with in ordinary coal-gas, hut are to 
be found in the mechanical action of the products of the decomposing steam by carrying 
off very rapidly the heavy hydrocarbons from the retort, so that these are withdrawn in 
time from the decomposing influence of high temperature, thereby lessening the forma¬ 
tion of tar. Dr. Frankland summarises the results of this process as follows :— a. It can 
be employed without great expense in any gas-work. b. The quantity of gas yielded 
increases from 46 to 2go per cent. c. The illuminating power increases from 14 to 108 per 
cent. d. Less tar is made, a portion being converted into gas. e. The heat and forma¬ 
tion of carbonic acid accompanying the combustion is much less, as this gas contains 
more hydrogen and less carbon. 

Leprince’s Water-Gas. This is only a modification of White’s process, consisting chiefly 
in the use of retorts divided by means of horizontal partitions into three rooms or 
chambers, in which the two phases of the process, viz., the partial decomposition of water 
by means of coke or charcoal, and the carburation of the gas by means of the volatile 
products of the dry distillation of gas-coals, are carried on simultaneously. The Gas mixte 
Leprince is used in the broad-cloth factory of Simonis at Verviers, and at the Vieille 
Montagne zinc-works, both in Belgium, also at Maestricht and some places near Luik Liege. 

isoard’s Gas. In this process tar is used instead of charcoal or coke for the purpose of 

decomposing the steam. 

Baidamus and Grime's According to this plan the decomposition of steam and of the hydro- 
Gas - carbons is carried on simultaneously in the same vessel, so that the 

hydrogen contained in the steam is not evolved in free state, but in combination with 
carbon as a light-giving hydrocarbon. The gas-making material, brown coal, peat, 
bituminous shale, &c., is fully utilised without any by-products, for the tar is entirely 
converted into gas, forming with the hydrogen of the water a real hydrocarbon. 

Carburetted Gas. The process proposed by Kirkham and several others simply consists in 
the impregnation of water-gas with the vapours of fluid hydrocarbons, benzol, photo¬ 
gen, petroleum, &c. This impregnation may take place at the works where the gas is 
made, but better where the gas is consumed, just before issuing from the burners. Not¬ 
withstanding that a great many apparatus have been contrived for the purpose of carbu- 
retting water-gas and ordinary coal-gas, the process has never answered very well, 
because it is difficult to find suitable materials for carburetting, and because erroneous 
calculations have been made in respect of the quantity of carburetting materials required 
to render a non-luminous gas luminous. If, for instance, benzol (CgHe) be the hydro¬ 
carbon to be used for carburetting purposes, 

1000 cubic feet of gas require I ° 0 ’ 2 | 4 2 & ims * L benzol. 

b 1 l » 15 , 5694 » i 

The improvement of coal-gas by impregnating it with the vapours of some volatile hydro¬ 
carbon has been frequently suggested and practically tried in England; but, although 
various apparatus have been contrived for this purpose, such apparatus being generally 
fixed to the outlet-pipe of the house-meters, the results have not been so satisfactory as to 
lead to a general introduction of these so-called carburetters. Among other reasons why 
these appliances have been discarded, is the fact that the gas. especially in London, con¬ 
tains sulphuretted hydrocarbon compounds in very small quantity, which, by becoming 
dissolved in the hydrocarbon used for impregnating the gas, accumulate in the carbu¬ 
retter, and are, when fresh carburetting oil is added, carried on to the burners and escape 
partly in the state of vapour, causing a very foul atmosphere in the rooms where the gas 
is burnt. 

Air-Gas. Longbottom suggested to free air from carbonic acid and moisture, and then 
to impregnate it with the vapours of very volatile fluid-hydrocarbons, such as benzine and 
benzoline. Air can be used as an illuminating gas in this way, but it requires burners 
with wide openings and a low pressure, because if the current of the gas be too rapid the 
flame is cooled too much and readily extinguished. Apparatus for preparing air-gas have 
been devised and constructed by Marcus, Mille, Methei, and others.* 

ou-Gas, Resin-Gas. V. The fatty, or so-called fixed oils, are among the best gas-makiim 
materials, yielding a very pure gas and of high illuminating power. This follows 
from their composition:—Lefort found the formula of rape-seed oil to be C^HjsOa; 
olive oil and poppy-seed oil, linseed oil, C I5 H 28 0 2 ; hemp-seed oil, 

CnH 22 0 2 . The fatty oils yield by dry distillation chiefly elayl-gas or a mixture of 

* See “ Jahresbericht der chem. Technologie,” 1S66, p. 701; 1868, pp. 763 and 765. 


ARTIFICIAL LIGHT. 


675 

Aydrogen and marsh-gas with the vapours of fluid hydrocarbons, the illuminating 
power of which is equal to that of elayl-gas. As oils yield further only a small 
quantity of carbonic acid gas and no sulphuretted hydrogen, oil-gas does not require 
any purifying, and hence the apparatus may be very simple ; while, owing to the high 
illuminating power, smaller gas-holders, smaller pipes, and burners of different con¬ 
struction are required. But notwithstanding all these advantages, oil-gas is a thing 
of the past. The Binnenhof, at the Hague, with some of the adjacent public build¬ 
ings, was lighted with oil-gas until within some ten or twelve years, when the 
apparatus requiring renewal was removed, and coal-gas, as in the other parts of the 
town, substituted. The sp. gr. of oil-gas amounts on an average to 076 and 0-90, 
but may be as high as ri. Half a kilo, of oil yields 22 to 26 cubic feet of gas, equal 
to 90 to 96 per cent. 

Gas from suint. By this we understand a gas prepared from the fatty materials 
present in the soap-suds used in washing raw wool and spun-yarns. The water 
containing the suint and soap-suds is run into cisterns and is there mixed with milk 
of lime and left to stand for twelve hours. A thin precipitate is formed, which, after 
the supernatant clear water has been run off, is put upon coarse canvas for the 
purpose of draining off any impurities, sand, hair, &c., while the mass which runs 
through the filter is put into a tank, in which it forms after six to eight days a pasty 
mass, which having been dug out and moulded into bricks, is dried in open air. 
At Bheims the first wash-water of the wool is used for making both gas and potash, 
because the water contains no soap and only suintate of potash (see p. 132). 
Havrez, at Yerviers, has recently proposed to employ suint, which, by-the-bye, is 
very rich in nitrogen, for the purpose of making ferrocyanide of potassium. 

The dried brick-shaped lumps are submitted to distillation, yielding a gas which 
does not require purification, and which possesses an illuminating power three times 
that of good coal-gas. The wash-water of a wool spinning-mill with 20,000 spindles 
yields daily, when treated as described, about 500 kilos, of dried suinter, as the sub¬ 
stance is technically termed. 1 kilo, of this substance yields 210 litres of gas. 
Annually about 150,000 kilos, of suinter are obtained, and this quantity will yield 
31,500,000 litres =1,112,485 cubic feet of gas. Every burner consuming 35 litres 
of gas per hour, and taking the time of burning at 1200 hours, the quantity of gas 
will suffice for 750 burners, and as a spinning-mill of 20,000 spindles only requires 
500 burners, there is an excess of gas supply available for 250 other burners, or the 
owner may dispose of 5000 kilos, of suinter, which is valued at Augsburg at about 
3s. per 50 kilos., and at about 4s. at Mulhouse. 

Gas from Petroleum VI. The so-called posidonian schist of the lias formation, met 

Oil, or Oil from . . ... . 

Bituminous shales, with near Reutlingen, in W urtemberg, yields by dry distillation 
about 3 per cent of tar, which on being submitted to distillation, yields an oil 
which cannot be burned in lamps owing to its containing sulphur; but the oil is an 
excellent material for gas manufacture, According to Haas, 1 cwt. (50 kilos.) of the 
oil, valued at 16s., yields 1300 English cubic feet of gas, so that 1000 cubic feet 
inclusive of fuel ( T \ klafter of wood; the klafter is a cubic measure by which wood 
is sold, and is =108 cubic feet) and labour cost 16s., a low price considering the high 
illuminating power of the gas. The gas, according to W. Reissig’s researches (1862) 
was found to consist of:— 


676 


CHEMICAL TECHNOLOGY. 


Heavy hydrocarbons 

. 2530 

Marsh-gas. 

. 6480 

Carbonic oxide. 

. 665 

Hydrogen. 

. 3‘°5 

Carbonic acid . 

. 020 

Oxygen and nitrogen 

. traces 


10000 


According to experiments made at Stuttgart, the illuminating power of this gas is 
2*5 to 35 times that of coal-gas. 

Petroleum-Gas. In America and on the Continent of Europe petroleum is now used 
for the purpose of gas-making, being either converted into gas or used to carburate 
water-gas. 

According to the method of Thompson and Hind (1862) the petroleum is converted 
into gas by causing it to pass through a red-hot retort, which, in order to increase 
the contact surface, is filled with lumps of fire-brick or is fitted with a series of tray¬ 
like iron plates, and the gas so obtained mixed with that made by passing steam over 
red-hot charcoal. The crude gaseous mixture is washed by causing it to bubble 
through hydrochloric acid and then through a series of purifying apparatus, so that 
the gas collected in the gas-holder is devoid of smell. The arrangement of the 
retort used in this process is the following:—The retort is placed horizontally; to the 
lid is fitted a hollow cylinder which is filled with coke or charcoal. In the space 
between this cylinder and the sides of the retort is placed a serpentine iron plate. 
Through the lid of the retort two tubes are carried; one of these, communicating 
with the serpentine iron plate, is destined for the introduction of the petroleum oil, 
while the other is used for passing in the steam, and communicates with the cylinder 
filled with coke or charcoal. At the other end of the retort a tube is fitted for 
carrying the gas to the purifier. When the petroleum is converted into gas without 
water-gas, 1 cwt. of Pennsylvanian oil yields 1590 cubic feet of gas, which, when 
purified, consists, according to Bolley, of:— 



I. 

H. 

Heavy hydrocarbons 

. 316 

33‘4 

Light hydrocarbons 

. 457 

40’c 

Hydrogen... ... 

- . 327 

260 


1000 

1000 


H. Hirzell prepares gas from the residues of the refining of petroleum, which are 
less volatile, as well as from petroleum itself. Hirzel’s apparatus, already largely 
used in Germany, Austria, Bussia, and elsewhere, is especially adapted for the 
'purpose of making gas for ra!ilway-stations, barracks, factories, hotels, and isolated 
country seats; its mode of action will be readily understood with the aid of Fig. 300. 
d is a wrought-iron vessel confaining petroleum or the residues of the refining 
This vessel is fitted with a suction- and force-pump, e, the piston of which can be 
filled with petroleum by winding up the clockwork with which it is connected. As 
soon as the retort is red-hot, weights are put on the piston, after which the pendulum 
of the clockwork is set in motion and the rope unreeled, allowing the piston to sink 
slowly into the pump-body, thus forcing the petroleum through i uniformly into the 
retort a. The petroleum is converted into gas, and this is carried through the tube d 












ARTIFICIAL LIGHT . 


677 


into the receiver, b, and thence 
through the condenser, c, which is 
filled with pieces of brick, into 
a gas-holder. In b the pipe dips 
under the surface of the petro¬ 
leum, so that a hydraulic valve 
is provided, preventing the gas 
from returning to the retort. In 
order to keep this column of 
petroleum at the same height, 
there is fitted to e the U-shaped 
tube c, by means of which any 
superfluous oil entering 0 is run 
off into a pail. The tube b, 
fitted to the gas-tube d , is, by 
means of a pipe, connected with 
a water-pressure gauge, by the 
aid of which the pressure in the 
retort during the operation can 
be ascertained; this pressure 
amounts usually to 8 to 12 centims. 
of water. The lid, e, of the con¬ 
denser, c, is kept gas-tight by the 
rim dipping in water poured into 
an annular space. The working 
of this apparatus is very simple. 
The clock-motion is maintained 
for an hour, and in that time 
about 200 cubic feet of gas are 
made. If by any chance the 
tubes are choked, the manometer 
will indicate the accident. When 
in regular use the apparatus 
should be cleaned once in five or 
six weeks, and after every twelve 
distillations the retort should be 
opened and the crust of coke 
picked off with a sharp iron bar. 
Petroleum-gas is the best that 
can be made, and it has the ad¬ 
vantage that even under strong 
pressure and intense cold it does 
not deposit tarry matter, nor 
does it lose any of its illumi¬ 
nating power. It is absolutely free 
from ammoniacal and sulphur 
compounds and from carbonic 
acid. The sp. gr. of petroleum- 



Fig. 300. 








































































6/8 


CHEMICAL TECHNOLOGY. 


gas is 0*69, and it consists chiefly of acetylen (C 2 H 2 ). It is burnt from burners 
which consume per hour only one-quarter of a cubic foot to a maximum of 2 cubic 
feet. 200 cubic feet of this gas are equivalent to 1000 cubic feet of coal-gas. At the 
suggestion of L. Ramdohr (1866), the sodium carbolate (creosote soda), which is 
obtained in large quantities in the paraffin and mineral-oil works, is used for gas¬ 
making under the name of creosote-gas. 

Eesin-Gas. VII. When the substance known as Venice turpentine, a mixture of oil 
of turpentine and resinous matter, is submitted to distillation with water, there 
remains colophonium, or commonly resin, which essentially consists of sylvic and 
pinic acids, these being isomeric and corresponding to the formula C 2 oH 30 0 2 . 
Before the late American war colophonium was imported in very large quantity into 
Europe, and was used in England as well as on the Continent for the purpose of gas 
manufacture. 

When decomposed under the influence of heat colophonium yields an oily fluid, 
so-called resin oil, which, when submitted to red-heat, is converted into gas. This 
oil is very complex, and contains bodies which are volatilised below red-heat, an 
inconvenience in gas-making, because these compounds as soon as formed become 
volatilised instead of being converted into gas. Consequently it is necessary to pass 
the first products of the decomposition through several retorts in order to convert 
them completely into gas, thereby complicating the apparatus and increasing the cost 
of fuel. Another difficulty in the making of resin-gas is occasioned by the fact that 
colophonium is a solid substance which, in order to be fitted for gas-making, so as to 
supply the retorts uniformly and constantly, has to be first liquefied. This has been 
in some instances effected by dissolving the resin either in oil of turpentine or in 
resin oil, while in other instances the resin has been first molten, and then caused to 
flow into the retorts filled with coke or lumps of fire-brick to increase the surface. 
The hot gas from the retorts is washed with cold water in order to free the gas from 
any adhering resin oil. It is next purified from the carbonic acid it contains (on an 
average about 8 per cent) by passing it through a solution of caustic soda. 100 lbs. 
of resin yield about 1300 English cubic feet of gas, a quantity which is greatly 
increased when the Wliite-Frankland hydrocarbon process is employed. This 
process, however, is obsolete in consequence of the very fluctuating supply of resin 
since the last American war and the greatly increased price of that article. 

The lime-light, Tessie du Motay’s oxyhydrogen light, the magnesium light, and the 
electric light have to be considered as appendices to the illuminating and artificial 
light producing materials. 

Lime-Light. When a mixture of two volumes of hydrogen and one volume of oxygen 
is ignited, each gas being supplied from a separate gas-holder, we obtain what is 
known as the oxyhydrogen blowpipe, the heat evolved being sufficient to fuse 
platinum. The flame of this mixture is not luminous, but if it is made to impinge 
against a piece of quick-lime, the latter being rendered intensely white-hot, emits a 
light of very great intensity. For the general purposes of artificial illumination the 
lime-light is not suitable, arising partly from the high price of oxygen; but for 
scientific purposes and for signals, the lime-light, also known as the Drummond-, or 
sideral-light, is very manageable. According to the “Journal of Gas Lighting” 
(1869) the authorities of the British War Department have arranged to use the lime¬ 
light in military barracks and cavalry stables, having instituted a series of 
experiments in the yard of the Queen’s Barracks. The illuminating apparatus and 


ARTIFICIAL LIGHT. 


679 


reflecting mirror were placed on a temporarily-erected wooden frame-work, 18 feet 
high, and when the lime was ignited the yard was lighted up so strongly, that at 
100 yards distance from the light the smallest type could be read. A smaller light 
surrounded by a glass globe was tried, and found to be so efficient, that at 30 yards 
distance from the light a pin could be distinguished lying on the pavement. The 
liglit-apparatus tried in one of the barrack-rooms was still smaller, but lighted the 
room very brilliantly. 

TcsS of d niuminaUon? tllod For some years Tessie du Motay’s method of illumination has 
been often before the public. During the latter part of 1871 and the earlier months 
of this year, this method has made considerable progress in improvement, and is 
used in some parts of Paris and Vienna, and lias been tried at the Crystal Palace. 
The gas-mixture used is either water-gas—a mixture of hydrogen and carbonic 
oxide—or hydrogen only, or also coal-gas, burnt with a regulated supply of oxygen 
instead of air. The oxygen is obtained by the decomposition of the vapours of 
sulphuric acid or from manganate of sodium, or by the decomposition of oxychloride 
of copper. The flame of the oxyhydrogen gas is made to play against a small 
cylindrical piece of magnesia or zirconia; but more recently (1869) Tessie du Motay 
has somewhat altered his method, by causing the oxygen to become saturated with 
a solution of naphthaline in petroleum. It appears that the latest and most practi¬ 
cally available method is the feeding of good coal-gas with oxygen, a very excellent 
light being produced. 

Mr. Crookes has found a supply of good coal-gas best adapted to the oxy-hydrogen 
flame, the oxygen being supplied from a burner quite separate from the hydrogen burner, 
and having a broad slit from which the gas issues. The oxygen should be supplied at a 
steady but full pressure. The material upon which the flame impinges may, with advan¬ 
tage, be of dolomite. Under these conditions, Mr. Crookes has always found the lime¬ 
light to work satisfactorily. The dolomite does not crack nor splinter, as is the case with 
quick-lime or magnesia. There are also the advantages in employing separate burners, of 
decreased expense of apparatus, and of perfect safety. 

MM. Deville and Gernez proposed some time since to make a series of experiments to 
ascertain, in a chamber containing compressed air, whether the tension of steam (which is 
said to be complementary to the tension of dissociation) in the flame of the oxyhydrogen 
blowpipe is augmented by exterior pressure, and if the augmentation extends to the tem¬ 
perature of the flame. In a cylindrical chamber of forty metres contents, and the sides 
of which have been proved to eleven atmospheres, is arranged the necessary apparatus. 
The operators enter the cylinder, and the air is compressed by means of a steam-pump, 
when the experiments are proceeded with as in the open air. The endeavour has at pre¬ 
sent been confined to ascertaining the condition of various substances at the moment they 
combine in homogeneous flames, and the resulting temperatures. The homogeneous 
flame employed is that of carbonic oxide and oxygen. With this flame and a pressure of 
1-7 atmospheres platinum melts, flying off in* sparks with a facility it never exhibits 
in air; it melts in those portions of the flame which in the air would only heat it to red¬ 
ness. We must then deduce that the temperature of these flames augments with 
the pressure they support, and, consequently, the quantities of matter which combine 
are greater, and the dissociation diminished. Dr. Frankland has shown that the 
brilliancy of the flame of hydrogen gas increases considerably with the pressure, so that 
with a pressure of twenty atmospheres it surpasses that of a normal candle. Similarly 
when a mixture of oxygen and hydrogen is ignited in an eudiometer the flame is intense, 
while in open air it is scarcely visible. M. Deville thinks that if the quantity of heat 
disengaged by a substance burning with brilliancy be measured, the result would not be 
the same in operating with an opaque calorimeter as with one which transmits the light 
and chemical rays. This remark when worked out will probably produce results of tech¬ 
nical interest. 

magnesium Light. The very intense light which is produced by the burning of magne¬ 
sium (see p. 114) has been of late frequently employed for photographing purposes. 
Magnesium lamps—as exhibited in 1867 at the International Exhibition, at Paris— 


6So 


CHEMICAL TECHNOLOGY. 


are arranged for the use of magnesium wire or magnesium dust, while in eacli 
instance a spirit-flame is employed to ensure the continuity of combustion. In the 
lamps with wire, this is pulled forward by the aid of clockwork ; while in the lamps 
burning the dust, this, mixed with very dry and fine sand (one-tliird magnesium and 
two-thirds sand), in order to ensure to the magnesium particles a sufficient access of 
air, is, on opening a stop-cock, supplied from a reservoir. The magnesium light was 
used on a large scale in the Abyssinian war, several cwts. of magnesium having 
been supplied by Mr. Mellor, the director of the Magnesium Metal Company, at 
Manchester. 

Chatham night. Under this name is known in England a kind of flash-light, obtained 
by blowing a mixture of pulverised resin and magnesium dust through the flame of 
a spirit-lamp. This flash-light is used for military signals. 

Electric Light. Although the electric light has not been generally employed it 
deserves a lengthy notice. As is well known, the discharge of an electric spark, or 
a continuous voltaic or magneto-electric current, is capable of producing in pieces of 
graphite an intense light; and when this is obtained by suitably constructed apparatus, 
it may be rendered available for practical purposes. More recently Professor 
Jacobi has, with the assistance of M. Argeraud, of Paris, made a series of experi¬ 
ments on street lighting with the electric light. Upon the tower of the Admiralty 
buildings at St. Petersburg, an electric light apparatus was placed, and with it three 
of the largest streets of the city, viz. Newslty Prospect, Erbsen Strasse, and Wos- 
nesensky Prospect, were illuminated at night from seven until ten o’clock. The 
light was intense, and the very clear sky appeared as by sunlight, while the gaslights 
became lurid. The battery employed was a carbon battery of 185 cells. In 1854, 
the works for the construction of the Napoleon docks, at Rouen, were for several 
nights illuminated with the electric light for three to four hours consecutively; 
800 men were at work, and could continue their labour at a distance of 100 metres 
from the source of light. A Bunsen battery of large size with 100 cells was 
used. This light was very cheap, the cost per man being about three farthings; 
while the labour could proceed as in daylight. Several lighthouses, among them the 
North Foreland on the Kentish coast, and also that of Cape la Heve near Havre, 
have been fitted with apparatus for the electric light. This light is also used in 
many cases in dissolving views, and for the illumination of pleasure gardens at 
London, Paris, Berlin; and permanently for lighting the slate quarries situated near 
Angers, France. The electric light has been tried for submarine illumination with 
success, and also for photographing purposes. Colonel von Weyde invented a 
submarine electric illuminating apparatus, used by the French men-of-war in' the 
late conflict between France and Germany. In Spain, in 1862 and 1863, the electric 
light was frequently employed during the night in the construction of railways. The 
magneto-electric apparatus invented by Dr. Siemens (1867) is of great importance, 
as proved by the experiments made at Burlington House. By means of this machine 
it becomes possible to obtain electric currents at a cheap rate, of enormous power 
and especially adapted for lighthouses. 

By the exercise of great ingenuity, the difficulties attending the maintenance of the 
carbon points at an equal distance have been overcome. The lamps in which this result 
is effected are, however, more or less complicated, expensive, apd liable to get out of 
frder. The electric lamps of Foucault, Serrin, and Duboscq, described admirably in 
Dr. Schellen’s “ Spectrum Analysis,” and engravings of which are to be met with in most 
treatises on physics, are delicate pieces of mechanism peculiarly unsuited to the rough 


ARTIFICIAL LIGHT. 


681 


handling to which apparatus in use for technical or signalling purposes must be sub¬ 
mitted. The electric lamp devised by Mr. Browning is simple in construction, but even 
this requires more attention than could be bestowed upon the source of light for general 
purposes. 

The purity of the carbon points has much to do with the intensity of the light 
emitted by batteries of the same strength; while their distance from each other is also of 
consequence. 50 or 60 Bunsen’s elements will yield a light equal to that of 400 to 1000 
stearine candles, according to the purity of the carbon points. Taking the sunlight at 
noon on an August day to bo represented by 1000, Foucault and Fizeau have found the 
chemical power of the light obtained, under the best conditions, from 46 Bunsen’s 
cells, expressed by the number 235. Despretz states that the light from 100 Bunsen 
elements produces much discomfort to the eyes, while that from 600 elements, even at a 
glance, is sufficiently intense to cause considerable injury. But the duration of the 
electric light as obtained from battery power is not continuous. Whether from polarisa¬ 
tions in the battery or from many other causes, the light sometimes fails for several con¬ 
secutive minutes. It becomes then necessary to have recourse to some source of elec¬ 
tricity in which these objections are eliminated. To a great extent this is the case 
with magneto-electricity. The light from Messrs. Wilde’s large machine is the most 
powerful artificial light which has ever been produced, giving about eight times the light 
of former magneto-electric machines. Like most practical applications of science, the 
important results which Mr. Wilde has obtained depend more upon an ingenious combi¬ 
nation of several known facts, united with considerable engineering skill, than upon any 
really new and striking discovery. The principle of the machine can be expressed in a 
few words. It consists in the application of a current from an electro-magnetic machine, 
armed with permanent magnets, for the purpose of exciting a powerful electro-magnet; 
this electro-magnet being now used as the basis of a still larger electro-magnetic machine, 
for the purpose of having induction currents generated by its agency. In other words, by 
well-known means, an electric current can be obtained by the rotation of an armature 
close to the poles of a magnet. If this electric current be passed round an electro¬ 
magnet, it may be made to produce a far greater amount of magnetism than was 
possessed by the first magnet. There is no difficulty, therefore, in comprehending how, 
by the mere interposition of a rotating armature, and the expenditure of force, a small 
and weak magnet may be made to actuate a very powerful magnet. But as the power of 
the magnet increases, so does the power increase of the electric current which may 
be generated by induction in an armature rotating between its poles. We have, therefore, 
only to pass this No. 2 induced current from No. 2 magnet round a still larger magnet, 
No. 3 ; and by rotating an armature between its poles, we can get a still more energetic 
current, No. 3. Theoretically there is no limit to this plan—it is a species of involution ; 
and when it is considered that each conversion.from magnet No. 1 to magnet No. 2, &c., or 
from induced current No. 1 to induced current No. 2, &c., multiplies the power very many 
times, it will not be surprising that after three involutions the induced current possesses 
such magnificent powers.* 

Some erroneous opinions are pretty generally entertained as to the actual discovery 
claimed by Mr. Wilde, and the splendour of the result, for achieving which he deserves 
the very highest credit, is liable to cause earlier investigators in the field to be overlooked; 
this would be most unfair, for it is through their instrumentality that the way has 
been paved for the success now achieved. In 1838, Abbes Moigno and Baillard proved 
that by taking an electro-magnetic machine, the original magnet of which would sup¬ 
port only a few grammes, and passing the electric current generated by it round a 
large electro-magnet, the latter could be made to support a weight of 600 kilogrms. The 
Abbes carried the multiplication of power only so far as to obtain the more powerful 
magnet, No. 2, from the weak magnet, No. 1. 

With the three armatures of Mr. Wilde’s machine driven at a uniform velocity of 1500 
revolutions per minute, an amount of magnetic force is developed in the large electro¬ 
magnet far exceeding anything which has hitherto been produced, accompanied by the 
evolution of an amount of dynamic electricity from the quantity armature so enormous 
as to melt pieces of cylindrical iron rod fifteen inches in length and fully one quarter of 
an inch in diameter. With this armature in, the physiological effects of the current can 
be borne without inconvenience. When the intensity armature was placed in the 7-inch 
magnet cylinder, the electricity melted 7 feet of No. 16 iron wire, and made a length of 
21 feet of the same wire red-hot. The illuminating power of the current from this arma¬ 
ture was of the most splendid description. When an electric lamp, furnished with rods 


* See “A New Era in Illumination,” by W. Crookes, F.B.S.; “ Quarterly Journal of 
Science,” October, 1866. 




682 


CHEMICAL TECHNOLOGY. 


of gas carbon half an inch square, was placed on the top of a lofty building, the 
light evolved from it was sufficient to cast the shadows of the flames of the street lamps 
a quarter of a mile distant upon the neighbouring walls. "When viewed from that 
distance, the rays proceeding from the reflector have all the rich effulgence of sunshine. 
With the reflector removed from the lamp, the bare light is estimated to have an intensity 
equal to 4000 wax candles. A piece of ordinary sensitised paper, such as is used for 
photographic printing, when exposed to the action of the light for twenty seconds, at a 
distance of 2 feet from the reflector, was darkened to the same degree as a piece of the 
same sheet of paper was when exposed for a period of one minute to the direct rays of 
the sun at noon on a very clear day in the month of March. Paper could be easily set on 
fire with a burning-glass introduced in the path of the rays from the reflector. 

It will be of interest, apart from all questions as to economical production, to ascertain 
what is the theoretical quantity of coal required to be consumed in the production 
of this amount of electric force. Mr. Wilde says that a 7-horse engine is required to 
drive the machine. One horse-power is equal to 1,980,000 foot-pounds per hour; that 
multiplied by seven is 13,860,000 foot-pounds per hour, which therefore represents 
the actual power required to drive the machine. Now, by multiplying the British 
Fahrenheit units of heat produced by the combustion of one pound of coal by Joule’s 
equivalent, 772 foot-pounds, the result will be the total heat of combustion expressed in 
foot-pounds. In the best coal this is as high as 12,000,000 foot-pounds. We arrive, 
therefore, at the conclusion that, to overcome the friction of the different parts of the 
machine; to whirl a mass of metal, weighing several hundredweights, round with 
a velocity of 1500 revolutions per minute ; to generate a current of electric force far sur¬ 
passing anything before produced ; and, after allowing for the waste inherent in its pas¬ 
sage through the conducting wires and electric lamp, to cause it to blaze forth with an inten¬ 
sity of light paling the rays of the sun; to keep up this intense development of energy 
for one hour—requires an expenditure of force represented by the combustion of less than 
i8£ ozs. of coal. This is the theoretical calculation; but if reduced to actual practice,the 
results are scarcely less astonishing. The efficiency of an engine, i.e. the ratio of the 
work actually performed to the mechanical equivalent of the heat expended, varies in 
extreme cases between the limits 0’02 and 0*2. Taking an average efficiency as o'i, or one- 
tenth, we find that the ordinary consumption of coal required to work a 7 horse-power’ 
engine, midway between excessive wastefulness on the one hand, and rigid economy 
on the other, is 10 x i8£ ounces, or ii£ lbs. of coal per hour, worth about one halfpenny. 
This is, of course, only one item in the cost—to it must be added the expense of carbon 
rods for the lamp, which will be about ten inches per hour, worth perhaps a penny; 
there must also be added interest of the cost of purchase of machines, expense of main¬ 
tenance and repairs, which will perhaps bring up the total expense per hour to 
sixpence or eightpence. Comparing this with the hourly expense of the electric lights 
already in existence, we find, according to the Abbe Moigno, that the French machine 
costs altogether sixpence per hour for a light equal to 900 wax candles; whilst the actual 
working expenses of maintaining the electric light at Cape La Heve, during a period of 
twenty-seven months have been, exclusive of salaries, about one shilling per hour, 
cr inclusive of salaries, two shillings. According to a calculation made by the Abbe 
Moigno respecting the economy of the light evolved by the French machines, it appears 
that to maintain a light equal to 4000 wax candles for one hour would cost—with gas, 
£1 2s. 6d.; with colza oil, £1 7s.; and with the electricity produced by a Bunsen’s pile, 
£1 15s. 6d. The annual expenditure at a first-class lighthouse on the old system is, on an 
average, £400 per annum; and on the assumption that the light burns for 4000 hours per 
annum, that would come to two shillings per hour. The expenses of the old and 
the electric system are therefore not very dissimilar; and the problem of the adoption 
of electricity to supersede oil must be decided on grounds of convenience and efficiency 
alone. 

One cause of inconstancy in tho electric lamp which hinders the adaptation to the pur¬ 
poses of lighthouse illumination is the unequal consumption of the carbon points. From 
experiments recently conducted for the Trinity House, Mr. Stevenson finds that the 
employment of a modified form of vacuum-tube removes this objection. The subject 
upon which we cannot enter more fully here is very exhaustively treated in Mr. Stevenson’s 
recent work on the illumination of lighthouses. 

The following Table exhibits the comparative illuminating power of the principal 
artificial lights:— 


ARTIFICIAL LIGHT. 


683 



a. 

| 3 . 

y 

S. 

t. 

T . , , , . Consumption Intensity of light. 

Light-producing perho i in (lwa i cand ! e 

Light obtained 
from 10 grms. of 

Illuminating 
power (wax 



grms. 

— 100). 

this material. 

candles = 100). 

Wax . 

9*02 

102*00 

111 "02 

100 

Stearic acid. 

9*94 

95*50 

9603 

84 

Spermaceti. 

8-87 

108-30 

123*17 

108 

Tallow. 

8-87 

90-25 

101*70 

90 

Paraffin (1 st quality) ... 

8-83 

— 

94*69 

83 

9 

, (2nd „ ) ... 

8-49 

— 

139*87 

123 

d 1 

1 Moderator lamp ... 

4069 

694*00 

170-07 

159 

0 1 
eJ J 

1 Kitchen lamp 

7*33 

45*67 

62*30 

55 

•3 

I Reading lamp, with - 





O 1 

[ out glass chimney 

986 

114*01 

II5-80 

102 

Photogen . 

2002 

— 

149*03 

* 3 i 

Solar oil ... . 

26*82 

— 

225-64 

199 

Petroleum . 

15-06 

— 

174-40 

180 


,, 

8*09 

—■ 

i86*oi 

i 95 


According to Dr. Frankland’s researches, the following quantities of illuminating 
materials exhibit equal illuminating power :— 

Young’s paraffin oil from Boghead coal 4*53 litres. 

American petroleum (No. 1). 5 70 „ 

„ ,» (No. 2). 5-88 „ 

Paraffin candles . 842 kilos. 

Spermaceti candles. 10-37 „ 

Wax „ . . . 11-95 > 

Stearine ,, ... .. 12*50 „ 

Tallow „ . 16*30 


Paraffin and Solar or Petroleum Oils. 

Paraffin oils. Paraffin was discovered in the year 1830 by Karl von Reiclienbacli 
among the products of the dry distillation of beech-wood tar, and has obtained its 
name from parum, little, and affinis , related to, on account of its incapability of 
chemically uniting with other substances. Paraffin is not acted upon by alkalies or 
acids, nor is it decomposed at a red-heat. It was afterwards found that paraffin is 
also formed by the dry distillation of peat, brown coal, Boghead, and some cannel 
coals, but not by the dry distillation of real coal. Paraffin is found native and occurs 
in large quantities in:—1. Petroleum, Rangoon and Persian, which sometimes con¬ 
tains 6 to 40 per cent. 2. In impure state, under the names of ozokerite, neft-gil, 
or mineral wax. 3. In bitumen, asphalte as contained in some schistose rocks, and 
as met with at Trinidad and elsewhere. 

Manufacture of Paraffin. The mode of obtaining this substance differs according to its 
being an educt or a product. It is an educt as obtained from petroleum, ozokerit, 
neft-gil; but a product of the dry distillation of brown coal, peat, and the Boghead 
shale. 








684 


CHEMICAL TECHNOLOGY . 


Pre ffomPetroieum affin lt That petroleum contains paraffin was known in the year 1820, 
when A. Buchner discovered in the earth oil of the Tegernsee, in Upper Bavaria, a 
solid, fatty substance, which was afterwards ascertained by V. Kobell to be paraffin. 
Hence Buchner is locally considered to be the discoverer of paraffin; while later 
researches have proved that the earth oil of Baku, on the Caspian Sea ; of Amiano, 
near Parma; and of Gabian, Herault, France; contain this substance to greater or 
less extent. The idea of using these oils for the industrial preparation of paraffin 
dates only from 1856, when some samples of petroleum which were found to contain 
a large quantity of paraffin were imported into Europe. The American petroleums 
contain only a very small quantity of paraffin; but in those derived from Burmah 
and Rangoon, Gregory, De la Rue, and H. Muller found 10 per cent. Bleekrode 
investigated a sample of Java petroleum which contained 40 per cent of paraffin. 
The mountain naphtha of Eastern Galicia is with great advantage employed for pre¬ 
paring paraffin. According to Jacinsky, 45,000 cwts. of this material were in 1866 
obtained from this naphtha. 

The Rangoon oil obtained from Burmah as a native product flowing from springs 
in the neighbourhood of the river Irawadi is, according to De la Rue’s patent 
(1854), treated in the following manner for the purpose of preparing paraffin and 
hydrocarbon oils. The crude oil is first put into a still, which can be heated by fire 
externally while steam is admitted internally. By this operation about 25 per cent 
of a fluid is obtained, which on being submitted to fractional distillation yields 
hydrocarbon, the sp. gr. of which varies from 0'62 to 0 86, while the boiling-point 
varies from 26*7° to 200°. The lightest and most volatile of these hydrocarbons is 
used as an anaesthetic, under the name of Sherwood oil, while the heavier oils 
are burnt in paraffin lamps. The residue of this first distillation—about 75 per cent 
of the original quantity—is again distilled, but with steam at 150° to 200°; and the 
products of variable volatility are separately collected. The last portions of the dis - 
tillate contain chiefly paraffin, which is in crude state separated from the liquid 
by the application of artificial cold. The heavy oil is used as lubricating oil, and the 
paraffin is purified as already described. 

Para andN°ea-giL kerite Paraffin is prepared from ozokerite and neft-gil, on the island 
Swatoi-Ostrow, in the Caspian Sea, about a verst (=106678 metres) from the 
peninsula Apscheron, on the Caucasian shore. The neft-gil is carried by ships from 
Truchmenia. Paraffin is largely manufactured in Galicia from the mineral wax 
which occurs near Drohobicz and Boryslaw, also on the northern slopes of the Car¬ 
pathian mountains, and in other parts of the Austrian Empire. The chief works are 
found at Aussig, Florisdorf, Ostrau, Vienna, New Pesth, Temisvar, &c. Mineral wax 
is also largely found in Texas. 

Neft-gil, according to F. Rossmassller, is treated in the following manner:— 
15 cwts. of the crude material is put into iron stills provided with a leaden worm, and 
submitted to fractional distillation, yielding 68 per cent of distillate, consisting of 
8 per cent of oil and 60 per cent of crude paraffin. The oil thus obtained is yellow, 
opalescent, possesses an ethereal odour, and a sp. gr. of 075 to 081. Each distilla¬ 
tion yields a quantity of a light oil boiling below ioo°, which is used for the purpose 
of purifying the paraffin. The crude paraffin obtained by the first distillation is 
tolerably pure, has a yellow colour, and can at once be treated by the hydraulic press 
and centrifugal machine. The oil from these operations is again submitted to 
fractional distillation in order to obtain more paraffin. The pressed paraffin is 


ARTIFICIAL LIGHT. 


685 

molten and treated at 170° to 180 0 with sulphuric acid, which is next neutralised by 
means of lime, and the paraffin again rapidly distilled; then again submitted 
to strong pressure, and the material obtained treated with 25 per cent of the light 
oil; then again molten, again pressed, and finally treated with steam for the purpose of 
eliminating the last traces of essential oil. The material obtained by this treatment 
is a perfectly pure, colourless material, free from smell, transparent, and so hard as 
to exhibit in large blocks an almost metallic sound. The fusion-point is 63° 
Kossmassler states that the raw. material yielded to him in a week’s time, after 
a previous continued distillation of two months, 148! cwts. of paraffin ready 
for second pressure. The Galician ozokerite juelds by distillation only 24 per cent of 
paraffin, and 45 per cent of paraffin oil, also termed ozokerite oil. 

Paraffin from Bitumen. c. Paraffin is made in England from bitumen, asplialte, mineral 
tar, and the bituminous organic matter present in certain shales; among these, the 
so-called Kimmeridge clay, Boghead coal, and a few cannel coals. The asplialte 
occurring in Trinidad, Cuba, Nicaragua, Peru, California, and other countries, is 
used for the purpose of preparing paraffin and paraffin oils. The Cuba and Trinidad 
asphaltes yield 175 per cent paraffin. The extensive deposits of bituminous shale in 
Hungary are treated for paraffin and oil at Oravicza. According to Wunschmann, the 
shale yields 5 to 6 per cent of paraffin, 49 per cent of oil suited for burning in lamps, 
and 6 per cent of lubricating oil. 

P r e p aration of Paraffin by The preparation of paraffin by the dry distillation of peat, 
brown-coal, coal-shale, Boghead coal, &c., involves two operations:—1. The prepa¬ 
ration of tar. 2. The application of the latter to the preparation of paraffin, oil 
and paraffin. The coal-tar of the gas-works does not contain paraffin, but naphtha¬ 
line and anthracen. 

Preparation of the Tar, x. This operation is one of the most important and difficult of 
the industry, and during the last fifty years many enterprises undertaken for the 
application of fossil fuel to the preparation of illuminating materials have failed 
solely on account of the imperfect preparation of the tar. The making of the tar is 
carried on in retorts or in peculiarly constructed ovens, the distillation being in many 
cases assisted by the application of superheated steam. The principle of the con¬ 
struction of the tar oven is very simple, being that by a portion of fuel burning in the 
lower part of the oven, a layer, more or less thick, of superincumbent fuel, is sub¬ 
mitted to a slow carbonisation, resulting in the production of tar, which flows down¬ 
wards, while the gaseous products are lost. In order to prevent its violent combus¬ 
tion, the fuel is covered with a layer of clay. But as experience has shown that this 
mode of distillation is not well suited for the production of tar intended to yield 
paraffin and the oils, it is not general in practice on the large scale, although it has 
the advantage of being a continuous and uninterrupted process. According to 
report, an oven constructed by L. Unger, the manager of a paraffin works at Doll- 
nitz, near Halle, yields suitable products, while a saving is effected in labour as well 
as in the quantity of fuel required for the distillation. 

Horizontal retorts are frequently used for the preparation of tar, but experience 
has taught that if in the construction of the furnaces containing the retorts the 
arrangement is similar to that of a gas-works where four to eight retorts are worked 
in one furnace, no satisfactory results can be obtained, one of the reasons being that 
the principles of gas- and of tar-making are entirely opposed. It appears to be 
necessary to construct a furnace for every retort, and that the furnace should be 


686 


CHEMICAL TECHNOLOGY . 


of such dimensions as to he suited to hold a retort io feet long, 30 inches wide, and 
15 inches high, forming in section a shallow oval. More recently there have been 
built in Bohemia and elsewhere brickwork retorts, shaped Somewhat like a bakers 
oven. These seem to answer well, but are difficult to repair although of small first 
cost. Yohl observed that a quantity of 20 to 25 per cent of water present in the 
fossil material very greatly assists the formation and increases the yield of tar, 
owing to the superheated steam formed from the water during the distillation 
carrying off the vapours of the tar rapidly from the hot retort. This has given rise 
to the construction of Lavender’s tar-producing apparatus, the principle of which is 
the same as that of Yioletti’s wood-charring apparatus used for the preparation of 
the charcoal in gunpowder manufacture. Lavender’s apparatus consists of an iron 
cylinder provided with holes at the bottom for the purpose of admitting superheated 
steam, while to the top of the cylinder a tube is fitted for carrying off the products of 
the distillation. It would appear that L. Ramdohr’s method of preparing tar from 
brown-coal by means of steam yields a tar which contains 22 to 24 per cent of 
paraffin and 36 to 38 per cent of oil. 

vapours a of°the Tar The condensation of the products of the dry distillation is one of 
the most important operations, and greatly influences the yield of tar. Yohl has 
lately proved that even when the construction of the retorts is not of the best, an 
average yield of tar may be obtained by attention to the condensation of the vapours. 
The complete condensation of the vapours of the tar is one of the most difficult 
problems the paraffin and mineral oil manufacturer has to deal with, while the means 
usually adopted for condensation, such as large condensing surfaces, injection of cold 
water, and the like, have proved ineffectual. It has often been attempted to condense 
the vapours of tar in the same manner as those of alcohol, but there exist essential 
differences between the distillation of fluids and dry distillation. In the former case 
the vapours soon expel all the air completely from the still and from the condenser, 
and provided, therefore, that—in reference to the size of the still and bulk of the 
boiling liquid—the latter be large and cool enough, every particle of vapour must 
come into contact with the condensing surfaces. In the process of dry distillation 
the case is entirely different, because with the vapours, say of tar, permanent gases 
are always generated. On coming into contact with the condensing surfaces, a 
portion of the vapours are liquefied, leaving a layer of gas as a coating, as it were, 
on the condensing surface. The gas being a bad conductor of heat, prevents to such 
an extent the further action of the condensing apparatus, that a large proportion of 
the vapours are carried on and may be altogether lost. A sufficient condensation of 
the vapours of tar can be obtained only by bringing all the particles of matter which 
are carried off from the retorts into contact with the condensing surface, which need 
neither be very large nor exceedingly cold, because the latent heat of the vapours 
of tar is small, and consequently a moderately low temperature will be sufficient to 
condense these vapours to the liquid state. The mixture of gases and vapours may 
be compared to an emulsion, such as milk, and as the particles of butter may be 
separated from milk by churning, so the separation of the vapours of tar from the 
gases can be greatly assisted by the use of exhausters acting in the manner of 
blowing fans. It is of the utmost importance in condensing the vapours of tar that 
the molecules of the vapours be kept in continuous motion, and thus made to touch 
the sides of the condenser. The condenser should not be constructed so that the 
vapours and gases can flow uninterruptedly in one and the same direction. The 


ARTIFICIAL LIGHT. 


6S7 


temperature at which the distillation is conducted greatly influences the yield of tar, 
and consequently of the paraffin and oil. As regards the influence of the shape of 
the retorts and mode of distillation, H. Volil made the undermentioned comparative 
researches by distilling French and Scotch peat in horizontal retorts (No. I.}, in 
vertical retorts (No. II.), and in ovens somewhat like coke-ovens (No. III.) 

100 parts of peat yield of tar,— 

French peat. 5*59 4 67 2 69 

Scotch peat . 9*08 6-39 4*16 

The sp. gr. of the tar from the different kinds of apparatus was as follows :— 

i. 11. in. 

French peat.0 920 0 970 roo6 

Scotch peat.0*935 0*970 -'037 

It appears from these results that horizontal retorts yield the largest, and ovens 
the smallest, quantity of tar; moreover, the duration of the operation of distilling is 
shortest in horizontal retorts, which also yield less gas, while in the ovens both tar 
and coke are burnt away to a considerable extent by the too great supply of oxygen. 

Properties of Tar. The tar obtained from the retorts in distilling peat, brown-coal, 
lignite, bituminous shales, Boghead coal, &c., at as low a temperature as possible, 
and hardly higher than dull red-heat even towards the end of the operation, exhibits 
a coffee-brown colour, generally an alkaline, in some instances an acid, reaction, and 
possesses the very penetrating odour characteristic of tar. By exposure to air the 
colour of the tar becomes deeper, and sometimes even brownish-black. This tar 
often semi-solidifies at a temperature of 9 0 to 6°, owing to the paraffin it contains. 
The sp. gr. varies from o'85 to 0'93, and consequently the tar floats on water. The 
so-called steam-tar, obtained by the aid of superheated steam from brown-coal 
(according to Ramdohr’s plan, 1869) always has an acid reaction, and is completely 
saponified by alkalies ; this tar becomes solid at a temperature of 55 0 to 6o°, and can 
therefore be preserved in solid blocks in summer time. Its sp. gr. is o 875. 

As regards the quantity of tar obtained from 100 parts of raw material, the fol- 


lowing results are most general:— 

Foliated bituminous 

Tar. 

Sp. gr. 

*- -- N 

Crude paraffin. 
Per cent. 

shale, 

Siebengebirge 

20*00 

o*88o 

0750 

>> » 

Hesse 

25*00 

o*88o 

1*000 

Brown-coal, 

Prussian Saxony 

7 00 

0*910 

0*500 



1000 

0920 

0750 

• y 

>9 

600 

0915 

0*500 

99 


5*00 

0*910 

0*250 

99 

Bohemia 

11*00 

o*86o 

— 

99 

Westerwald 

550 

0*910 

— 

99 

99 

350 

0*910 

— 

99 

Nassau 

4*00 

0910 


99 

99 

3 00 

0910 

— 


Frankfort 

900 

0*890 

—— 

Lignite, 

Silesia 

300 

0*890 

0*25 

Shale, 

Vendee 

1400 

0*870 

1000 





688 CHEMICAL TECHNOLOGY. 




Tar. 

r ~ 

Sp. gr. 

Crude paraffin. 
Per cent- 

Shale, 

Westphalia 

5 00 

0920 

0050 

Schist, 

Wiirtemburg 

9'63 

0‘975 

0*124 

Peat, 

Neumark 

5 00 

0910 

0*330 

99 

Hanover 

900 

0920 

0*330 

99 

Erzgebirge 

570 

0902 

0*350 

99 

99 

5 ’ 3 ° 

0905 

0*400 

99 

Russia 

5-86 

— 

— 

99 

9 i 

7*00 

— 

— 

Boghead coal, 

Scotland 

3300 

o*86o 

1—1*4 

Cannel coal, 

99 

— 

— 

1—13 

Peltonian coal, 

99 

— 

— 

1*000 

Coarse coal. 

99 

9*00 

0*910 

1—1-25 


M with 0 the P Tar tins The first thing to be done with the crude tar is to separate the 
water, which is effected by pumping the tar into the dehydrating apparatus. These 
apparatus consist of tanks of boiler-plate, placed within a larger tank, so that a space 
of io centims. intervenes, into which water is poured and maintained by means of 
steam at a temperature of 6o° to 8o° for ten hours. After this time the ammoniacal 
water and other impurities, together about one-tliird of the bulk of the crude tar, 
have become separated, while the small quantity of water still adhering to the tar is 
of no consequence in the further operations. The tar is decanted by opening a stop¬ 
cock or valve placed near the top of the tank, and the ammoniacal water is removed 
by opening a stop-cock at the bottom. 

Specifically light tars are of course readily separated from the water, while heavy 
tars are more difficult to deal with. If to the ammoniacal water of such tars salts 
are added, for instance, common salt, Glauber salt, chloride of calcium, and the like, 
the specific gravity of the water is increased, and the heavy tar more readily sepa¬ 
rated ; but according to Dullo these means are either too expensive or do not quite 
answer the purpose. The complete separation of the tar from the water is of the 
greatest importance, because in the subsequent distillation the presence of water may 
cause the tar to boil over and give rise to serious accidents by coming in contact 
with the fire under the stills. 

Distillation of the Tar. This operation is usually carried on in cast-iron stills large 
enough to hold 20 cwts. of tar. In order to prevent the flame impinging on the 
bottom of the still, it is protected by a fire-brick arch. v The still is usually built in 
two separate parts, which are joined with a flange and bolts, so that if the lower part 
is burnt out, only that requires to be renewed. 

The helms of these stills are rather flat and the spout very wide. The vapours of 
the various oils have a high density and low latent heat, so that these vapours have 
a tendency to condense readily and flow back into the still; therefore the helm is 
covered with sand or ash, being bad conductors of heat. When the tar is thoroughly 
dehydrated, the distillation proceeds quietly and without ebullition ; but if any water 
be mixed with or adheres to the tar, the liquid in the still boils violently and is very 
apt to boil over. At below ioo° the tar loses the very volatile sulphide of ammonium 
and the pyrrhol bases, while gases are evolved which ought to be allowed to escape 
by a safety-valve. The true distillation begins at ioo°, yielding at first a distillate 



ARTIFICIAL LIGHT. 


689 

consisting of very strong ammoniacal liquor and some light oils. The boiling-point 
of the tar is not constant, the oil coming over uninterruptedly when the temperature 
has risen to above 200°; then the boiling-point becomes somewhat constant, while 
with the oil some water comes over, due to the chemically-combined water of the 
carbolic acid being set free. The distillation then again becomes somewhat inter¬ 
rupted, and can be maintained only by stronger firing of the retort. The oils now 
distilling over become solid on cooling, owing to the large proportion of paraffin they 
contain. The distillation is continued to dryness, the asphalte left in the still being 
removed after about four or five operations, and for this purpose the still is some¬ 
what cooled and the molten asphalte run off by a tap at the bottom of the still. If 
the distillation is carried to dryness, some water finally distils over, due to the 
decomposition of the organic matter. A still of 500 litres capacity can be distilled 
off in twelve to fourteen hours, if the operation is pushed so far as to decompose 
the asphalte, leaving only a carbonaceous residue ; but if the asphalte is to be col¬ 
lected, the distillation must be stopped after eight to ten hours. The still is sepa¬ 
rated from the condensing apparatus by a massive wall, through which the spout of 
the helm is passed into the leaden worm serving as a condenser, and kept cool by 
being placed in a wooden tank filled with cold water. But as soon as the paraffin 
magma begins to come over the water is allowed to become warm, in order to 
prevent the paraffin solidifying in the worm. The gases which are evolved towards 
the end of the distillation are carried off by a'pipe communicating with the chimney. 

Treat “f e Di3°tii t iation ? duct3 The mixed products or raw oils obtained by the distillation 
are poured into a large cast-iron cylinder and mixed with a solution of caustic soda 
so as to cause the latter to act upon, and intimately combine with, the acid sub¬ 
stances (homologues of carbolic acid)—simply termed creosote in the works—and 
pyroligneous acid—which impart an offensive odour and dark colour to the oils. 
When the mixture of the oils and caustic soda solution has been effected, the fluid is 
run into an iron tank and allowed to settle; the creosote-soda is then removed, and 
the oil washed with water to eliminate any adhering alkali. The crude oil is next 
similarly treated with sulphuric acid for the purpose of removing basic substances, 
which impart odour and colour. The quantity of acid to be used and the duration 
of its action, aided sometimes by heat, depend upon the nature of the crude oil— 
5 per cent of acid of 170 sp. gr. and five minutes action are sometimes sufficient, 
while in other cases 25 per cent of acid will be required, and three hours’ contact 
with the oil. The action of the sulphuric acid should be carefully watched, as it may 
injure the quality of the oil by decomposing some of the lighter hydrocarbons, whereby 
sulphurous acid is given off. The mixture of acid and oil is allowed to settle; 
the former is run off, and the latter washed first with water then with very dilute 
soda ley, and is finally poured into the rectifying stills. The solution of creosote-soda 
is neutralised with the sulphuric acid from the preceding operation, the result being 
that crude carbolic acid is obtained, which is used for various purposes; such as 
impregnating wooden railway sleepers, as a disinfecting material, or for preparing 
certain tar-colours (seep. 580). More recently the creosote-soda has been used for 
gas manufacture, leaving a coke containing soda, the soda being abstracted by 
lixiviation with water. 

Eect crcdeOiis f the This operation is conducted precisely as the distillation of the tar. 
The oils are separated according to their greater or less volatility and specific 
45 


CHEMICAL TECHNOLOGY. 


5 go 

gravity, or are kept mixed, as paraffin oil, at a sp. gr. of 0 833, and sent as such to the 
market. When the oil which comes over begins to solidify on cooling or exhibits a 
sp. gr. of o‘88 to 0*9, it is separately collected and placed in a cool situation for the 
purpose of crystallising the paraffin. The vessels in which the paraffin magma 
is placed for the purpose of solidifying are rectangular iron tanks, fitted with a tap, 
or are conical, sugar-loaf shaped vessels, made of iron or wood, and from r6 to 2 
metres high, and 1 metre wide at the top, being provided with a tap for the purpose 
of removing the oily matter which has not solidified after the lapse of about two 
to four weeks. This thick oil is next cooled to far below the freezing-point of water, 
in order to obtain more paraffin and other hydrocarbons mixed with it. Any 
still non-solidified matter is, when it has a low specific gravity, again refined by dis¬ 
tillation, and will yield paraffin oil; but if its sp. gr. is high—say from <rg25 to 0940— 
it is used as a lubricating oil, known abroad as Belgian waggon grease. 

Refiningofjthecrude The crude paraffin is in England sold to the refiners, who are 
also paraffin-candle makers; but on the Continent every manufacturer of crude 
paraffin refines his product and converts it into candles. The crude paraffin, so- 
called paraffin butter, is treated in various ways : some manufacturers crystallise it 
by the aid of cold, and press it for the purpose of removing any oil; others again 
first treat the crude material with caustic alkali ley, next with sulphuric acid, 
and then again distil it or leave it to crystallise. The caustic soda ley removes 
from the paraffin all the acid substances and other impurities it may contain. The 
partly purified paraffin is now treated with 6 to 10 per cent of sulphuric acid, 
whereby alkaline and resinous matters are removed. The loss in bulk of the crude 
material by these operations amounts to about 5 per cent. The purified paraffin is 
next allowed to remain in a very cool place for some three or four weeks; after 
which the nearly solid mass is filtered, then submitted to the action of centrifugal 
machines, and finally strongly pressed. The oil which is separated from the 
paraffin is again distilled, yielding paraffin oil and paraffin butter. The solid paraffin 
is molten, cast into blocks, and these submitted to very powerful hydraulic pressure. 
The pressed cake is next treated at 180 0 with 10 per cent of sulphuric acid .for two 
hours, then washed with hot water, again cast into blocks, again pressed, and 
then washed with a solution of caustic soda. Instead of treating the paraffin with 
active agents, it has been proposed to use neutral solvents for the removal of the 
oily materials; for this purpose, benzol, light tar oils, benzoline, and sulphide 
of carbon, have been employed in the following manner;—The crude paraffin 
is first hot-pressed, and the pressed mass fused with 5 to 6 per cent of the solvent; 
having been again cast into blocks, these are pressed, and the operation repeated if 
necessary. The paraffin having thus been made quite white and pure, is again fused 
and treated with high-pressure steam, forced into the molten mass for the purpose of 
volatilising the last traces of the solvents. The sulphide of carbon, first employed 
by Alcan (1858) for refining paraffin, is used in the following manner :—The paraffin 
is melted at the lowest possible temperature, then well mixed with 10 to 15 per cent 
of sulphide of carbon, after which the cooled and solidified mass is strongly pressed, 
the expressed fluid being submitted to distillation for the purpose of recovering the 
sulphide of carbon. The paraffin is next fused and kept in liquid state for some 
time for the purpose of eliminating the adhering sulphide of carbon. 

Slparin^SSn 0 .* lAstead of following the preceding method with the crude tar, 
Hiibner treats it first witli sulphuric acid, and next distils the tar, separated from the 


ARTIFICIAL LIGHT . 


691 

acid, over quick-lime. The crude paraffin obtained is pressed, and then further 
refined by treating it with colourless brown-coal tar oil. The advantages of this 
method—by which one distillation is saved—are:— 
a. A larger yield of paraffin. 

( 3 . A material of better quality and greater hardness than by the usual method. 

With the paraffin the so-called paraffin oils are obtained; but this industry 
has been greatly crippled by the extensive importation of paraffin oils (really 
petroleum oils) from America, so that the aim of the paraffin makers is to increase 
the yield of paraffin. By Hubner’s method of distillation over quick-lime, 
40 to 50 per cent of impurities (chiefly empyreumatic resins and creosote) are 
removed, which by the old process are only got rid of at greater expense by the use 
of caustic soda. 

Yield of Paraffin. As regards the yield of paraffin, paraffin oil, and lubricating oil, from 
the various kinds of raw materials, we quote the following particulars. At the Ber- 
nuthsfeld works, near Aurich, the excellent peat yields 6 to 8 per cent of tar; 
20 per cent of paraffin oil, of sp. gr. = ©’830; and 0*75 per cent of paraffin. H. Yohl 
obtained from 100 parts of peat-tar from the peat of undermentioned localities :— 


( 

Paraffin Oil. 

Lubricating Oil. 

Paraffin. 


Sp. gr., 0*820. 

Sp. gr., 0*860. 

Celle (Hanover) . 

3460 

36*00 

8*oi 

Coburg . 

20*62 

26*57 

3-12 

Damme (Westphalia) 

x 9‘45 

x 9‘54 

33 1 

Zurich (Switzerland) 

I 4 ’ 4 ° 

8*66 

042 

Russia . . 

20*39 

20*39 

3 * 3 b 

Westphalia . 

11*00 

19*48 

2*25 


Brown-coai. In the works situated in the Weissenfels brown-coal mineral district, 
1 ton ( = 275 to 300 lbs.) of the mineral yields 35 to 50 lbs. of tar. 100 lbs. of this 
tar yield 8 to 10 lbs. of hard paraffin suited for candle-making, and further 8 to 10 
lbs. of soft paraffin for use in stearine-candle making, as well as 43 lbs. of paraffin 
oil. Hubner’s works at Relimsdorf, near Zeitz, yield annually from 360,000 cwts. 
of brown-coal about 40,000 cwts. of tar, yielding 18,000 cwts. of crude oil, 
4000 cwts. of refined paraffin oil, and 6000 cwts. of paraffin. 

100 parts of retort-tar (in contradistinction to steam-tar) from brown-coal yield:— 


Brown-coal from— 

Paraffin oil. 
Sp. gr., 0*820. 

Lubricating oil. 
Sp. gr., o*86o. 

Paraffin. 

Aschersleben, Prussia. 

33*50 

40*00 

3 ’ 3 ' 


Frankenhausen „ . 

33 * 4 1 

40*06 

67 


Mtinden „ . 

I 7 ' 5 ° 

26*21 

50 


Oldisleben „ . 

1772 

26*60 

4‘4 

Analysed by 

Cassel „ . 

16*42 

27*14 

4*2 

f Yohl. 

Der Rhon, Bavaria . 

10*62 

x 9’37 

1*2 


Tilleda, Prussia ... 

16*66 

18*05 

4’4 


Stockheim, near Duren „ ... 

I 7 ' 5 ° 

26*63 

3*2 


Bensberg,near Cologne „ ... 

16*36 

x 9‘53 

3 * 4 - 

) 

Tscheitch, Austro-Hungary... 

9*04 

28*86 

3*2' 


Eger „ 

9* x 4 

54*00 

5*3 „ 

Analysed by 

Herwitz „ 

22*00 

48*32 

5*2 

C. Muller. 

Schobritz „ 

21*68 

4633 

4*3/ 











CHEMICAL TECHNOLOGY. 


&Q2 


Ramdohr obtained (1869) from steam-tar from brown-coal on an average— 


rc ( 15 per cent fusing at 56 to 58' 

22 to 24 Per cent paraffin | jtQ > » __ o 38-to 47' 

36 to 38 per cent of oil. 


and 


With careful management steam-tar may yield 28 to 30 per cent paraffin. 

The quotations of the yield from cannel and Boghead coals vary very much. 
100 parts of tar from bituminous shale were found to yield :— 


Mineral oil. Lubricating oil. Paraffin. 


English bituminous shale. . 

24*28 

40*00 

0*12 

Bituminous shale from Romerickberg, Prussia 

25*68 

43-oo 

Oil 

„ „ Westphalia „ 

27*50 

1367 

III 

„ „ Oedingen on the Rhine „ 

. 18-33 

38-33 

5*00 


According to Muller (1867), 100 parts of Galician mineral wax (ozokerite) yield 
24 per cent of paraffin and 40 per cent of oil. 

Properties of Paraffin. Pure paraffin is a white, wax-like, tasteless, and inodorous sub¬ 
stance, with a slightly fatty appearance. Its sp. gr. is 0-877. It is harder than tallow, 
but softer than wax. Its properties vary, however, according to the raw materials 
from which it has been obtained. Paraffin from Boghead coal has been obtained, 
after melting, in a very crystalline state, and with a fusion-point at 45 *5°; while, 
again, it has been obtained granular as bleached wax, with a fusion-point of 52 0 . 
Paraffin from Rangoon oil was found to fuse at 6i°, and that from peat at 46‘7°. The 
paraffin from the tar of Saxony brown-coals fuses at 56°, and the oil paraffin at 43 0 . 
The native paraffin from ozokerite fuses at 65-5°. The composition of the various 
kinds of paraffin is:— 


From Saxony From 
Brown-coal. Ozokerite. 


From Boghead 
mineral. 


From Peat. 


From 

Petroleum. 


Carbon ... 85*02 
Hydrogen . i4'98 


85*26 85*00 

I 4'74 i 5‘36 


84-95—85*23 8515 

15*05—15*16 15*29 


From these figures the conclusion may be drawn, contrary to the view generally 
adopted, according to which all varieties of paraffin should be mixtures of hydro¬ 
carbons constituted as C„H« (whether the paraffin be obtained from brown-coal, peat, 
ozokerite, or petroleum), that paraffin is a mixture of hydrocarbons homologous with 
marsh-gas, many of which contain no less than C 27 . Paraffin is insoluble in water, 
but soluble to some extent in boiling alcohol; 100 parts, however, dissolve when 
boiling only 3 parts of paraffin. Paraffin is soluble in ether, oil of turpentine, oil of 
olives, benzol, chloroform, and sulphide of carbon. Paraffin boils above 300°, 
and may be distilled without undergoing any alteration. Acids, alkalies, and 
chlorine do not at all act upon paraffin at the ordinary temperature; but when 
chlorine is caused to pass into molten paraffin, hydrochloric acid is evolved and 
chlorinated products formed. Paraffin may be fused with stearine, palmitine, 
and resins in all proportions. Paraffin is used for making candles (see p. 630), but 
nas been employed now and then as a lubricating material; also for preserving 
timber; for rendering wine and beer casks water-tight; for the purpose of preventing 
the foaming and boiling over of the sugar solutions in the vacuum pans at the 
beginning of the ebullition. It has been suggested to use paraffin for preserving 
meat; for waterproofing fabrics (Dr. Stenhouse’s process); for use instead of wax 


ARTIFICIAL LIGHT. 


693 


for waxing paper (employed in pharmacy under the name of charta cerata) ; instead 
of stearic acid for soaking plaster-of-Paris objects. Finally, paraffin is used in the 
manufacture of the better varieties of matches, as a waterproof varnish for coating 
the phosphorus composition; and in chemical laboratories to replace oil in the oil- 
baths. 

Paraffin oiL As already mentioned, the dry distillation of Boghead mineral, brown- 
coal, peat, and bituminous shales, yields tar, the quantity of which varies according 
to the nature of the raw material and other conditions, mode of distillation, degree 
of heat, &c. As regards the nature of tar we cannot say that it is fully elucidated. 
Until the year 1830, tar was considered to be simply a solution of empyreumatic 
resins, rich in carbon, in empyreumatic oil or oils, the nature of these substances 
being left undecided. The late Baron von Reichenbach was the first who seriously 
investigated the nature of tar, and the result was the discovery of paraffin and 
of eupion, a very volatile liquid, highly inflammable, and found to boil at 47 0 to 169°, 
consequently a mixture of various substances. Notwithstanding the high merits of 
Reichenbach’s researches, the constitution of tar was not fully elucidated. In 
an industrial point of view tar has many important applications, especially for the 
preparation of illuminating materials ; for by a rectifying and fractioned distillation, 
tar yields paraffin and paraffin oils, when the heavy oils ’ and acids have been 
previously separated. Paraffin oils—met with in the trade under various names, 
such as solar oil, pliotogen oil, ligroine oil, &c.—are very similar to petroleum oils, 
and consist like them of carbon and hydrogen, and are, when thoroughly rectified, 
almost colourless and free from smell. 

The mineral oils now met with in commerce are distinguished as:—Photogen, 
prepared in Saxony, and consisting of a mixture of oils boiling between ioo° and 
300°. It is a colourless, very mobile fluid, exhibiting a characteristic ethereal smell, 
and a sp. gr. of o‘8oo to o - 8io; but the sp. gr. of its constituent oils varies from 076 to 
o-86. Formerly there were met with in the trade light photogens of a sp. gr. of 078, 
consisting chiefly of a so-called essence, of 072 sp. gr. and boiling below 6o°; but this 
oil was found to be too inflammable, and is now used as benzoline (also known as 
naphtha, ligroine, Canada oil, &c.) in the sponge-lamps, and for other purposes. 
Solar oil, or German petroleum, is a colourless or faintly yellow-coloured fluid of 
about the same consistency as colza oil, and of a sp.,gr. of 0-830 to 0-832. The 
boiling-point lies between 255 0 and 350°; cooled to — io° it should not deposit 
paraffin, while its vapour is not inflammable below ioo°. Pyrogen is a kind of 
paraffin oil invented by Breitenlohner and prepared from residues of crude oils which 
contain carbolic acid, paraffin, and other substances, and exhibit a sp. gr. of 0*895 
to 0-945 ; these materials, which accumulate in tar-works, are converted into pyrogen 
by a process presently to be described, yielding a light straw-yellow oil of 0*825 to 
0*845 S P- g r - Engine-oil, or lubricating oil, also known as Vulcan oil, is a thickly 
fluid oil imported in large quantities from the United States, and which deposits, 
when submitted to cold, a large quantity of crystals of paraffin. This oil is obtained 
largely in the paraffin oil and petroleum-refining works. According to A. Ott’s 
account, the American lubricating oil is not obtained by distillation, but simply by 
defecating a specifically heavy native petroleum with charcoal so as to eliminate 
the colour. This lubricating oil is sometimes mixed with a certain percentage of 
vegetable or animal fats. The oil is largely used for lubricating cotton-spinning 
machinery, but notwithstanding its extensive employment, the production far exceeds 


594 


CHEMICAL TECHNOLOGY . 


the consumption; it should be as much as possible re-converted into paraffin oil and 
pyrogen. In America and on the Continent a large quantity is employed for 
making gas. 

Preparation of Mineral ou. The manufacture of these oils is a collateral industry with the 

manufacture of paraffin. The products of the distillation of tar are first treated with 
a solution of caustic soda. This operation aims at the removal of carbolic and acetic 
(pyroligneous) acid compounds, which impart to the oil a disagreeable odour and 
dark colour. The quantity of soda to be used may vary from 5 to 6 or even 20 per 
cent, and the operation requires, in some instances, the aid of heat for about two 
hours, while in others, again, the end is attained in two minutes and at the ordinary 
temperature of the atmosphere. The mixture of soda ley and other substances is then 
run into a large tank for the purpose of depositing the soda ley and combined com¬ 
pounds, which, when settled, are run off, and the oil washed with water until it has 
become free from alkali. The oil is next treated with sulphuric acid of 17 sp. gr., 
the quantity of which may vary from 5 to 25 per cent, while the duration of the 
operation may vary from one minute to three hours. The treatment with sulphuric 
acid greatly influences the quality of the oil, because it might happen that, by this 
treatment, oils originally free from sulphur would become impregnated therewith, 
in consequence of the fact that the more volatile portions of these oils are essentially 
mixtures of aldehydes and ketones, bodies which readily combine with sulphurous 
acid. The mixture of oil and sulphuric acid is run into a tank for the purpose of 
depositing the specifically heavier portions of the liquid; the supernatant lighter 
oil is afterwards tapped off, and washed with plenty of water, then with weak caustic 
soda ley, being finally rectified by distillation. According to H. Yohl, paraffin oils are 
sometimes bleached with hydrofluoric acid, whereby fluorine compounds are stated 
to be formed, which, on burning the oil, give off noxious vapours. The alkaline and 
acid liquors used in the operation are utilised in the following manner :—The crude 
alkaline carbolic acid liquor is saturated with sulphuric acid, and crude carbolic 
acid obtained. The latter is used for various purposes, among which #re the 
creosoting of timber, for disinfecting, &c.; or it is used for preparing pyrogen by 
causing the vapours to pass through a red-hot tube, the condensing product being, 
after treatment with soda ley and sulphuric acid, as well fitted for burning in lamps 
as paraffin oil. Perutz submits the alkaline liquid containing carbolate of soda to 
distillation in an iron still, pushing the operation on to dryness, and obtaining a 
mixture of carbolic acid with light fluid hydrocarbons. If it is desired to prepare pure 
carbolic acid, the liquid which comes over between 140° and 240° is separately 
collected and treated in the ordinary manner. The residue left in the still, a mixture 
of alkalies and coke, is calcined, the ash lixiviated, and the resulting liquor 
causticised with lime. The sulphuric acid is employed for preparing sulphate of 
iron. The rectification of the oils is performed in the ordinary manner. 100 parts 
of peat tar yield of rectified products:—Sclar oil of 0*865 sp. gr., 26’4 ; photogen, 
0*830 sp.gr., 207; paraffin, 23*3; crude carbolic acid (peat-tar creosote), ii*g 
parts. 100 parts of Saxony brown-coal tar yield on an average :—Paraffin, 10 to 15 
photogen, 16 to 27; solar oil, 34 to 38; creosote, 5 to 10; coke, 15 parts. The 
commercial value of these articles fluctuates and depends on the demand and supply. 
There were prepared in 1870 in Prussia from 5^ millions of cwts. of brown-coal in 
sixty-seven different works, 100,000 cwts. of paraffin and 250,000 cwts. of mineral 01 
paraffin oil. 


ARTIFICIAL LIGHT 


t >95 


Petroleum. 

1 it t 3 r o 1 ccurrence? ud Since the year 1859 native petroleum has become a most important 
illuminating material. Petroleum was known to the ancients and was used by them 
for various purposes. Greece obtained it from the Island of Zante; and the 
petroleum from Agrigentum was burnt in lamps under the name of Sicilian oil. 
The inspissated oil which was used under the name of mineral-pitch, or asphalte, 
as a cement in building Babylon, was obtained from the neighbourhood of 
the River Euphrates. Mineral pitch was used by the ancients fo? embalming 
their dead, while it wohld appear that some black-coloured earthenware was 
prepared with asphalte gently burnt in. In some parts of Central Asia large 
quantities of inspissated petroleum occur, and the Dead Sea is especially a locality 
where this substance is met with; hence the name of laeus cisphaltites. In the Island of 
Trinidad a large lake (Pitch Lake) occurs, filled with mineral pitch, which according 
to the prevailing temperature is more or less soft. Petroleum is found in a great 
many localities in different parts of the world—Amiano, near Parma, where this oil 
has been used for burning in street lamps; Tegernsee, Bavaria, the oil-spring 
having been known since 1430, but yielding only 42 litres annually; Neufch&tel, 
Switzerland ; Selinde, near Hanover; Kleinsclioppenstedt, Brunswick; Bechelbronn, 
Alsace; Coalbrookdale, England ; in the Pyrenees, and other portions of Spain and 
France; also in Galicia. In far larger quantity petroleum occurs on the Caspian 
seaboard at Apscheron, and especially on the Island of Tschellekan (39I 0 N. lat.), 
where more than 3400 sources are found, which yield annually 54,000 cwts. of 
petroleum. At Rangoon, in Burmali, petroleum occurs in such large quantity that 
annually 400,000 casks, weighing 6 cwts. each, are exported thence. But in no 
country is petroleum found in such inexhaustible quantity as in the United States, 
in a tract parallel to the Alleghany mountains, and extending from Lake Ontario 
into the Valley of the Kanawha, in Virginia. The oil region includes the western 
counties of the State of New York and Pennsylvania, and part of Ohio. The most 
important petroleum-wells are at Mecca (Trumhall Co., Ohio), and at Titusville, Oil 
City, Pitliole City, Rouseville, McClintockville (Venungo Co., Pennsylvania, the 
country of the Seneca Indians). This territory is termed Oil Creek. The wells are 
bored to a depth of 22 to 23 feet: some wells are flowing wells, the oil being yielded 
spontaneously; other wells are pumped. In Canada petroleum is met with in 
different localities; as, for instance, at Gaspe, near the St. Lawrence, and in Lambton 
Co.; also on the western portion of the peninsula formed by the lakes Huron, Erie, 
and Ontario, in the Enniskillen district. California yields enormous quantities of 
petroleum, which occurs also in many parts of South America, and in the islands of 
Java, Borneo, and Timor. 

0 rif, o£ PetTOieum. tion As regards the origin and formation of petroleum, several hypo¬ 
theses have been brought forward. According to some the formation of petroleum is 
intimately connected with the occurrence of li3 7 drocarbons met with—according to 
the observations of Dumas, H. Rose, and Bunsen—in compressed condition in many 
rock-salt deposits, from which they are set free either in the state of gas or as 
naphtha, when the salt comes into contact with' water or is broken up. The crack¬ 
ling salt of the Wieliczka mine gives off marsli-gas ; but by condensation CH 4 might 
yield homologous hydrocarbons, C 6 H I4 and C 7 H i6 , which form the bulk of the vola¬ 
tile portions of petroleum and paraffin, the composition of the latter varying between 


5 g 6 


CHEMICAL TECHNOLOGY. 


C 20 H 42 and C 27 H 5 6. Tlie association of petroleum, rock-salt, and combustible gases 
is met with in a great many localities ; as, for instance, in the Bavarian Alps, in Tus¬ 
cany, Modena, Parma, the Carpathian mountains, on the Caspian Sea, in India, and 
also in America. According to another view, petroleum is the product of the 
slow decomposition of vegetable and animal matter, and results from a re-arrangement 
of their elements. The American geologists suppose petroleum to be due to the dry 
subterraneous distillation of accumulations of sea-plants and marine animals, and 
that the petroleum is forced upwards by water, always present in the bored wells. 
Of course the hj-pothesis involves the action of subterraneous heat at great depth, 
which, according to existing observations on the increase of temperature in deep coal 
mines, reaches the boiling temperature of water at 8000 feet. According to 
Berthelot’s view (1866), there should be formed subterraneous^, from carbonic acid 
and alkali metals, acetylides, which again should yield with aqueous vapour acetylen, 
C 2 H 2 , which in its turn should be converted into petroleum and tar products. 

lle petroieum! ude Almost all the native petroleums require to be refined before they 
can be used as illuminating material, the mode of refining differing according to the 
nature and consistency of the oil. The oils met with at Apscheron, in Russia, and 
in the neighbourhood of Baku, are nearly all colourless, and can be directly used for 
burning in lamps after having been simply rectified by distillation. The Rangoon 
oil contains so large a quantity of paraffin that it has at the ordinary temperature 
the consistency of butter, and is therefore employed for extracting paraffin. The 
native petroleums of many of the East Indian islands contain sulphur compounds, 
and cannot therefore be burnt in lamps until they have been treated with caustic 
soda and sulphuric acid, and rectified by distillation. The specific gravity of the 
native petroleums met with in Canada and the United States varies very much; 
that from Venungo Co., Pennsylvania, has a sp. gr. of 0 8, while oils in other 
localities have a sp. gr. of cr85 to 09. Galicia produces large quantities of native 
petroleum, which is refined in some twenty-two works, situated near Boryslav and 
Drohobicz; while a large quantity of paraffin oil is obtained as a by-product of the 
distillation of paraffin from ozokerite. The lighter petroleums yield about 90 per 
cent of photogen and solar oil, but the heavier kinds yield only 40 to 50 per cent, the 
remainder being tar. The methods of refining native petroleums consist in treat¬ 
ment with caustic soda, sulphuric acid, and finally fractioned distillation. 

constitution of Petroleum. As far as researches have been instituted, all the native 
petroleums, irrespective of consistency and specific gravity, are mixtures of the 
higher series of the homologous compounds, of which marsli-gas, CII 4 , is the first 
term.* Amyl hydrogen, hydride of amyl, C 5 II I2 , boiling at 68°, and hydride of 
caproyl, CeH I4 , boiling at 92 0 , constitute the more volatile portion of crude American 
petroleum; these burn like marsh-gas with a faintly luminous flame. The con¬ 
stituents of the oil used in lamps are represented by the hydrocarbons C 7 H X 6 and 
Ci 2 H 26 . The higher series of the marsh-gas group exhibit a butter-like consistency, 
and are composed according to the formulae C 20 H 42 and C 27 H 5 6, and belong to the 
paraffins met with in petroleums. 

* Ronalds proved in 1865 that the gases evolved from crude American petroleum are 
essentially hydride of ethyl (C 2 H6), and hydride of propyl (C 3 H8), which are the 
second and third terms of the above series. The researches of Fouque (1869) agree with 
those of Ronalds, for he found that the gases evolved from petroleum are partly a 
mixture of the hydrides of propyl and butyl, and partly a mixture of marsh-gas 
and hydride of ethyl. 


ARTIFICIAL LIGHT. 


697 

Technology of Petroleum. According to an Act of Congress crude petroleum may not be 
exported, owing to its high degree of inflammability, and a sample of every cask of 
petroleum is to be tested. The oil ought not to give off inflammable vapours 
(hydride of butyl) below 38° C. = ioo° F. In the United Kingdom, as elsewhere, 
legislative measures have been taken in order to insure safety in the petroleum 
trade. Consequently crude petroleum is chiefly refined by submitting it to fraction. 1 
distillation in order to separate from it the naphtha of 0715 sp. gr. (the benzoline of 
the shops), which begins to boil at 6o°. Wiederhold found that the naphtha yields 
by fractional distillation:— 

48 6 per cent of 070 sp. gr. boiling at ioo° (a) 

457 » 073 „ „ 200° (6) 

57 „ 0*80 „ „ above 200° (e) 

(c) is refined petroleum ; (a) is too volatile for burning in lamps; ( b ) maybe used in 
properly constructed or sponge lamps. H. Vohl calls petroleum naphtha, canadol 
or Canada oil, and applies it to the carburetting of illuminating gas; and also as a 
solvent for caoutchouc, colophonium, mastic, dammar, copal, amber, shellac, oils 
and fats, and for preserving anatomical preparations. The most volatile and lightest 
portion of the naphtha (sp. gr. 0 65, boiling-point between 40° and 50°), known 
as Sherwood oil, keroselen, petroleum ether, and rhigolen, is used as an anaesthetic, 
and applied externally in neuralgia. The less fluid petroleum oils are used as 
lubricating oils under a variety of names—Globe oil, Vulcan oil, Phoenix oil, &c. 
Crude petroleum is used as fuel in the Russian navy, in steamers on Caspian Sea, 
and by the United States navy in some cases; it has been tried with success in 
France as fuel for locomotive engines. Refined petroleum, the paraffin oil of 
the London shops, is an opalescent fluid, somewhat yellow, boiling at 150°, not 
miscible with water, alcohol, and wood -spirit; but readily miscible with ether, oil of 
turpentine, and sulphide of carbon. Petroleum dissolves, especially when hot, 
asphalte, elemi, Venice turpentine, and caoutchouc. As is well known, petroleum is 
largely used for burning in lamps. The fluid known as kerosine, also used for 
burning in lamps, has a sp. gr. of 078 to o’825- Pitt oil seems to be identical, and 
both are prepared from American petroleum by distillation. As a great confusion 
exists in the names of the various distillation products of petroleum, we quote the 
following particulars communicated by Kleinschmidt, of St. Louis :— 


Oils distilling over below 
,, at 


377 ° S P- g r - o 6o° = 90°—97 0 B. = Rhigolin. 

76 6° „ 0 63—o*6i = 8o°—90° B. = Gasolin. 

„ „ 137-o° „ 067—0*63 = 70°—8o° B. = Naphtha. 

M „ i48'o° „ 073—0 67 = 6o°—70° B. = Benzine. 

. „ 183°—219 0 „ 078—0*82 — 40°—6o° B. = Kerosen. 

At higher temperatures paraffin and illuminating gas come over. In order to give 
some idea of the enormous consumption of petroleum, it may be mentioned that the 
imports in the German Customs Union,* amounted in 1866 to 918,954 cwts., and in 
the first half-year of 1S70 to 1,260,630 cwts. 


* Embraces all the States of Germany, including the Grand Duchy of Luxembourg, 
but no Austrian territory. 




DIVISION VIII. 

FUEL AND HEATING APPARATUS. 


A. Fuel. 

Fuel. We understand by fuel such combustible materials as may be burnt with the 
view of obtaining heat. Wood, peat, brown-coal, coal, anthracite, wood-charcoal, 
peat-charcoal, coke, petroleum, combustible gases, such as carbonic oxide and 
hydrocarbons, are fuel. Excepting the gases, all kinds of fuel are closely related to 
each other as far as regards their origin, because fuel consists of cellulose or has 
been formed from it. Native fuel, coal, wood, peat, anthracite, consists of carbon, 
hydrogen, and oxygen, with larger or smaller quantity of ash (silica, alumina, 
oxide of iron, alkalies, and alkaline earths), and as regards coals, also nitrogen, 
sulphur, and phosphorus. Only hydrogen and carbon are combustible substances, 
and these, therefore, determine the value of fuel by complete combustion, leaving 
only ash, water, and carbonic acid. In wood-asli, carbonate of lime, in the asli 
of mineral fuel, alumina, chiefly prevail. The effect of fuel depends upon :— 

a. Combustibility. 

b. Inflammability. 

c. Calorific effect. 

combustibility. By combustibility is understood the greater or less readiness with 

which fuel is kindled and continues to burn after having been kindled. This 

property depends upon the composition of the fuel. A porous fuel kindles more 
readily than a denser and more compact fuel. With regard to the relation 
between combustibility and composition, it has been found that the more hydrogen a 
fuel contains, the more readily it burns. 

inflammability. By the inflammability of fuel we understand its property of 

bursting into flame when kindled; and as flame is due only to burning gases, 
it is evident that the fuel containing most hydrogen is that which burns with 
the most intense flame. In the case of coke, charcoal, and similar fuel, there can be 
no flame other than that due to the formation of carbonic oxide owing to incomplete 
combustion. 

calorific Effect. The heat evolved by the complete combustion of fuel may be 

measured in two different ways:— 

1. As regards the quantity of heat evolved. 

2. As regards the degree of temperature or intensity of the heat. 



FUEL . 


Gog 


When the heat evolved is measured according to its quantity, we obtain the com- 
bustive power, the specific or absolute calorific effect, of the fuel. 

When the degree of heat is measured, the heating power or pyrometrical effect 
of the fuel is ascertained. These two measurements together determine the 
technical value of a combustible material. When the absolute calorific effect of a 
fuel is referred to its cost, we determine its combustible value in the locality where it 
is to be consumed. 


dombustiv^power. As we do not possess a particular measure for heat, we have, 
when desirous of determining the quantity of heat yielded by a fuel, to institute 
trials for the purpose of ascertaining the relative quantity of heat evolved by various 
kinds of fuel, in order that by comparison we may find how much more heat is 
evolved by one kind of fuel than by another. If the results thus obtained are 
referred to a given bulk of the fuel experimented with, we obtain its specific calorific 
effect; but if it be referred to a given weight, we obtain the absolute heating effect. 
The following table exhibits the heat of combustion of several substances:— 


Hydrogen. 

Carbon (when completely burned and yielding car¬ 
bonic acid) . 

Carbon (when yielding carbonic oxide) . 

Carbonic oxide. 

Marsh-gas .. ... # . 

Elayl-gaS. 

Crude petroleum . 

Ether. 

Alcohol . 

Wood-spirit . 

Oil of turpentine . 

Wax. 

Wood. 

Wood-charcoal. 

Peat . 

Compressed peat . 

Coal (anthracite) . 

Fat . 


yields 34,462 units of heat. 

,, 8080 „ 

,, 2474 „ 

,, 2403 „ 

» 13.063 „ 

„ 11,857 >, 

„ H.773 „ 

„ 9027 „ 

,, 7^3 

„ 5307 

„ 10,852 

„ 10,496 „ 

„ 3 6 oo „ 

„ 7640 

,, 3000 

„ 43 oo 

,, 6000 ,, 

„ 9000 „ 


The absolute heating effect is determined according to the methods of Karmarsch 
and of Berthier, or by elementary analysis. 

Karmarsch-s Evaporation According to this method, applied by Dr. Playfair to English 
coals, by Brix to Prussian, by Hartig and Stein to Saxony coals, the quantity 
of water is determined which 1 lb. of the fuel will evaporate. According to 
Regnault’s formula, 652 units of heat are required to convert 1 kilo, of water at o° 
into steam at 150°. Consequently— 

1 kilo, of carbon can evaporate = I2 '4 kilos. °f water 


1 kilo, of hydrogen 

- (W-™ 

” 

Experiments instituted by Dr. 

R. Wagner and others gave 

the following results:— 

Bed beech wood . 

. 

378 kilos, of steam. 

Zwickau caking coal 

(6'o per cent ash) 

645 

Bohemian coal from Niirschau 

(19-0 „ ) 

5*53 

Forge or smith’s coals from Saarbruck (21-5 „ ) 

6'o6 „ 

Bulir coals 

( 5'5 „ ) 

6'go „ 

Cannel coal 

( 4'0 „ ) 

774 
























CHEMICAL TECHNOLOGY. 


; oo 


Berthier’s Reduction According to tlie law of Welter (which, however, is not confirmed 
by experience, since recent researches have proved that, especially as regards 
hydrogen, great deviations from the law exist), the quantities of heat evolved from 
different kinds of fuel are relatively proportioned as the quantity of oxygen required 
for their combustion. Assuming this to be correct, it is easy to ascertain the 
absolute calorific effect of fuel if its composition is known, it being only required to 
calculate the amount of oxygen which will effect the complete combustion of the 
constituents of the fuel, careful account being taken of the oxygen it contains. 
Practical experience has proved that Berthier’s method yields results which, owing 
to a constant error, are about one-ninth below the truth. The fuel to be tested 
by this method is finely pulverised, and i grm. is mixed with a quantity of litharge 
slightly more than required for the complete reduction to metallic lead, the minimum 
quantity being 20, and the maximum 40 grms. This mixture is put into a fire-clay 
crucible, and covered with a layer of 20 to 40 grms. of litharge. The crucible is 
covered with another crucible and placed in a charcoal fire, where it is gradually 
heated. When the contents of the crucible are fused the fire is increased for a few 
minutes, and the crucible then cooled and broken up in order to obtain the 
lead button, which is usually clean. This experiment has to be repeated with 
the same kind of fuel two to three times, and the results should not differ from each 
other more than o*i to 0*2 grm. G-. Forchhammer epploys instead of litharge a mix¬ 
ture of 3 parts of that oxide with 1 part of chloride of lead (consequently an oxy¬ 
chloride of Kfad), which mixture previous to use is fused in a crucible, and 
after cooling, pulverised. Pure wood-charcoal yields, when ignited with litharge or 
with oxychloride of lead, 34 times its weight, and hydrogen 103*7 times its weight of 
metallic lead; the hydrogen, therefore, rather more than three times as much as the 
charcoal (carbon). By means of these data it is possible to estimate the absolute 
calorific effect of any kind of fuel. As 1 part of carbon can by its combustion raisp 
the temperature of 8080 parts of water i°, and as pure carbon yields, according 
to Berthier, 34 parts of lead, every part of lead reduced by the fuel under examina¬ 


tion is equivalent to 


(tt) 


= 237*6 units of heat. 


The application of Berthier’s 


method is suited only to fuel which contains but a small quantity of hydrogen, 
owing, as already observed, to the incorrectness of the law of Welter; and the 
method is not applicable to fuel which becomes decomposed below red heat, as in this 
case a portion of the gaseous matter evolved does not react upon the lead. 


Example1 grm. of compressed peat yields 1776 grms. of lead, equal to 4124-5 units 
of heat (since 237-6 x 17*76 = 4124-5) ; in other words, 1 kilo, of compressed peat yields 

1 4 I5 i4J> _ 6-3). 

52 


6-3 kilos, of steam at 150° (since 


Elementary Analysis. Although it lias been proved that, as regards isomeric organic 
bodies, the quantity of heat evolved by their combustion is not precisely proportional 
to the quantity of oxygen* required for that combustion; and whereas the same 
quantity of oxygen may yield, under different conditions, different quantities of heat, 
it may still for all practical purposes be assumed, that as regards fuel of the same or 
similar composition, the results of elementary analysis give the means of ascer- 


* The composition of butyric acid and of acetic ether is the same, and is expressed by 
the formula C 4 H80 2 ; yet the former yields on combustion 5647 units of heat, and 
the latter 6292. 



FUEL . 


701 

taining the calorific value of such fuel, provided the quantity of ash it contains 
be first determined. 

Example ;—1 grm. of compressed peat yielded on analysis 0-4698 grm. of carbo.i, and 
0-0143 grm. hydrogen, equivalent to 4288*7 units of heat; because— 

Carbon, 0-4698. 8080 = 3795'9 

Hydrogen, 0-0143. 34,462 = 492-8 


The compressed peat contained— 

15-50 per cent of hygroscopic water, and 
31-78 ,, chemically combined water 


4288-7 


= 48-28 per cent water. 


Requiring for evaporation 255*3 heat-units ; hence 4288-7 — 255-3 = 4033-4 units of heat. 
The evaporating power of the compressed peat is therefore— 


4033'4 

-= 6*19 kilos. 

652 

stromeyer’s Test. According to this method (1861) the fuel is ignited with oxide of copper, 
the residue treated with hydrochloric acid and chloride of iron, whereby the latter is 
partly reduced to protochloride, which is estimated by permanganate of potash. This 
method yields very correct results, but is rather tedious. 

specific calorific ESect. By specific calorific effect we understand the relative qu unities 
of heat evolved by equal bulks of different kinds of fuel. The specific calorific effect 
is obtained by multiplying the absolute calorific effect by the specific gravity of the 
fuel under trial. 

pyrometricai Calorific Effect. The pyrometrical calorific effect of a fuel is that indicated by 
the temperature resulting from its complete combustion. As there does not exist any 
pyrometer the indications of which are sufficiently reliable to be converted into 
tliermometrical degrees, we have to content ourselves for the present with an 
approximative knowledge of the pyrometrical calorific effect as deduced from calcula¬ 
tion. The pyrometrical effect of a fuel is equal to the heat-units of absolute heating 
effect divided by the sum of the relative quantities by weight of its products of com¬ 
bustion, each of these quantities by weight being multiplied by the corresponding 
specific heat. The flame-yielding substances of the combustible matter of wood and 
coals are, therefore, possessed of a lower pyrometrical effect than the non-inflam¬ 
mable carbonised substances ; while in reference to the absolute calorific effect, the 
reverse obtains. This is due to the fact that the aqueous vapour formed by the 
combustion of hydrogen takes up nearly four times as much heat to acquire a 
certain temperature as does carbonic acid. The difference of pyrometrical effect of 
fuels is far greater when they are burnt in oxygen than when they are burnt in air. 
In order to approach in practice as nearly as possible the pyrometrical effect of 
tlieorv, it is necessary to burn all the carbon completely to carbonic acid, because 
the temperature of its combustion to carbonic oxide amounts in air to only 1427 0 , 
with 2480 units of heat; while if the carbon is burnt to carbonic acid the tem¬ 
perature rises to 2458°, with 8080 heat-units. This complete combustion may be 
greatly promoted by proper treatment of the fuel; for instance, by keeping wood- 
charcoal and coke in drying houses for a considerable time; by compressing peat to 
increase its density; by preparing dense coke; heating the fuel previous to 
introducing it into the furnace; by the use of heated air ; and, lastly, by effecting 
the combustion with compressed air. 

The temperature of combustion is not only the product of the act of combustion 


/02 


CHEMICAL TECHNOLOGY . 


itself, but is essentially modified by the action of the active principles of the air 
during the combustion. For complete combustion there are required :— 

For 1 kilo, of carbon, at 15 0 , 97 cubic metres of air. 

„ 1 „ „ hydrogen, at 15 0 , 280 „ „ „ 

From these data we deduce the following quantities of air as required for the 
complete combustion of the subjoined quantities of fuel 

1 kilo, of wood (with 20 per cent of hygroscopic water) = 5‘2 cubic metres of air. 

1 „ wood-charcoal.. — 

1 „ pit-coal . 

1 „ coke . 

1 ,, brown-coal 

1 „ peat . 

In practice on the large scale these quantities of air require to be doubled in order 
to obtain complete combustion. 

MechamcarEquivaient The law of the conservation of energy teaches that heat can be 
converted into labour, and inversely labour into heat; and that 1 unit of heat corre¬ 
sponds to 424 metrical kilos, of labour. When heat does work it is dispersed in the 
proportion of 424 units of work for 1 unit of heat; consequently the number 424 
expresses the mechanical equivalent of heat. By a foot-pound is understood the 
force required to lift a weight of 1 pound 1 foot high. When instead of the pound 
the kilo., and instead of the foot the metre are taken, the term kilogrammetre is 
employed. 1 kilogrammetre = 677 Bhenish foot-pounds ; 1 English foot-pound is 
equal to o - 13825 kilogrammetre; 75 kilogrammetres = 542 English foot-pounds; 

1 horse-power (33,000 pounds lifted 1 foot high in 1 minute) is equal to 76 0390 
kilogrammetres; 1 unit of heat per English pound is equal to |ths of a French calorific 
unit per kilo. The starting-point of the mechanical theory of heat is the axiom first 
put forward by R. Clausius, that “ in all cases in which heat does work a propor¬ 
tional quantity of heat is dispersed or consumed, and inversely, by the performance 
of an equal amount of work, the same quantity of heat can be regenerated.” 

Wood. 

wood. Wood consists of several structurally different parts, which may be seen in 
the transverse section of the wood, viz.:—The axis, or pith, a rather spongy, 
regularly shaped tissue of parenchyma cells, which radiate towards the bark. This 
is surrounded by the wood, consisting of an aggregation of bundles of vascular 
tissue. The wood is surrounded by the bark, and between wood and bark is 
deposited a very thin layer of cells filled with a turbid fluid, from which the further 
growtli of the tree proceeds by the gradual deposition of newly formed cells towards 
both the wood and bark side. The bark is externally covered with a layer of 
peculiarly shaped cells, which with the rind form the bark, covered by, in young 
trees, epidermis. The pith-cells become obliterated in old trees, and leave a hollow 
tube. The wood-cells become thicker by the deposition of cellulose, and as this 
deposition increases in spring but decreases in summer and autumn, the effect is the 
formation of the so-called annual rings, which are separated from each other by the 
more compact and harder layers deposited in autumn. The wood-cells are internally 
hollow, and are separated from each other by intercellular meatus, which contain 
usually air, but sometimes also gum, resin, &c. The largest quantity of cellulose is 


... = 90 „ 

... = g o j, ,, 

... = 7'3 » 




















FUEL. 


703 


deposited in the wood and vascular cells, which essentially constitute the wood; the 
wood is the harder and more compact, when in a given space the cellulose is 
deposited in larger quantity, while in the so-called soft wood the walls of the cells 
are thinner and their number smaller in a given space. The trees of which the 
wood is used as fuel in Central Europe are :— 


Leaved trees. 


Oak (Quercus pedunculata and robur) ... 

fit for felling in 

50— 

60 

years, 

Red beech ( Fagus sijlvatica) . 

,, 99 

80- 

■120 

99 

White beech ( Carpinus bet ulus) . 

99 99 

I IQ- 

■120 

99 

Elm tree ( Ulmus campestris and effusa) . 

99 99 

20— 

• 30 

99 

Ash tree [Fraxinus excelsior) . 

99 99 

20— 

' 30 

99 

Alder ( Alnus glutinosa and incana) 

99 99 

20— 

• 30 

99 

Birch ( Betula alba and pubescens) . 

99 99 

20— 

• 25 

99 

Coniferous trees. 





White fir [Pinus abies) . 

99 99 

50 — 

• 60 

99 

Red fir (Scotch fir) ( Pinus picea) . 

99 99 

70 - 

■ 80 

99 

Common fir ( Pinus sylvestris ). 

99 99 

80— 

•IOO 

99 

Larch or larix tree (Pinus larix) . 

99 99 

50— 

■ 60 



Oak, beech, elm, birch, and ash, are hard woods. Sycamore, larch, and common 
fir are half-hard; while poplar, lime tree, willow’s, are soft woods. 

constituents of wood. Wood essentially consists of woody fibre, small quantities of ash 
and sap, and a variable quantity of hygroscopic water. Woody fibre, or cellulose, 
constitutes about 96 per cent of dry wood, and is composed of C6 H io 0 5 ; in 100 parts, 
of—Carbon, 44-45; hydrogen, 6*17 ; oxygen, 49*38. The vegetable sap consists 
chiefly of water, but contains organic as well as inorganic matters, partly in 
solution and partly suspended. The inorganic constituents of the sap (the ash left 
after the incineration of the wood) are the same in all kinds of wood (see p. 123). 
In practice it is assumed that wood leaves about 1 per cent of ash; but there is a 
difference for certain portions of the tree, the trunk yielding about 1-23 per cent of 
ash, the branches and knotty parts 1-34 and 1*54, and the roots 2-27 parts of ash 
respectively. 


The quantity of water contained in wood 

is generally larger in 

soft than in hard 

woods. 100 parts of wood recently felled 

are found to contain 

on an average the 

following quantities of water:— 




Beech . 

186 

Common fir. 

. 397 

Birch . 

30-8 

Red beech . 

. 397 

Oak. 

347 

Alder . 

. 41*6 

Oak (Quercuspeclunculata) ... 

35'4 

Elm . 

. 44*5 

White fir . 

37 ' 1 

Red fir. 

. 45*2 


Air-drv wood may be considered as consisting of:— 

40 parts of carbon (inclusive of 1 part ash). 

40 „ „ chemically combined water. 

40 „ „ hygroscopic water. 

Wood dried at 130°—at which temperature all the hygroscopic water is driven 

off—is composed of:— 

50 parts of carbon (inclusive of 1 part ash). 

50 „ ,, chemically combined water. 















7°4 


CHEMICAL TECHNOLOGY. 


Air-dry beech wood, as used for fuel, contains in ioo parts:— 

Carbon . 39 ' 10 

Hydrogen. 4’go 

Oxygen . 3600 

Water and ash. 20*00 


100*00 


Heating value of wood. The heating value of soft wood is greater than that of hard 
wood. The wood from coniferous trees is, on account of the resin it contains, the 
most readily inflammable. Birch wood is very similar to coniferous wood. Besinous 
woods yield the longest flame. According to Winkler’s researches on the heating 
power of the various kinds of wood, it appears that for 1 klafter of red fir wood 
might be substituted :—1*07 klafter of lime-tree wood, 0 94 klafter of common fir, 
0*92 klafter of poplar, 0 91 klafter of willow wood, 0*89 klafter of tanne, 0*70 klafter 
of beech, 0*665 klafter of birch, 0*65 klafter of sycamore, 0*635 klafter of elm, 
0*59 klafter of oak.* Scheerer assumes that the absolute calorific effect of the 
different varieties of uniformly dried wood is the same, and that the specific caloric 
effect of wood containing the same amount of hygroscopic moisture is proportionate 
to the specific gravity. The pyrometric heating effect of kiln half-dried wood, with 
10 per cent of moisture, is, according to Scheerer, = 1850°; while that of fully kiln- 
dried wood is = 1950°. According to Peclet, the combustion of clean dry wood 
evolves a temperature of 1683°, provided the oxygen of the air supplied for com¬ 
bustion be all consumed, for if that is not the case, or only half the oxygen be 
consumed, the temperature is only 960°, as happens in stoves of the ordinary 
construction. 

According to Brix’s investigations, the evaporative power of different kinds of 




Undriod. 

Dried. 



Per cent. 

Per cent. 

Fir wood, containing water, per cent 

16*1 

4*13 

5 'n 

Elm wood, „ „ 

147 

3'84 

4*67 

Birch, „ 

12*3 

372 

4'39 

Oak, „ „ 

187 

3'54 

4*60 

Bed beech, „ „ 

22*2 

3‘39 

4*63 

White beech, „ „ 

12*5 

362 

4*28 


That is to say. 1 kilo, of fir wood, containing 16*1 per cent of water, evaporates 
4*13 kilos, of water. 

wood charcoal. Nearly all organic compounds become decomposed by heat, and leave 
carbon if access of air is prevented. If the escape of gases and volatile vapours 
evolved when wood is submitted to dry distillation is permitted, a residue is left 
known as wood-charcoal. Among the volatile products of this operation are gaseous 
substances, such as carbonic acid, carbonic oxide, and marsli-gas, while the con¬ 
densable portion of the volatile products consists of tar and an aqueous fluid. This 
latter consists of crude pyroligneous (acetic) acid (see p. 469) and of wood-spirit. 
The tar contains a large number of fluid and solid substances, among which are 
paraffin, creosote (oxyphenate of methyl), oxyphenic and carbolic acids (that is to 
say, true carbolic acid, cresylic acid, and plilorylie acid), and several hydrocarbons; 


A klafter is a cubical measure = 108 cubic feet. 





FUEL 


7°5 


all these substances are combustible. The following diagram exhibits the chief 
products of the dry distillation of wood:— 


rAcetylen. 

. Illuminating J Elayl. 
gas. j Benzol. 

vNaplithalin (?) 


Wood. 


1 a. Real wood. 

b. Hygroscopic 
water. 


/3. Tar. 


f Benzol. 
Naphtlialin (?) 
- Paraffin. 
Reten. 

.Carbolic acid. 


Carbonic oxide. 
Carbonic acid. 
Marsh-gas. 

Hydrogen. 

Oxyphenic acid. 
Cresylic acid. 
Phlorylic acid. 
Empyreumatic resins. 
Creosote. 


7. Pyroligneous J Acetic acid. Aceton. 

acid. (Propionic acid. Wood spirit. 

\c. Wood charcoal. 


carbonisation of wood. Wood is carbonised chiefly for the purpose of concentrating the 
fuel or combustible matter it contains, to obtain a more readily transportable 


material, and for the purpose of 
converting the wood into a fuel for 
use in metallurgical and technical 
processes in which wood, as such, 
cannot be employed. 

Wood may be carbonised with 
the sole view of making tar (Stock¬ 
holm tar), or with that of making 
wood-gas or charcoal. In the latter 
case the wood is very frequently 
carbonised in the forests where it is 


Fig. 301. 





felled, in heaps, pits, or ovens. 

Carbonisation in A regularly con- 
Heaps. structed heap of blocks 

of timber covered with a layer of earth 
and charcoal-dust is formed, the wood 
being placed vertically or horizon¬ 
tally as regards the direction of 
the axis of the heap. In the first 
case the heap is termed a “ stand¬ 
ing,” in the other a “laid” heap. 
The axis is a pole or several poles of 
wood. 

Construction Of The building of the 
the Heap. heap is commenced by 

putting up the axis pole or poles. 
Vertical heaps are, according to 
their construction, distinguished in 
Germany, as :— a. Walsh heap, Fig. 
301. b. Slavonian heap, Fig. 302. 
c. Schwarten heap, Fig. 303. 

The Walsh, or Italian heap (Fig. 
301) is constructed with a hollow 
central support of planks or stout 
laths, kept apart from each other by 
the balks, n. The heap contains 
two or three layers of wood and is 
conical in shape. The layer of earth 
on the wood is termed the chemise. 


Fig. 302. 


Fig. 303. 


resinous wood is placed for kindling the pile. 


In the lower part of the hollow pole or shaft 


40 

















706 


CHEMICAL TECHNOLOGY. 


The Slavonian heap (Dig. 302) is distinguished from the former by the fact that tlio 
axis is a solid pole and by the channel, b , by means of which the wood is tired. A third 
kind of vertical heap, termed the Schwarten, is in use in Norway, the name being derived 
from the word “ Schwarten,” signifying irregular. Three of the larger logs form the 
central pole, a a, round which light combustible material is placed for the purpose of 
kindling the heap; while the blocks of wood are next built up. The horizontal heaps 
have the outward appearance of the former, but the blocks of wood are placed horizontally 
and radially. The pole or axis is a solid shaft, and air holes or channels are made in the 
wood. In order to prevent the layer of earth which covers the heap falling in and choking 
the progress of the smouldering fire, a layer of leaves and twigs is first placed on the 
wood', and on that the earth, mixed with charcoal-dust. At first the heap of wood is not 
quite covered with earth, an uncovered space of some 6 to 12 inches being left at the foot 
of the heap for the purpose of admitting air. The layer of earth usually has a thickness 
of 3 to 5 inches, but at the top it is thicker. In order to protect the heap from the effects 
of strong wind, it is usual to put up what are termed wind-blinds, simply planks of wood 
placed close together and supported by stout poles. 

There are two methods in use for kindling or firing the heaps of wood:—1. Kindling at 
the bottom, access to the centre of the heap being obtained by a channel, into which 
ignited straw is introduced. 2. Ignition from the top, or roof, by throwing into the 
central shaft ignited charcoal and wood-shavings. 

Charcoal Burning. We have to distinguish three stages or phases in this operation :— 
1. The sweating. 2. The full combustion. 3. The slow smouldering. In order that the 
fire may spread through the heap, it requires at first a more plentiful supply of air, and 
for that purpose the heap is left entirely uncovered, or at least left open at the bottom. 
The first effect of the firing is that a large quantity of watery vapour and products of dry 
distillation are formed within the heap, which becomes consequently wet, or begins to 
sweat. During this time there is the risk of explosion of the mixture of air with hydro¬ 
carbon gases and vapours, by which explosion the overthrow of the heap, or if not so 
violent, a shaking of the covering layer of earth, may take place. It may happen, also, 
that at this period the combustion becomes internally so active as to completely consume 
more or less of the wood. Any holes which may be observed externally are at once filled 
xip with earth, grass, wet wood, clay, or any suitable material. When the vapours issuing 
from the bottom of the heap become brighter in colour, complete ignition of the wood has 
commenced, and it then becomes necessary to prevent the access of air by covering the 
entire heap with earth mixed with charcoal-powder ; this operation is termed the encom¬ 
passing ( umfassen ) of the heap, which is left in that condition for three, four, or six days, 
the high temperature being sufficient to complete the carbonisation of the wood without 
further access of air. I11 order to insure the complete carbonisation of the outer portions 
of the heap, the combustion must be carefully conducted from the top and centre out¬ 
wards by partially removing the covering layer towards the bottom, and by making small 
channels at various parts of the covering, an operation known as the slow smouldering or 
burning off. When the smoke which issues from the channels becomes bright and blue- 
coloured, the charcoal is well burnt, and therefore the channels and apertures are all 
closed with earth, in order to extinguish the fire. I11 this condition the heap is left for 
twenty-four hours. Then the layer of earth is raked off, and dry earth thrown on the 
heap for the purpose of filling the insterstices between the still red-hot charcoal, which 
becomes gradually extinguished. As soon as the heap is quite cold externally, it is once or 
twice gently watered by means of a watering-pot, then broken up, and the charcoal taken out. 

Carbonisation in Beds. This mode of charcoal-burning is in use in Southern Germany, 
Kussia, and Sweden, and is a continuous operation in so far as the wood is gradually 
carbonised, fresh green wood being added while the charcoal is withdrawn. The wood is 
sawn into logs and not hewn to smaller blocks. The carbonisation-bed is a rectangular 
wooden box, Digs. 304 and 305, the latter being a vertical section. The bed is, in 
fact, a kind of kiln, of wliich a a are the poles and outer logs, h the covering layer of 
earth, b the hearth. While the slow combustion proceeds from b towards the 
opposite end, the charcoal formed is gradually withdrawn. The burner, or workman, has 
to see that the combustion proceeds regularly and keeps parallel to the sides of the bed. 

Carbonisation in Ovens This process is an imitation in brickwork of the carbonising process 
or Kilns. in heaps, because the carbonisation of the wood is effected by the 

combustion of a portion of wood of the heap. The oven, or kiln, admits of a more perfect 
collection of the products of the dry distillation—tar, pyroligneous acid, &c.,—but the 
charcoal is not quite so good as that obtained by the preceding methods. The shape and 
mode of construction of these kilns may vary, as will be presently seen. 

Kig. 306 exhibits one of the most simply constructed kilns. The wood is placed either 
vertically or horizontally, being thrown into the kiln through the opening, a, or carried in 


FUEL. 


707 


through the doorway, b, which also serves as the channel through which the firing of the 
wood is performed. During the ignition all the apertures of the kiln are closed with 
brickwork, with the exception of a small opening at b and at a. The small apertures seen 
at the top of the kiln are intended for the escape of the smoko. 


Fig. 304. 


a 

Cm3 



In the kiln exhibited at Fig. 307, the doorways, a and b, are intended for the intro¬ 
duction of the wood, and b also for withdrawing the charcoal, ccc are draught-holes 
provided with plugs. The iron pipe, d, is intended for carrying off the volatile products of 



the dry distillation. During the operation a and b are closed with brickwork or with 
tightly-fitting iron doors lined with fire-clay slabs. The tar is collected.in a reservoir. 
Below b a small aperture indicates the mouth or outer opening of the firing channel. 


Fig. 306. 

cr 



The kiln represented in Fig. 308, in vertical section, is constructed for the admission of 
air through the ash-pit, e , and fire-bars, r ; the wood is introduced through a and b ; q is 
the pipe for carrying off the volatile products. 




























;o8 


CHEMICAL TECHNOLOGY. 


Carbonisation of wood The carbonisation of wood is also effected in closed vessels :—i. Retorts, 
in ovens. 2 . In tubes or cylinders, heated air, blast-furnace gases, or super¬ 
heated steam being sometimes used for the purpose of carbonising the wood. As regards 
the carbonisation of wood in retorts, this is effected by placing the wood in cast-iron 


Fig. 307. 



Fig. 308. 


or fire-clay retorts, which are heated externally, and are provided with pipes for conveying 
away the volatile products of the carbonisation, this process being carried on chiefly for 

obtaining tar or wood-gas. In the case of 
tubular kilns, the firing of the wood is effected 
by the aid of a series of iron tubes, placed in 
the kiln and connected outside with a source 
of heat as well as with a chimney-stalk. The 
hot air and flame of a furnace are passed 
through these tubes, or may be directly led 
into the kiln, provided the hot air and flame 
are deprived of their oxygen. Upon these 
principles is constructed the kiln invented by 
Schwarz, and known as the Swedish kiln, of 
which Fig. 309 exhibits a vertical section, b is 
the carbonisation space enclosed by the brick¬ 
work, a. Through the apertures, cc, the hot 
air is admitted which effects the carbonisation. 
The liquid products of the dry distillation are 
collected on the sloping floor of the kiln and 
conveyed by means of the syphon-tubes, ee, 
into the tar-vessels, //. The vapours of the 



Fig. 309. 




volatile fluids (pyroligneous acid, wood-spirit, Ac.), pass through the tubes, gg, into the 
condensing vessels, h h, which are connected with a high chimney (see i, Fig. 310), to aid 

















































FUEL. 


7°9 


the draught of the apparatus. The openings, dd, serve for the introduction of the wood. 
There are no fire-bars in the hearth of this kiln. 

The carbonisation of wood with the view of producing tar is best effected by the method 
in general use in Russia, of which Hessel has given (1861) the following description. 
The wood, generally of coniferous trees, is cut up with an axe, being distinguished as 


Fig. 310. 



Brawican and Luczina; the former wood from the trunk of the trees, the latter the 
knotty roots. The wood is heaped up on a plot of ground, Fig. 311, which is somewhat 
elevated above the level of the soil, and is funnel-shaped, the whole being constructed of 
clay and lined with roofing-tiles, on which the tar collects and flows off into a vessel 
placed in the vault, as exhibited in the cut. The wood is heaped in six to eight layers, 
and is first covered with hay or dung, next with a layer of a few inches in thickness of 
sand or earth. The wood in the heap is ignited at the bottom, where forty to fifty 

Fig. 311. 



apertures are left in the covering, these apertures being closed with wet sand as soon as 
the combustion of the wood becomes active, and has spread through the whole heap. 
After about six days’ smouldering, the top of the heap falls in and a strong flame bursts 
out. After ten to twelve days the tar begins to collect and is removed daily. The 
smouldering of the wood continues for three to four weeks; the quantity of charcoal 
obtained is very small. According to Thenius, wood-tar is obtained by a similar process 
in Lower Austria from the wood of the black fir, which does not yield turpentine ; but in 
Bohemia a very resinous wood is used for tar-making. 100 parts of fir wood yield in 
Russia 17*6 parts of tar and 23*3 parts of charcoal. 

Since the year 1853 there has been in use in Sweden an apparatus for the distillation of 
tar from wood, known as a thermo-boiler. According to Hessel’s description, this 
apparatus consists of a boiler-shaped iron vessel, a, Fig. 312, of about 8 cubic metres 
capacity, and fitted with a man-hole for introducing the wood. This vessel is heated by a 
tire at a, and the flues, ft ft. In order to heat the wood rapidly to ioo°, a jet of steam is 































7 io 


CHEMICAL TECHNOLOGY. 


forced into the vessel through e. The tar which might collect and condense in the vessel 
is carried off by the aid of the pipe c to b, while the vapours of tar and other volatile 
products are conveyed through d into b'. The matter there condensed flows through 
h to b, while the more volatile products are rendered liquid in the condenser, c. The 
combustible gases are returned to the fireplace. In addition to tar, there are, at the 
outset of the operation, also obtained oil of turpentine and pyroligneous acid. The 
charcoal, which is extinguished by means of steam, is removed from the boiler by the 
opening a. According to an investigation by Thenius (1865), with the view of ascertaining 
whether the tar obtained in making wood-gas is equally fitted for naval purposes and for 
boiling down to pitch as the tar obtained by other methods, it was found that such is not 
the case. This agrees with Dr. Owden’s researches, made at his extensive acetic acid and 
wood-spirit works at Sunderland, where the tar obtained is burnt, or used with lime and 


Fig. 312. 



fire-clay for making a kind of asphalte. Owing to the cheapness of coal in the locality, 
the wood-charcoal is almost a waste product. 

properties of charcoal. We distinguish between hard wood and soft wood charcoal, and 
as regards the latter, again between charcoal obtained from leaf-bearing trees and 
from coniferous trees. According to the degrees of carbonisation, we distinguish 
between well-burnt black-coal and the so-called charbon roux, a more or less deep 
brown torrified charcoal, often used in gunpowder making. 

According to the size, charcoal is—at least abroad—divided into :— 

1. Coarse log-coal, the largest and most compact lumps. 

2. Forge-coal, compact lumps about 4 inches diameter. 

3. Coal from the centre of the heap, small lumps and porous. 

4. Small coal, nut and pebble-sized lumps, mixed with dust. 

5. Raw coal, or not well-burnt lumps. 

As regards the yield of charcoal by bulk, this may be referred either to the real 
volume of the mass, after deduction of interstices present in the heap, or to the 
apparent volume without that deduction being made. We can compare :— 

a. The apparent volume of the wood with the apparent volume of the charcoal. 

b. The real volume of the wood with the real volume of the charcoal. 

c. The real volume of the wood with the apparent volume of the charcoal. 

The first method may be called the production according to the apparent 
volume (I.) ; the second, the yield according to the real volume (II.) ; the third, the 
yield according to both volumes (III.) : — 





















FUEL. 


711 


Method (I.) gives the following results:— 

Oak wood . 

Red beech wood. 

Birch wood. 

Dwarf beech wood (as grown for hedges abroad) 
Fir wood . 


718—747 per cent charcoal. 
730 
68-5 
. 57*2 
63-6 


According to the real volume (II.) the average of several experiments gave a yield 

(III), the following results were 


of 47 - 6 per cent. According to both volumes 
obtained at Eisleben 


Oak wood . 

Red beech wood ... 

Birch wood. 

Dwarf beech wood 
Fir wood . 


Composition of Wood- 
Charcoal. 


Apparent Both 

volume. volumes. 

71B per cent 987 per cent 
730 „ „ 1004 „ „ 

68-5 „ „ 94-2 „ „ 

57-2 „ „ 78-6 „ „ 

63*6 „ ., 87-2 „ „ 


Weight. 

... 213 per cent 

... 227 „ „ 

... 20'9 „ ,, 

... 206 „ ,, 

. 25 0 „ 

Omitting the small quantities of hydrogen and oxygen present in 
charcoal, its average composition in air-dry state is the following:— 

Carbon . 85 per cent 

Hygroscopic water . 12 „ ,, 

A sh. 3 „ „ 

C ^aUng b Effe y ct a . nd The combustibility of freshly burnt charcoal is very great, for it 
continues to burn, with proper access of air, when once ignited; but as charcoal 
does not contain any volatile combustible matter, it requires a great heat to become 
ignited, more especially as it is a very bad conductor of heat. 

The heating effect of various kinds of wood-charcoal is shown by the figures of the 
subjoined table, the heating effect of carbon being taken as the unit:— 


Well-burnt charcoal, air-dry .. 
Well-burnt charcoal, quite dry 
Birch wood 
Ash wood 
Red beech wood 
Red fir wood 
Sycamore w’ood 
Oak wood 
Alder wood 
Linden wood 
Fir tree 
Willow wood 


097 

084 


0*20 

OI9 

o'i8 

017 

<ri6 

0-15 

013 

010 


Ph 

2450 

2350 


0^0 
-4J O 

o m 

las-g 


® § 
as* 
*5 

H O 


r3 £ M 


337 1 

33'57 

33 ' 5 i 

3374 

3240 

3279 

33*53 

33*49 


& 

t'- 


a 

cJ 

p 

O 


The evaporative power of fir wood charcoal containing 10*5 per cent of water and 
2 7 per cent of ash amounts to 6 75 kilos., viz., 1 kilo, of the charcoal evaporates 
6 75 kilos, of water. This charcoal, in perfectly anhydrous state and with 3*02 per 
cent ash, evaporates 7^59 kilos, of water. 

charbon charcoai Torrified As the complete carbonisation of wood entails a loss of about 
40 per cent of fuel, it lias been recently tried to prepare a kind of charcoal exhibiting a 
orown-black colour, and obtained from wood by torrifying rather than by carbonising 




CHEMICAL TECHNOLOGY. 


712 

it, experience having shown that such a charcoal is obtained when the aii-diy 
wood has lost by torrifying some 60 to 70 per cent of its weight. This kind of char¬ 
coal is intermediate to real black charcoal and kiln-dried wood; it contains more 
oxygen, is readily pulverised, but is less porous than either kiln-dried wood or 
ordinary charcoal, than which it is far more inflammable, and is hence preferred in 
gunpowder making. Cliarbon roux, or torrified charcoal, is a very useful and 
important fuel for industrial and metallurgical purposes. 

Freshly prepared torrified charcoal has the following composition :— 

Carbon. 74*° P er cent 

Chemically combined water . 24*5 „ „ 

Ash . 1 *5 1* » 

The composition of this charcoal after keeping is :— 

Carbon. 66 5 per cent. 

Chemically combined water . 22*0 „ „ 

Hygroscopic water . 10 0 „ 

Ash . i ‘5 m ». 

Boasted wood; The Association for Promoting Chemical Industry at Mains prepares an 
BoisBoux. ' intermediate product to wood and torrified charcoal, to which the name 
red wood (roasted wood, hois roux) is given. It is made from beech wood, and is the by¬ 
product of the preparation of acetic acid and creosote. It has all the external appearances 
of wood, but the colour, which is deep brown. It is highly inflammable, and consists on 


an average of:— 

Carbon.52*66 per cent 

Hydrogen . 578 „ „ 

Ash . .•*.*• • • °‘43 » >» 

Water (moisture or constitutional ?) . 4*49 ,, ,, 

Oxygen.36-64 „ „ 


According to R. Fresenius’s researches, the evaporative power of air-dry beech wood is 
to that of bois roux as 54*32 : 100. 

Peat. 

reat. This is the product of the spontaneous decay of vegetable matter, more 
especially of marsh plants, mixed with various mineral matters, sand, clay, marl, 
lime, iron pyrites, iron ochre, &c. Peat is especially formed in places where shallow, 
stagnant pools of water abound, in which the plants grow, while at the same time 
the peat is precluded access of air. The following plants are chiefly met with in peat 
bogs and form the peat:— Eriophorum, Erica, Calluna, Ledum palustre, Hypnum, 
and also Sphagnum, a plant especially fitted for the formation of peat, because 
it never wholly dies, but continues to vegetate towards the surface of the water or 
bog, while the older parts decay. 

The different qualities of peat are partly due to the plants from which the peat is 
formed, but chiefly to the more or less complete decay these plants have undergone, 
to the mineral substances mixed with the peat, and to the compression to which 
it has been submitted by the weight of other mineral materials deposited upon 
it. Abroad, and in countries where peat abounds, several varieties are dis¬ 
tinguished, such as—1. Moor peat, chiefly derived from kinds of Sphagnum, and 
found in several parts of the United Kingdom as very young peat—for instance, at 
Aldershot, and on moor lands. 2. Heath peat, in Holland known as plaggenturf, is 
the surface soil of heather-growing places. 3. Meadow-land peat, decayed coarse 






FUEL. 


7*3 


grass mixed with a soft subsoil. 4. Wood or forest peat, met with in forests, 
and formed by the decayed wood, leaves, &c. 5. Marine peat, formed by the decay 

of sea plants, various kinds of Fucus , &c. 

Peat is directly obtained by simply cutting it with a spade from the surface of the 
soil, either with or without the necessity of first removing a layer of other soil, 
while some peat can be obtained only by dredging for it under water. In the 
latter case a mud is dredged up which (as happens in Holland, where the land peat is 
known as hoog veen, while the peat from under water is termed laag veen ), has to be 
dried gently in open air, and afterwards cut up in brick-shaped lumps, and 
further air-dried. Peat is often artificially compressed for the purpose of obtaining 
a more compact fuel. The quantity of water contained in freshly dug peat is very 
large, and by keeping this peat in dry situations it may lose 45 per cent of its 
original weight. Assuming the organic matter of peat to consist of— 


Carbon. 

60 per cent. 

Hydrogen . 

2 

„ 

Water. 

38 


The best solid air-dry peat consists of— 

Solid peat mass (inclusive of ash) 

... 

... 75 per cent. 

Hygroscopic water . 

... 

... 25 

or of— 

Carbon . 

... 

45*0 per cent. 

Hydrogen. 

... 

i ‘5 

Chemically combined water . 

... 

28-5 

Hygroscopic water. 

... 

25'5 


The following analyses exhibit the composition of peat-ash, which is characterised 
by containing a far larger quantity of phosphoric acid than wood-ash. 

According to E. Wolff, two kinds of peat-ash from the Mark (a and b), and another 


from South Bavaria ( 0 , analysed by Dr. Wagner) contain:— 



a. 

b. 

c. 

Lime . 

15*25 

20*00 

i 8*37 

Alumina. 

20-50 

47*00 

45’45 

Oxide of iron . 

5 ' 5 ° 

7*59 

7-46 

Silica . 

41*00 

I 3 ’ 5 ° 

20*17 

Phosphate of calcium and gypsum ... 

3 ‘ 10 

2*60 




Alkali, phosphoric 1 




acid, sulphuric 

- 8*55 



acid, &c. J 



Drying Peat. The use of peat as fuel and its value as such depend in a great measure 
upon the quantity of water and the mineral substances it contains. Peat may be 
more or less dried:— 

1. By exposure in stacks in open air, or better in sheds where the peat is protected 
from rain, but where a free circulation of air obtains. Air-dried peat contains 25 per 
cent water. 

2. By artificial heat, kiln drying at ioo° or 120°, in kilns or stoves heated by a distinct 
fire-place, or by waste heat from other operations. 

3. By compressing peat. The compression has the following advantages:— a. Ren¬ 
dering the peat more compact and thus increasing its pyrometric effect. 1 . Lessening its 
bulk, and consequently lessening the cost of transport.by water, in which mode of trans¬ 
port the cost is calculated by bulk or cubic measurement, c. The compression aids 



CHEMICAL TECHNOLOGY. 




7 I 4 


the drying. The operation of compressing freshly dug peat, simple as it appears, has been 
found in practice to be accompanied with difficulties which hitherto have not been, and 
are not likely to be, overcome, for several reasons, among which is the fact that peat, as a 
heterogeneous material, cannot be dealt with satisfactorily by compression. But a step in 
the right direction towards the utilisation of the enormous masses of peat soil has been 
made, by submitting the soil first to a kind of grinding lixiviation, which converts it into a 
homogeneous mass, from which the greater part of the mineral matters can be eliminated. 

In the works at Staltach, near Munich, the following process has been introduced 
by Weber for preparing peat. The peaty material having been brought from the moor in 
lumps is put into a kind of pug-mill moved by steam-power, and which reduces the peaty 
substance to a uniform paste. This paste is moulded, compressed, and dried in a stove. 
Schlickeysen has invented a machine of improved construction; in its application 
it is unnecessary to pour any water on the peaty material, consequently the drying pro¬ 
cess is less tedious and expensive. Dr. Yersmann’s peat-preparing machine consists 
chiefly of a funnel-shaped stout sheet-iron vessel provided with small holes on its 
periphery and internally fitted with an iron core-piece, which bears cutters fastened 
spirally on its surface. By the action of these cutters the peaty matter is reduced to 
a pulp, and in that state issues from the holes, while any coarse particles, such as pieces 
of root, vegetables, &c., are discharged at the lower opening of the funnel-shaped 
iron vessel. On the Haspel moor peat bog situated between Augsburg and Munich, 
there has been in use up to the year 1856 a peat-preparing machine, originally invented 
by Exter, at Munich, and consisting essentially of solid iron cylinders, provided with 
strong teeth 6 centims. long, and arranged in the same manner as obtains in bone¬ 
crushing mills. The peaty material is reduced with the aid of water to a pulp, which 
is next pressed, moulded, and dried. The unreduced vegetable matter and roots are 
separated from the peaty mass by the machine. Challeton’s peat-preparing machine, 
invented in 1824, and worked at Montanger, near Corbeil, Seine et Oise, France, consists 
of a set of cylinders, 1*3 metres in length, and fitted with cutters. The peaty mass is 
first cut into shreds and is next transferred to another portion of the machinery, in the 
particulars of its construction very similar to a coffee-mill. With the assistance of some 
water the peaty material is converted into a pulp, which is next lixiviated, and thus 
deprived of mineral impurities. The thin, pasty, peaty mass is run into a large tank or 
pit dug in the soil, and left there until it has acquired sufficient consistency to be moulded. 
This mode of treating peaty matter has been employed at Bheims and St. Jean on 
the Bieler Lake, Switzerland. By Challeton’s process—100 cwts. of peaty material 
( veen )* yield 14 to 15 cwts. of peat, containing about seven-eighths less ash than in 
natural state. 

It is evident that a process of lixiviation, however suitable in regard to its application to 
peaty matter, is, in a certain sense, an irrational mode of treating a substance which has 
to be again dried thoroughly, and which, even after being submitted to the several 
operations, is not a fuel equal to coal. It is, therefore, a very great improvement in 
the utilisation of peat-soil that the peaty matter should be treated in a different manner, 
or by the so-called dry compression process, as carried out by Gwynne and Exter. 
According to this method the peaty mass is first deprived of its natural excess of water by 
means of a hydro-extractor; next pulped, and this pulp dried by artificial means; the 
material obtained is ground to powder, which is finally moulded with the aid of strong 
pressure and the simultaneous application of heat. The peat thus prepared is of a deep 
brown-black, a hard, stone-like material, excellently suited for use as fuel, especially 
for manufacturing and metallurgical purposes. Another process of peat preparation con¬ 
sists m first cutting and drying the peat in air. The air-dried peat is ground to a coarse 
powder and then dried in a stove. The dried peat is moulded and pressed by means of an 
eccentric press, heat (50° to 6o°) being simultaneously applied. Peats from the Kolber 
moor (a), and from Haspel moor (&), thus prepared, were found to contain in 100 parts:— 



a. 

b. 

Ash 

4-21 

8-34 

Water 

I 5 ' 5 ° 

15-50 

Carbon 

46-98 

49-82 

Hydrogen .. 

4-96 

4’35 

Nitrogen .. 
Oxygen 

072 | 
27-63/ 

26-99 


100-00 

ioo-oo 


* There is no word in English equivalent to the Dutch Veen, a term applicable to all 
soils which consist either entirely or chiefly of peaty matter. There is no equivalent 
term also in German, but there is in the Danish and Kussian languages. 








FUEL. 


115 


Heating Effect of Peat. The combustibility and inflammability of peat are, owing to the 
large quantity of ash and water it contains, less than that of wood. 

According to Karmarsch the absolute heating effect of:— 


100 kilos, of yellow peat = 

100 „ brown „ = 

100 ,, hard „ = 

100 „ pitch „ = 

100 cubic metres of yellow peat = 
100 „ brown „ = 

100 „ hard „ = 

100 pitch „ = 

These results agree with those obtained by 
tive and boiling operations— 


94/6 kilos, of air-dry fir wood. 

107*6 „ „ „ 

104-0 

1107 

33'2 cubic metres of fir wood. 

897 

144*6 „ 

184*3 » 

Karsten states that for evapora- 


Brix. 


2i parts by weight of peat are = 1 part by weight of coal 
4 parts by volume „ = 1 part by volume „ 


According to Vogel, the evaporative effect of peat is the following :— 

Water. * Evaporative effect. 

Air-dry fibre . 10 per cent 5-5 kilos. 

Machine-made peat... 12—15 ,, 5*0—5-5 ,, 

Compressed peat ... 10—15 5 8—60 „ 


New Method of During the last twenty years peat has been employed for the preparation of 
utilising Peat, paraffin, peat-creosote, and paraffin oil. As far back as the year 1849, Reece 
tried to utilise Irish peat in the preparation of paraffin; and the experiments of 
Drs. Kane and O'Sullivan proved that 1 Ion of Irish peat yielded about 1*36 kilos, of 
paraffin, 9 litres of paraffin oil, and 4-54 litres of lubricating oil. According to Wagen- 
mann, the peat of the Isle of Lewis, Scotland, yields from 6 to 8 per cent tar, and 
this again yields 2 per cent of photogen or paraffin oil, 1-5 per cent of solar oil, and 0-33 
per cent of paraffin. 


Carbonised Peat. 

carbonised Peat. In many parts of Germany, and of all countries where peat bogs 
abound, the use of peat as fuel is out of all proportion to the enormous quantity of 
material left untouched ; this is due to the fact that peat is as fuel in many respects 
a very inferior material. Its bulk in reference to its heating effect'is very large ; its 
combustion evolves a very disagreeable odour and pungent smoke, so that peat 
is therefore not suited for heating rooms. On this account peat is carbonised. As 
peat varies greatly in composition, the carbonised peat or peat-coke also varies, and 
the composition of the peat-coke may be represented as follows :— 



Superior quality. 

Inferior quality. 

Carbon . 

86 

34 

Hygroscopic moisture ... 

... 10 

10 

Ash. 

4 

56 


Nothing is known as to the absolute and specific calorific effect of peat-coke, since 
no experiments have been instituted. Ordinary peat-coke appears to approximate 
charcoal in its specific calorific effect, but peat-coke is otherwise inferior to charcoal 
because it is less dense, and cannot on account of its dusty ash produce an intense 
heat. Peat-coke is not suited for fuel in blast-furnaces or other metallurgical opera¬ 
tions, but answers well for heating steam boilers, evaporating pans, and similar 


CHEMICAL TECHNOLOGY. 


716 


apparatus. But peat-coke made from compressed peat is a highly valuable fuel for 
metallurgical operations, so that it becomes a matter of importance to find a means of 
compressing peat inexpensively. In Holland, peat, especially that known as spoil 
turf, or hoogeveensche turf, is very largely used for industrial purposes, and on 
account of not containing sulphur is used at the Utrecht mint for melting silver and 
gold. 

Brown-Coal. 


Brown coal. This mineral fuel is also the product of a peculiar decomposition of 
wood, but the decay has in this instance been more complete. It is not easy to draw 
a clear line of demarcation between brown-coal and coal, when only the properties of 
these substances are to be considered. Therefore the palaeontological and geological 
relations have to be taken into account when it is required to estimate the value of a 
fossil fuel. In general it may be said that any fossil coal of more recent date than 
the chalk formation may be termed brown-coal; while all fossil coals found below 
the chalk formation are really pit-coal. As the latter contain more nitrogen than the 
former, this fact may be utilised in testing to distinguish between pit-coal and brown- 
coal. Brown-coal, on being heated in a dry test-tube, yields fumes which exhibit an 
acid reaction, because brown-coal is somewhat similar to cellulose; whereas, if the 
same test be applied to pit-coal, ammoniacal fumes are given off (containing 
ammonia, aniline, lepidin, &c.), which exhibit an alkaline reaction. When finely pul¬ 
verised pit-coal is boiled for some time with a rather concentrated solution of caustic 
potash, the fluid remains colourless; but when brown-coal is similarly treated, 
the liquid becomes brown- coloured by the formation of humate of potash. This test 
does not, however, apply to the brown-coal found in the tertiary formation of 
the northern slope of the Alps. E. Bichter and Hinrichs state, that when pit-coals 
are dried at 115 0 , and caused to lose a very small quantity in weight, this loss disap¬ 
pears again, in consequence of an oxidation which takes place; while if brown-coal 
is so treated, the subsequent increase in weight is not observed. 

According to the various degrees of decay, several kinds of brown-coal are 
distinguished:—1. Fibrous brown-coal, fossil or bituminous wood, lignite, is similar 
to wood, the structure of stem, branches, and roots being apparent. 2. Common 
brown-coal forms compact brittle masses, exhibiting a conchoidal fracture. 3. Earthy 
brown-coal is a mixture of brown-coal and earthy matter. In'several parts of Ger¬ 
many and the Austro-Hungarian Empire, brown-coal of excellent quality is found, 
especially suited for the purpose of preparing paraffin and paraffin oils. 

Brown-coal is frequently found mixed with the rhombic variety of iron pyrites. When 
that mineral and earthy matter predominate, there is formed what is termed alum- 
shale, under which name, however, is also known a kind of clay mixed with bitumen 
and iron pyrites. The average quantity of ash contained in brown-coals amounts to 
5 to 10 per cent. The ash contains chiefly alumina, silica, lime, magnesia, oxides of 
iron and manganese; while the quantity of hygroscopic moisture in freshly dug 
brown-coal may amount to 50 per cent. The substance contains in air-dry state 
20 per cent water, and the average composition of brown-coal may therefore 
be quoted as :— 


Carbon . 

Hydrogen. 

Chemically combined water ... 
Hygroscopic water. 


48—56 per cent. 
1—2 
3 1 —3 2 


FUEL. 


717 


The combustibility of brown-coal is less than that of wood, while its inflamma¬ 
bility varies between that of wood and pit-coal. The heating effect of brown-coal 
is with— 

o 



grosco 
water, 
er ceni 

Ash. 
er ceni 

0 


a 

0 


H 

pu 

dq 

<0) 

pH 

£ 




m 

Pi 

Air-dry fibrous brown-coal, containing 20 and 

l 0 

0'48 

o*55 

1800 

99 99 99 99 

20 „ 

IO 

°*43 

— 

— 

„ earthy „ ,. 

20 ., 

0 

o’6i 

079 

1975 

„ ,, ,, „ 

20 „ 

10 

o'55 

— 

— 

„ conchoidal „ ,, 

20 „ 

0 

069 

o-88 

2050 

99 99 9 * »» 

20 „ 

10 

0*62 

— 

— 

Kiln-dried fibrous brown-coal „ 

20 ,, 

0 

0*61 

— 

2025 

>» >> >> >» 

20 „ 

10 

o'55 

— 

— 

„ earthy „ „ 

20 „ 

0 

076 

— 

2125 

99 99 99 99 

20 „ 

10 

0*69 

— 

— 

„ conchoidal „ „ 

20 „ 

0 

0-85 

— 

2200 

99 99 99 99 

20 „ 

10 

0 76 

— 

— 


It appears from this table that the absolute and pyrometric calorific effect of air - 
dry brown-coal is more than twice that of kiln-dried wood; and this remark applies 
to the specific calorific effect of brown-coal, which is more than twice that of the best 
wood. 

The evaporative effect of brown-coal is the following: 



Water. 

Ash. 

Evaporative effect. 

Bohemian brown-coal 

287 per cent. 

io’6 per cent. 

5*84 kilos. 

Bituminous wood 

237 »» 

39 .» 

576 „ 

Earthy coal . 

47‘ 2 

4-8 „ 

5 55 » 

Lump coal . 

477 

3 1 „ 

5-08 ,. 


Brown-coal as FueL Brown-coal is a less suitable fuel and its applications are far more 
limited than those of pit-coal, for brown-coal cannot be used in those cases where a 
caking coal is required. Brown-coal is useful as fuel for certain chemical operations—dis¬ 
tillation, evaporation, &c.—and may be used for heating rooms in dwelling houses, when 
burnt in well-constructed stoves. Earthy brown-coal is not well fitted for use as fuel, 
unless it has first been lixiviated with water, moulded into bricks, compressed, and dried. 
It has been found in practice that brown-coal freshly dug is a better fuel than brown-coal 
which has been exposed to the air for some time, because by the combined action of air 
and moisture, even when the material does not contain pyrites, a slow combustion takes 
place, whereby the combustibility of the material is greatly impaired. As already 
observed, from brown-coal paraffin and paraffin oils may be extracted 

Pit-coal, or Coal. 

coal. Iron ores and coal are the most useful minerals, and the most important of all 
inorganic products of nature. Without coals the industry of the world as now 
existing would have been simply impossible. Coals supply heat and are a source of 
power ; and cheap coal is a most important incentive to extensive industry. 

Coals are the mummified and carbonised remnants of an ancient flora belonging to 
a former phase of existence of our globe; and they exist as a distinct geological for¬ 
mation, which extends in some localities over an area of several square miles. 
As regards the mode of formation of coal different opinions are current. The 



CHEMICAL TECHNOLOGY. 


7 ia 


simplest view is that a peculiar kind of decay, aided by the internal heat of the 
earth, and modified by the pressure of superincumbent rocks and sedimentary 
deposits, has taken place among the plants, which have been gradually converted 
into a more or less pure carbon. Hence anthracite is a nearly pure carbon; while 
the different varieties of coal which contain bituminous and volatile matter are 
less completely decayed. The hydrogen and oxygen escape in combination with 
carbon as marsh-gas and carbonic acid and as petroleum. Anthracite must be viewed 


as the final product of the slow process of decay through ' 
coal pass. 

Carbon. 

which brown-coal and pit- 

Hydrogen. Oxygen. 

Cellulose . 

52-65 

5’ 2 5 

42*10 

Peat from Vulcaire . . 

60-44 

5'96 

33 '60 

Lignite . 

6696 

5*2 7 

2776 

Earthy brown-coal . 

74*20 

5*89 

19-90 

Coal (secondary formation) . 

76-18 

5*^4 

18-07 

» (coal „ ) . 

90-50 

5‘°5 

4*40 

Anthracite. 

9285 

3‘96 

3*19 

The most important explored coal deposits in 

Europe 

are:—In En 

gland:* The 


South Wales coal formation extending over an immense area; the Staffordshire and 
Yorkshire coal basins, the latter of which stretches to the Durham and Northum¬ 
berland basins, and these again to those met with in the Southern parts of Scotland. 
2. In Belgium: The basin of the Maas, near Liege, and those of the Sambre and 
of Mons. 3. In France : The basins of the Loire, of Valenciennes, of Creuzot and 
Blanzy, of Aubin, of Alais. 4. In Germany; The Silesian coal basin, those of the 
Saar, of the Ruhr, a tributary river of the Rhine, the basins near Zwickau and 
Plauen, &c. 5. In Austria: the Bohemian coal basin at Pilsen, and those of 

Brandau and Schlan. I he largest of the European coal deposits or basins is very 
small compared with those situated in North America. The largest of the American 
deposits is that which stretches from near Lake Erie to the Tennessee river, through 
the states of Pennsylvania, Virginia, Kentucky, Tennessee, and known as the 
Apalachian coal field. The coal fields of Illinois and of Canada are not much 
smaller. 


Accessory Constituents 
of Coal. 


Iron pyrites, or mundic, as the pitmen term it, is in the tesseral 
or in the rhombic shape, a very common accessory constituent of coal, which 
by being impregnated with this material may not only become unfit for use in 
certain operations, but is liable to crumble to dust, as is the case with many kinds of 
the Welsh coals which are thoroughly incorporated with pyrites, because the pyrites 
on coming into contact with air are oxidised and increase in bulk, forcing the 
coal asunder. This oxidation may become so active as to give rise to spontaneous 
combustion of the coal even m the seams. Galena, copper pyrites, and black-jack 
(native black sulphuret of zinc), also occur occasionally in coal. Among the earthy 
minerals, carbonate of lime, gypsum, heavy spar, clay, ironstone, and blackband (an 
iron ore), are frequently met with. 

Classification of coals. Abroad coals are classified with respect to their behaviour under 
combustion, as—1. Caking coals, which on having been reduced to powder and then 

8omMomof W° a !n T«r8 Britai . 1 ? 1 . is annuall y increasing, for in i860 it amounted to 
mimons of tons ’ I<H ; m 1869 t0 108 millions i ^ in 1870 to 113 










FUEL. 


7 1( 3 

ignited in a closed crucible to red heat, cake together. 2. Sintering coals, the 
powder of which agglutinates without fusing. 3. Sandy coals, the powder of which 
neither cakes nor agglutinates when ignited. In England coals are usually classified 
as—1. Gas coal. 2. Household coal. 3. Steam coal. 

Comparing the elementary composition of the coals with their chemical and 
physical properties, it appears that caking coals contain a bitumen consisting of 
carbon and hydrogen ready formed, or what is more likely formed at a high tem¬ 
perature. The larger quantity of oxj’-gen present in sintering coals causes less 
bitumen to be formed; while in sandy coals a still smaller quantity of bitumen 
is formed- The most recent researches on coal disprove the opinion, that with 
an increase of the quantity of oxygen the caking should decrease, and that, 
consequently, the coals which contain the largest quantity of oxygen should be 
sandy coals. Coals exhibiting almost the same elementary composition behave very 
differently when exposed to heat.* 

Anthracite. This carbonaceous mineral is to be considered as the final product 
of the process of decay which has converted plants into coal. Anthracite is found 
in the metamorpliic rocks deposited in seams between clayey slate and greywacke, 
also between deposits of mica slate. Anthracite is amorphous and thereby distinguished 
from graphite; it is deep black coloured, brittle, exhibits a conchoidal uneven 
fracture, burns with a scarcely luminous flame, and without producing smoke. 
It does not become soft in the fire, but frequently decrepitates. 

Jacquelain’s analysis of several anthracites led to the following results:— 


Carbon. Hydrogen. Oxygen. Nitrogen. Ash. 


From Swansea. 

90*58 

3-60 

381 

0-29 

1-72 

„ Sable . 

87-22 

2-49 

ro8 

2-31 

6-90 

„ Vizille . 

94*09 

1*85 

„ 

2*85 

190 

„ Isere Department, France ... 

94-00 

1-49 

„ 

0-58 

400 


Anthracite is an excellent fuel for many purposes, and yields, especially with the 
blast, a very strong heat. It is therefore largely used in Wales in metallurgical 
operations, for burning lime and bricks, and in stoves for household purposes. 
In Pennsylvania, anthracite is met with and used largely in the reduction of iron 
ores. 

Caking Coal. In addition to its behaviour under combustion, this coal is charac¬ 
terised by its deep black colour, ready inflammability, and by yielding when heated 
in closed vessels a compactly fused coke. Designating, with Fleck, the quantity per 
cent of carbon in ash-free coaly matter as C, the free hydrogen as W r , the combined 
hydrogen as W, the oxygen and nitrogen as S; then (C-|-(W-f-W I )4-S=ioo). 
Wi is found by calculation on the supposition that 8 per cent oxygen holds in com¬ 
bination 1 percent of hydrogen; consequently Wi — |; and this deducted from the 
total quantity of hydrogen, gives as difference the free hydrogen ==W. The caking 
property of a coal is due to the proportion that upon 100 parts of carbon there should 
not be less than 4 of hydrogen. Caldng-coals are especially suited for gas manu¬ 
facture, though Fleck designates as such, in the widest sense - all coals containing 
upon 1000 parts of carbon at least 20 of combined hydrogen. But as the value of 
such a gas-coal depends upon the free hydrogen, which with carbon will yield volatile 

* E. Eichters has recently described a method for the comparative determination of 
different kinds of coal. See Dingler’s Polyt. Journ., vol. 195, p. 72. 


720 


CHEMICAL TECHNOLOGY. 


hydrocarbons, for the purpose of rendering the flame luminous, coal containing upon 
ioo parts of carbon 2 parts of combined (or fixed) and 4 of free or disposable 
hydrogen may be considered as the best gas coal and the strongest caking coal. 

Because they contain a larger quantity of hydrogen than other kinds of coals, 
caking-coals are more readily inflammable and evolve the strongest flame. Strongly 
caking coals, however, are not well suited for use as fuel by themselves, owing to the 
fact that by the fusion, as it were, they undergo, they greatly impede access of 
air at the open fire-bars. Caking-coal is an excellent fuel on the forge-hearth, 
because by caking together it forms a receptacle for the blast from the bellows, and 
increases the heating effect. The peculiar kind of small coal used by blacksmiths is 
known in the French language as charbon de forge , liouille marecliale , and is in 
England termed smithy-coal. 

Sandy-coal is the poorest quality. It contains much oxygen, suffers great 
contraction when converted into coke, leaving a sandy, small coke. This kind of 
coal contains less than 4 per cent of free hydrogen; it is used as fuel for burning 
bricks, lime, and for similar purposes where a cheap fuel is required. 

Sintering-coal exhibits an iron-grey colour, is frequently very lustrous, far less 
readily ignited than caking-coal, often contains much pyrites, and is employed where 
a strong and lasting heat is required. It is, therefore, used industrially on the large 
scale as a steam coal, as fuel for metallurgical purposes, &c. This kind of coal 
yields only a small quantity of gas, and when burnt for coke in coke-ovens it is 
scarcely changed in bulk, yielding a loose somewhat porous coke. 100 parts of the 
combustible portion of this coal contain less than 4 parts of free and less than 2 parts 
of combined hydrogen. Some kinds of anthracite belong to this class of coal; but 
the real anthracite is to be viewed as a native coke produced in a peculiar manner, 
not comparable with the process of coke-making as carried on industrially. 

The physical properties of coal may be judged from the quantity of hydrogen 
contained, and we find that:— 

Caking coals contain upon 100 C., more than 4 W t , less than 2 W. 

Gas and caking coals „ „ 100 C., „ „ 4 W I} more than 2 W. 

Gas and sandy coals „ „ 100 C., less than 4 Wi, „ „ 2 W. 

Sintering coals „ ,, 100 C., „ „ 4 W It less than 2 W. 

Assuming coals to contain on an average 5 per cent of hygroscopic and 5 per cent 
of chemically combined water, the average composition is :— 

Carbon . 69—78 

Hydrogen . 3— 4 

Chemically combined water and hygroscopic water . 13—23 

Ash. 3 

The composition of the ash varies, greatly depending, not only as regards quality, 
but also the quantity of the constituents, upon a variety of causes, among which the 
geological age of the coal, the formation in which it is found, and others, have great 
influence. The ash consists chiefly of an alumino-silicate, or of gypsum and 
sulphuret of iron, mixed with larger or smaller quantities of lime, magnesia, carbonic 
acid, oxides of iron and manganese, with very small quantities of chlorine and 
iodine. Ash which contains much alumina and little silica is infusible. Ash con¬ 
taining much silica, but not any or only a small quantity of oxide of iron, sinters, 
but does not fuse; but ash which contains oxide of iron and alkaline silicates readily 


FUEL. 


721 

forms a slag, and may give rise to loss of fuel by enveloping the particles of coal. The 
quantity of ash found by incinerating coal in a small crucible varies from 0-5 to 20 
and 30 per cent. By washing coals, small coal especially, a portion of the mineral 
matter may be eliminated. 

Calorific Effect. The subjoined table exhibits for average coals the calorific effect, 
specific gravity, and composition:— 


Composition:— 

Anthracite. 

Caking coal. 

Sintering coal. 

Sandy Coal. 

Carbon . 

85 

78 

75 

69 

Hydrogen. 

3 

4 

4 

3 

Chemically com- 

, bined water ... 

2 

8 

11 

18 

Hygroscopic water 

5 

5 

5 

5 

Ash . 

5 

5 

5 

5 

Calorific effect:— 

Absolute . 

0*96 

°'93 

089 

0 

^Ji 

to 

Specific . 

1-44 

ri 7 

1*16 

I "06 

Pyrometric. 

2350° 

2300° 

2250° 

2IOO C 

1 part reduces lead 

26—33 

23—31 

19—27 

21—31 

1 part heats water 

from o°—100 

6o’5—747 

52-87—2-0 

44-06—1 "6 

50-0—71‘0 

S P- g r . 

i* 4 i 

1-13—1-26 

1 * 13 — 1 * 3 ° 

2 - 05 —I -34 


It is assumed in practice that the heating effect of a good coal is very nearly that 
of wood-charcoal, and twice that of dry wood. In smelting operations the heating 
effect of coals is taken by bulk to that of wood by bulk as 5 : 1, and by weight as 
15 : 8. According to Karsten’s researches:— 

100 parts by bulk of coal in the reverberatory furnace = 700 parts by bulk of wood. 
100 „ by weight „ „ „ =250 „ by weight of wood. 

In boiling operations:— 

100 volumes of coal = 400 volumes of wood = 400 volumes peat. 

100 parts by weight of coal = 160 parts by weight of wood = 250 parts by weight of 
peat. 

Evap ofcoais E£tect This forms the most important industrial investigation which can 
be made with coals. In order to ascertain the evaporative effect, we must know— 

1. The quantity of hygroscopic water contained. 2. The quantity of ash or non¬ 
combustible matter it contains. 3. The composition of the organic matter. 

As Hartig’s experiments have proved that the evaporative effect of the organic 
matter of coal is the same for nearly all kinds of coal (= 8*04 to 8*30 kilos, of steam), 
the evaporative effect of any giveD sample of coal can be ascertained by estimating 
the quantity of water and ash it contains. According to W. Stein, the practical 
evaporative effect on the large scale may be taken as equal to two-thirds of that 
which has been calculated from the chemical composition of the coal. The practical 
evaporative effect of the coals in use in Southern Germany is, according to laboratory 
experiments and experiments made on the large scale, the following:— 




CHEMICAL TECHNOLOGY. 




Ash. 

Practical 

evaporative effect. 

Ruhr coals, 

I. 

quality . 5*00 

7"20 

Zwickau black pitch-coal, 

I. 

,. . 6"o6 

6-45 

11 »• »» 

II. 

. . I5'4i 

5 * 6 i 

Bohemian coal, 

I. 

„ . 6'6o 

5 *8 o 

11 1 * 

II. 

„ . 6-90 

4*90 

11 11 

III. 

. 10-30 

4-20 

Saar coal. 


. 21-50 

6 06 * 

Stockheim coal, 

I. 

. ••• 630 

272 

11 

II. 

00 

0 

3-86 

The average evaporative effect 
lb. of coal. 

of the Hartley steam coals is 

14 lbs. of water for 


Boghead coal.. Tliis mineral, also known as Torbane Hill coal, found in the neigh¬ 
bourhood of Bathgate, a town situated between Edinburgh and Glasgow, belongs, 
with the blattel-coal of Bohemia, to a peculiar fossil fauna, and is especially suited 
for the manufacture of paraffin and oils, owing to the large quantity of bituminous 
matter it contains. Boghead coal is now solely employed in the preparation of 
paraffin and oils; and the supply, which is very limited, because the seam is almost 
exhausted, has been secured by Mr. Young, of Bathgate Works, 
ioo parts of Boghead coal contain: 


Carbon. 

. 60-9 

65*3 

Nitrogen . 

. o *7 

07 

Hydrogen . 

. 9*i 

9*3 

Sulphur . 

. 03 

O’l 

Oxygen . 

.. 4*3 

5 * 4 

Water. 

. 03 

05 

Ash . 

. 24-1 

i8‘6 


Boghead coal was formerly employed for gas-making, i ton yielding 15,000 cubic 
feet of a highly illuminating and very durable gas. Many varieties of the Scotch 
cannel-coals are suitable and are used for the preparation of paraffin and oils, and 
have therefore so greatly increased in price that these coals—the Wemyss, Rigside, 
and others—are now seldom employed for gas manufacture. 


Petroleum as Fuel. 

petroleum as Fuel. Native, as well as artificially prepared petroleum, is, under certain 
conditions, a very valuable heating material. The sp. gr. of this oil varies, at o°, 
from 0786 to 0*923, while its coefficient of expansion for i° varies from 0-00072 to 
0*000868. The experiments as to the application of petroleum as fuel for marine 
purposes in America have proved that petroleum is three times more efficient than 
coal; and as the complete combustion of petroleum does not produce smoke, but 
simply evolves carbonic acid and .watery vapour, a tall chimney is not required. 
Coals may be burned in marine boilers with the same effect, proved by a series of 
experiments made about fifteen years ago, on the large scale, by the late Dr. Rich¬ 
ardson, of Newcastle-upon-Tyne, in conjunction with Messrs. J. A. Longridge and Sir 
William Armstrong. As petroleum contains 14 per cent of hydrogen, the condensa¬ 
tion of the gases of combustion yields a large quantity of water which may serve for 























FUEL. 


723 


feeding the boilers, while the heat thus set free may be employed for the purpose of 
heating the feed-water. According to H. Deville, there is no difficulty in regulating 
the supply of petroleum, and it is not necessary to heat it previously. According to 
Fr. Storer, 1 kilo, of crude petroleum evaporates 10-36 kilos, of water, while 1 kilo, 
of anthracite coal evaporates only 5*1 kilos, of water. The theoretical evaporative 
effect of the purest petroleum is 18-06 kilos., as may be deduced from the percentage 
composition of petroleum, viz.:— 


C 

H 


o-86 

014 


8080=6948 

34,462=4824 


-772 


11,772 units of heat; 


= 18-06 kilos. 


The heating effect of different kinds of petroleum has been ascertained by 
II. Deville (1866—1869) to be as follows:— 


Heavy oil from West Virginia . 

Light oil from „ „ . 

Light oil from Pennsylvania . 

Heavy oil from Ohio . 

Oil from Java (Rembang) . 

Oil from Java (Cheribon) . 

Oil from Java (Soerabaya) . 

Petroleum from Sckwabwiler (Alsace)... 

Petroleum from East Galicia . 

Petroleum from West Galicia . 

Crude shale oil from Autun (France)... 


10,180 units of heat. 
10,223 „ 

9>963 

10,399 „ 

10,831 „ 

9*593 » 

10,183 

10,458 

10,005 

10,235 

9*95° *» >» 


More recently, R. Foote, Wyse, Field, Aydon, H. Deville, Dorsett, and Blyth, have 
constructed petroleum furnaces suitable for steam-boilers, which answer the purpose well. 
Petroleum lamps are used abroad, instead of spirit-lamps, for domestic purposes, viz., 
heating tea- and coffee-urns, tea-kettles, <fcc. 


Coke. 

coke. By coke we generally understand carbonised coal; and in England there is 
no other description of coke than oven- and gas-coke, referring of course to the mode 
of production. 

Coke is prepared for the purposes:—1. Of increasing or rather concentrating the 
quantity of carbon in coal, and thus to obtain a fuel which will yield a more intense 
heat than coal. 2. For the purpose of converting coal into a fuel deprived of its 
volatile constituents, so as to obviate the unpleasant smell emitted by the combustion 
of coal when used to heat rooms in dwelling-houses. 3. For the purpose of 
converting coal into a fuel which does not become pasty when ignited, coal, in con¬ 
sequence of this property, being unsuitable for use in blast, cupola, and other 
furnaces. 4. For the purpose of eliminating from the coal a portion of the sulphur 
contained as pyrites. Before being converted into coke, coal, and especially small 
coal or coal mixed with slaty shale, fire-clay, and other heterogeneous mineral 
matter, is washed, as it is technically termed, the operation consisting in a process of 
purification by means of suitably constructed machinery, and the aid of a stream of 
water, the rationale of the process being that the mineral matter, which is about 
three times heavier than the coal, is deposited. The machinery in use for this 
purpose is similar in construction to that employed for washing metallic ores. By 
this method of purifying coal, the quantity of ash (mineral matter) it contains may be 










724 


CHEMICAL TECHNOLOGY. 


reduced from io or 12 to 4 or 5 per cent; but it should be borne in mind that 7 to 8 per 
cent of the coal is lost as dust. Bessemer has suggested the use of a solution 
of chloride of calcium, so concentrated that the coal may float on its surface, while 
the mineral matter will sink. The residues of coal-washing may contain so much 
iron pyrites as to be fit for use in the preparation of sulphuric acid (see p. 203). 

The operation of coking is carried on in heaps, in ovens, or in retorts ; but in the 
latter case the object is not so much to prepare coke as to obtain gas’, tar, and other 
products from coal. The construction of coke-ovens according to Knab’s plan, 
admits of obtaining from the coal, tar, ammoniacal water, and other volatile products. 

coking in Heaps. This method of converting coal into coke is very similar to that in use 
for converting wood into charcoal; but the central shaft, 1 to 1*5 metres in height, is in 
this instance made of fire-bricks, having a diameter of 0*3 metre, and provided with 
several lateral air-holes, Fig. 313, by means of which the mass of coals is brought in 


Fig. 313. 



connexion with the central shaft. The largest lumps of coal are placed next to the shaft, 
being filled up with small coal, technically termed cinders and culm. At the bottom of 
the heap channels are constructed radiating towards the centre. The bottom of the shaft 
is filled with dry wood, which is kindled from the top. The opening at the top is not 
closed with the iron cover fitted to the shaft as long as any smoke from the smouldering 
coal is emitted. When no more smoke is emitted, the air-channels at the bottom of the heap 
are stopped with wet sand and coal-dust. In England the cooling of the glowing heap is 
hastened by pouring on cold water, whereby a greater degree of desulphuration of the 
coke is obtained. 

Coking in Ovens. In the present day coal is converted into coke almost exclusively in 
ovens constructed for this purpose ; because it has been found that by the use of 
ovens the operation is more readily conducted, while a larger quantity and a better 
quality of coke are obtained. As regards the construction of coke-ovens, some are 
so built that the gases and vapours evolved during the operation of coking, escape 
without being utilised. Others again are so arranged that the combustible gases are 
employed as fuel for coking the coal, or as fuel for steam-boilers or other purposes. 
This kind of oven is constructed with or without admission of air. To the latter 
class belongs Appolt’s coke-oven, which is essentialty similar to a vertical gas-retort, 
fitted with apertures for the exit of the evolved gaseous matter. Other coke-ovens 
again are so constructed that the tar and volatile products of the dry distillation of 
the coal may be condensed, collected, and utilised. Knab’s coke-oven is thus arranged. 

Among the coke-ovens of older construction is one, Fig. 314, in use at the 
Gleiwitz ironworks in Silesia, a is the body of the oven or kiln, with lateral 
openings, 000, which can be closed by dampers or iron plugs ; similar apertures are 
made in the bottom of the oven. The top of the kiln is vaulted, with the large 





FUEL. 


725 


opening, b, which serves, as well as the lateral doorway, a, for the introduction of the 
coals. The large lumps are placed at the bottom of the kiln, which is entirely filled, 
with the exception of a small space towards th6 top of the doorway, left for the pur¬ 
pose of throwing in ignited coals. The doorway, a , is bricked up, only a small channel 
being left for the introduction of the ignited coal. / is an iron pipe for carrying off 
the volatile products of the smouldering of the coals ; d is an iron lid fitting tightly 
in the opening b. At the commencement of the operation all the openings of the 
oven, excepting those at/and those at the bottom, are closed; and as soon as there 
appears at the lower apertures an orange-coloured glow, these openings are closed, 
and those of the next row opened, and kept open for about ten hours; the third row 
of openings being then unplugged and kept open for sixteen hours; finally, the 
fourth row is opened for about three hours, after which the oven is left to cool—all 
openings being plugged—for twelve hours. The door, t, is then broken up, and the 
coke drawn from the oven by means of iron rakes. This description of oven contains 
35 to 40 cwts. of coal, and the average yield of coke is 53 per cent by weight and 
74 per cent by bulk. The gases and vapours issuing from f are carried to a 
condenser. 1 cwt. of coals yields 10 litres of tar. 

The coking of small coal, culm, coal-dust, either previously washed or not, 
is carried on in ovens similar in construction to those used for bread-baking. Small 
coal, especially of the caking quality, yields excellent coke, and in many instances, 
this fuel is now guaranteed not to contain more than 6 per cent of ash. The mode 
of construction of coke ovens for small-coal coking differs in various countries. 
Fig. 315 exhibits a vertical section of such an oven in use by tlie Leipzig-Dresden 
Railway Company. The coking-room, a , is 3*3 metres high. The doorway, d, 
1 metre high and wide, can be closed with an iron door, provided at the top with four 

Fig. 314. Fig. 315. 



air holes. The chimney stalk, b, is rather more than 1 metre high. At each side of 
t lie doorway an iron hook, e , is fixed, for the purpose of supporting the rakes used 
by the labourers when drawing the coke. In this description of oven 50 Dresden 
bushels * of small coal and coal-dust are converted into coke in seventy-two hours. 
The coke obtained is very compact; but if the oven be lightly filled, a more spongy 
coke is the result. Fig. 316 exhibits the construction of the coke-oven at the 
Zaukerode colliery, near Dresden. The bottom or hearth of the coking-kiln is of a 
circular shape slightly inclined towards the doorway. The width of the hearth 


* 1 Dresden bushel = 103’8 litres. 


























726 


CHEMICAL TECHNOLOGY. 


is 3*6 metres. The top of the vault c is 3*08 metres above the hearth, bb are two 
chimneys, each 1*3 metres in height, for carrying off the volatile product. The cast- 
iron door is so arranged that at the top of the doorway an opening is left for 
the admission of air into the oven ; e is a hook serving the purpose mentioned in the 

description of Fig. 314. Fig. 317 
exhibits the vertical section, and 
Fig. 318 the ground plan of the 
coke-ovens in use at the collieries 
situated in the Saar district. The 
hearth of the kiln is egg-shaped, 
3 metres long and 2 metres wide; 
while the height of the kiln is at 
most only 1 metre. The chimney, 
175 metres high, also serves for the 
introduction of the coals. The 
admission of air to this oven is 
regulated by a channel at a height 
of o - 3 metre above .the hearth ; this channel, Fig. 318, communicates on both sidesof 
the doorway, t, with the outer air, and communicates by means of the channels, 000, 
with the interior of the oven. The door, t, fits rather tightly in the doorway. 
A quantity of 1 to 1*25 cubic metres (from 40 to 50 cubic feet) of small coal is con¬ 
verted into coke with this oven in 24 to 30 hours. 

Fig. 317. 

I, 



Among the coke-ovens constructed to utilise the escaping gases and heat for 
the purpose of making coke, that of Appolt deserves notice. The first of these ovens 
was built in 1855 at St. Avoid. This coke-oven is distinguished from those 
described by its peculiar shape, which is that of a vertical shaft, heated externally, 
the heat being supplied by the ignition of the gases and vapours evolved from the coals 
while becoming coked. Fig. 319 exhibits a vertical section, and Fig. 320 a horizontal 
section of this oven. In order that the heat may reach the centres of the shafts, a a, 
their shape is that of a parallelogram, 0*45 by i - 2 metres, and 4 metres deep ; 12 of 
such shafts form one oven. The separate shafts, the walls of which consist of 
hollow double walls, b, are connected with each other as well as with the lining 
walls, which forms a series of intercommunicating channels. Every compartment is 
provided with an upper and a lower aperture, through the former of which the coals 
are introduced, while through the latter—closed during the coking operation with an 
iron trap door—the coke is withdrawn. The apertures e e in the brickwork serve for the 
purpose of carrying off the gases and vapours which are burnt in the channels by the 


Fig. 316. 



























FUEL. 


727 


aid of the air rushing in at ff. The heat produced by this combustion converts the 
coals into coke, and the products of the combustion are carried off through the 
channels g and h. The dampers, n, serve to regulate the draught. The channels g 
communicate with the horizontal channel, i , the channels h with the channel j . 





pn 

m 

mu 

mi 


r~ " 






Fig. 318. 


the channels i and j are carried into the chimney stalk, 7 c. The compartments of 
the kiln, Fig. 319, are united at the top by a contraction of the brickwork, leaving to 
each only a small opening, closed by a cast-iron lid, fitted with an iron tube for the 
purpose of conveying a portion of the gases and volatile matter. On the top of the 


Fig. 319. 



Fig. 320. 



oven rails are placed, on which an iron truck runs, laden with the charge—25 cwts-.— 
for each compartment. The coals are discharged into the compartments by 
opening a trap-door in the bottom of the truck. Under the vaulted brickwork, u, 
of the oven, trucks can be run for the purpose of being laden with the coke. 











































728 


CHEMICAL TECHNOLOGY. 


In order to set tlie oven in operation dry wood is thrown into the compartments, and 
this having been kindled, coals are thrown upon it. The interior of the oven soon 
becomes hot by the combustion of the gases issuing from the openings e. When the 
heat of the oven is sufficient to effect the decomposition of the coals and the combus¬ 
tion of the volatilised products, the compartments are charged, the iron lid being 
tightly luted to the top with clay. The charging is so conducted that the twelve 
compartments of the oven are filled in twenty-four hours, after which the coke in the 
first compartment is ready for being drawn, and fresh coal put in, an operation which 
is continued every second hour. As may be expected from the mode of construction, 
Appolt’s coke-oven is rather expensive in the first building, the cost abroad being 
about T6oo, while an ordinary coke-oven maybe built for <£72 to £120; but Appolt’s 
oven yields daily about 240 cwts. of coke—66 to 67 per cent from Duttweil coal, 
which in ordinary coke-ovens yields only 61 per cent. It should be mentioned, tha* 
with Appolt’s ovens, the coke from the inner and outer compartments is not of the 
same quality and compactness, owing to the higher degree of heat prevailing in the 
former. 

We may mention briefly the following contrivances for preparing coke, based upon the 
same principle as Appolt’s. Marsilly’s oven is covered with a brick arch, communicating 
with a flue through which the gases and vapours are carried under the hearth of the oven, 
and by burning there heat it. Jones’s oven is similarly constructed, but with the differ¬ 
ence that the combustion of the gases and vapours is made to take place in the coking 
kiln. This arrangement, used only with very dry, non-bituminous coals, certainly assists 
the coking process, because the air is heated previous to entering the kiln. Frommont’s 
double cooking oven, in use on the Maas, in Belgium, as well as in Westphalia, and 
at Saarbriicken, is a stage oven, so constructed that the gases formed in the lower coking 
compartment are carried through channels to the upper hearth; thence with the 
gases formed in the upper compartment, are conveyed under the hearth of the lower 
oven, and thence through lateral channels to the chimney, so that the heat is thoroughly 
utilised. Gendebien’s coking-oven is distinguished from that of Frommont, in so far that 
one of the tipper coking compartments is placed over two of the lower; these ovens are 
chiefly used on the Sambre (Belgium). The coke-ovens according to Smet’s plan are 
inclusive of the principles of all ovens built to utilise the heat of the combustible gases. 

Dubochet’s coking-oven, constructed in 1851 by Powell, is a tubular oven with sloping 
hearth, consisting of two shallow curved parts placed one above the other, and separated 
by doors. The upper part is the distillatory furnace or oven, the gases and vapours 
there evolved being conveyed under the oven, and burnt with admission of air, the heat 
evolved by this combustion serving to coke the coals. The coke is caused to fall into a 
cooling oven, from which it is removed when extinguished. The combustible gases evolved 
by this process are sometimes employed for the purpose of heating a steam-boiler 
belonging to the coal-washing machinery. In the coke-oven built upon Knab’s plan, the 
gases evolved from the coal are, previous to being burnt, deprived of the tar and 
ammoniacal water carried off by them. For this purpose the gases are conveyed to two 
large cylindrical vessels filled with coke, and in which nearly all the tar is deposited • 
thence the gases are conveyed to a system of tubes connected with water reservoirs for the 
purpose of eliminating the ammoniacal products. The purified gases are then conveyed 
to the furnace to be there burnt from a large circular burner, to the centre of which air is 
admitted. The necessary motion is imparted to the gases by bell-shaped exhausters, 
which draw the gases from the furnace through the purifying apparatus and force them to 
the burner. According to the statement of Gaultier de Claubry, there are 150 tons of 
coal converted daily into coke, in eighty-eight ovens belonging to tlie Societe de Carbonisa 
Lion de la Loire, near St. Etienne. The yield in 100 parts is :— 


Coarse coke (large lumps) .. 

70*00 

Tar. 


Small coke. 

I * 5 ° 

Ammoniacal water .. 

Q*no 

Breeze . 

2-50 

Gas. 


Graphite . 

0*50 

Loss. 



It is questionable whether the coke thus obtained is equal in quality with that obtained 
by the ordinary coke-ovens; because experience proves that all coke prepared in close 








FUEL. 


729 

vessels, is rather porous and less suitable for use on locomotive engines and in blast¬ 
furnaces. 

Very small coal and dust are converted into coke in ovens built similarly to those used 
for baking bread. The large quantities of refuse coal, screenings, <fec., formerly waste, to 
be found in enormous heaps near coal-pits, and to effect their removal being frequently 
set on fire, burning for month after month, producing huge volumes of smoke, are now 
utilised and made into excellent coke, after having been first washed. 

The coke drawn from the ovens is extinguished with water or under ash. The former 
plan, however, is most frequent, and has the advantage of giving to the coke a peculiar 
silvery gloss. There is, however, more than one objection to this mode of extinguishing 
coke, because in the first place the coke absorbs and retains some water, which as it has to 
be evaporated when the coke is burnt, absorbs a portion of the heat generated by the 
combustion. Secondly, the weight of the coke is increased, and may be increased 
fraudulently to a large extent, as some portions of the coke—the more porous lumps—take 
up 120 per cent of their weight of water, while the dense metallic portion takes up only 
i£ per cent., and the coke from the bottom part of the oven 13 per cent. On an average 
the coke takes up by being extinguished by water 6 per cent of its weight; but cold coke 
takes up when thrown into water hardly half as much. 

properties of coke. Well burnt coke or oven coke, is a hard, uniform, compact, solid 
mass, difficult to break, and not honeycombed, nor very porous. Its colour is black- 
grey or iron-grey, with a dull metallic gloss. Good coke should contain very little 
sulphur. All the sulphur contained in coal, chiefly as iron pyrites, cannot be com¬ 
pletely eliminated by the coking process, as the sulphuret is only reduced to a lower 
degree of sulphuration. In the north of England it has been found, that if the coal, 
even when highly sulphurous, is first treated with a strong brine and powdered rock- 
salt, a coke very free from sulphur is obtained. The sulphur in coke is objectionable, 
from its action upon the ironwork of the furnaces, the fire-bars, &c. 

Indus' value as Fue! The average composition of good coke is the following 

Carbon . 85—92 per cent. 

Ash . 3 — 5 » 

Hygroscopic water . 5—10 „ 

Owing to the great density and compact structure of coke, and the fact that it does 
not contain any combustible gases, it is ignited with difficulty, and requires for kind¬ 
ling a strong red heat, with a blast for continued burning. 

According to a series of experiments in Prussian ironworks with coke in furnaces 
with hot blast:— 

100 parts by weight of coke = 80 parts by weight of charcoal. 

100 ,, bulk „ — 250 „ „ „ 

Brix found that a coke made from upper Silesian coals, and containing 5 9 per 
cent of water and 2'5 per cent of ash, yielded for every kilo, burnt 7^5 kilos, steam. 


Artificial Fuel. 

Artificial Fuel. Under this name we understand an originally pulverulent, combus¬ 
tible fuel, such as small cool or coke, breese, sawdust, refuse wood, &c., mixed with 
tar or thin clay liquor, and by strong pressure subsequently moulded in the shape of 
bricks. Compressed peat and compressed spent tan are in a certain sense aitificial 

fuel. 

reras. Under this name is known an artificial fuel first prepared from caking coal 
by Marsais, the viewer and manager of some collieries near St. Etienne. The small 
coal, screenings, dust, and other refuse, are first lixiviated for the puipose of 


CHEMICAL TECHNOLOGY . 


7JO 


removing mineral impurities, such as gangue, clay, pyrites, &c. The purified coal 
is drained, then ground to powder by suitably constructed mill-work, afterwards 
dried by the application of heat, then mixed with 7 to 8 per cent of thick coal-tar, 
and finally moulded into bricks by the aid of strong pressure, the brick-shaped 
lumps weighing each about 20 lbs. Peras is less fragile than ordinary coal, and being 
of a uniform shape, can be better stored than coal, taking up about one-fiftli less room, 
a matter of considerable advantage on board steamers. Similar to peras are the 
patent coals made by Wylam and Warlich. 

The so-called moulded charcoal, or Parisian coal, introduced about fifteen years 
ago by Popelin-Ducarre, is an artificial fuel composed of charcoal refuse with coal- 
tar. The small lumps and dust of charcoal are mixed with 8 to 12 percent of water, 
then ground to powder, and to 100 kilos, of the powder are added 33 to 40 litres of 
coal-tar. This magma is thoroughly incorporated and next moulded into cylinders. 
These are dried, and finally carbonised in a muffle-furnace. This fuel is far less 
fragile than ordinary charcoal, better fitted for transport, burns better than coke, and 
even when only sliglitty kindled, continues to burn in air, which is not the case with 
coke. 

Briquettes. When strongly caking coal is heated in closed vessels to 260° to 400°, 
and then compressed in moulds, the result is the formation of a hard brick-shaped 
fuel, very suitable for domestic use as well as for steam production.* It has been 
found that the manufacture of briquettes can be advantageously combined with the 
preparation of tar for the purpose of extracting benzol, carbolic acid, naphthaline, 
asphalte, and anthracen. 

' Gaseous Fuel. 


Gaseous Fuel. The utilisation of certain combustible gases and mixtures of these 
gases as fuel has been practically solved only during the last few years, although in 
metallurgical operations the idea of such utilisation is of more remote date. The 
combustible gases used on the large scale as fuel are those evolved from blast¬ 
furnaces, and from coke-ovens and other apparatus in which these combustible gases 
are formed as the by-product of industrial operations. The composition of the blast¬ 
furnace gases varies of necessity according to the kind of fuel used, the temperature 
of the furnace, the shape, build, and height of the latter, the pressure on the blast, &c. 
The combustible gases escaping from these furnaces consist chiefly of carbonic oxide, 
hydrocarbons, hydrogen, carbonic acid, nitrogen, and of ammonia where coal or coke is 
used as fuel. The so-called generator gases are those combustible gases which are 
evolved from solid fuel, coke, peat, or wood, by its carbonisation in a separated 
furnace, kiln, or oven, with or without the aid of a blast. These combustible gases may 
be utilised in various ways and obtained from fuel which is not otherwise applicable 
as such. According to Ebelmen these gases are composed as follows 

Generator gases obtained from :— 


Nitrogen. 

Carbonic acid... 
Carbonic oxide 
Hydrogen 


Wood-charcoal. 

Wood. 

Peat. 

Coke. 

... 64-9 

53‘ 2 

631 

648 

... 08 

ir6 

140 

r 3 

... 34-1 

34'5 

22*4 

33 8 

0‘2 

07 

OS 

01 


* See Th. Oppler, “ Die Fabrikation der kiinstlichen Brennstoffe, insbesondero der 
gepressten Kohlenziegel oder Briquettes,” Berlin, 1864; also “ Jahresbericht der chem 
Tecbnologie,” 1864, p. 760 ; 1866, p. 333 ; 1868, p. 800. 


WARMING. 


73 * 


There lias long been in use in England a gas mixture obtained by passing 
high-pressure steam over red-hot coke contained in retorts. Siemens’s regenerative 
gas-furnace, described on pp. 24 and 273, belongs to this category. Combustible 
gaseous bodies are largely utilised in metallurgical operations, puddling-furnaces, 
zinc-smelting, &c. 

Gas Poroses? 8 It has of late years been frequently suggested that a cheap gas 
should be manufactured for heating purposes. In Berlin a company has been 
formed under the technical guidance of C. Westphal and A. Putsch, the object being 
to prepare gas from brown-coal at Fiirstenwald, a distance of about 38 kilometres 
from the city. The intention is to construct twelve retort-houses, each to contain 
seventy furnaces provided with ten retorts, to be fired as in Siemens’s regenerative 
gas-furnace. The purified gas is to be forced by blowing-machines, actuated by 
steam-engines of 360 nominal or 500 indicated horse power, into a main pipe of 
1 3 metres diameter constructed of boiler-plates and carried above ground supported 
on iron pillars. The gas will be collected at Berlin in twelve gas-holders, each of 
750,000 cubic feet capacity. The pressure of the gas in the mains and service-pipes 
within the city will be 1 '5 centims. water-gauge, in order that pipes of smaller 
diameter may be used. According to Ziureck, the composition of the gas obtainable 
from the brown-coal is, at a sp. gr. of 0 5451, as follows:— 


Hydrogen . 

Carbonic oxide . 

Marsh gas . 

Nitrogen. 

Carbonic acid. 

Condensable hydrocarbons 


. 42 36 per cent. 

.. 4O'00 „ „ 

. 11 '37 

. 3'i7 - >• 

. 201 „ „ 

. 1’09 „ 


A gas of this composition will answer admirably for heating purposes. 3000 cubic 
feet of it are in heating effect equal to 1 ton of brown-coal, and equal to £ ton of 
pit-coal, the ton being equal in this case to 275 to 300 lbs. The price will be 74d. 
per 1000 cubic feet, so that the heating effect yielded by it as compared with the 
price of a ton of coals will be about 4s. 6d. The works are constructed for an annual 
production of 9500 millions of cubic feet of gas, or a daily supply of 2| millions of 
cubic feet. 


Heating Apparatus * 

Warming. We understand by warming the heating of any room or space by heat 
evolved from the combustion of fuel. The room or space may be an apartment in a 
dwelling-house, a church, a steam-boiler, a glass-house, a hothouse in a botanical 
garden, &c. It is the aim of technology to apply the fuel so as to yield by its most 
economical use the greatest amount of heat. In order to obtain by the combustion 
of fuel as nearly as possible its absolute and specific calorific effect, the combustion 
should not only be complete, but the gaseous products should suffer the highest 
degree of oxidation; in other words, neither smoke nor any combustible gases 


* The following works afford very valuable information on this subject:—C. Schinz, 
‘ Die Warme Messkunst,” Stuttgart, 1858 ;E. Peclet, “ Traite de laChaleur,” 3rd edition, 
Paris, 1861-62, 3 vols ; and for stoves for domestic use, “ Die Badische Gewerbezeitung,’ - 
edited by H. Meidinger. 











732 


CHEMICAL TECHNOLOGY. 


should be evolved. The practical importance of this principle is exhibited by the 
following:— 

i part of carbon yields, when burnt to carbonic oxide, 2480 units of heat. 

1 „ „ ,, „ „ carbonic acid, 8080 „ ,, 

In order to obtain complete combustion, the fuel should be supplied with the 
requisite quantity of air, while the vitiated air should be carried off with the gaseous 
products of the combustion. This supply of air or draught can be assisted artificially 
by means of blast- or exhaust-apparatus; but in most cases the draught is natural, 
i.e., produced by the calefaction of the air, which becoming specifically lighter, 
ascends. 

All heating apparatus consist of three distinct parts—the fire-place or hearth, the 
heating-room, and the chimney. The hearth is that portion where combustion takes 
place. The heating-room is the portion of the apparatus where the heat generated 
is utilised, and the chimney is a channel, usually placed in a vertical position, and 
often connected by means of flues with the heating-room and hearth—through which 
the gases evolved by the combustion of the fuel are carried off, and a draught 
created maintaining an efficient combustion of the fuel. 

The hearth or fire-place may vary greatly in shape and mode of construction. 
The most primitive, but also the most defective kind of hearth, is that on which the 
fuel, usually wood or peat, is placed on tiles or bricks under the chimney. Such 
arrangements are still in use in many remote country places, especially in the 
country districts of Ireland and Scotland, where faggots of wood and peat are thus 
burnt. In this manner a very great amount of heat is wasted and the supply of air 
not properly regulated; there is an excess of air supplied, and hence loss of fuel. 
The air required for the complete combustion of the fuel should be made to pass 
through the fuel, which for that purpose is placed on a grating, consisting of bars of 
iron or fire-brick. The space under the fire-bars is called the ash-pit, through which 
the air is supplied to the fuel. The hearth is usually provided with iron-doors, 
which are opened when fresh fuel has to be introduced. This plan is accompanied 
with the objection, that during the period of feeding and raking up the fire, a large 
quantity of cold air enters the hearth, and causes the combustion to become irregular 
and much smoke to be produced. The use of the so-called stage fire-bars, placed in 
the manner of steps, one above the other, is not attended with this defect. 

When the fuel contains much sulphur, the iron fire-bars are soon worn out, owing 
to the formation of sulpliuret of iron; in order to prevent this, it is often usual to 
leave a layer of clinkers and slag on the bars for the purpose of protecting them from 
the direct action of the fuel. In order to regulate the draught, dampers or similar 
contrivances are fitted to the flues, chimney, or funnel. 

a. Heating Dwelling Houses. 

Heating Dwelling Houses. The heating of dwelling-houses and public buildings, halls, 
theatres, churches, &c. (in connection with the ventilation), can be effected in 
various ways, either by radiant or conducted heat. According to the construction 
of the heating apparatus, we distinguish:—1. Heating by flues. 2. By stoves, or 
with hot air. 3. Air heating. 4. By means of steam or hot-air pipes. 5. Hot-water 
heating. 6. Heating by means offgas. 

Direct Heating. The direct heating of rooms by the combustion of wood and other 
fuel on an open hearth, or in chaufing-dishes and small stoves without chimneys, is 


WARMING. 


733 

undoubtedly tlie most ancient and primitive method of heating. In the centre of 
the huts in Ireland and the Highlands of Scotland, a rough hearth is constructed, 
while the smoke evolved by the fuel escapes through a hole in the roof. In some 
paits of France, Italy, Spain, and Turkey, rooms are heated by means of a chaufing- 
dish containing burning charcoal, by the combustion of which the air of the room is 
vitiated, becoming unfit to be respired by the lunga. It is evident that for this 
reason and owing to the risks of fire this mode of heating is very dangerous. 

Chimney Heating. This mode of heating, in general use in England and the larger 
towns of Scotland, Ireland, and Wales, is of ancient use, and is based upon the 
heating of the air of the rooms by the direct radiation of the heat of the fire. It is 
undoubtedly the most imperfect and wasteful method, as there flows into the chimney 
a very large excess of air above that required for maintaining the combustion of the 
fuel, the consequence being that strong draughts of cold air are felt near the windows 
and doors of the rooms, while a downward current of air is frequently created, 
causing the chimney to smoke. This mode of heating only suits countries enjoying 
an average mild climate and possessed of plenty of fuel. It would appear that 
among the reasons why this mode of heating is continued is the pleasure of seeing 
the fire and of warming the feet by it, notwithstanding that the other parts of the 
body remain comparatively cool. The arrangements of the method of warming by 
the radiant heat from chimneys are in the most primitive form the following:—At 
the lower part of the wall from which the chimney is built, a niche or recess is 
constructed in which the fuel burns; but in grates of better construction, the recess 
is not very deep, and less contracted where it issues in the chimney, while frequently 
the hearth is fitted with a sliding door, and a valve or trap-door in the upper part of 
the flue leading into the chimney. 

In order to utilise a portion of the conducted heat, yet still to leave the heating to 
be effected chiefly by radiation, the flow of hot air into the chimney is to some extent 
intercepted, so as to form a combination of the methods of stove- and chimney¬ 
heating. 

stove Heating. This method of heating is in general use in the colder parts of the 
Continent, in America, Canada, &c. A well constructed stove should not consume 
too much fuel, the combustion of which should be complete, while the heat generated 
should be uniformly radiated, and only a very small quantity allowed to escape into 
the chimney. As a stove is placed at some distance from the chimney, the radiating 
as well as the conducted heat is utilised. The loss of heat is prevented by a series 
of flues; but in order to keep up a sufficient draught, the air escaping into the 
chimney should have a temperature of at least 75 0 . The fuel is generally intro¬ 
duced into the stove from the room, although some kinds of stoves are so constructed 
that they may be fed with fuel from the outside of the house similarly to the hot¬ 
house stoves ; this method of construction entails a larger consumption of fuel and 
some loss of heat. 

Stoves are made of cast-iron, sheet-iron, and fire-clay. Iron readily absorbs heat, 
and as the sides of the stove are usually not very thick, the heat is rapidly and 
readily dispersed. As iron stoves may become red-hot, the air surrounding the 
stove is chemically changed in consequence of the permeability of red-hot iron to 
carbonic oxide. This gas, according to the experiments of Deville and Troost, 1868, 
is absorbed and evolved by red-hot iron to 0*0007 to 0*0013 its volume. Fire¬ 
clay stoves yield a very uniform heat, given off only slowly and gradually. 


734 


CHEMICAL TECHNOLOGY. 


Compound stoves are those in which the hearth is made of cast-iron, on which is 
placed a sheet-iron column closed at the top, and provided with a lateral opening 
communicating by sheet-iron pipe with the chimney. 

We distinguish according to the material of which stoves are constructed:— 

a. Those simply of iron. 

b. Those of fire-clay. 

c. Compound stoves. 

Iron stoves are usually so constructed that the heat generated by the combustion 
of the fuel is rapidly communicated to the air of the room. The heat generated in 
fire-clay stoves is communicated to the great mass of fire-clay of which the 
stoves are constructed, so that even long after the fire has been extinguished 
the stove continues to give off heat; these stoves are especially used in Sweden 
and Russia. 

iron stoves. The construction of these stoves varies greatly. When made of cast- 
iron the shape is frequently cylindrical, a short pipe being cast on, to which is fitted 
a sheet-iron pipe leading to the chimney. In some cases the length of this pipe is 
considerable, in order that the heat evolved by the combustion of the fuel may be 
better utilised. 

Sometimes iron stoves are constructed with an outer mantle which is perforated 
and usually exhibits an ornamental appearance; this mantle is placed at some few inches 
distance from the inner stove, in which the combustion of the fuel takes place. 

Fire-clay stoves. These stoves, made of a peculiar kind of cla} r , are externally glazed 
similarly to the so-called Dutch tiles. The construction of these stoves is very massive. 
They consist of a series of channels made of burnt clay and put together with a 
mixture of the same clay unburnt and gypsum. The thickness of the pipes forming the 
channels is 7 inches. The number of channels or flues is four to six, or even twelve. 
The Russian stove, Fig. 321 in ground plan, is fitted with six flues. Fig. 322 is a front, 

Fig. 323 a side view, and Fig. 324 a vertical section. 
a is the vaulted fire-place, the flame and smoke 
evolved by the combustion of the fuel being carried 
upwards in flue 1, downwards in flue 2, again up¬ 
wards in flue 3, again downwards in flue 4, again 
upwards in flue 5, and again downwards in flue 6, 
and thence into the chimney by means of an iron 
pipe fitted to the stove. 

Each of these stoves has a separate chimney, a 
tube 18 to 30 centimetres wide, carried straight up to 
above the roof of the house. These narrow 
chimneys, also in use in Edinburgh, Glasgow, and 
other Scotch towns, are constructed of fire-clay 
tubes fitted into the stone of the walls. As a Russian 
stove is really intended to he a store of heat, it has to be hermetically closed as soon as 
the fire is extinguished; this is effected by the following contrivance, termed in the Russian 
language, Wiuschke. Near the junction of the last flue and the stove-pipe a plate of cast- 
iron, Figs. 325, 326, and §27, is fitted to the stove, the plate being provided in the centre 
with an opening of 21 to 24 centimetres diameter. This opening has an internal vertical 
flange or collar of 2 centimetres, and an external vertical flange of 3 centimetres height. 
An iron cover, a, Fig. 327, fits closely on to the inner flange, and a larger cover, b , fits on 
to the outer flange, thus securing a tight joint. These ovens are heated with wood, 
which is sawn into small blocks. No smoke is evolved, because the high temperature pre¬ 
vailing in the flues consumes the smoke completely, and the wood is not used until it is 
thoroughly dry. The Swedish stove is usually cylindrical in shape, and very tall, reaching 
nearly to the ceiling of the rooms. The flues (four in number) of these stoves are o.’ 
rather complicated construction. They communicate laterally with each other. The 
chimney pipe is placed at the top and is provided with a damper, closed when the fire is 
extinguished. The fuel, dry wood, required for one heating of the stove, is put into the 
stove at one charge, and when the combustion has ceased, the damper and the stove door 
are tightly closed. 


Fig. 321. 






















WARMING. 


735 


Compound stoves. Feilner !:as constructed a stove of this description, Figs. 328 to 331, 
which is a modification of the Bussian stove. Fig. 328 shows a front view, and Figs. 329 


Fig. 322. 


Fig. 323. 



Fig. 324. 



and 330 vertical sections. The section exhibited in Fig. 329 is through the ground plan, 
Fig. 331, as indicated by the dotted line a a. The section shown in Fig. 330 is according to the 


Fig. 325. 



Fig. 326. 

i_ 


Fig. 327. 



dotted line bb and the section exhibited in Fig. 331 to the line cc. The hearth of this 
stove is constructed of iron surrounded by a burnt clay mantle or box. The products of 


Fig. 328. 



Fig. 329. 



Fig. 330. 
















































































































































































































































736 


CHEMICAL TECHNOLOGY. 


Fig. 331. 



the combustion are forced through a cylindrical tube, of 12 to 18 centims. width, and 
thence issue inln the flues. The combustion is very complete, no soot or smoke being formed. 

This stove is divided into two compartments by means of a 
vertical wall; and horizontal shelves are fitted to this wall, 
thus forming a series of channels or flues, through which 
the products of combustion are made to pass. The length 
of these flues varies, according to the size of the stove, from 
g to 20 metres. As the hearth is so placed as to he a sepa¬ 
rate part of the stove, the room becomes heated as soon as the 
fire is lighted. In the lower part of the stove a kind of air¬ 
heating is arranged, because by two openings, a a, Fig. 328, 
cold air enters and becomes strongly heated while passing 
through the stove. When the combustion of the fuel has ceased 
the damper in the pipe leading to the chimney is closed; the clay portion of the stove having 
then been so strongly heated that one firing answers for a whole day. bbb is the brick¬ 
work foot of the stove; cc are supports for carrying the cast-iron bed-plate, cl d, of the 
iron hearth; e are the side plates ; ff the top plate of the fire-room; g is a tube fitted to 
the top plate, and intended for carrying off the gases and other products of the combus¬ 
tion of the fuel. On the top plate are placed fire-bricks supporting hli, which is made of 
boiler-plate, and provided with a circular hole so situated as to be free from the tube g. 
On this boiler-plate are roofing tiles, which reach to the side walls of the stove, and are 
covered with sand or dry ash. This construction is necessary for the purpose of pre¬ 
venting the iron hearth in its expansion forcing asunder the brickwork. 

The vertical partition wall, i, is built of brick ; it supports k. I l are also built of 
brick, n n are so short that each of the openings is 7 inches distant from the opposite 
side. The smoke is carried upwards through the openings 00. p p is the iron pipe, 
which communicates with the chimney. The heat and gases generated by the combustion 
of fuel in this stove proceed from the hearth, e, through g, are returned by k, flow along i , 
pass through the opening 0 into the flue n, and finally into the pipe, which communicates 
with the open air. 

Henschel’s stove, constructed to burn brown-coal, deserves notice. Fig. 332 exhibits a 
vertical section, and Fig. 333 a horizontal section at the line a b. This stove consists of 


Fig. 332. 



Fig- 333 - 



two iron cylinders, the outer, a , being of cast-iron, the inner, b, of stout sheet-iron 
The outer cylinder is supported by the ash-pit, c d, fitted with fire-bars towards the upper 
end. The inner iron cylinder does not reach to the fire-bars, and is closed at the top by 


























































WARMING. 


737 


a tightly-fitting cover, g, while the outer cylinder is closed by the lid h. When it is 
intended to heat this stove it is first filled with brown-coal, thrown in from the top after 
removal of the lids. The fuel is kindled at i, through k. The combustion can only take 
place on the fire-bars, the hot air flowing upwards between the two cylinders, and thence 
into l, the iron pipe leading to the chimney. The fuel contained in the inner cylinder 
gradually sinks downwards as the combustion proceeds. The ash is removed by imparting 
motion to the crossed iron bars, m, Fig. 333, to which are fitted pieces of iron passing 
between the fire-bars. The handle, n, projects outside the stove. Any smoke which 
might reach the upper part of the stove is carried off by the pipe o. This kind of stove 
having once been filled with fuel continues to supply heat for forty-eight hours. 
Meidinger, of Carlsruhe, has constructed many very excellent stoves of this description. 

Air Heatmg. This method of heating is effected by means of stoves, but is dis¬ 
tinguished from the ordinary stove-heating by the situation of the stove, which is 
in most cases not placed within the space or room to be heated, being within a 
chamber from which the heated air is conveyed by channels to the space intended 
to he warmed. The aim of air heating or central heating is to heat a large space 
uniformly with one stove, pr to heat by means of one fireplace all the rooms and 
apartments in the same building, when it is not found convenient to construct fire¬ 
places in each apartment. There are in use three modes of air heating, which 
differ from each other in the method of ventilating the space to be heated. 

(a.) The cold air enters the heating apparatus, becomes warm, and is conveyed through a 
pipe or channel into the room or space to be heated, while an equal bulk of vitiated air 
escapes from the imperfectly-closed windows and doors. 

(&.) The heated air is returned to the heating apparatus, becomes again warmed, and 
re-enters the room. While the method (a) has the advantage of constantly supplying 
fresh air to the room, thus creating an uninterrupted ventilation, the method (6) has the 
advantage of saving that quantity of heat which is lost in the efflux of warm air in the 
first method. 

(c.) The outer air becomes heated at the fireplace, and is then conveyed to the room to 
be warmed. The vitiated air from the room is conveyed through a flue to the fire, this 
air serving the purpose of maintaining the combustion. This method combines all the 
advantages of (a) and (&), while, with constant ventilation, a saving of fuel is effected. 

As regards the methods of employing air heating, we distinguish according to the 
construction of the apparatus:— 

- (a.) Air heating by means of a mantle oven. 

(&.) Air heating by means of a heating chamber. 

The first method is very similar to ordinary stove-heating, and only distinguished 
from it in the respect that the stove is surrounded by an outer mantle of bricks 
or fire-clay slabs, some 6 to 8 inches from the stove. This mantle is provided with 
openings, through which the heated air escapes, and is uniformly distributed through 
the room. 

In warming with a separate chamber we have to consider the form of the chamber, 
a small vaulted room, built of brickwork, and containing the furnace. The heating 
chamber should be comparatively very small, so that the heated air shall be carried 
as rapidly as possible to the room intended to be warmed. The channels for 
carrying off the heated air are placed at the top of the heating chamber, while the 
channels for conveying the cold air are situated at the bottom. The space between 
the furnace and the walls of the heating chamber measures from 12 to 16 centims., 
but the vault is elevated 1 to 1*3 metres above the top of the furnace. 

The furnace or stove is the most essential part of this air-heating apparatus. It 
is made either of cast-iron or of boiler plate ; and as regards size 1 square foot of 
heating surface is capable of heating 800 to 1000 cubic feet of air. Another kind 
of air-heating apparatus consists of the following arrangement:—A series of rows 
48 


CHEMICAL TECHNOLOGY. 


73 $ 

of cast-iron tubes, which communicate, are so placed in a furnace or oven that cold 
air enters into the lowest row of the series, while the heated air escapes from 
the upper row. Since the hot air having become specifically lighter always tends 
to rise, it is clear that the apparatus should be placed in the cellar or lowest room 
of the building to be heated. The hot-air pipes should be as vertical as possible. 

The apertures through which the hot air gains admission to the rooms to be 
heated are best situate in the floor, in this case generally a double one; or the hot¬ 
air pipes are placed in channels covered with an iron grating, and sometimes 
provided with a damper so that the supply can be regulated. 

Heating with hot air is usually attended with a serious defect, viz., that the air 
is exceedingly dry or even burnt. This defect can be remedied only by supplying 
air with aqueous vapour by placing in the current of hot air shallow basins filled 
with water, or by suspending wet sponges near the pipes. Dr. von Pettenkofer has, 
however, proved that these expedients do not quite answer the purpose. Air heating 
is not very suitable for dwelling-houses, but answers best for public buildings, which, 
as churches, theatres, and concert rooms, require to be only occasionally heated, the 
defect of the too great dryness of the air being in these instances counterbalanced 
by the watery vapour exhaled in the process of respiration by the persons assembled, 
and by the gas lights. 

Caioriferes. A system of air-heating by means of so-called caloriferes has become 
rather general in the United Kingdom, North America, Sweden, Russia, Holland, 
Belgium, and also to some extent in Germany. It is usually employed in large 
buildings, but is also applicable to. dwelling houses. Among the best of this kind of 
heating apparatus are those supplied by the London Warming and Ventilating Com 
pany, who employ the modification of a plan successfully introduced by Sir Golds¬ 
worthy Gurney in both houses of Parliament. Steam, hot water, gas, and coal or 
coke, in open or enclosed fire-places, are equally available for the process, while 
the cost is less and the effect greater than with any other known means. The 
apparatus are successfully in use in St. Paul’s Cathedral, York Minster, eighteen other 
cathedrals, 1000 churches in England, and a large number of government, public, 
and private buildings, and mansions. Abroad, Hartmann at Augsburg, Boyer and 
Co. at Ludwigshafen, Bacon and Perkins at Hamburg, have invented more or less 
excellent caloriferes. Those by Reinhardt and Sammet, at Mannheim, appear to be 
of very great efficacy ; they are so contrived that the fuel is thoroughly burnt, not 
even any soot or smoke being left, while the air is rendered agreeably moist by the 
gentle dripping of water on the hot-air gulls. The temperature of the air can 
be kept uniform for days and weeks consecutively. As this apparatus if used in a 
dwelling-house is placed in the cellar and the whole house heated, there is no dust 
nor other inconvenience attending the ordinary fire-places. This apparatus con¬ 
sumes only a small quantity of fuel, and requires as an attendant an ordinary 
labourer. In fche air-heating apparatus invented by Boyer and Co., Ludwigshafen, 
now in use in many large buildings in Munich, Wurzburg, and other Bavarian 
towns, the heating pipes are not made of wrought-iron but of charcoal cast-iron, 
while the dimensions and shape are so arranged as to expose the pipes as little as 
possible to injury from the fire, and yet to afford a large heating surface. For every 
kilo, of coals hourly burnt, 2-5 square metres of heating surface are present. In order 
thoroughly to utilise the heat of the products of combustion, these products are 
caused to pass through a series of pipes, some of which are coated with a smooth 


WARMING. 


739 


layer of mortar, for the purpose of preventing loss of heat by radiation. The heat 
of the products of combustion escaping into the chimney is below ioo°; and these 
products consist only of watery vapour and carbonic acid. In order to render the 
hot air supplied by this apparatus pleasantly moist, water is evaporated with 
the heated air at the rate of 1*5 to 2 litres per 100 cubic metres heating surface. 

Flue Heating. This mode of heating, now confined to hothouses for plants, and even 
there superseded by better methods, consists chiefly in carrying the products of 
combustion of a stove or furnace through a series of pipes which are placed within 
the room to be heated, and are at the opposite end to the furnace connected with a 
chimney. If this plan is adopted for heating dwelling-houses, the furnace is placed 
in the cellar; but experience has shown that this method of heating, except in the 
case of hothouses, is too crude, and, moreover, dangerous, as by overheating of 
the flues fire may ensue. 

Hot-water Heating. Instead of heating air directly, it is often heated intermediately by 
water, which, owing to its high specific heat, is eminently adapted to this purpose. 
This kind of heating is known as hot-water heating. 1 kilo, of water at ioo° emits, 
while cooling to 20°, 80 units of heat, capable of heating 32 kilos., or 24/61 cubic 
metres of air to io°. The system of liot-water heating is based upon the placing of 
a vessel filled with hot water in the space to be heated, care being taken to keep up 
the temperature of the water. In the ordinary hot-water apparatus, the fluid is 
never heated higher than its boiling-point, and is usually kept many degrees below 
that temperature ; hence this method is termed low-pressure water heating. 

This low-pressure or ordinary liot-water heating is maintained— 

a. By circulation through a closed boiler which i^heated. 

b. By circulation and syphon action between an open and a heated vessel. 

a. In this method there is fitted to a boiler, quite closed, a series of pipes, through 
which the hot water is conveyed from and the cooled water returned to the boiler. 
The principle of the circulation of the water may be elucidated by Fig. 334. The 
water is - heated in a, c is the ascending tube, tlf are the 
tubes through which the water is returned to the boiler. 

The tube e serves for the purpose of filling the apparatus 
with fresh water, as well as for the escape of any air or 
steam which might be evolved. The hot water ascending 
in c causes a circulation in the apparatus, which when once 
commenced is maintained as long as the heating is con¬ 
tinued. From time to time it is necessary to unscrew the 
cap at e, for the purpose of adding a small quantity of water. 

Usually e is provided with a stop-cock, which admits of the 
introduction of a funnel. For 100 cubic feet of space to be 
heated, 20 to 30 square feet of heating surface are required. 

The heat of the warm-water apparatus is imparted to the 
rooms through stoves, usually made of sheet-iron. These stoves are cylindrical 
in shape, 2 to 3 metres high, by 0*3 to 07 metre diameter, and fitted with a 
series of pipes in which the air becomes heated by a larger hot-water tube. 

b. The other method of hot-water heating by means of an open boiler with 
syphon action, or the so-called thermo-syphon of Fowler, as compared with the first 
method, has the disadvantage that from an open boiler a considerable loss of heat is 
unavoidable, while it is difficult also to prevent accumulation of air on the upper 


Fig. 334. 





















740 


CHEMICAL TECHNOLOGY 


part of the syphon tube. The height to which the tubing can be carried is in this 
system, too, limited to the height equivalent to the atmospheric pressure, about 30 feet 
for a column of water. 

Perkins’s so-called high-pressure hot water system, wherein the temperature 
of the water in immediate contact with the fire is raised to 150°, 200°, and even 500°, 
consists of a closed tube filled with water. One-sixth of the length of this tube is 
coiled and placed in a furnace ; the other five-sixths are heated by the circulation of 
the hot water. The tubes are of malleable iron, capable of resisting a pressure 
of 3000 lbs. per square inch. More recently the hot water from native hot springs, 
or obtained from bored artesian wells, has been, as for instance at Baden-Baden, 
employed for the purpose of heating. At Baden-Baden the hot water (67°) from a 
native spring is used to heat a church. 

Heating with steam. This method of heating is based upon the latent heat contained in 
steam. 1 kilo, of steam at ioo° contains so much latent heat that by it 5‘5 kilos, of 
water can be heated from o° to ioo°. 

A steam-heating apparatus consists of a boiler, steam-pipes, and pipes, which re- 
convey the condensed water to the boiler. The boiler may be constructed in the 
usual manner. The steam pipes are of cast-iron and placed vertically, or if hori¬ 
zontally, with a gentle slope towards the boiler. If several stories of a building 
have to be heated, a main steam-pipe is carried to the highest story, and branch 
pipes are fitted to it. The pipes are here and there fitted with air valves for the pur¬ 
pose of permitting the expulsion of the air compressed by the steam. The boiler, if 
low-pressure steam be used, should also be provided with an air valve, in order to 
prevent the collapse of the boMer by the outer atmospheric pressure if the generation 
of steam ceases. Heating by means of steam is advantageously applicable in works 
where steam is used as a motive power. 

Combination of steam and Very recently it has been proposed to combine steam- with hot- 

Hot-water Heating. water-heating, and to heat from one central locality a series of 
buildings and houses, in the same manner as these are now supplied from one central 
reservoir with gas or water. 

Gas-Heating. It is well known that illuminating gas is now very generally used for 
the purpose of heating, being in this application best mixed with air, as is the case, 
for instance, in the Bunsen burner. 

Gas is used for cooking in stoves specially constructed for the purpose, and also for 
heating apartments and buildings. As a rule it may be assumed that the combus¬ 
tion of 5 cubic feet of gas is sufficient to elevate the temperature of 1000 cubic feet 
of air 12 0 , and one-fifth of this quantity of gas suffices by its combustion to keep the 
temperature constant. 

Heating without There is no doubt that an inexhaustible supply of heat exists as latent 

ordinary Fuel, heat, which can be set free by friction, or, in other words, by the conversion 
of mechanical force into heat. 

Notwithstanding many mechanicians have constructed apparatus for producing heat by 
mechanical force, none of these have been found practically available, and some were found 
to be extremely wasteful. The heat generated by the fermentation of manure is usefully 
applied to heating hothouses, by placing under the manure heap thin sheet-iron pipes, 
which convey the heat into the hothouse. 

/ 3 . Boiler Heating and Consumption of Smoke. 

noiier Heating. Steam-boilers are as a rule built in brick-work, and in their con¬ 
struction, as well as that of the furnace they are fitted with, economy of fuel is the 
great object. The furnace is of course built with fire-bars and ash-pit. The grate 


WARMING. 


74* 

or fire-bars consist of parallel cast-iron bars, the size and shape of which depend 
upon the kind of fuel to be used, while as regards the space between the bars expe¬ 
rience has taught that the sum should not amount to more than one-fourth of the 
total surface of the grate. A large grate has the advantage of more freely admitting 
air to the fuel, while obstruction by clinker and slag is less to be feared. The 
operation of firing with a large grate is more easily conducted, and can take place at 
longer intervals of time. Of course the grate must be kept entirely covered with 
fuel. Small grates may be preferable in some instances, especially where a vivid 
combustion is required. Grates for wood fuel may have half the surface required for 
coal, as with the former the openings between the bars do not become choked with 
clinker and slag. According to E. Kochlin a grate for burning in one hour 350 kilos, 
of old oak wood should be of 1 square metre surface with \ square metre for space 
between the bars. Usually, however, the grates for wood fuel are made four times 
smaller than those for coal. 

The fire-place or furnace should of course be constructed of sufficient height, 
width, and depth to admit of the proper combustion of the fuel. The fuel should be 
thrown into the furnace in sufficiently large quantity at once to keep up the steam 
adequately. Too frequent firing is not economical, because a large quantity of cold 
air is admitted, which cools the boiler and interferes with the proper combustion of 
the fuel. The dimensions of the furnace doors must bear a proper proportion to the 
size of the furnace, and these doors must close tightly so as to prevent draughts of 
air impinging on the burning fuel. 

Sm °Apparatus ning While we cannot here enter into any further details on boiler- 
furnaces, a subject really belonging to engineering, we may now turn our attention 
to smoke-consuming furnaces, contrived with the view not only of abating the 
nuisance arising from the smoke evolved in huge volumes from large factory and 
other chimneys, but also for the saving of fuel, it having been ascertained that by 
the ordinary combustion of 1 ton of coals 25 lbs. of soot are evolved, having a 
heating power of four-fifths of the coal. The loss occasioned by the carbon thus 
carried off amounts to T x 2 th, or not quite 1 per cent. 

When green coals are put in quantity on a bright boiler furnace, there is suddenly 
evolved an immense volume of combustible gases and vapours containing a large 
amount of carbon (benzol, toluol, carbolic acid, anthracen, naphthalin, paraffin, &c., 
the oxygen of the air contained in and supplied to the furnace being usually insuffi¬ 
cient to cause the complete combustion of these substances, so that only the hydrogen 
burns, while the carbon is separated as smoke and soot, the evolution being promoted 
by the comparatively cool state of the boiler-plates, as well as by the large influx of 
cold air at the time of firing. The contrivances for preventing and consuming 
smoke are based upon different principles; for instance:— a. Air is sometimes 
conveyed to the fire-bridge by means of a separate pipe or channel, b. Two 
adjoining furnaces are connected and alternately fired in such a manner that the 
smoke of the furnace last fired is consumed in the high red heat of the other furnace. 
c. The fresh fuel is spread over only the front of the fire nearest the furnace-door, so 
that the evolved gases may be consumed b/the red-hot fire on the bars. cl. The 
feeding is effected by mechanical means, uninterruptedly, in such a manner that the 
fuel on the bars remains in a high state of incandescence, e. The construction of 
very high chimneys has been resorted to for the purpose of supplying a rapid current 
of air; but this expedient, a very expensive one, does not answer the purpose, and 
leads to loss cf heat. 


742 


CHEMICAL TECHNOLOGY. 


We may mention briefly the following smoke-preventing and consuming appa¬ 
ratus :— 

i. Mechanical removal of the smoke by washing the products of combustion. In 
some chemicarworks near Newcastle-upon-Tyne the smoke of the different furnaces 
is washed by a spray of water previous to being passed into the chimney. For this 
purpose the smoke of the different furnaces of the work is conducted into subter¬ 
ranean brick-work channels, so constructed with knee-bends that the smoke is caused 
to flow upwards and downwards alternately, while at the mouth of the furnace-flue a 
continuous spray of water is caused to impinge upon the smoke, whereby all solid 
particles are thrown down and are removed from the channels as soot. There is in this 
case only one chimney, in which the draught is kept up by means either of a blast of 
air or a jet of injected steam. Jean, at Paris, has somewhat modified this method by 
causing the smoke and waste steam of a high-pressure engine to be conveyed into a 
subterranean channel covered with a layer of water several centimetres in depth, 
while a jet of cold water is made to play upon the smoke and steam. The channel 


Pig. 335- 



is provided with a land of waiter-wheel, which does not quite touch the surface of the 
water, but is fitted with brushes, which, touching the water, project it as spray 
through the channel. The water becomes heated, and serves after filtration as feed 
water. 

2. Application of improved fire-bars, to be distinguished as (a) immovable, and 
(b) movable. 

step orate. Among the immovable grates are the step- and stage-grates. The 
former consists of a series of step-like stages of fire-bars, to which the poker has 
access from the ash-pit. By the heat of the fire on the lower steps the fuel on the 
higher step is converted into coke, and only afte* this process has continued for some 
time is the partly-coked fuel raked down to a lower step, while fresh green coal is 
placed on the higher. The air enters this kind of grate not only through the space 
between the bars, but also lateral^ tlfrough the grated space between the steps. 
Caking-coal, or coal which makes much slag, does not answer as fuel in this grate, 
but small coal, refuse peat, sawdust, &c., are well adapted. Instead of iron fire-bars 
MM. Longridge and Mash make use of slabs of fire-clay, provided with channels 
and perforations so as to constitute a grating. 




















WARMING. 


743 


Etage or stage Grate. This is a modification of the grate just described, and was invented 
by Langen (1866). The green fuel is not placed above the burning fuel, but under 
it, for which purpose the grate is constructed in stages, the fire-bars being inclined 
to the horizon at an angle of about 28°. There is between each etage , or stage, of 
the grate a space of about 12 centims. The fuel becomes coked, and the volatile 
products pass, mixed with air, through several stages of incandescent fuel, thus 
insuring complete combustion. 

Movable Grates. The leading idea of these grates is to effect the firing by mechanical 
means. Among these the chain grate and rotating grate deserve notice. 

chain Grate. Notwithstanding the expensive nature of this invention, it has been 
found useful in practice and is employed in many establishments. It consists 


Fig. 336. 



(Fig. 335) of two endless flat chains, gg, which run on two octo-geared rollers. 
Between these chains the fire-bars are placed longitudinally, so that the grate 
consists of an endless series of bars. The distance of the two rollers from each 
other determines the length of the grate. A rotating motion is imparted at 0 in such 
a manner that the grate moves through 27 to 30 millimetres per minute. The fresh 
fuel is thrown in at b, and is carried continuously towards the fire. The height of 
the layer of fuel is regulated by means of the slide-damper, d, which can be moved 
by means of the lever, p. The chains and rollers are supported by the truck, 1, 
running on the iron rails, h h. The velocity of the grate is so regulated that the 
fuel is entirely consumed when arriving at the end of the fire-place. There are 
several serious defects in this apparatus. It is complicated, soon out of repair, 
requires a considerable amount of force to maintain its motion, and it does not 
altogether prevent smoke, while, finally, it is found wasteful for fuel. 













































































744 


CHEMICAL TECHNOLOGY. 


Rotating Grate. This contrivance, invented by Collier, consists of a rotating disc 
which supplies the coal to the furnace uniformly through a slit cut below the furnace 
doors. This apparatus has never been extensively in use. 

improved Fuel supply. 3. Among the numerous suggestions for the better feeding of lur- 

naces are the following:— 

Collier’s feeder (1823) consists essentially of two horizontal crushing rollers 
provided with projections, so that the coal is broken up into uniform lumps, and 
then thrown into the fire by wheels provided with scoops revolving 200 times a 
minute. This mechanism requires a half nominal horse-power to maintain its motion. 

Stanley’s feeder, Fig. 336, consists of a funnel, a, fitted with toothed crushing 
rollers. The crushed coals fall on the distributor, b , which rotating with great 
velocity throws the coals uniformly 011 to the fire. Notwithstanding the defects of 
this invention, the chief being that it is not possible for the stoker to fire hard if 
required, this apparatus certainly prevents smoke, but is also liable to be quickly 
out of repair. 

puit Fires. Puit fires were first introduced by Wedgwood for porcelain furnaces. 
The characteristic feature is the mode of admitting air, which instead of entering as 
ustial from below is forced downwards. The grate is placed in a sloping position. 
The fire-doors remain open, while the ash-pit is quite closed. This arrangement 
fulfils certainly all the conditions of complete combustion, but in practice has not 
answered and is only applicable with wood fuel. 

Vogi’s Grate. The fire-bars in this grate are placed at an angle of 33 0 . The coals are 
supplied by means of a funnel, and the bars can be shaken up and down by mechanical 
means. 

Boquiiion’s Grate. An arrangement of rather complicated nature intended to be applied to 
house stoves, and so constructed that the green fuel is brought under the glowing fuel. 
The grate consists of a horizontal movable cylinder, upon which the fuel rests. When 
fresh fuel is added, this cylinder is turned so as to cause the fuel to be placed below the red- 

Apparatus of Cutler hot cinders. In practice this grate has not answered, being too compli- 
and George. cated. In many cases it has been attempted to feed the fires in an ascending 
mode, as, for instance, in Cutler’s grate, improved upon by Arnott in 1854. The coals 
are burnt from an iron vessel which is by mechanical means lifted over the fire, the supply 
of coals in the vessel being regulated to last for twenty-four hours. In George’s apparatus 
the fuel is supplied to the grate by means of a screw propeller. 

Apparatus with unequal 4 - Among the apparatus in which smoke is prevented by an 
Distribution. unequal distribution of fuel on the grate, that of Dumery, deserves 
notice. This arrangement is distinguished from those of Cutler and George by the fresh 
fuel being put on from both sides of the grate under the red-hot cinders. For this 
purpose the grate is strongly curved upwards, exhibiting a saddle shape. The fuel 
is forced on to the grate by mechanical means in such a manner that it is first placed on 
the lowest fire-bars, and gradually forced towards the centre. This principle was known 
to Watt in 1785, and was applied by him in a slanting grate. 

Tenbrinck also places the grate in a sloping direction, so that the coals tumble towards 
the fire-bridge, and accumulating there as incandescent coke cause the complete combus¬ 
tion of the fuel. In Corbin’s grate a partition of fire-brick is employed. Fairbairn (1837) 
appears to have been the first to contrive smokeless grates. In his double grate the fur¬ 
nace is provided with two hearths, two grates, and two furnace doors. The grates 
are separated from each other by a partition of fire-bricks. The stoking is so regulated 
that while the one furnace is in full combustion, the other is supplied with fresh fuel, this 
operation occurring at regular intervals and alternately. The result is that the smoke 
and gases evolved are burnt by the highly incandescent fuel of the other furnace. De 
Buzonniere contrives to force the smoke of one furnace under the incandescent fuel 
of the other. With a properly regulated supply of air and regularity of stoking, it has 
been proved, by a series of experiments made on the large scale with a 40 horse-power 
marine multi-tubular boiler, by the late Dr. Richardson, of Newcastle-on-Tyne, and by Messrs. 
Longridge and Sir William Armstrong, that with all kinds of coal and with every variety 


WARMING. 


745 


of steam boiler, smokeless and complete combustion of the fuel may be obtained without 
difficulty, the plan being attended with a considerable saving of fuel and production of its 
highest calorific effect. 

oyl^ndofCollateral 5 * Nearly all attempts in this direction have proved an utter 
Air Currents. ‘ failure in practice. Parkes’s (1820) split bridge was constructed with 
the view of causing the air to flow partly as usual under the grate, partly to act at the 
end of the furnace so as to effect a complete combustion. Palazot’s invention, highly 
commended by Burnat, Tresca, and others, appears to be somewhat similar. Chanter’s 
arrangement consists essentially of two grates placed parallel to each other. The green 
fuel is put upon one of these, and having been coked by the incandescence of the fuel on 
the other grate is raked on to that, thus insuring complete combustion increased by 
lateral jets of air. 

GaU’s Fire-place. Gall, reversing the rule that the dimensions of a factory chimney should 
bear a proportionate relation to the quantity of fuel to be burnt, has constructed 
chimneys, the highest point of which above the buildings is only o - 6 metre, and which, 
therefore, simply serve to carry off the products of combustion. As the difference of 
temperature is the cause of the draught of a furnace, Gall maintains a very high tem¬ 
perature in the combustion room; and in order to carry this out all the causes of loss of 
heat are reduced to a minimum in the following manner:— a. While in the ordinary mode 
of stoking the heat of the combustion room is necessarily lowered by the influx of cold 
air, the grating in Gall’s arrangement is partitioned in such a manner that each compart¬ 
ment is gradually supplied with fresh fuel, by which arrangement the formation of smoke 
is prevented, b. The furnace is constructed so that the stoker cannot possibly put on too 
heavy a charge of green coals, while he is compelled to spread these uniformly over the 
fire. c. The loss of heat by radiation from the brick-work, fire-doors, &c., is prevented 
by causing the air required for the combustion of the fuel to pass these hot surfaces. 
d. Gall retards the velocity of the gases which escape to the chimney, while the surface of 
the grate and the section of the chimney are enlarged. Indeed, the entire arrangement is 
quite different from that in ordinary use, as the fire-bars are placed 3 metres below the 
boiler, while the grate is very deep. It was found, however, that when well built there 
was a sufficient draught, and steam could be kept up. Nothing is stated as regards 
the nature of the gases issuing from the chimney. 

Resume. As regards smoke consuming and preventing apparatus, it is only too 
evident that most of these do not answer the purpose so completely as might 
be expected. Practical experience has, however, taught that if the conditions 
of complete combustion are well attended to in the construction of the furnace, that 
with proper management and regular mode of stoking, adequate supply of air, 
and the application of the well-known means of preventing loss of heat by radiation, 
with coal, peat, or any other fuel, the combustion may be so conducted as to 
be smokeless ; and at the same time the fuel thoroughly utilised. 





INDEX 


♦ 


A CETATE of alumina, 263 

-lead, 64 

Acetometry, 468 

Adamantine or diamond-boron, 256 

Adulteration of white-lead, 72 

Aerostatical lamps, 641 

Air drains, 475 

— gas, 674 

Alabaster glass, 290 

Albumen glue, 536 

Alkali for treating gold, 106 

Alcohol, 424 

— and its technically important pro¬ 
perties, 424 
— vinegar from, 461 
Alcoholometry, 447 
Alizarine, 5S4 
Alkalimetry, 224 

Alloys and preparations made and 
obtained from metals, 4 
— of copper, 51 

-gold, 109 

-lead, 62 

-nickel and copper, 41 

-silver, 103 

— platinum, 96 
Aloe hemp, 341 
Alpaca wool, 495 

Alum and sulphate of alumina, uses 
of, 263 

-earths, 257 

-roasting, 257 

— flour, 258 
— from Bauxite, 259 

-blast furnace slag, 260 

-felspar, 260 

— manufacture, material of, 256 
— preparation, 257 
— — from alum-stone, 257 
-clay, 258 

-alum-shale and alum earths, 

257 

-cryolite, 258 

— production, 256 
— properties of, 260 

—- shale, 257 

— works, preparation of green vitriol 
as a by-product in, 32 
Alumina acetate, 263 
— sulphate of, 261 
Aluminate of soda, 262 
Alnminates, 256 
Alnminum, applications of, 114 
— preparations, 113 
— properties of, 113 


Amalgamation, extraction of silver bv, 
97 

— process, American, 98 
-European, 97 

American amalgamaten process, 98 

Ammonia-alum, 260 

Ammonia and ammoniacal salts, 226 

— as a by-product of beetroot sugar 

manufacture, 236 

— carbonate, 238 

— from bones, 235 

-gas-water, 230 

-lant, 234 

— inorganic sources of, 228 

— nitrate, 238 

— preparation of liquid, 227 

— sulphate, 238 
Ammoniacal liquor, 666 

— salts, technically important, 236 
Amorphous phosphorus, 545 
Ananas hemp, 341 

Aniline, 573 

— black, 579 

— blue, 578 

— brown, 579 

— colours, 575 

— green, 578 

— orange, 579 

— printing, 614 

— red, 575 

— violet, 577 

— yellow, 579 
Annatto or arnotto, 595 
Annealing, 20 
Annular kilns, 317 
Anthracen pigments, 584 
Anthrachinon, 584 
Anthracite, 719 
Antichlor, 349 

Antimonial pieparations in technical 
use, 84 

Antimony, 82 

— black sulphuret of, 85 

— cinnabar, 85 

— oxide, 14 

— properties of, 84 

— sulphuret for refining gold, 106 
Apparatus for consuming smoke, 741 
Apparatus for distilling, 432 

-heating, 731 

Areometer, 447 

— to test milk, 558 
Arrow-root starch, 360 
Arsenic, 85 

— acid, 86 



INDEX. 


U 

Arsenic, red, or realgar, 87 

— sulpburets, 86 

— yellow sulphuret, 87 
Arsenious acid, 85 
Artificial illurainaii >n, G17 
Asphalte, 484 
Assay, dry, 103 

— hvdrostatical, 104 

— ot silver, 103 

— wet, 104 
Augsburg method of mash-boiling, 410 
Augustin’s method of silver ex¬ 
traction, 99 

Aurum musivum, mosaic gold, 75 

Aventurin glass, 291 

Azale, 587 

Azaleine, 575 

Azuline, 578, 581 

Azurine, 578 

B ALDAMUS and Grune’s gas, 
674 

Balling's saccharometrical beer test, 
420 

Bandanas, 616 
Bat iron, 20 

-properties of, 26 

Bark of oak, 509 • 

— or red tanning, 509 
Bauxite, preparation of alum from, 
259 

Beer brewing, 403 

-materials, 403 

— constituents of, 418 
— processes of brewing, 405 
— testing, 420 

— wort fermentation, 405, 414 
Beet, chemical constituents of, 368 
— molasses, 382 
— species of, 367 
— washing and cleansing, 371 
Beet-root juice, components of, 373 

-- evaporating, 380 

-filtration through animal char¬ 
coal and evaporation of, 374 
— separating the juice from, 371 
>— soda from, 171 
— sugar, 367 

-manufactory, ammonia as a by¬ 
product of, 236 
Bell-metal. 51 
Benzol, 570 
Berlin blue, 36 
-soluble, 37 

Berlin or Prussian blue on wool, 604 
Berthier’s reduction method, 700 
Berzelius's indigo test, 593 
Bessemer steel, 27 
Bicarbonate of soda, 190 
Bismuth, applications of, 77 
— occurrence and mode of obtaining, 
76 

Bismuth, properties of, 77 


Bisulphate of soda, 214 
Bitumen, paraffin from, 685 
Black-jack, mode of obtaining zinc 
from, 79 

Black platinum, 95 

— suphuret of antimony, 85 
Blast, blowing engine and, 12 
Blast-furnace, chemical process going 

on in the interior of, 13 

— description of, 11 

— gases, 15 

— process, 10 

— temperature of at different points, 

15 

Blasting powder, new kinds, 154 
Bleaching, 597 

— glass, 270 

Bleacbing-powder and hypochlorites, 
214 

— preparation, 214 

— properties of, 220 

— theory of the formation of, 220 
Blistered metal; refining, 49 
Blowing engine and blast, 12 
Blue vats, 602 

— vitriol, 54 

-applications of, 56 

Boghead coal, 722 
Bohemian crystal glass, 268 
Boiler heating, 740 
Boiler plate, rolling, 24 
Bois roux, roasted wood, 712 
Bombay hemp, 341 

Bone-ash decomposition by sulphuric 
acid, 538 

Bone-black preparation, 553 

— properties, 554 

— substitutes, 555 
Bones, ammonia from, 235 

— glue from, 532 
Boquillon’s grate, 744 
Boucherie’s method of mineralising 

wood, 477 

Boracic acid, formation, 250 

-production, 250 

-properties and uses, 251 

Borax, 252 

— from boracic acid, 252 

— octahedral, 255 

— purifying. 254 

— uses of, 255 

Boric or boracic acid and borax, 249 
Brandy distilling, relation of to agri¬ 
culture, 448 
Brazil or camwood, 588 
Brass, 52 

— tinning of, 75 
Bread baking, 451 

— composition of, 459 

— impurities and adulteration, 460 

— making, modes of, 451 

— oven, 454 
Bremen blue, 56 


INDEX. 


Ill 


Bremen green, 56 
Brewing by steam, 418 

— betr, 403 

— pic cess, by products of, 423 
Brick material. 311 

— moulding, 312 
Bricks, 310 

— and lime kilns for burning, 325 

— field burning of, 318 

— fire, 319 

— floating, 318 

— fiom dried clay, 314 

— the burning of, 315 
Brine, boiling down, 168 

— common salt from, 168 

— concentrating, 168 
Briquettes, 730 
Bromine preparation, 193 
Bronze, 51 

Brown coal, 691, 716 
Brunswick-green, 56 
Buckthorn dyers, 596 
Burners for woed gas, 670 
Burning of the bricks, 315 
Butter, 558 

— chemical nature of, 559 

C ADMIUM, 82 

Caking coal, 719 

Calcining or roasting the ores, 48 
Calcium-soap, 249 
Calico dyeing, 608 
— printing, 612 

-discharges, 611 

-resists or reserves, 610 

-thickenings, 610 

Caloriferes, 738 
Calorific effect, 698 
Campeacby, 594 
Camwood or Brazil, 588 
Candle making, 627 
Candles from fatty acids, 631 
— light from, 620 
— moulding, 628, 633 
— paraffin, 630 
— sperm, 634 
— stearine, 621 
— tallow, 629 
— wax, 631 
Cane-sugar, 364 
Caoutchouc, 484 

— and gutta-percha, mixture of, 488 

— production and consumption of, 486 

— solvents of, 485 

— vulcanised, 486 

Capsule, or sagger, 301 

Carbolic acid dyes, 580 

Carbon, 211 

— imparting to wrought-iron, for 
steel-making, 28 
— sulphide, 210 
Carbonate of ammonia, 238 
-potassa, 118, 121 


Carbonised peat, 715 
Cardboard, 354 
Carinthian cast-steel, 27 
Carmine-red, 589 
Carrara and Parian, 304 
Cartridges of needle-guns, mixture for 
igniting, 157 
Cassava starch, 360 
Casein as a cement, 562 

— — glne, 536 
Cashmere, 500 

— wool, 495 
Casselmann’s green, 57 
Cassius's purple, ill 
Cast-iron, 16 

— crude, re-melting, 18 

— enamelling, 20 

— grey, 16 

— white, 16 
Cast-steel, 29 
Caustic potassa, 133 

— soda, 189 

Cement, artificial, manufacture in 
Germany, 330 
Cements, 327 

— artificial, 328 

— lutes and putty, 491 
Cementation process, 107 
Centrifugal drier, 381 

— machine, 391 

Ceramic or earthenware manufacture, 
293 

Cereals, vinous mash fmm, 426 

Chair grate, 743 

Chamber acid, 206 

Charbon roux, torrified charcoal, 711 

Charcoal, animal. 553 

-Berlin blue as a by-product in 

manufacture of, 37 

— burning, 706 

— combustibility and heating effect, 

711 

— properties of, 710 

— revivification of, 555 

— sulphur obtained by the reaction of 

sulphurous acid on, 198 

— torrified, or charbon roux, 711 

— wood, 704 
Chatham light, 680 
Cheese, 559 

Chemical metallurgy, 4 
Chestnut starch, 360 
Chili-saltpetre, iodine from, 192 

— preparation of nitrate of potassa 

from, 138 

Chimney heating, 733 
Chinese galls, 511 
China gras?, 340 
Chlorate of potassa, 223 
Chloride of sulphur, 211 

-zinc, 81 

-potassium, 119 

Chlorine, 214 


IV 


INDEX. 


Chlorine, apparatus for preparing, 216 
Chlorine, condensing apparatus, 217 

— preparation without manganese, 

215 

— production residues, utilisation, 218 

— residues, other methods of utilising, 

219 

Chlorometry, 221 
Chlorometrical degrees, 222 
Chromate of lead, 64, 66 
-zinc, 81 

Chromates of potassa, applications of, 
65 

Chrome-alum, 67 

Chrome, oxide or chrome green, 67 

— red, 66 

— yellow, 66 
Cinchonine pigments, 585 
Cinnabar, 91 

Clay, kinds of, 294 

— pipes, 309 

— preparation of alum from, 258 
-for brick-making, 311 

— ware dense, 296 

-kinds of, 296 

-porous, 297 

Clays and their application, 293 

— colour of, 294 

— plasticity of, 294 

— technically important qualities of, 

293 

Clinkers, Dutch, 318 

Cloth, bough, washing and milling, 499 

— dressing, 499 

— fabrics, 500 

— teasling and shearing, 499 

— white, 606 

— weaving, 499 
Coal, 717 

— Boghead. 722 

— brown, 716 

— caking, 719 

— accessory constituents of, 718 
Coal-tar. 666 

— colours, 569 
Coal-gas, 646 

— Berlin blue as a by-product in 

manufacture of, 37 

— composition of, 668 

— manufacture of, 648 

— manufacture, by-products of, 665 
Coals, calorific effect, 721 

— classification of, 718 

— evaporative effect of, 721 

Cobalt and potassa, nitrate of prot¬ 
oxide of, 39 

— bronze, 39 

— colours, 37 

— green, 39 

— metallic, 37 

— protoxide, chemically pure, 39 

— speiss, 38 

— ultramarine, 38 


Caeruleum, 39 

Cochenille, or cochineal, 589 
Cocoa-nut fibre, 341 
Cocoon, killing of the pupa in, 503 
Coke, 665, 723 

— composition and value as fuel, 729 

— properties of, 729 
Coking in heaps, 724 

— in ovens, 724 
Collodion, 162 
Colorine, 588 
Coloured fires, 157 
Colours, aniline, 575 

— coal-tar, 569 

— topical, or surface, 613 
Colza oil, 637 
Common pottery, 310 
Coolers for water, 309 
Copper, 43 

— alloys, 51 

— amalgam, 54 

— and nickel alloys, 41 

— blistered or crude, 49 

— from oxidised ores. 49 

— hydrometallurgical method of pre¬ 

paring, 49 

— ores, treating of for extraction, 44 

— pigments, 56 

— preparations of, 54 

— properties of, 50 

— refining, 46 

— smelting. English mode, 47 

— solution for electro-plating, 116 

— stannate of oxide of, 58 

— sulphate, 54 

— tinning of, 75 

Coppen-plate engravings, reproduction, 

Copperas, 31 
Coralline, 581 

Cordwain, Cordovan leather, 521 
Cordials, preparation of, 482 
Cork pommels to raise the grain of 
leather, 519 
Cotton, 342 

— combing or carding, 342 

— detection in linen fabrics, 343 

— fabrics, 343 

— species, 342 

— spinning, 342 

— substitutes, 343 
Crucibles, 321 

— distillation of zinc in, 79 

Crude iron, statistics concerning the 
production of, 18 

Cryolite, decomposition of by ignition 
with carbonate of lime, 259 

with caustic lime by the 
wet way, 259 

— glass, 29*1 

— preparation of alum from, 258 

— t>oda from, 188 
Crystal-glass, 285 


INDEX. 


V 


Cupola, or shafc furnace, 18 
Cutch, 512 

Cyanide of potassium, 35 

D amascene, so 

Decoction method of preparing 
the wort, 409 

Decomposition furnace, new, 173 
Defuseling, 445 

De-liming, or saturating the juice with 
carbonic acid, 373 
— the juice, other methods, 374 
Deville and Debray's method of 
extracting platinum, 95 
Dextrine, 361 

Diamond boron, or adamantine, 256 
Dinas bricks, 321 
Discharge style, 614 
Discharges, calico printing, 611 
Distillation of the mash, 431 
Distillery apparatus, 432 

-continuous, 440 

Dividivi, 511 • 

Dorn'S apparatus, 433 

Drain tiles, 318 

Dumont s filter, 375 

Dunlop's process. 218 

Dutch clinkers, 318 

— tiles, 318 

Dye-materials, blue, 591 

— red, 586 

Dyeing and printing in general, 568 
— blue, and with logwood and a 
copper salt, 604 
— calico, 608 
— linen, 609 

— spun yarn and woven textile fab¬ 
rics, 599 
— silk, 606 
— wool blue, 601 

- red, 605 

— woollen fabrics, 601 
— yellow, 604 
Dyes, 568 
— black, 605 

— brown, green, and black, 596 
— carbolic acid, 580 
— green, 605 
— red, less important, 591 
— yellow, 595 
Dynamite, Nobel’s, 160 

E ffervescing wines, 399 
Elayl platino-chloride, 96 
Electric light. 680 
Electro-metallurgy, 114 
Electro-plating with gold and silver, 
115 

Eleciro-stereotyping, 117 
Electrolytic law, 114 
Electrotyping, 115 
Emerald green, 58 


Enamel, bone glass, 290 
E oamelling of cast-iron, 20 
Engraving steel, 31 
Etage or stage grate, 742 
Etching by galvanism, 117 
Etruscan vases, 309 
European amalgamation process, 97 
Explosive compounds, technology of, 
148 

F AGGOT gradation, 168 

Fatty acids, candles from, 631 

-manufacture, 627 

Fayence ware, 307 

-flowing colours, 309 

— ornamenting, 308 
Felspar, 293 

— mode of obtaining potassa from, 
122 

Fermentation, 386 
— after, in the casks, 416 
— alcoholic or vinous, conditions ol, 

389 

— of ttie grape juice, 393 

-potato mash, 429 

-beer wort, 414 

-- mash, 427 

— sedimentary, 415 
— surface, 417 
Ferments, substitutes for, 456 
Fibre vegetable, technology of, 338 
Filter for beet-root juice, 375 
Fire-bricks, 319 
Fire-clay stoves, 734 
Fire-gilding, 110 
Fireplace gulls, 745 
Fire, requisites for producing, 546 
Firework mixture 8 , commonly used, 156 
Fireworks, chemistry of, 148 
— chlorate of potassa mixture, 156 
— friction mixtures, 156 
— grey-coloured mixtures for, 156 
Flame, 618 
Flannel, 500 
Flax, 338 
— combing, 340 
— beating or batting, 339 
— hot-water cleansing, 339 
— spinning, 340 
Flaxes from New Zealand, 341 
Fleck’s process of preparing phospho¬ 
rus, 543 

Floating bricks 318 
Flowers of sulphur, 197 
Flue heating. 739 
Franklinite, 9 
Frieze, 500 

Fritte porcelain, French, 304 

-English, 304 

Fuchs’s beer test, 422 
Fuchsin, 575 
Fuel artificial, 729 
— and heating apparatus, 698 


vi 


INDEX. 


Fuel, brown coal as, 717 

— combustibility of, 698 

— determination of combustive power, 

699 

— elementary analysis, 700 

— inflammability of, 698 

— gaseous, 730 

— petroleum as, 722 

— pyrometrical calorific effect, 701 

— specific calorific effect, 701 

— supply improved, 744 

— Stromeyer's test. 701 

— value of coke as, 729 
Fulling soaps, 245 
Fulminating mercury, 92 
Furnace, cupola or shaft, 18 

— reverberatory, 18 

— working copper ores in, 44 
Fustic, yellow dye, 595 
Fusel oils, removing, 445 

G ALACTOSCOPE to test milk, 558 
Gall-nut, 511 
Gall’s apparatus, 435 
— fireplace, 745 
Galvanism, application of, 114 
— etching by, 117 
Galvanography, 117 
Galena, 59 
Garancine 587 
Garanceux, 587 

Gas, Baldamus and Grune's, 674 
— burners, 665 
— carburetted, 674 
— charging the retorts and distilla¬ 
tion, 650 

— cooling or condensing apparatus, 652 
— distribution of, 660 
— exhauster, 654 

— general introduction and historical 
notes, 645 
— beating, 740 
— Gillard's platinum, 672 
— for heating purposes, 731 

-illuminating testing, 661 

— from peat, 670 

-petroleum, 676 

-petroleum oil, or oil from bitu¬ 
minous shales, 675 

-suint, 675 

-wood, 668 

— holders, 656 
— hydraulic valve, 631 
— Isoard's, 674 
— lighting, raw materials of, 646 
— lime, 667 

— manufacture, sulphur as a by-pro¬ 
duct, 198 
—■ meters, 664 
— oil, resin, 674 
— pressure regulator, 661 
— products of the distillation, 647 
— purifying, 654 


Gas, retorts, 648 

— the scrubber, 653 
Gas-water, 671 

-ammonia from, 230 

Gaseous fuel, 730 
Gases, blast-furnace, 15 

— heating with, 24 
Gatty's process, 219 
Gay-Lussac's chlorometric method, 

221 

Gentele's method of preparing phos¬ 
phorus, 544 

Gerland's method < f preparing phos¬ 
phorus, 544 

German iron refining process, 21 

— silver, 53 

Germination of the softened grain, 406 
Gilding, 110 

— by the cold process, 110 
-wet way, 110 

—- porcelain, bright, 303 

Gillard’s gas, 672 

Glass, aluminium-calcium alkali, 269 

— aventurin, 291 

— bleaching. 270 

— bottle, 282 

— classification of the various kinds, 

268 

— clear melting, 275 

— cold stoking, 275 

— coloured, and glass staining, 289 

— crown, 277 

— cryolite, 291 

— crystal, 285 

— defects in, 276 

— definition and general properties 

of, 268 

— filigree or reticulated, 292 

— ice, 291 

— making, raw materials, 269 

— material melting, 275 

— melting and clearing, 280 

— optical, 286 

— oven, 271 

— painting, 289 - 

— pearls, 292 

— plate, 279 

-casting and cooling, 281 

-or window, 276 

-polishing, 281 

— platinising, 282 

— potassium-calcium, 268 

— potassium-lead, 269 

— preparation of the material and 

melting, 274 

— pressed and cut, 283 

— refuse, utilisation, 270 

— relief, 291 

— sheet or cylinder, 278 

— silvering, 281 

-by precipitation, 281 

— sodium-calcium, 268 

— technology of, 268 


INDEX. 


vii 


Glass, the melting vessel, 270 

— tools for, 277 

— various kinds, 276 

— water, 283 
Glauber’s salt, 213 
Glue boiling, 528 

— drying, 531 

— from bones, 532 
-leather, 529 

— liquid, 533 

— substitutes for, 536 

— test for quality of, 533 

— treating with lime, 529 
Gluten glue, 536 
Glycerine, 634 
Glyphography, 117 

Gold alloys, i09 

— applications of, 110 

— chemically pure, 108 

— colour of, 109 

— and silver, electro-plating with, 

115 

— extraction from other metallic ores, 

106 

-poor materials, 106 

— leaf for gilding, 110 

— mode of extracting, 105 

— mode of extracting by means of 

mercury, 106 

— mosaic, 75 

— occurrence and mode of extracting, 

105 

— properties of, 108 

— refining, 106 

— salts, 111 

— size, 489 

— smelting for, 106 

— solution for electro-plating, 116 

— testing the fineness of, 109 

— treating with alkali, 106 
Grain germinated drying, 407 
Grape-juice fermentation, 393 
Grape-sugar, 383 

— preparation, 384 

— uses of, 386 
Grapes, pressing, 391 
Grate, Boquillon's, 744 

— chain, 743 

— etage or stage, 743 

— rotating, 744 

— step, 742 

— Vogl’s, 744 
Grates, movable, 743 
Green vitriol, 31 

-preparation of. as a by-product 

in alum works, 32 
Grenate brown, 581 
Gruneberg’s method of estimating 
the value of potash, 226 
Gun-cotton, 160 

— as a substitute for gunpowder, 162 

— other uses, 162 

— properties of, 161 


Gun-metal, 51 
Gunpowder, 148, 156 

— caking or pressing, 150 

— composition, 152 

— drying, 151 

— granulated, polishing, 150 

— granulation of the cake, and sort¬ 

ing tbe powder, 150 

— manufacture, 148 

-mechanical operations, 149 

— mixing the ingredients, 149 

— products of combustion of, 153 

— properties of, 151 

— .pulverising the ingredients, 149 

— sifting the dust from, 151 

— testing strength of, 154 

— white, 154 

Gutta-percha and caoutchouc, mixture 
of, 488 

— solvents, 487 

— uses of, 487 
Gutter tiles. 318 
Gypsum, 333 

— casts, 336 

— grinding, 335 

— hardening of, 336 

— kilns or burning ovens for, 334 

— naiure of, 333 

— uses of 335 

H ABANA brown, 580 

Hmmatinon astralite, 291 
Haematite iron ore, 8 
Heat, mechanical equivalent of, 702 
Heating apparatus, 731 
— by flues, 739 

-hot air, 737 

-water, 739 

— direct,732 
— dwelling-houses, 732 
— with gases, 24 
— — steam, 740 
— without ordinary fuel, 740 
Heaton steel, 28 
Hemp, 340 
— substitutes, 340 
Hides, cleansing, 514 
— swelling, 515 
— stripping off the hair, 515 
— Hofmann s process, 219 
Hollander mill, 347 
Hops, 404 
— adding, 412 
— quality of, 404 
— substitutes for, 405 
Hot-pressing, finishing, and dressing 
616 

Houses, heating, 732 
Hungarian tawing process, 524 
Hyalography, 292 
Hydraulic main for gas, 650 
— mortar, 327 
— valve, 661 


49 


Pill 


INDEX. 


Hydrocarbon process (White’s) for 
water-gas, 673 
Hydrochloric acid, 211 

-properties of, 213 

-uses of, 213 

Hypochlorites alkaline, 223 
Hyposulphite of soda, 201 
Hyposulphurous acid, 199 

I CE-GLASS, 291 

Illumination, artificial in general, 
617 

— Tessie du Mot ay's method, 679 

— with lamps, 636 

Ind ia-rubber,preparation and use of ,486 

Indigo, 591 

— properties, 592 

— recovery from rags, 604 

— testing, 592 

Indigo-blue, 594, 602 

Ink for marking, 105 

— — printing, 489 

Iodine from carbonised sea-weed 192 

-Chili-saltpetre, 192 

— preparation, 191 
— properties and u'es of, 193 
Iron, 8 
— cast, 16 
— cement, 493 
— crude 16 
— extraction, 9 

-process, theory of, 10 

— foundry work, 18 
— malleable, tinning of, 75 
— metallic, green vitriol from, 32 
— minium, 32 
— ore haematite, 8 

-magnetic, 8 

-marsh, 9 

-pea, 9 

— —• spathose, 8 

— refining by mechanical means, £d 

-German, 21 

-Swedish, 22 

— sheet, tinned, 75 
— stones, 734 
— wire manufacture, 25 
Isinglass, 535 
Isoard’s gas, 674 

JUTE, 341 

K AOLTN, 293 

Karmabsch’s evaporation 
method, 699 
IveJp, 130 

— preparation of iodine from, 191 
Kilns, annular, 317 
— for burning lime and bricks, 325 

-gypsum, 334 

-lime, continuous, 324 

-occasional or periodic, 323 

Kino, 512 


Knapp's leather, 525 
Kneading machines, 453 

L AC dye,590 

Lacquered leather, 521 
Lactose, sugar of milk, 557 
Lake pigments, 568 
Laming mixture, 667 
Lamp with constant oil level, 640 
Lamps, 636 

— for illumination, 636 
— petroleum oil and paraffin oil, 644 
— pressure, 641 

— statical, mechanical, clockwork, 
moderator, 642 
— suction, 639 
— various kinds, 639 
Lamy’s refining apparatus for sulphur, 
196 

Langier's apparatus, 443 
Lant, ammonia from, 234 
Lead acetate, 64 
— alloys, 62 

— basic chloride of as a substitute 
for white-lead, 71 
— chloride, white-lead from, 71 
— chromate, 64, 66 
— containing silver, mode of pre¬ 
paring, 100 

— metallic, applications of, 62 
— obtained by calcination, 60 

-precipitation, 59 

— occurrence of, 59 
— oxide, 63 

-combinations of, 64 

— preparations of. 63 
— properties of, 62 
— sulphate, white-lead from, 70 
— peroxide, 64 

Leaden pans, concentration in, 207 
Leather, coidwain, Cordovan, 521 
— dressing or cuirjing, 518 
— finishing, 519 
— for glovi g, 524 
— glue, 529 
— graining, 519 
— greasing, 519 
— Knapp s process, 525 
— lacquered. 521 
— morocco, 520, 521 
— polishing with pumice-stone, 519 
— preparation of white, 522 
— Kussia, 520 
— side, 518 
— the paring, 518 
— the scraping or smoothing, 

— upper, 518 

Leblanc's process theory of, 183 
Leprince's water-gas, 674 
Ley, 242 

—- evaporation of, 180, 257 
Light, materials and apparatus for 
producing artificial, 617 


INDEX. 


IX 


Lime and bricks, kilns for burning, 325 
-lime-burning, 322 

— cements, 491 

— light, 678 

— preparation of fatty acids by means 

of, 621 

— properties of, 322, 225 

— slaking, 326 

— sulphite of, 201 

— treating glue with, 529 

— uses of, 326 
Linen-dyeing, 609 

— fabrics, detection of cotton in, 343 

— goods printing, 616 
Litharge, 63 

— revivification of, 61 
Lithophame, 303 
Litmus, 594 
Liquation process, 47 
Liquid glue, 533 
Lixiviation, 257 
Loam, 296 
Logwood, 594 

— and a copper salt to dye blue, 604 
London board, 354 

Lucifer matches manufacture, 548 
Lunge’s apparatus, 232 
Lustres, 309 

Lye, raw, breaking up of, 136 

-boiling down, 136 

-treatment of, 136 

A/TACHINE for paper-cutting, 353 
jJIjL — paper, 352, 

Machines for moulding bricks, 312 
Madder, 586 

— flowers of, 587 

— lake, 587 
Magdala rt d, 583 
Magenta, 575 
Magnesium, 114 

— light, 679 
Magnetic iron ore, 8 
Malachite, 43 

Malleable, bar, or wrought iron, 20 

Mallet’s apparatus, 230 

Malt, the bruising of, 408 

Malting, 405 

Mandarin printing, 616 

Manilla hemp, 341 

Manganese and its preparations, 111 

— soap, 249 

— testing the quality of, 111 
Marking ink, 105 . 

Marl, 295 
Marsh iron ore, 9 
Martin steel, 28 
Martius yellow* 582 
Mash boiling thick, 409 

— distillation of, 431 

— from potatoes, 427 

— — roots, 429 

— with sulphuric acid, 428 


Mashing, 408 
Massicot, 63 

Matches anti-phosphor, 552 

— lucifer, manufacture of, 548 

— wax or vesta, 553 
Mauve, 575 

Meat, constituents of, 562 

— the cooking of, 563 

— generalities, 562 

— preservation of, 564 

— salting, 565 

— smoking or curing, 566 

— the boiling of, 564 
Meerschaum pipes, artificial, 337 
Mercurial compounds, 91 
Mercuric chloride, 91 
Mercury, applications of, 91 

— extracting by Spanish method, 89 

— extraction of gold by mean* of, 106 
—* fulminating, 92 

— method of decomposing by the aid 

of other substances, 90 

— method of extracting, pursued in 

Idria, 87 

— occurrence and mode of obtaining. 

87 

— or quicksilver, 87 

— preparations of, 91 

— properties of, 91 

Metal, coarse, roasting or calcining, 
49 

Metals, alloys and preparations from, 4 

— steel and other, 30 

Metallic iron, green vitriol from, 32 
Metallochromy, 117 
Metallurgy, chemical, 4 

— meaning of the term, 4 
Meters for gas, 664 
Milk, 556 

— means to prevent becoming sour, 

557 

— sugar of—lactose, 557 

— testing, 557 
Millifiore work, 292 

Minary's process of preparing phos¬ 
phorus, 544 

Mineral green and blue, 57 

— ojl, preparation of, 694 

— potash, 121 
Mineralising wood, 476 
Minium, red-lead, 63 
Mohair, 495 
Mohr's me'hod, 225 
Moire-meiallique, 75 
Molasses, 366 

— beet, 382. 

— potash from, 122 
Mordants, 601, 609 
Morocco leather, 520, 521 
Mortar, 326 

— hardening, 327 

— hydraulic hardening of, 331 
Mosaic gold, 75 


INDEX. 


£ 

Moulds, making, 19 
Muffles, distillation of zinc in, 78 
Muriatic acid, 211 
Must, chemical constituents of, 391 
My coderm a aceti, vinegar with the 
help of, 4G6 

N aphthaline blue and naptha- 
line violet, 583 
— pigments, 581 
Neapolitan yellow, 85 
Neft-gil, paraffin from, G84 
Nettle cloth and muslin, 341 
Nickel and copper alloys, 41 
— and its ores, 39 
— metallic preparation, 41 
— properties of, 43 
— silver, 53 

Nitrate of ammonia, 238 
-potassa, 134 

-preparation from Chili- 

saltpetre, 138 

-silver, 105 

-soda, soda from, 189 

-tin, 76 

Nitric acid, 142 

-bleaching, 143 

-condensation, 144 

-density of, 14G 

— — fuming, 147 

-in saltpetre, quantitative esti¬ 
mation of, 140 

-manufactuie, o'her methods, 

145 

-uses of, 147 

Nitro-benzol, 572 
— pigment directly from, 581 
Nitro-glycerine, 158 
Nobel’s dynamite, 160 
Nut-galls, 511 

O AK bark, 509 
Oil, blue, 57 
— cements, 491 
— colza, mineral, 637 
— gas, resin gas. 674 
— varnishes, 488 
Oils crude, rectification of, 689 
— essential and resins, 480 

-extraction by fatty oils, 481 

-preparation of, 481 

— paraffin, 683 
— purifying or refining, 636 
— treatment of the products of dis¬ 
tillation of, 689 
Oleic acid soap, 245 
Olive-oil soap, 243 
Optical glass, 286 
Ores, 4 

— calcining, or roasting, 48 
— dressing of, 5 
— oxidised, copper from, 49 
— preparation of, 5 


Ores, smelting, 48 

— smelting of, 5 
Orchil and Persio, 590 
Orpiment, 87 

Ovens, coking in, 724 

— for burning gypsum, 334 

— for porcelain, 301 

— or kilns, carbonisation of wood in 
> 706, 708 

Oxide of antimony. 84 
Oxidised silver, 105 
Oxysulphuret of antimony, 85 
Ozokerite and neft-gil, paraffin from, 
684 

"pASONINE or coralline, 581 

Pans for evaporating beet-root juice 

375 

Paper-cutting machine, 353 

— different kinds, 351. 

— drying, 351 

— history of, 345 

— machine-made, 352 

— making, 345 

— manufactuie by hand, 346 

— materials of manuf a/ture, 346 
—- pressing, 351 

— pulp-bluing, 350 

— sheets straining, 350 
—• sizing 351 

— sizing the pulp, 350 
Papier-mache, 355 
Paraffin candles. 630 

— crude, refining of, 690 

— Horn bitumen, 685 

— from ozokerite and neft-gil, 684 

— Hubner's method of preparing, 

690 

— manufacture, 683 

— oils, 683, 693 

— oil lamps, 644 

— preparation by dry distillation, 68 

— from petroleum. 6S4 

— properties of, 692 

— yield of, 691 
Parchment, 527 

— paper, 355 

Parian and Carrara, 304 
Paste. 493 

Pasteboard making, 353 
Pattinson's method of refining silver, 
101 

Pea-iron ore, 9 
Pearls, blown, 292 

— solid, 292 

— glass, 292 

Peat, 712 * 

— carbonised, 715 

— drying, 713 

— gas, 670 

— heating effect of, 715 

— new method of utilising, 716 


INDEX. 


Xi 


Pecquer evaporating pan, 376 
Penny’s indigo test, 593 
Penot's test, 221 
Per as, 729 
Percussion caps, 93 

— powders, 156 
Perfumes chemical, 482 
Perfumery, 481 
Permanganate of potassa, 112 
Petroleum as fuel, 722 

— constitution, 696 

— crude, refining, 696 

— oil and its occurrence, 695 
-gas from, 675 

-lamps, 644 

— origin and formation of, 695 

— technology, 697 

Pettenkofer’s process for restoring 
pictures, 490 

Phenicienne, phenyl brown, 581 
Phenyl blue, 581 
Phosphorus, distillation of, 538 

— Fleck s process, 543 

— making, burning the bones to ssb, 

538 

— manufacture, 537 

— other proposed methods of pre¬ 

paring, 543 

— preparing byGENTELE, Gerland, 

Minary, and Sondry's methods, 
544 

— properties of, 544 
-and preparation, 537 

— red or amorphous, 515 

— refined, moulding, 541 

— refining and purifying, 540 
Physic, or nitrate of tin, 76 
Picric acid, 580 

Pictures, Pettenkofer’s process for 
restoring, 490 
Pig or crude iron, 9 
Pikaba hemp, 341 
Pigments from cinchonine, 535 

— lake, 568 

— naphthaline, 581 

— red, 586 
Pipes of clay, 309 
Pistorius’s apparatus, 435 
Pit coal, 717 

Plaster of Paris forms, moulding in, 
299 

Platinum alloys, 96 

— black, 96 

-vinegar, with the help of, 467 

— gas, 672 

— hammered or cast, 95 

— method of Deville and Debray, 

95 

— occurrence of, 93 

— ores, 93 

— properties of 96 

— retorts, 207 

— spongy, 95 


Platinum, Wollaston’s method of 
extracting, 94 

Porcelain articles, preparation with¬ 
out moulds, 299 

— bright gilding, 303 

— casting. 299 

— clay, 293 

— drying, 299 
-the mass, 297 

— faulty ware, 302 

— French fritte, 304 

— glaze applying, 300 

— glazing, 299 

— kneading the dried mass, 298 

— grinding and mixing the material, 

297 

— hard, 297 

— ornamenting, 303 

— oven, 301 

— painting, 302 

— oven, emptying and sorting the 

ware, 302 

— silvering and platinising, 303 

— tender, 304 

— moulding, 298 

— the potter’s wheel, 298 
Portland cement, 329 
Potash from molasses, 122 

— from the ashes of plants, 122 

— Gruneberg's method of estimating 

the value of, 226 

— purified preparation of, 133 
Potasea and cobalt, nitrate of prot¬ 
oxide of, 39 

— carbonate of, 118 

— chlorate of, 223 

— chromates, applications of, 65 

— mode of obtaining from felspar, 122 

— neutral or yellow chromate of, 64 

— nitrate of, 134 

— permanganate of, 112 

— salts from sea-water. 122 

-sea-weeds, 129 

-suint, 132 

— -the Stassfurt salt mincra’s, 

118 

— sources wheoce, derived, 118 

— sulphate of, 121 

— yellow prussiate of, 32 
Potassium, chloride of, preparation. 119 

— cyanide, 35 
Potatoes, mash from, 427 

— starch from, 357 
Potato-mash fermentation, 429 

— starch drying, 358 
Potter’s clay, 295 
Pottery common, 310 

Printing and dyeing in general, 568 

— ink, 489 

— linen goods, 616 

— silk goods, 616 

— woollen goods, 616 

— of woven fabrics, 609 


INDEX. 


£U 

Prussian blue on wool, 604 
Paddling furnace, 22 

— process, 22 

Pulp, bleaching, for paper, 349 
Pult fires, 744 

Pumice-stone to polish leather, 519 
Purple, Cassius's, 111 
Pyrites distillation, green vitriol from 
residues of, 32 

— preparation of sulphur from, 197 

— use of for the preparation of sul¬ 

phurous acid, 206 
Pyrotechny, 148 

— chemical principles of, 155 

Q UARTATION, 107 
» Quercitron bark, 596 
Quicksilver or mercury, 87 

AGS, cutting and cleaning, 347 
— for paper,additions of mineral 
to, 346 
— substitute f< r, 346 
Raw lead. 61 
Realgar, 87 
Ked arsenic, 87 
Red lead, 63 
— phosphorus, 545 
— prussiate of potash, 35 
Refined s’eel, 29 
Refining copper, 46 
Resins, 483 
Ret in cements, 492 
— gas, 678 

-oil gas, 674 

Resin-tallow soap J , 245 

Resin, use of as sealing wax, 4S3 

Resume, 745 

Retort furnaces, 650 

Retorts for gas, 648 

— glass, concentration in, 208 

— platinum, 207 

Reverberatory furnace. IS 

Rhea grass, 341 

Rice starch, 360 

Rinmann’s, or cobalt green, 39 

Rock salt, 165 

-mode of working, 167 

Roll "sulphur, 197 
Roofing tiles, 318 
Roots, mas'i from, 429 
Roseine, 575 
Rose's apparatus, 232 
Rough steel, 27 
.Busina, 87 
Russia leather, 520 
Russian stoves, 734 

Q ACCEfAR1METRY, 369 
k3 Saccharometrical beer test, Bal¬ 
ling’s, 420 

Sago, 361 
Safilower, 589 


Sal-ammoniac, application of gases to 
the manufactu'e of, 16 
Salines, method of obtaining common 
salt in, 164 

Salt, common, direct conversion of 
into soda, 188 

-method of obtaining in salines, 

164 

— — method of preparing from sea¬ 

water, 163 

-occurrence of, 163 

-properties of, 169 

-uses of. 170 

Saltpetre, 134 

— and sulphur mixture, 156 

— crude, refining, 137 

— mode or obtaining, 135 

— occurrence of native, 134 

— of the earth, treatment of, 135 

— quantitative estimation of nitric 

acid in, 140 

— testing, 140 

— uses of, 141 

Salt-springs, mode of working, 167 
Samian, or oil-tawing process, 525 
Sandal wood, 588 
Sanitary ware, 321 

Sap, chemical alteration of the con¬ 
stituents of, 475 

— elimination of the constituents of, 

474 

Saponification, theory of, 242 

— with lime, 623 
-sulphuric acid, 624 

-water and high pressure, 626 

S auerwein’s m ethod < >f decomposition 
cryolite with caustic lime, 259 
Saxony blue. 603 

Schaffnkr's sulphur )egen ration 
process, 185 
SCHEELE s green, 57 
Schist or alum-shale, 257 
Schwarz's arparatus, 436 
Schweinfurt green, 58 
Sealing-wax, u9e of resin as, 483 
Sea-weed carbooLed, iodine from, 192 
Sea-weeds, potassa salts from, 129 
Sea-water, method of preparing com¬ 
mon salt from, 163 

— potassa salts from, 122 
Sericiculture, 501 

Shaft or cupola furnace, 18 

Shagreen, 537 

Shear-steel, 29 

Sheep-shearing, 498 

Shot manufacture, 62 

Siderography, 31 

Siderolite and terralite w*re, 307 

Siemens’s apparatus, 440 

Silica ultramarine preparation, 267 

Silk, 501 

Silk bleach ins", 599 

— dyeing, 606 



INDEX. 


xiii 


Silk goods, printing, 616 

— manipulation, 503 

scouring or boiling the gum out, 
504 

— testing, 504 

— to distinguish from wool and vege¬ 

table fibre, 506 * 

— weaving, 505 
Silkworms, 501 
Silver, alloys of, 103 

— alloy for plate, 103 

— and gold for electro-plating, 115 

— and its occurrence, 96 

— assay, 103 

— chemically pure, 102 

— extraction by amalgamation, 97 

-Augustin's method, 99 

-the dry way, 100 

-from its ores, 96 

-sundry hydro-metallurgical me¬ 
thods of, 99 

— German or nickel, 53 

— mode of preparing the lead con¬ 

taining, 100 

— n.trate of, 105 

— oxidised, 105 

— properties of, 102 

— reduction by means of zinc, 102 

— refining process, 100 

— smelting for, directly, 97 

— solution for electro-plating, 116 

— ultimate refining of, 102 
Silvering, 104 

— by the wet way, 105 
-- fire or igneous, 104 

— in the cold, 104 
Sizing the paper, 351 
Skins, 513 

Skin of animals, anatomy of, 508 
Slaking lime, 326 
Smalt, 38 

Smelt, the mixing of the, 5 
Smelting for gold, 106 

-silver directly, 97 

-white metal, 49 

— of nickel ores, 40 
-the ore, 5 

— operation, products of, 7 

— process, course of, 13 
Smoke consumption, 745 
Smoke-consuming apparatus, 741 
Snulf, 480 

Soap-boiling, raw materials of, 
239 

Soap, chief varieties of, 243 

— insoluble, 249 

— making. 239 

— tests, 248 

— transparent, 248 

— uses of, 248 
Soaps, toilet, 247 

— various, 247 
Soda-alum, 261 


Soda-ash, 171 
Soda, aluminate of, 26 

— bicarbonate of, 190 

— caustic, 189 

— crude, conversion of sulphate into, 

174 

-lixiviation of, 176 

— direct conversion of common salt 

into, 188 

— from chemical processes, 172 
-cryolite, 188 

-niirate of soda,-189 

-soda plants, and from beet¬ 
root, 171 

— furnace, with rotatory hearth, 175 

— hyposulphite of. 201 

— manufacture,^ 70 

— occurrence of native, 170 

— preparation from sulphate of soda 

187 

— stannate of. 76 

— sulphate, 213 

— sulphate uses of, 214 

— ultramarine preparation, 266 

— waste, sulphur from, 198 

— waste utilisation, 184 
Sodic nitrate, 141 

Soft soap, 246 
Solferino, 575 

Son dry s process of preparing phos¬ 
phorus, 544 

Spathic iron ore, green vitriol from, 32 

Spathose iron ore, 8 

Sperm, or spermaceti candles, 634 

Spinning cotton. 342 

Spinning flax, 340 

Spirit from dry distillation of wood, 
472 

— manufacture raw materials, 425 

— varnish, 489 

Spirits from the by-pToducts of sugar 
manufacture, 430 

— from wine and marc, 430 

— the preparation or distillation ci, 

424 

Spongy platinum, 95 
Stags, 5 

Stage, or etage grate, 743 
Stamp machine, 347 
Stanford and Moride’s method of 
preparing iodine from carbonised 
sea-weed, 192 
Stannate of soda, 76 
Starch, 355 

— commercial, constituents and uses 

of, 360 

— from potatoes, 357 

— nature of, 356 

— rice, chestnut, Cassava arrow-root, 

360 

— sources of, 357 

Starch-meal, boiling with dilute sul¬ 
phuric acid, 384 


XIV 


INDEX. 


Starch sugar composition, 386 
Statistics concerning the production 
of crude iron, 18 
Statistics of Bteel production, 31 
Steam brewing, 418 

— for heatiDg, 740 
Stearine candles, 621 
Steel, 26 

— and other metals, 30 

— engraving, 31 

— from malleable and crude cast 

iron, 29 

— production, statistics of, 31 

— properties of, 29 

— hardening, 29 
Step grate, 742 
Stereochromy, 2S5 4 
Stibium, 82 
Stoneware, 305 

— lacquered. 307 

— ovens, 303 
Stove heating, 733 
Stoves, compound, 735 

— iron, 734 

— of fire-clay, 734 
Strass, 288 
Styrian cast-steel, 27 
Sugar-beet, vinegar from, 463 
Sugar-candy, 382 
Sugar-cane, 364 

— components, 364 

Sugar, draining the crystals, 381 

— history of, 362 

— manufacture, 362 

— beet-root, 367 

— spirits from the by-products of, 430 

— nature of, 362 

— of the grape, 392 

— preparation from the beet, 370 

— preparation of moist, raw, or loaf, 

380 

— raw, preparation from the sugar¬ 

cane, 365 

— production, 367 

— refining, 366 

— removing from the form, 381 

— solution, evaporating and purify¬ 

ing, 385 

— starch, composition, 386 

— varieties of, 366 
Suint, gas from, 675 

— potassa, salts from, 132 
Sulphate of alumina, 261 

-alumina and alum, uses of, 263 

-- ammonia, 238 

-copper, 54 

-potassa, 121 

— — soda-, 213 
-zinc, 81 

— or decomposing furnace, 172 
Sulphates of alumina, 256 
Sulphide of carbon, 210 
Sulphite of lime, 201 


Sulphur, 194 

— as a by-product of gas manufac¬ 

ture, 198 

Sulphur, by heating sulphuretted 
hydrogen, 198 

— chloride, 211 

— flowers of, 197 

— for refining gold, 107 

— from soda waste, 198 

— obtained by the reaction of sulphu¬ 

rous acid on charcoal, 198 

— preparation of from pyrites, 197 

— production by the reaction of 

sulphuretted hydrogen upon sul¬ 
phurous acid, 198 

— properties and uses of, 199 

— regeneration process, Schaffner's, 

185 

— smelting and refining, 194 
Sulphurets of arsenic, 86 
Sulphuric acid, 201 

-concentration, 206 

-decomposition of bone-ash by, 

538 

-green vitriol from. 32 

-for refining gold, 107 

-fuming. 202 

-manufacture, other methods of, 

208 

-mash with, 428 

-ordinary or English, 203 

-present manufacture of, 203 

-properties of, 209 

-saponification by means of, 624 

-separation from the sugar solu¬ 
tion, 385 

Sulphurous acid, 1S9 

-use of pyrites for tne preparation 

of sulphurous acid, 206 
Sumac, 510 
Sun hemp, 341 
Swedish iron refining, 22 

r SHALLOW candles, 629 
JL Tanning, 508, 516 

— in liquor, 517 
-the bark, 516 

— materials, 509 

-estimation of value of, 512 

— quick process, 517 

— the several operations, 513 

Tar, condensation of the vapours of, 
686 

— distillation of, 688 

— mode of operating with, 688 

— preparation of. 685 

— properties of, 687 

Tawer’s softening iron to smooth the 
leather, 519 
Tawing, 522 

— common, 522 

Temperature of blast-furnace at dif¬ 
ferent points, 15 


INDEX. 


XV 


Tempering, 20 

— steel, 30 
Terra-cotta, 311 

Terralite and siderolite ware, 309 
Thickenings, 610 

Thomsen’s method of decomposition 
of cryolite by ignition with car¬ 
bonate of lime, 259 
Tiles drain and gutter, 318 

— roofing and Dutch, 318 
Tin, 73 

— applicat ; ons, 74 

— nitrate of, 7 6 

— preparatiot s of, 75 

— properties of, 74 
Tinned sheet iron, 75 
Tinning, 75 

— of copper, brass, and malleable 

iron, 75 
Tin salt, 75 
Tobacco, 477 

— leaf, chemical composition of, 478 

— manufacture, 478 
—■ smoking, 479 

Tow, or tangled fibre, 340 
Tubes, distillation of zinc in, 79 
Turkey red, 608 
Turmeric, 596 
Turnbull's blue, 37 
Turpentine oil varnishes, 490 
Tyr aline, 575. 

U CHATIUS’S steel, 2S 
Ultramarine, 264 
— artificial, 264 
— cobalt, 38 
— constitution of, 267 
— conversion of green into blue, 266 
— green preparation, 265 
— manufacture, 264 
— native, 264 
— properties of, 267 
— sulphate of, preparation, 265 

Y ACUUM pans, 377 
Yalonia nuts, 511 
Varnish, polishing dried, 490 
— spirit, 489 
Varnishes, 488 
— oil, 489 

— spirit, coloured, 490 

— turpentine oil, 490 

Vases, Etruscan, 309 

Vegetable fibre, technology of, 338 

Vellum, 527 

Verdigris, 58 

Vicuna wool, 495 

Vienna yeast, 450 

Vine and its cultivation, 390 

Vinegar and its origin, 460 

— formation, phenomena of, 462 

— from alcohol, 461 

-the sugar-beet, 466 


Vinegar from wood distillation, 469 

— making, older method, 462 
-quick process, 463 

— testing, 467 

— with the help of the Mycoderma 

aceti, 466 

— platinum black, 467 

— the manufacture of, 460 
Vinous fermentation, 387 

— mash ficm cereals, 426 
Vintage, 390 

Vitriol blue, 54 
-applications of, 56 

— double, 55 

— green, 31 

-from metallic iron and sul¬ 
phuric acid, 32 

-from the residues of pyrites 

distillation, 32 

-in beds, preparation of, 32 

-preparation of, as a by-product 

-m alum works, 32 

-uses of, 32 

— white, 81 

Violet and blue naphthaline pigments, 

583 

— imperial, 577 
Vogl’ s grate, 744 

Voltaic electricity, copper obtained 
by, 50 

Volumetrical method, 224 
Vulcanised caoutchouc, 486 

ALKEKITE, 295 
Warming, 731 
Water, 405 

— cooler?, 309 

— gas, 671 

-carburetted, 672 

-Leprince’s, 674 

— hot, for heating, 739 
Wax candles, 631 
-making, 633 

— or Vesta matches, 553 
Weaving silk, 505 

— the cloth 499 

-linen threads, 340 

Weld, 596 

Weldon’s chlorine process, 219 
Wheat staTch, preparation of, 358 
Whey, 557 

White gunpowder, 154 

— lead, 67 

-adulteration of, 72 

-application of, 72 

-English method of manufac¬ 
turing, 68 

-French method of preparing, 69 

-from chloride of lead, 71 

-sulphate of lead, 70 

-manufacture at Clichy, appa¬ 
ratus used in, 69 
-properties of, 71 



INDEX. 


XVI 

White-lead, theory of preparing, 70 

— vitriol, 81 
Wine, 390 

— clearing and fining, 399 

— constituents of, 393 

— drawing off and casking, 393 

— making, 390 

-the residue or waste. 399 

— must, improving the, 401 
Wines, ageing and conservation of, 39 1 

— effervescing, 399 

— maladies of, 396 

Wire, iron, manufacture, 25 
Wollaston's method of extracting 
platinum from its ores, 94 
Wood, 702 

— charcoal, 704 

— — composition of, 711 

— Boucherie's method of mineral¬ 

ising, 477 

— carbonisation of, 705, 708 

— constituents of, 703 

— drying, 474 

— gas, 668 

— burners, 670 

— heating value of, 704 

— in general, durability, of, 472 

— preservation, 472, 474 

— roasted, rois boux, 712 

— spirit, 472 . 

— vinegar, 469 
Wood's alloy, 82 

Wool and vegetable fibre, to distinguish 
silk from. 506 

— artificial, 499 

— carding, 498 

— chemical composition of, 495 

— colour and g'oss, 497 

— dyeing, 498 

— — red, 605 

— oiling or greasing, 498 

— origin and properties of, 494 

— preparation, 497 

— properties of, 497 

— spinning, 498 


Wool sorting, 498 

— washing, 498 

— willowing or devilling, 498 
Woollen fabrics, dyeing, 601 

— goods, printing, 616 

— industry, 494 
Wootz-steel, 30 
Worsted wool, 500 
Wort, boiling, 411 

— cooling, 413 

— extractives of, 411 

— preparation of, 408 

— preparion, intus : on method, 410 

Y east. 387 
— dry, 449 

— so-called artificial, 450 
Yellow chromate of potassa, 64 
— dyes, 595 

— prussiate of potash, applications 
of, 35 

— sulphuret of arsenic, 87 

— wood, 595 

Yufts, Russia leather, 520 

Z IEItVOGEL'S method of silver 
extraction, 99 

Zinc and tin solution for electro¬ 
plating, 116 
— applications of, 80 
— chloride, 81 
— chromate, 81 
— distillation in crucibles, 79 

-muffles, 78 

-tubes, 79 

— method of extracting, 77 
— mode of obtaining from sulphuret 
of zinc, 79 
— occurience of, 77 
— preparations of, 80 
— properties of, 79 
— reduction of silver by means of, 
102 

— sulphate, 81 
— white, 80 




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Prof. W. Kingdon Clifford, M. A., The First Principles of the 
Exact Sciences explained to the Fun-Mathematical. 

Prof. T. H. Huxley, LL. D., F. R. S., Bodily Motion and Con¬ 
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Dr. W. B. Carpenter, LL. D., F. R. S., The Physical Geogra¬ 
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Prof. Wm. Odling, F. R. S., The Old Chemistry viewed from 
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W. Lauder Lindsay, M. D., F. R. S. E., Mind in the Lower 
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Sir John Lubbock, Bart., F. R. S., On Ants and Bees. 

Prof. W. T. Thiselton Dyer, B. A., B. Sc., Form and Habit in 
Flowering Plants. 

Mr. J. N. Lockyer, F. R. S., Spectrum Analysis. 

Prof. Michael Foster, M. D., Protoplasm and the Cell Theory. 

H. Charlton Bastian, M. D., F. R. S., The Brain as an 
Organ of Mind. 

Prof. A. C. Ramsay, LL. D., F. R, S., Earth Sculpture; Hills, 
Valleys, Mountains, Plains, Rivers, Lakes; how they were 
produced, and how they have been destroyed. 

Prof. Rudolph Virchow" (Berlin University), Morbid Physiolo¬ 
gical Action. 

Prof. Claude Bernard, Ilis'ory of the Theories of Life. 

Prof. H. Saint-Claire Deville, An Introduction to General 
Chemistry. 

Prof. Wurtz, Atoms and the Atomic Theory. 

Prof. De Quatrefages, The Human Race. _ 

Prof. Lacaze-Duthiers, Zoology since Cuvier. 

Prof. Berthelot, Chemical Synthesis. 

Prof. C. A. Young, Ph. D. (of Dartmouth College), The Sun. 

Prof. Ogden N. Rood (Columbia College, New York), Mod¬ 
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D. APPLETON 6- CL 


Dr. Eugene Lommel (University of Erlangen), The A ature of 
Light. 

Prof. j. Rosenthal, General Physiology of Muscles and Nerves. 

Prof. James D. Dana, M.A., LL. D., On Cephalization; or, 
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Prof. S. W. Johnson, M. A., On the Nutrition of Plants. 

Prof. Austin Flint, Jr., M. D., The Nervous System, and its 
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Prof. Bernstein (University of Halle), The Five Senses of Man. 

Prof. Ferdinand Cohn (Breslau University), Thallophytes 
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Prof. Hermann (University of Zurich), On Resjciration. 

Prof. L buck art (University of Leipsic), Outlines of Animal 
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Prof. Liebreich (University of Berlin), Outlines of Toxicology. 

Prof. Kundt (University of Strasburg), On Sound. 

Prof. Rees (University of Erlangen), On Parasitic Plants. 

Prof. Steinthal (University of Berlin), Outlines of the Science 
of Language. 

P. Bert (Professor of Physiology, Paris), Forms of Life and 
other Cosmical Conditions. 

E. Alglaye (Professor of Constitutional and Administrative 
Law at Douai, and of Political Economy at Lille), The 
Primitive Elements of Political Constitutions. 

P. Lorain (Professor of Medicine, Paris), Modern Epidemics. 

Prof. Schutzenberger (Director of the Chemical Laboratory 
at the Sorbonne), On Fermentations. _ 

Mons. Freidel, The Functions of Organic Chemistry. 

Mons. Debray, Precious Metals. 

Prof. Corfield, M. A., M. D. (Oxon.), Air in its Relation to 
Health. 

Prof. A. Giard, General Embryology. 

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AN ELEMENTARY TREATISE. 

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Translated, with Extensive Additions, 

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Heat as a Mode of Motion. 

One vol., iemo. Cloth, $2.00. 

“My aim nas been to rise to the level of these questions irom a oasis so elementary, that a person pos¬ 
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Preface, 


On Sound. 

A Course 01" Eight Lectures delivered at the Royal Institution of Great Britain. 
One vol. With Illustrations. i2mo. Cloth, $2.00. 

“ In the following pages I have tried to render the science of Acoustics interesting to all intelligent per¬ 
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Fragments of Science for Unscientific 

People. 

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Light and Electricity. 

Notes of Two Courses of Lectures before the Royal Institution of Great Brit¬ 
ain. One vol., i2mo. Cloth, $1.25. 

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Hours of Exercise in the Alps. 

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Faraday as a Discoverer. 

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Forms of Water, in Clouds, Rain, Rivers, 

Ice, and Glaciers. 

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Contributions to Molecular Physics in the 
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Lectures on Light delivered in America. 

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DESCRIPTIVE CATALOGUE 


OF 


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USTIDKX OF SUBJECTS. 


PA OK 

Anatomy. 1(3 

Anaesthesia. 26 

Acne. 4 

Body and Mind. 18 

Breath, and Diseases which give it a Fetid 
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Cerebral Convolutions. 7 

Chemical Examination of the Urine in Dis¬ 
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Chemical Analysis. 14 

“ Technology.31 

Chemistry of Common Life. 17 

Clinical Electro-Therapeutics. 12 

“ Lectures and Essays. 24 

Comparative Anatomy. 6 

Club-foot. 27 

Diseases of the Nervous System.10,12,13 

“ “ “ Bones. 20 

“ “ Women. 26, 27 

“ “ the Chest. 26 

“ “ Children. 25, 29 

“ “ the Rectum. 28 

“ “ “ Ovaries. 31 

Emergencies. 15 

Electricity and Practical Medicine. 19 

Foods. 27 

Galvano-Therapeutics. 20 

Hospitalism. 26 

Histology and Histo-Chemistry of Man.... 8 

Infancy. 6 

Insanity in its Relation to Crime. 12 

Materia Medica and Theiapeutics. 5, 23 

Medical Journal. 32 

Mental Physiology. 6 


PACK 

Midwifery. .. 26, 27 

Mineral Springs. 30 

N euralgia. 2 

Nervous System. 12,13 

Nursing...*. 22 

Obstetrics. 3, 7,26,27 

Ovarian Tumors. 23 

“ Diagnosis and Treatment.80 

Paralysis from Brain-Disease. 3 

Physiology. 6, 9, 10,11 

Physiology of Common Life. 17 

Physiology and Pathology of the Mind.18 

Physiological Effects of Severe Muscular 

Exercise. 12 

Pulmonary Consumption. 4 

Practical Medicine. 21 

Physical Cause of the Death of Christ. 26 

Popular Science. 32 

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Reports. 24 

Recollections of Past Life. 15 

“ of the Army of the Potomac.. 17 

Responsibility in Mental Diseases. 18 

Sea-Sickness. 2 

Surgical Pathology. 4 

“ Diseases of the Male Genito-Uri- 

nary Organs . 28 

Surgery, Conservative. 2 

“ Orthopedic. 25 

Syphilis. 28 

Science.32 

Skin-Diseases. 22 

Therapeutics. 5 

Uterine Therapeutics.27 

Winter and Spring. 4 


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I). Appleton & Co.’s Medical Publications. 


ANSTIE. 

Neuralgia, and Diseases which resemble it. 

By FRANCIS E. ANSTIE, M. D., F. R. C. P., 

Senior Assistant Physician to Westminster Hospital; Lecturer on Materia Medica in West¬ 
minster Hospital School; and Physician to the Belgrave Hospital for Children; Editor of 
“'J lie Practitioner" (London), etc. 

1 vol., 12mo. Cloth, $2.50, 

“It is a valuable contribution to scientific medicine. 1 ’— The Lancet {London). 

BARKER. 

The Puerperal Diseases, cunicai Lectures 

delivered at .Bellevue Hospital. 

By FORDYCE BARKER, M. D., 

Clinical Professor of Midwifery and the Diseases of Women in the Bellevue Hospital Medical 
College; Obstetric Physician to Bellevue Hospital; Consulting Physician to the New York 
State Women’s Hospital; Fellow of the New York Academy of Medicine; formerly Presi¬ 
dent of the Medical Society of the State of New York; Honorary Fellow of the Obstetrical 
Societies of London and Edinburgh; Honorary Fellow of the Royal Medical Society of 
Athens, Greece, etc., etc., etc. 

Third Edition. 1 vol., 8vo. Cloth. 526 pages. Price, $5 ; Sheep, $6. 

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on the puerperal diseases. Having had rather exceptional opportunities for the study of these 
diseases. I have felt it to be an imperative duty to utilize, so far as lay in my power, the advan¬ 
tages which T have enjoyed for the promotion of science, and, I hope, for the interests of human¬ 
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inculcated. At the present day, for the first time in the history of the world, the obstetric depart¬ 
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graded by its importance to society, or by the intellectual culture and ability required, as com¬ 
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physician, and yet know very little of obstetrics; or he may be a successful and distinguished 
surgeon, and be quite ignorant of even the rudiments of obstetrics. But no one can be a really 
able obstetrician unless he be both physician and surgeon. And, as the greater includes the less, 
obstetrics should rank as the highest department of our profession . 11 —From Author's Preface. 

o n Sea-Sickness, byfordyce barker, m. d. 

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number of that journal containing the paper, it is now presented in book form, with such pre¬ 
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BUCK. 

Contributions to Reparative Surgery: 

Showing its Application to the Treatment of Deformi¬ 
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and Cicatricial Contractions from Burns . 

By GURDON BUCK, M. D. 

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D. Appleton ct CoSs Medical Publications. 


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BARNES. 

ObstetllC Operations, including the Treatment of 

Haemorrhage , forming a Guide to the Management 

of Difficult Labor. 

By ROBERT BARNES, M. D., London, F. R. C. R, 

Obstetric Physician and Lecturer on Obstetrics and the Diseases of Women and Children (o St. 
George's Hospital: Examiner in Obstetrics to the Koval College of Physicians and t lx- IJoval 
College of Surgeons: President of the Metropolitan Branch of the British Medical A ssocia- 
tion ; late Examiner to the University of London ; formerly Obstetric Physician to the Lon¬ 
don and to St. Thomas Hospitals; and late Physician to the Eastern Division of the Koval 
Maternity Charity. 

Third Edition. Revised and extended. 1 vol„ 8vo. 606 pages. Cloth, $4.50. 

“ Snell a work ns Dr. Barnes's was greatly needed. It is calculated to elevate the practice of 
the obstetric art in this country, and to be of great service to the practitioner.”— Lancet. 

“ I'lii- book of Dr. Barnes is not. properly speaking, a dogmatic treatise-on obstetric opera¬ 
tions. 1 1 is a series of original lectures, corapi ising, at one and the same time, a practical analysis 
of the serious accidents in parturition, the rcasoned-out indications for, and the most judicious 
researches in the manner of operating, the method to choose, the instrument to prefer, and ihe 
details <>f the itiano-uvres rei|iiired to insure success. The clearness of the style is perfect.. The 
order, without being altogether riuorous, is what it is able to be generally in a scries of clinical 
lectures. The description of the instruments, the application of the forceps, cephalotripsy, em¬ 
bryotomy. Ciesart-an section, the practical reflections on narrowing and malformation of tlio pel¬ 
vis. ruptures of the uterus, placenta pra-via, haemorrhage, and, in fact, all tbo grand questions in 
obstetrics are treated with accurate good sense. At each instant, by some remark or other, is 
revealed a superior mind, ripened by having seen much and meditated much.”— From Preface 
to the French Edition by Prof. Pajot. 


B ASTI AN. 

Paralysis from Brain Disease in its 

Common Forms. 

By H. CHARLTON BASTIAN, M. A., M. D., F. R. S., 

Fellow of the Koval College of Physicians; Professor of Pathological Anatomy in University 
College. London: Physician to University College Hospital; and Senior Assistant Physician 
to the National Hospital for the Paralyzed and Epileptic. 

With Illustrations, 1 vol., 12mo. Cloth. $1.75. 

PREFACE. 

These Lectures were delivered in University College Hospital last year, at a time when I was 
doing duty for one of the senior physicians, and during the same year—after they had been re¬ 
produced from very full notes taken by my friend Mr. John Tweedy—they appeared in the pages 
of The Lancet,. 

They are now republished at the request of many friends, though only after having undergone 
a very careful revision, during which a considerable quantity of new matter has been added. It 
would have been easy to have very much increased the size of the book by the introduction of a 
larger number of illustrative cases, and by treatment of many of the subjects at greater length, 
but tiiis the author lias purposely abstained from doing, under the belief that in its present form 
it is likely to prove more acceptable to students, and also perhaps more useful to busy practi¬ 
tioners. 

Notwithstanding its defects and many shortcomings, the author is not without a hope that 
this little Iwiok may be considered in some measure to supply a deficiency which has long existed 
in medical literature. No department of medicine stands more in need of being represented in 
a text book of moderate compass; so that, imperfect as it is, this small work may perhaps be of 
some service till it is superseded bv something better. In it the author has endeavored to treat 
the subject with more precision than has hitherto been customary, and, while the lectures contain 
some novelties in method and mode of exposition, he hopes they may also be found not unfaith¬ 
fully to embody the principal facts at present known concerning this very important class of 
diseases. 





4 


D. Appleton <£• Co.\s Medical Publications , 


BENNET. 

On the Treatment of Pulmonary Con- 

sumption , by Hygiene , Climate , cmc? Medicine , m tV* 
Connection with Modern Doctrines. 

By JAMES nENRY BENNET, M. D., 

Member of the Royal College of Physicians, London ; Doctor of Medicine of the University of Paris, etc., etc. 

1 vol., thin 8vo. Cloth, $1.50. 

An interesting and instructive work, written in the strong, clear, and lucid manner which appears in all the con¬ 
tributions of Dr. Bennet to medical or general literature. 

*• We cordially commend this book to the attei.tion of all, for its practical common-sense views of the nature and 
treatment of tiie scourge of all temperate climates, pulmonary consumption .”—Detroit Review of Medicine. 


Winter and Spring on the Shores of 

the Mediterranean; or , the Riviera , Mentone , Italy , 
Corsica , Sicily , Algeria , Spain , Biarritz , as JPm- 

ter Climates. 

ThU work embodies the experience of ten winters and springs passed by Dr. Bennet on the shores of the Mediter¬ 
ranean, and contains much valuable information for physicians in relation to the health-restoring climate of the re¬ 
gions described. 

1 vol., 12mo. 621 pp. Cloth, $3.50. 

“ Exceedingly readable, apart from its special purposes, and well illustrated .”—Evening Commercial. 

“ It has a more substantial value for the physician, perhaps, than for any other class or profession. . . . We com¬ 
mend this book to our readers as a volume presenting two capital qualifications—it is at once entertaining and instruc¬ 
tive.”— N. Y. Medical Journal. 


BILLROTH. 

General Surgical Pathology and The- 

rapeutics , in Fifty Lectures. A Text-book for Students 
and Physicians. 

By Dr. THEODOR BILLROTH. 

Translated from the Fifth German Edition, with the special permission of the Author, by 

CHARLES E. HACKLEY, A. M., M. D., 

Surgeon to the New York Eye and Ear Infirmary; Physician to the New York Hospital; Fellow of the New York 

Academy of Medicine, etc. 

J vol., 8vo. 714 pp., and 152 Woodcuts. Cloth, $5.00; Sheep, $3.00. 

Professor Theodor Billroth, one of the most noted authorities on Surgical Pathology, gives in this volume a complete 
resume of the existing state of knowledge in this branch of medical science. The fact of this publication going through 
four editions in Germany, aud having been translated into French, Italian, Russian, and Hungarian, should be some 
guarantee for its standing. 

“ The want of a book In the English language, presenting in a concise form the views of the German pathologists, 
has long been felt; and we venture to say no book could more perfectly supply that want than the present volume! 
. . . We would strongly recommend it to all who take any interest in the progress of thought and observation in surgi¬ 
cal pathology, and surgery .”—The lancet. • 

“We can assure our readers that they will consider neither money wasted in its purchase, nor time in its perusal.” 
— 77. e Medical Investigator. r 

BULKLEY. 

Acne ; its Pathology, Etiology, Prog- 

nosis , and Treatment. 

By L. DUNCAN BULKLEY, A. M., M. D., 

New York Hospital. 

A monograph of about seventy pages, illustrated, founded on an analy¬ 
sis of two hundred cases of various forms of Acne. {In press.} 



5 


D. Appleton dc Co.'s Medical Publications. 


BARTHOLOW. 

A New Scientific and Practical Work 

on Materia Medica and Therapeutics. 

By ROBERTS BARTHOLOW, M. A., M. I)., 

Professor of the Theory and Practice of Medicine, and of Clinical Medicine, and formerly Profess¬ 
or of Materia Medica and Therapeutics in the Medical College of Ohio; Physician to the 
Hospital of the Good Samaritan; Corresponding Member of the New York Neurological 
Society; Author of a Manual of Hypodermic Medication, of the Russell Prize Essay on 
Quinine, of the American Medical Association Prize Essay on Atropia, and of the Eiske Eund 
Prize Essay on the Bromides, etc. 

One vol., 8vo. Cloth. 548 pages. Price, $ 5 . 00 . 


In this work, a volume of moderate compass, is condensed the whole subject 
of Materia Medica and Therapeutics, less the botanical and chemical details. The 
author has included just that kind of information which is required by the student 
and practitioner, and has omitted all those details now universally committed to 
the druggist and apothecary. The official names of individual remedies, and the 
German and French synonyms, are first given; then follows the list of pharma* 
•ceutical preparations, the composition of these and the doses; next the antago¬ 
nists and incompatibles, and the synergists. The author gives a full account of 
the physiological actions and the therapeutical applications of remedies, and he 
is especially full and explicit on these important topics. As he states in his 
preface: “In describing the physiological action of drugs, two methods may be 
pursued: to present in chronological order a summary of the opinions of various 
authorities on the subject in question; or to condense in a connected description 
that view of the subject which seems to the author most consonant with all the 
facts. I have adopted the latter plan, from a conviction of its advantages for the 
student, and of its utility for the practitioner.” 

The utmost brevity consistent with clearness is kept in view throughout. A 
very considerable portion of the book is devoted to the therapeutical applications 
of remedies. The author states on this point: “ As respects the therapeutical 
applications of remedies, I have, as far as practicable, based them on the physio¬ 
logical actions. Many empirical facts are, however, well founded in professional 
experience. Although convinced that the most certain acquisitions to therapeu¬ 
tical knowledge must come through the physiological method, I am equally clear 
that well-established empirical facts should not be omitted, even if they are not 
explicable by any of the known physiological properties of the remedies under 
discussion.” The practitioner will find in the therapeutical portion of the work 
numerous valuable formulae, adapted to the-exigencies of practice. 

This treatise discusses subjects not heretofore introduced into therapeutical 
works. The chapter on Aliment is quite full, and includes such topics as animal 
and vegetable aliment, special plans of diet, denutrition, dry diet, vegetable diet, 
animal diet, milk-diet, alimentation in acute diseases, in cachectic diseases, nutrient 
enemata, etc. The importance of knowledge on these subjects can hardly be 
over-estimated. 

Part I. treats of “the modes in which medicines are introduced into the organism.” 

Part II. treats of “ the actions and uses of remedial agents,” under the several subdivisions 
of “agents promoting constructive metamorphosis,” “agents promoting destructive metamor¬ 
phosis,” “agents used to modify the functions of the nervous system,” and “ agents used to cause 
some evacuation from the body.” 

Part III. treats of “ topical remedies,” and includes such topics as “ Antiseptics,” “ Counter- 
irritants,” “Epispastics,” “Acupuncture” “Baunscheidtismus,” “ Aquapuncture,” “Bloodlet¬ 
ting,” “ Escharotics“Emollients, Demulcents, and Protectives.” 

Scarcely any topic in therapeutics fails to receive attention, and all are dis¬ 
cussed with great conciseness, but clearly and adequately. 







6 


D. Appleton & Co's Medical Publications. 


CARPENTER. 

Principles of Mental Physiology, with 

their Applications to the Training and Discipline of the 
Mind and the Study of its Morbid Conditions. 

By WILLIAM B. CARPENTER, M. D., LL. D., F. R. S., F. L. S., F. G. S., 

Registrar of the University of London ; Corresponding Member of the Institute of France and of the American Philo. 

sophical Society, etc. 

1 vol., 8vo. Price, $3.00. 

u Among the numerous eminent writers this country has produced, none are more deserving of praise for having at* 
tempted to apply the results of Physiological Research to the explanation of the muturl relations of the mind and 
body than Dr. Carpenter. To him fielongs the merit of having scientifically studied and of having in many instances 
supplied a rational explanation of those phenomena which, under the names of mesmerism, spirit-rapping, electro- 
biolojry, and hypnotism, have attracted so large an amount of attention during the last twenty years. . . . We must 
conclude by recommending Dr. Carpenter’s work to the members of our own profession as applying many facts, that 
have hitherto stood isolated, to the explanation of the functions of the brain and to psychological processes "generally. 
—The Lancet. 


COMBE. 

The Management of Infancy, Physiologi¬ 
cal and Moral. Intended chiefly for the Use of 
Parents. 

By ANDREW COMBE, M. D. 

REVISED AND EDITED 

By Sir JAMES CLARK, K. C. B., M. D., F. R. S., 
Physician-in-ordinary to the Queen. 

First American from the Tenth London Edition. 1 vol., 12mo. 302 pp. 

Cloth, SI. 50. 

“This excellent little book should be in the hand of every mother of a family; and, if some 
of our lady friends would master its contents, and either bring up their children by the light of 
its teachings, or communicate the truths it contains to the poor by whom they are surrounded, 
we are convinced that they would effect infinitely more good than by the distribution of any 
number of tracts whatever. . . . We consider this work to be one of the few popular medical 
treatises that any practitioner may recommend to his patients; and, though, if its precepts are 
followed, he will probably lose a few guineas, he will not begrudge them if he sees his friend’s 
children grow up healthy, active, strong, and both mentally and physically capable.”— The 
Lancet. 


CHAUVEATJ. 

The Comparative Anatomy of the 

Domesticated Animals. 

By A. CHAUVEAU, 

PROFESSOR AT THE LYONS VETERINARY SCHOOL. 

Second edition, revised and enlarged, with the cooperation of S. ARLOING, 
late Principal of Anatomy at the Lyons Veterinary School; Professor at the 
Toulouse Veterinary School. Translated and edited by GEORGE FLEMING, 
F. R. G. S., M. A. I., Veterinary Surgeon, Royal Engineers. 

1 vol., 8vo. Cloth. 957 pp., with 450 Illustrations. Price, $6.00. 




1 


D. Appleton & Co.'s Medical Publications. 


DAYIS. 

Conservative Surgery, as exhibited in remedying 

some of the Mechanical Causes that operate injuriously 
both in Health and Disease. With Illustrations. 

By HENRY G. DAVIS, M. D., 

Member of the American Medical Association, etc., etc. 

1 vol., 8vo. 315 pp. Cloth, $3.00. 

The author has enjoyed rare facilities for the study and treatment of certain classes of disease, 
and the records here presented to the profession are the gradual accumulation of over thirty 
years’ investigation. 

“Dr. Davis, bringing, as he does to his specialty, a great aptitude for the solution of mechani¬ 
cal problems, takes a high rank as an orthopedic surgeon, and his very practical contribution to 
the literature of the subject is both valuable and opportune. We deem it worthy of a place in 
every physician’s library. The style is unpretending, but trenchant, graphic, and, best of alL 
<quite intelligible.”— Medical Record. 


ECKER. 

The Cerebral Convolutions of Man, 

represented according to Personal Investigations, espe¬ 
cially on their Development in the Foetus, and with ref¬ 
erence to the Use of Physicians. 

By ALEXANDER ECKER, 

Professor of Anatomy and Comparative Anatomy in the University of Freiburg. 

Translated from the German by Robert T. Edes, M. D. 

1 vol., 8vo. 87 pp. $1.25. 

“The work of Prof. Ecker is noticeable principally for its succinctness and clearness, avoiding 
long discussions on undecided points, and yet sufficiently furnished with references to make easy 
Its comparisons with the labors of others in the same direction. 

“ Entire originality in descriptive anatomy is out of the question, but the facts verified by our 
author are here presented in a more intelligible manner than in any other easily-accessible work. 

“The knowledge to be derived from this work is not furnished by any other text-book in the 
English language.”— Boston Medical and Surgical Journal , January 20,1878. 

ELLIOT. 

Obstetric Clinic. A Practical Contribution to the Study 
of Obstetrics, and the Diseases of Women and Children . 
By the late GEORGE T. ELLTOT, M. D., 

Late Professor of Obstetrics and Diseases of Women and Children in the Bellevue Hospital 
Medical College; Physician to Bellevue Hospital and to the New York Lying-in Asylum; 
Consulting Physician to the Nursery and Child's Hospital; Consulting Surgeon to the State 
Woman’s Hospital; Corresponding Member of the Edinburgh Obstetrical Society and of the 
Royal Academy of Havana; Fellow of the N. Y. Academy of Medicine; Member of the 
County Medical Society, of the Pathological Society, etc., etc. 

1 vol., 8vo. 458 pp. Cloth, $4.50. 

This work is. In a measure, a resume of separate papers previously prepared by the late Dr. 
Elliot; and contains, besides, a record of nearly two hundred important and difficult cases in mid¬ 
wifery, selected from his own practice. It has met with a hearty reception, and has received th# 
highest encomiums both in this country and in Europe. 





8 


D. Appleton ci’ Co.'s Medical Publications. 

FREY. 

The Histology and Histo-Chemistry 

of Man. A Practical Treatise on tlxe Elements of Com - 
position and Structure of the Human Body. 

By HEINRICH FREY, 

Professor of Medicine in Zurich. 

Translated from the Fourth German Edition, "by Arthur E. J. Barker, 

Surgeon to the City of Dublin Hospital; Demonstrator of Anatomy, Royal College of Surgeons, 
Ireland; Visiting Surgeon, Convalescent Home, Stillorgan; and revised by the Author^ 
With 080 Engravings. 

1 vol., 8vo. Cloth, $5.00; Sheep, $6.00. 

CONTENTS. 

The Elements of Composition and of Structure of the Body: Elements of Composition—Al¬ 
buminous or Protein Compounds, Ilsemoglobulin, Ilistogenic Derivatives of the Albuminous 
Substances or Albuminoids, the Fatty Acids and Fats, the Carbohydrates, Non-Nitrogenous 
Acids, Nitrogenous Acids, Amides, Amido-Acids, and Organic Bases, Animal Coloring Matters, 
Cyanogen Compounds, Mineral Constituents; Elements of Structure—the Cell, the Origin of the 
Remaining Elements of Tissue; the Tissues of the Body—Tissues composed of Simple Cells, with 
Fluid Intermediate Substance, Tissues composed of Simple Cells, with a small amount of Solid 
Intermediate Substance, Tissues belonging to the Connective-Substance Group, Tissues com¬ 
posed of Transformed, and, as a rule, Cohering Cells, with Homogeneous, Scanty, and more or less 
Solid Intermediate Substance, Composite Tissues: The Organs of the Body—Organs of the 
Vegetative Type, Organs of the Animal Group. 

FLINT. 

Manual of Chemical Examination of 

the Urine in Disease. With Brief Directions for the 
Examination of the most Common Varieties of Urinary 
Calculi. 


By AUSTIN FLINT, Jr., M.D., 

Professor of Physiology and Microscopy in the Bellevue Hospital Medical College; Fellow of the 
New York Academy of Medicine; Member of the Medical Society of the County of New 
York; Resident Member of the Lyceum of Natural History in the City of New York, etc. 

Third Edition, revised and corrected. 1 vol., 12mo. 77 pp. Cloth, $1.00. 

The chief aim of this little work is to enable the busy practitioner to make for 
himself, rapidly and easily, all ordinary examinations of Urine; to give him the 
benefit of the author’s experience in eliminating little difficulties in the manipula¬ 
tions, and in reducing processes of analysis to the utmost simplicity that is con¬ 
sistent with accuracy. 

“ We do not know of any work in English so complete and handy as the Manual now offered 
to the Profession by Dr. Flint, and the high scientific reputation of the author is a sufficient 
guarantee of the accuracy of all the directions given .”—Journal of Applied Chemistry. 

“Wo can unhesitatingly recommend this Manual .”—Psychological Journal. 

“ Eminently practical .”—Detroit Review of Medicine. 





D. Appleton & Co.'s Medical Publications. 


9 


FLINT. 

The Physiology of Man. Designed to rep* 

resent the Existing State of Physiological Science as 
applied to the Functions of the Human Body. 


By AUSTIN FLINT, Jk., M. D., 

Professor of Physiology and Microscopy in the Bellevue Hospital Medical College, and in the 
to BeUeviw^Iospital.^ 08 ^ 1 ^ ’ * eow ^ ow Academy of Medicine; Microscopist 

lfew and thoroughly revised Edition. In Five Volumes. 8vo. Tinted Paper. 

Volume I .—The Blood ; Circulation ; Bespiration. 


8vo. 502 pp. Cloth, $4.50. 

“ If the remaining portions of this work are compiled with the same care and 
accuracy, the whole may vie with any of those that have of late years been pro¬ 
duced in our own or in foreign languages.”— British and Foreign Medico-Chirurqi. 
cal Review. * 

“ As a book of general information it will be found useful to the practitioner, 
and, as a book of reference, invaluable in the hands of the anatomist and physi¬ 
ologist.”— Dublin Quarterly Journcd of Medical Science. 

“ The complete work will prove a valuable addition to our systematic treatisea 
on human physiology.”— The Lancet. 

“ To those who desire to get in one volume a concise and clear, and at the 
same time sufficiently full resume of ‘ the existing state of physiological science,’ 
we can heartily recommend Dr. Flint’s work. Moreover, as a work of typographi¬ 
cal art it deserves a prominent place upon our library-shelves. Messrs. Appleton 
A Co. deserve the thanks of the profession for the very handsome style in which 
they issue medical works. They give us hope of a time when it will be very 
generally believed by publishers that physicians’ eyes are worth saving.”_ Medi¬ 

co/ Gazette. 


Volume II.— Alimentation; Digestion; Absorptionf 
Lymph and Chyle. 

8vo. 556 pp. Cloth, $4.50. 


“ The second instalment of this work fulfils all the expectations raised by the 
perusal of the first. . . . The author’s explanations and deductions bear 

evidence of much careful reflection and study. . . . The entire work is one 

of rare interest. The author’s style is as clear and concise as his method is 
studious, careful, and elaborate.”— Philadelphia Inquirer. 

“ We regard the two treatises already issued as the very best on human physi¬ 
ology which the English or any other language affords, and we recommend them 
with thorough confidence to students, practitioners, and laymen, as models of 
literary and scientific ability.”— F. Y. Medical Jow^nal. 

“ We have found the style easy, lucid, and at the same time terse. The prac¬ 
tical and positive results of physiological investigation are succinctly stated, 
without, it would seem, extended discussion of disputed points.”— Boston Medical 
and Surgical Journal. 

“ It is a volume which will be welcome to the advanced student, and as a 
work of reference.”— The Lancet. 

“ The leading subjects treated of are presented in distinct parts, each of which 
is designed to be an exhaustive essay on that to which it refers.”— Western Jour¬ 
nal of Medicine. 





i 


10 D. Appleton tO Co's Medical Publications. 


Flint’s Physiology. Volume III. — Secretion / 

cretion y Ductless Glands / Nutrition y Animal Heat y 
Movements y Voice Speech. 

8vo. 526 pp. Cloth, $4.50. 

“ Dr. Flint’s reputation is sufficient to give a character to the book among the 
profession, where it will chiefly circulate, and many of the facts given have been 
verified by the author in his laboratory and in public demonstration.”— Chicago 
Courier. 

“The author bestows judicious care and labor. Facts are selected with dis¬ 
crimination, theories critically examined, and conclusions enunciated with com¬ 
mendable clearness and precision.”— American Journal of the Medical Sciences. 

Volume IV. — The Nervous System. 

8vo. Cloth, $4.50. 

This volume embodies the results of exhaustive study, and of a long and 
laborious series of experiments, presented in a manner remarkable for its strength 
and clearness. No other department of physiology has so profound an interest 
for the modern and progressive physician as that pertaining to the nervous 
system. The diseases of this system are now engaging the study and attention 
of some of the greatest minds in the medical world, and in order to follow their 
brilliant discoveries and developments, especially in connection with the science 
of electrology, it is absolutely necessary to obtain a clear and settled knowledge 
of the anatomy and physiology of the nervous system. It is the design of this 
work to impart that knowledge free from the perplexing speculations and uncer¬ 
tainties that have no real value for the practical student of medicine. The 
author boldly tests every theory for himself, and asks his readers to accept noth¬ 
ing that is not capable of demonstration. The properties of the cerebro-spinal, 
nervous, and sympathetic systems are treated of in a manner at once lucid, 
thorough, and interesting. 

Although this volume is one, perhaps the most important one, of the author’s 
admirable series in the Physiology of Man, it is nevertheless complete in itself^ 
and may be safely pronounced indispensable to every physician who takes a pride 
and interest in the progress of medical science. 

Volume V. —Special Senses ; Generation. 

8vo. Cloth, $4.50. 

“ The present volume completes the task, begun eleven years ago, of preparing 
a work, intended to represent the existing state of physiological science, as ap¬ 
plied to the functions of the human body. The kindly reception which the first 
four volumes have received has done much to sustain the author in an under¬ 
taking, the magnitude of which he has appreciated more and more as the work 
has progressed. 

“ In the fifth and last volume, an attempt has been made to give a clear account 
of the physiology of the special senses and generation, a most difficult and delicate 
undertaking. . . . 

“ Finally, as regards the last, as well as the former volumes, the author can 
only say that he has spared neither time nor labor in their preparation; and the 
imperfections in their execution have beeu due to deficiency in ability and oppor¬ 
tunity. He indulges the hope, however, that he has written a book which may 
assist his fellow-workers, and interest, not only the student and practitioner of 
medicine, but some others who desire to keep pace with the progress of Natural 
/Science. ’ ’ — Extracts from Preface , 





D. Appleton & Co's Medical Publications. 


11 


Flint’s Text-Book of Human Physi- 

f or the Use of Students and Practitioners of Medi¬ 
cine. 

In one large octavo volume of 978 pages, elegantly printed on fine paper, and 
profusely illustrated with three Lithographic Plates and 313 Engrav¬ 
ings on Wood. Price, in cloth, $6.00; sheep, $7.00. 

While Prof. Flint’s “Physiology of Man,” in five octavo volumes, also published by D. Apple- 
ton & Co., is invaluable as a book of reference, giviDg an epitome of the literature of physiology, 
with copious references to other authors, the publishers have appreciated the necessity for a new 
text-book, for the use of students and practitioners of medicine. 

This new work is intended to meet this pressing want, and it contains most of the facts pre¬ 
sented in the larger treatise, without historical references or discussions of minor and contro¬ 
verted questions. The high reputation of the author as a public teacher, and the success of the 
larger treatise, render it certain that the “ Text-book ” will be admirably adapted to the wants of 
medical students. 

In the “ Text-book,” all important points connected with Human Physiology are treated of 
fully and clearly, and many subjects, such as the Nervous System, the Special Senses, etc., the 
treatment of which is barren and unsatisfactory in many works written or republished in this 
country, are brought fully up to the requirements of the day. 

The publishers have given great attention to the execution of the illustrations, few of which 
are familiar to American readers. It being almost impossible to reproduce some of the cuts 
taken from foreign works, they have succeeded in obtaining abroad about one hundred electro¬ 
types from the original engravings contained in Sappey’s great work upon Anatomy, which are 
unequaled in their mechanical execution. The subject of Generation is also illustrated by litho¬ 
graphic plates taken from Haeckel. 

The great care necessary in the printing of the elaborate illustrations has caused an unavoid¬ 
able delay in the appearance of the work; but the publishers feel confident that it will fully meet 
their expectations, and justify the reputation of its author. 

“ In preparing this text-book for the use of students and practitioners of medicine, I have en¬ 
deavored to adapt it to the wants of the profession, as they have appeared to me after a consider¬ 
able experience as a public teacher of human physiology. My large treatise in five volumes is 
here condensed, and I have omitted bibliographical citations and matters of purely historical in¬ 
terest. Many subjects, which were considered rather elaborately in my larger work, are here 

E resented in a much more concise form. I have added, also, numerous illustrations, which I 
ope may lighten the labors of the student. A few of these are original, but by far the greatest 
part has been selected from reliable authorities. I have thought it not without historical interest 
to reproduce exactly some of the classical engravings from the works of great discoverers, such 
as illustrations contained in the original editions of Fabricius, Harvey, and Asellius. In addition, 
I have reproduced a few of the beautiful microscopical photographs taken at the United States 
Army Medical Museum, under the direction of Dr. J. J. Woodward, to whom I here express my 
grateful acknowledgments. I have also to thank M. Sappey for his kindness in furnishing 
electrotypes of many of the superb engravings with which his great work upon Anatomy is illus¬ 
trated. 

“ My work in five volumes was intended as a book of reference, which I hope will continue to 
be useful to those who desire an account of the literature of physiology, as well as a statement of 
the facts of the science. I have always endeavored, in public teaching, to avoid giving undue 
prominence to points in which I might myself be particularly interested, from having made them 
subjects of special study or of original research. In my text-book I have carried out the same 
idea, striving to teach, systematically and with uniform emphasis, what students of medicine are 
expected to learn in physiology, and avoiding elaborate discussions of subjects not directly con¬ 
nected with practical medicine, surgery, and obstetrics. While I have referred to my original 
observations upon the location of the sense of want of air in the general system, the new ex¬ 
cretory function of the liver, the function of glycogenosis, the influence of muscular exercise upon 
the elimination of urea, etc., I have not considered these subjects with great minuteness, and 
have generally referred the reader to monographs for the details of my experiments. 

“ Finally, m presenting this work to the medical profession, I cannot refrain from an expres¬ 
sion of my acknowledgments to the publishers, who have spared nothing in carrying out mr 
views, ana have devoted special pains to the mechanical execution of the illustrations.”— Author # 
Prtfac4. 




D. Appleton Co.'s Jfedical Publicatiofis. 


u 


FLINT. 

On the Physiological Effects of Severe 

and Protracted Muscular Exercise. With special refer¬ 
ence to its Influence upon the Excretion of Nitrogen. 

By AUSTIN FLINT, Jr., M. D., 

Professor of Physiology in the Bellevue Hospital Medical College, New York, etc., etc. 

1 vol., 8vo. 91 pp. Cloth, SI.00. 

This monograph on the relations of Urea to Exercise is the result of a thorough and careful 
Investigation made in the case of Mr. Edward Payson Weston, the celebrated pedestrian. The 
chemical analyses were made under the direction of R. O. Doremus, M. D., Professor of Chemistry 
and Toxicology in the Bellevue Hospital Medical College, by Mr. Oscar Loew, his assistant. The 
observations were made with the cooperation of J. C. Dalton, M. D , Professor of Physiology in 
the College of Physicians and Surgeons; Alexander B. Mott, M. D., Pi-ofessor of Surgical Anat¬ 
omy; W. H. Van Buren, M. D., Pi-ofessor of Px-inciples of Sux-gery; Austin Flint, M. D., Px-o¬ 
fessor of the Principles and Practice of Medicine; W. A. Hammond, M. D., Px-ofessor of Diseases 
of the Mind and Nervous System—all of the Bellevue Hospital Medical College. 

“This work will be found interesting to every physician. A number of important results 
were obtained valuable to the physiologist.”— Cincinnati Medical Repertory. 


HAMILTON. 

Clinical Electro-Therapeutics. [Medical and 

Surgical.) A Manual for Physicians for the Treatment 
more especially of Nervous Diseases. 

By ALLAN McLANE HAMILTON, M. D., 

Physician in charge of the New York State Hospital for Diseases of the Nervous System; Mem¬ 
ber of the New York Neurological and County Medical Societies, etc., etc. 

With Numerous Illustrations. 1 vol., 8vo. Cloth. Price, $2.00. 

This work is the compilation of well-tried measures and i-eported cases, and is intended as a 
simple guide for the general practitioner. It is as free from confusing theoi-ies, technical terms, 
and unproved statements, as possible. Electricity is indorsed as a very valuable remedy in cer¬ 
tain diseases, and as an invaluable therapeutical means in nearly all forms of Nervous Diskasr; 
but not as a specific for every human ill, mental and physical. 

HAMMOND. 

Insanity in its Relations to Crime, a 

Text and a Commentary. 

By WILLIAM A. HAMMOND, M. D. 

1 vol., 8vo. 77 pp. Cloth, SI.00. 

“ A- P ar t of this essay, under the title ‘ Society versus Insanity,’ was contributed to Putnam's 
Magazine , for September, 1S70. The greater portion is now first published. The importance of 
the subject considered can scarcely be over-estimated, whether we regard it from the stand-point 
of science or social economy; and, if I have aided in its elucidation, my object will have been at¬ 
tained.”— From Author's Pi'eface. 


Clinical Lectures on Diseases of the 

Nervous System. Delivered at the Bellevue Hospital 
Medical College. 


By WILLIAM A. HAMMOND, M. D., 

Professor of Diseases of the Mind and Nervous System, etc. Edited, with Notes, by T. M. B. 
. CROSS, M. D., Assistant,to the Chairs of Diseases of the Mind and Nervous System, etc. 

In one handsome volume of 300 pages. Price, S3.50. 




D. Appleton & Co's Medical Publications. 


13 


HAMMOND. 

A Treatise on Diseases of the Nervous 

System . 

By WILLIAM A. HAMMOND, M. D., 

Professor of Diseases of the Mind and Nervous System in the Medical Department of the Univer¬ 
sity of the City of New York; President of the New York Neurological Society, etc., etc. 

Sixth Edition. 1 vol., 8vo. Strong- Cloth Binding, $6.00; Sheep, $7.00. 

The remarkable success attendant on the issue of the five previous editions of this work in 
less than four years has encouraged the author and publishers to attempt to make the work still 
more worthy the confidence of the medical profession. A great part of the treatise has been en¬ 
tirely rewritten, and several new chapters have been added. By a change in type, and enlarging 
the page, the new matter, amounting to one-half of the original work, has been added without 
increasing materially the bulk of the volume. Many new illustrations have been incorporated in 
the text, and the whole treatise has been brought fully up to the present time. In addition to 
the fund of personal observation and experience adduced by Prof. Hammond, the labors of Eng¬ 
lish, French, and German writers have received due attention. 

Among the diseases considered in the present edition, which were not treated of in the former 
editions, are: Chronic Verticalar Meningitis; Chronic Basilar Meningitis; Cervical Pachy-Men- 
ingitis; Spinal Paralysis of Adults; Amyotrophic Lateral Spinal Sclerosis; Facial Atrophy; 
Organic Diseases of Nerves; Chronic Alcoholic Intoxication; Delirium Tremens; Exophthalmic 
Goitre; and Anapeiratic Paralysis—paralysis induced by a frequent repetition of certain muscular 
actions. Besides which, extensive alterations and additions have been made to the remarks on 
other auctions— the departments of Morbid Anatomy, Pathology, and Treatment, being espe¬ 
cially amplified. 

NOTICES OF FORMED EDITIONS. 

“ Free from useless verbiage and obscurity, it is evidently the work of a man who knows what 
he is writing about, and knows how to write about it.”— Chicago Medical Journal. 

“Unquestionably the most complete treatise on the diseases to which it is devoted which has 
yet appeared in the English language.”— London Medical Times and Gazette. 

“This is a valuable and comprehensive book; it embraces many topics, and extends over a 
wide sphere. One of the most valuable parts of it relates to the Diseases of the Brain; while the 
remaining portion of the volume treats of the Diseases of the Spinal Cord, the Cerebro-spinal 
System, the Nerve-Cells, and the Peripheral Nerves.”— British Medical Journal. 

“The work before us is unquestionably the most exhaustive treatise, on the diseases to which 
it is devoted, that has yet appeared in English. And its distinctive value arises from the fact 
that the work is no mere rafficiamento of old observations, but rests on his own experience and 
practice, which, as we have before observed, have been very extensive.”— American Journal of 
Syphilography. 

“The author of this work has attained a high rank among our brethren across the Atlantic 
from previous labors in connection with the disorders of the nervous system, as well as from 
various other contributions to medical literature, and he now holds the official appointments of 
Physician to the New York State Hospital for the Diseases of the Nervous System, and Professor 
of the same department in the Bellevue Hospital Medical College. The present treatise is the 
fruit of the experience thus acquired, and we have no hesitation in pronouncing it a most valu¬ 
able addition to our systematic literature.”— Glasgow Medical Journal. 




14 


D. Appleton <& Co.’s Medical Publications. 


HOFFMANN. 


Manual of Chemical Analysis, as applied 

to the Examination of Medicinal Chemicals and their 
Preparations. A Guide for the Determination of their 
Identity and Quality , and for the Detection of Impuri¬ 
ties and Adulterations. For the use of Pharmaceutists , 
Physicians , Druggists , and Manufacturing Chemists , and 
Pharmaceutical and Medical Students. 

By FRED. HOFFMANN, Phil. D. 


One vol., 8vo. Richly Illustrated. Cloth. Price, $3. 

SPECIMEN OF ILLUSTRATIONS. 



This volume is a cnrefhlly-prepared work, and well np to the existing state of both the science 
ma art of modern pharmacy. It is a hook which will find its place in every medical and phar- 
maceutlcal laboratory and library, and is a safe and instructive guide to medical students and 
practitioners of medicine .”—American Journal of Science and Arte. 

In America this work has already met with general and unqualified approval; and in Europe 
is now being welcomed as one of the best and most important additions to modern pharmaceu¬ 
tical literature. 

Send for descriptive circular. Address 

D. APPLETON & CO., 549 & 551 Broadway, N. Y. City. 













D. Appleton & Co.'s Medical Publications . 


15 


HOLLAND. 

Recollections of Past Life, 

By SIR HENRY HOLLAND, Bart., M. D., F. R. S M K. C. B., etc., 

President of the Royal Institution of Great Britain, Physician-in-Ordinary to the Queen, 

etc., etc. 

1 vol., 12mo, 351 pp. Price, Cloth, $2.00. 

A very entertaining and instructive narrative, partaking somewhat of the nature of 
autobiography and yet distinct from it, in this, that its chief object, as alleged by the 
writer, is not so much to recount the events of his own life, as to perform the office of 
chronicler for others with whom he came in contact and was long associated. 

The “Life of Sir Henry Holland ” is one to be recollected, and he has not erred in giv¬ 
ing an outline ol it to the public.”— The Lancet. 

“ His memory was—is, we may say, for he is still alive and in possession of all his 
faculties—stored with recollections of the most eminent men and women of this cen¬ 
tury. ... A life extending over a period cf eighty-four years, and passed in the most 
active manner, in the midst of the b»st society, which the world has to offer, must neces¬ 
sarily be full of singular interest; and Sir Henry Holland has fortunately not waited until 
his memory lost its freshness before recalling some of the incidents in it.”— The New 
York Times. 


HOWE. 

Emergencies, and Howto Treat Them. 

The Etiology , Pathology , and Treatment of Accidents , 
Diseases , and Cases of Poisoning , which demand 
Prompt Attention. Designed for Students and Prac¬ 
titioners of Medicine. 


By JOSEPH W. HOWE, M. D., 

Clinical Professor of Surgery in the Medical Department of the University of New York 
Visiting Surgeon to Charity Hospital; Fellow of the New York Academy 
of Medicine, etc., etc. 

1 vol., Svo. Cloth, $3.00. 

“This work has a taking title, and was written by a gentlemen of acknowledged ability, to 
fill a void in the profession. ... To the general practitioner in towns, villages, and in the 
country, where the aid and moral support of a consultation cannot be availed of, this volume 
will be recognized as a valuable help. We commend it to the profession. -Oincinnatl Lancet 
and Observer. 

“ This work is certainly novel in character, and its usefulness and acceptability are as marked 
as its novelty. . . . The book is confidently recommended.”— Richmond and Louisville Med¬ 
ical Journal. , „ „ , , 

w This volume is a practical illustration of the positive side of the physician s life, a constant 
reminder of what he is to do in the sudden emergencies which frequently occur in practice. 

The author wastes no words, but devotes himself to the description of each disease as if 
the patient were under his hands. Because it is a good book we recommend it most heartily to 
the profession.”— Boston Medical and Surgical Journal. , 

“This work bears evidence of a thorough practical acquaintance with the different branches 
of the profession. The author seems to possess a peculiar aptitude for imparting instruction 
as well as for simplifying tedious details. ... A careful perusal will amply repay the student 
and practitioner. 1 — New York Medical Journal .” , . _ , 7 . « 

“This is the best work of the kind we have ever seen. — hew 5 ork Journal of Psychological 

Medicine. 






16 


I). Appleton db Co.'s Medical Publications. 


HOWE. 

The Breath, and the Diseases which give 

it a Fetid Odor. With Directions for Treatment . 

By JOSEPH W. HOWE, M.D., 

uthor of “Emergencies,” “Winter Homes,” etc; Clinical Professor of Surgery in the Medical 

Department of the University of New York; Visiting Surgeon to Charity and St. Francis 

Hospitals; Fellow of the New* York Academy of Medicine, etc. 

“ It is somewhat remarkable that the subject of fetid breath, which occasions so much annoy¬ 
ance. . . . should have attracted so little attention from authors and investigators. Hence a 
thoroughly scientific exposition of the whole subject, such as Dr. Howe has given us, has long 
been a desideratum. . . . This little volume well deserves the attention of physicians, to whom 
we commend it most highly.”— Chicago Medical Journal. 

“To any one suffering from the affection, either in his own person or in that of his inti¬ 
mate acquaintances, we can commend this volume as containing all that is known concerning the 
subject, set forth in a pleasant style.”— Philadelphia Medical Times. 

“ This little work is on a subject that has heretofore been almost entirely ignored by medical 
authors, yet its importance is well known by every practitioner. . . . The author gives a succinct 
account of the diseased conditions in which a fetid breath is an important symptom, with his 
method of treatment. We consider the work a real addition to medical literature.”— Cincinnati 
Medical Journal. 

HUXLEY AND YOUMANS. 

The Elements of Physiology and Hy- 

giene. With Numerous Illustrations. 

By THOMAS H. HUXLEY, LL. D., F.R.S., and 
WILLIAM JAY YOUMANS, M. D. 

New and Eevised Edition. 1 vol., 12mo. 420 pp. Si.75. 

A text-book for educational institutions, and a valuable elementary work for students of medi¬ 
cine. The greater portion is from the pen of Professor Huxley, adapted by Dr. Youmans to the 
circumstances and requirements of American education. The eminent claim of Professor Hux¬ 
ley’s “Elementary Physiology” is, that, while up to the times, it is trustworthy in its presenta¬ 
tion of the subject; while rejecting discredited doctrines and doubtful speculations, it embodies 
the latest results that are established, and repx-esents the present actual state of physiological 
knowledge. 

“ A valuable contribution to anatomical and physiological science.”— Religious Telescope. 

“ A clear and well arranged work, embracing the latest discoveries and accepted theories.”— 
Buffalo Commercial. 

“Teeming with information concerning the human physical economy.”— Evening Journal. 

HUXLEY. 

The Anatomy of Vertebrated Animals. 

By TIIOMAS HENRY HUXLEY, LL. D., F. R. S., 

Author of “ Man’s Place in Nature,” “ On the Origin of Species,” “ Lay Sermons and Addresses,” 

etc. 

1 vol., 12mo. Cloth, $2.50. 

The former works of Prof. Huxley leave no room for doubt as to the importance and value of 
his new volume. It is one which win be very acceptable to all who are interested in the subject 
of which it treats. 

“This long-expected work will be cordially welcomed by all students and teachers of Com¬ 
parative Anatomy as a compendious, reliable, and, notwithstanding its small dimensions, most 
comprehensive guide on the subject of which it treats. To praise or to criticise the work of so 
accomplished a master of his favorite science would be equally out of place. It is enough to say 
that it realizes, in a remarkable degree, the anticipations which have been formed of it; and that 
it presents an extraordinary combination of wide, general views, with the clear, accurate, and 
succinct statement of a prodigious number of individual facts.”— Mat" re. 







D, Appleton <fc Co.'s Medical Publications. 


17 


JOHNSON. 

The Chemistry of Common Life. 

Illustrated with numerous Wood Engravings. 

By JAMES F. JOHNSON, M. A., F. R. S., F. G. S., etc., eto., 

Author of “Lectures on Agricultural Chemistry and Geology,” “A Catechism of Agricultural 
Chemistry and Geology,” etc. 

2 vols., 12mo. Cloth, $3.00. 

It has been the object of the author in this work to exhibit the 
present condition of chemical knowledge, and of matured scientific 
opinion, upon the subjects to which it is devoted. The reader will not 
be surprised, therefore, should lie find in it some things which differ 
from what is to be found in other popular works already in his hands or 
on the shelves of his library. 

LETTERMAN. 

Medical Recollections of the Army of 

the Potomac. 

By JONATHAN LETTERMAN, M. D., 

Late Surgeon U. S. A., and Medical Director of the Army of the Potomac. 

1 vol., 8vo. 194 pp. Cloth, $1.00. % 

“ This account of the medical department of the Army of the Poto¬ 
mac has been prepared, amid pressing engagements, in the hope that 
the labors of the medical officers of that army may be known to an in¬ 
telligent people, with whom to know is to appreciate; and as an affeo 
tionate tribute to many, long my zealous and efficient colleagues, who, 
in days of trial and danger, which have passed, let us hope never to re¬ 
turn, evinced their devotion to their country and to the cause of hu¬ 
manity, without hope of promotion or expectation of reward.”— Preface. 

“We venture to assert that but few who open this volume of medical annals, 
pregnant as they are with instruction, will care to do otherwise than finish them 
at a sitting.”— Medical Record. 

“ A graceful and affectionate tribute.”— N. Y. Medical Journal. 

LEWES. 

The Physiology of Common Life. 

By GEORGE HENRY LEWES, 

Author of “ Seaside Studies,” “ Life of Goethe,” etc. 

2 V0l3., 12mo. cloth, $3.00. 

The object of this work differs from that of all others on popular 
science in its attempt to meet the wants of the student, while meeting 
those of the general reader, who is supposed to be wholly unacquainted 
with anatomy and physiology. 




18 


D. Appleton & Co's Medical Publications. 


MAUDSLEY. 

The Physiology and Pathology of the 

Mind. 


By HENRY MAUDSLEY, M. D., London, 

Fellow of the Royal College of Physicians; Professor of Medical Jurisprudence in University Col¬ 
lege, London; President-elect of the Medico-Psychological Association; Honorary Member of 
the Medico-Psychological Society of Paris, of the Imperial Society of Physicians of Vienna, 
and of the Society for the Promotion of Psychiatry and Forensic Psychology of Vienna; 
formerly Resident Physician of the Manchester Royal Lunatic Asylum, etc., etc. 

1 vol., 8vo. 422 pp. Cloth, $3.00. 

This work aims, in the first place, to treat of mental phenomena from a 
physiological rather than from a metaphysical point of view; and, secondly, to 
bring the manifold instructive instances presented by the unsound mind to bear 
upon the interpretation of the obscure problems of mental science. 

“ Dr. Maudsley has had the courage to undertake, and the skill to execute, what is, at least in 
English, an original enterprise.”—London Saturday Review. 

" It is so full of sensible reflections and sound truths that their wide dissemination could not 
but be of benefit to all thinking persons .”—Psychological Journal. 

“ Unquestionably one of the ablest and most important works on the subject of which it 
treats that has ever appeared, and does credit to his philosophical acumen and accurate observa¬ 
tion .”—Medical Record. 

“ We lay down the book with admiration, and we commend it most earnestly to our readers 
as a work of extraordinary merit and originality—one of those productions that are evolved only 
occasionally in the lapse of years, and that serve to mark actual and very decided advantages in 
knowledge and science.”— N. Y. Medical Journal. 


Body, and Mind : An Inquiry into their Con¬ 
nection and Mutual Influence , especially in reference to 
Mental Disorders; an enlarged and revised edition to 
which are added Psychological Essays. 

i 

By HENRY MAUDSLEY, M. D., London, 

Author of “The Physiology and Pathology of the Mind.” 

1 vol., 12mo. 155 pp. Cloth, $1.00. 

The general plan of this work may be described as being to bring man, both 
in his physical and mental relations, as much as possible within the scope of sci¬ 
entific inquiry. 

“ A representative work, which every one must study who desires to know what is doing in the 
way of real progress, and not mere chatter, about mental physiology and pathology.”— Lancet. 

“ It distinctly marks a step in the progress of scientific psychology.”— The Practitioner. 

Responsibility in Mental Diseases. 

By HENRY MAUDSLEY, M. D., London, 

Author of “ Body and Mind,” “ Physiology and Pathology of the Mind.” 

1 vol., 12mo. 313 pp. Cloth, $1,50. 

“ This book is a compact presentation of those facts and principles which require to be taken 
into account in estimating human responsibility—not legal responsibility merely, but responsi¬ 
bility for conduct in the family, the school, and all phases of social relation in which obligation 
enters as an element. The work is new in plan, and was written to supply a wide-felt want 
which has not hitherto been met.”— The Po/mlar Science Monthly. 




D. Appleton & Co.'s Medical Publications. 


19 


MEYER 

Electricity in its Relations to Practical 

Medicine . 


By Dr. MORITZ MEYER, 

Royal Counsellor of Health, etc. 

Translated from the Third German Edition, with Notes and Additions, 
A New and Revised Edition, 


By "WILLIAM A. HAMMOND, M. D., 

^ f Hosnitil D MwHpni Sy , 8te “’ and ° f Clinical Medicine. In the Bellevue 

InstW« C a e f® ; Vice-President of the Academy of Mental Science/s National 

institute of Letters, Arts, and Sciences; late Surgeon-General U. 8. A., etc. 


1 vol., 8vo. 497 pp. Cloth, $4.50. 

“ It is the duty of every physician to study the action of electricity, 
to become acquainted with its value in therapeutics, and to follow the 
improvements that are being made in the apparatus for its application in 
medicine, that he may be able to choose the one best adapted to the 
treatment of individual cases, and to test a remedy fairly and without 
prejudice, which already, especially in nervous diseases, has been used 
with the best results, and which promises to yield an abundant harvoet 
in a still broader domain .”—From Author's Preface. 


BPBCOTEN OF ILLUSTRATIONS. 



Sarton-Ettingh&usen Apparatus. 

“ Those who do not read German are under great obligations to William A. 
Hammond, who has given them not only an excellent translation of a most ex¬ 
cellent work, but has given us much valuable information and many suggestion! 
from his own personal experience.”— Medical Record. 

“ Dr. Moritz Meyer, of Berlin, has been for more than twenty years a laborious 
and conscientious student of the application of electricity to practical medicine, 
and the results of his labors are given in this volume. Dr. Hammond, in making 
a translation of the third German edition, has done a real service to the profession 
of this country and of Great Britain. Plainly and concisely written, and simply 
and clearly arranged, it contains just what the physician wants to know on the 
tubject.”— N. Y. Medical Journal. 

“ It is destined to fill a want long felt by physicians in this country.”— Journal 
of Obstetrics 





















20 


D. Appleton A Cojs Medical Publications . 


MARKOE. 

A Treatise on Diseases of the Bones. 

By THOMAS M. MARKOE, M. D., 

Professor of Surgery in the College of Physicians and Surgeons, New York, etc, 
WITH NUMEROUS ILLUSTRATIONS. 

1 vol., 8vo. Cloth, $4.50. 

This valuable work is a treatise on Diseases of the Bones, embracing their 
structural changes as affected by disease, their clinical history and treatment, in¬ 
cluding also an account of the various tumors which grow in or upon them. None 
of the injuries of bone are included in its scope, and no joint diseases, excepting 
where the condition of the bone is a prime factor in the problem of disease. As 
the work of an eminent surgeon of large and varied experience, it may be re¬ 
garded as the best on the subject, and a valuable contribution to medical litera¬ 
ture. 

“The book which I now offer to my professional brethren contains the substance of the lec¬ 
tures which I have delivered during the past twelve years at the college. ... I have followed 
the leadings of my own studies and observations, dwelling more on those branches where I had 
seen and studied most, and perhaps too much neglecting others where my own experience was 
more barren, and therefore to me less interesting. I have endeavored, however, to make up the 
deficiencies of my own knowledge by the free use of the materials scattered so richly through 
our periodical literature, which scattered leaves it is the right and the duty of the systematic 
writer to collect and to embody in any account he may offer of the state of a science at any given 
period .”—Extract from Author's Preface. 


NEFTEL. 

Galvano-Therapeutics. The Physiological and 

Therapeutical Action of the Galvanic Current upon 
the Acoustic, Optic , Sympathetic , and Pneumogastric 
Merves. 

By WILLIAM B. NEFTEL. 

1 vol., 12mo. 161 pp. Cloth, $1.50. 

This book has been republished at the request of several aural surgeons ami 
other professional gentlemen, and is a valuable treatise on the subjects of which 
it treats. Its author, formerly visiting physician to the largest hospital of St. 
Petersburg, has had the very best facilities for investigation. 

“ This little work shows, as far as it goes, full knowledge of what has been 
done on the subjects treated of, and the author’s practical acquaintance with 
them .”—New York Medical Journal. 

“Those who use electricity should get this work, and those who do not 
should peruse it to learn that there is one more therapeutical agent that they 
could and should possess .”—The Medical Investigator . 



1). Appleton cb Co.'s Medical Publications. 


21 


NIEMEYER. 

A Text-Book of Practical Medicine. 

With Particular Reference to Physiology and Patho¬ 
logical Anatomy. 

By the late Dr. FELIX VON NIEMEYER, 

Professor of Pathology and Therapeutics: Director of the Medical Clinic of the University of 

T llt)iD^6Ilt 

Translated from the Eighth German Edition, by special permission of 

the Author, 

By GEORGE H. HUMPHREYS, M. D., 

Late >ne of the Physicians to the Bureau of Medical and Surgical Relief at Bellevue Hospital fo* 
the Out-door Poor; Fellow of the New York Academy of Medicine, etc., 

and 

CHARLES E. HACKLEY, M. D., 

One of the Physicians to the New York Hospital; one of the Surgeons to the New York Eytf 
and Ear Infirmary; Fellow of the New York Academy of Medicine, etc. 

Revised Edition. 2 vols., 8vo. 1,528 pp. Cloth, $9.00 ; Sheep, $11.00, 

The author undertakes, first, to give a picture of disease which shall 
be as lifelike and faithful to nature as possible, instead of being a mere 
theoretical scheme; secondly, so to utilize the more recent advances 
of pathological anatomy, physiology, and physiological chemistry, as to 
furnish a clearer insight into the various processes of disease. 

The work has met with the most flattering reception and deserved 
success; has been adopted as a text-book in many of the medical college# 
both in this country and in Europe; and has received the very highest 
encomiums from the medical and secular press. 

“ It is comprehensive and concise, and is characterized by clearness and 
Originality.”— Dublin Quarterly Journal of Medicine. 

“ Its author is learned in medical literature; he has arranged his material# 
with care and judgment, and has thought over them.”— The Lancet. 

“As a full, systematic, and thoroughly practical guide for the student and 
physician, it is not excelled by any similar treatise in any language.”— ApplelonY 
Journal. 

“ The author is an accomplished pathologist and practical physician ; he is not 
only capable of appreciating the new discoveries, which during the last ten year# 
have been unusually numerous and important in scientific and practical medicine, 
but, by his clinical experience, he can put these new views to a practical test, and 
give judgment regarding them.”— Edinburgh Medical Journal. 

“ From its general excellence, we are disposed to think that it will soon tak# 
its place among the recognized text-books.”— American Quarterly Journal of 
Medical Sciences. 

“ The first inquiry in this country regarding a German book generally is, ‘ I# 
it a work of practical value?” Without stopping to consider the justness of thff 
American idea of the ‘ practical,’ we can unhesitatingly answer, ‘ It is ! ’ ’V-Afo* 
York Medical Journal. 

“ The author has the power of sifting the tares from the wheat—a matter of 
the greatest importance in a text-book for students.”— British Medical Journal. 

“ Whatever exalted opinion our countrymen may have of the author’s talent# 
of observation and his practical good sense, his text-book will not disappoint 
them, while those who are so unfortunate as to know him only by name, have i» 
store a rich treat.”— New York Medical Record 




22 


D. Appleton d Co.'s Medical Publications. 


NIGHTINGALE. 

Notes on Nursing: What it is , and what it is not. 

By FLORENCE NIGHTINGALE. 

1 vol.j 12mo. 140 pp. Cloth, 75 cents. 

Every-day sanitary knowledge, or the knowledge of nursing, or, in other 
words, of how to put the constitution in such a state as that it will have no dis¬ 
ease or that it can recover from disease, takes a higher place. It is recognized 
as the knowledge which every one ought to have—distinct from medical knowl¬ 
edge, which only a profession can have. 


NEUMANN. 

Hand-Book of Skin Diseases. 

By Dr. ISIDOR NEUMANN, 

Lecturer on Skin Diseases in the Royal University of Vienna. 

Translated from advanced sheets of the seoond edition, furnished by the 

Author; with Notes, 

By LUCIUS D. BULKLEY, A. M., M. D., 

Burgeon to the New York Dispensary, Department of Venereal and Skin Diseases; Assist¬ 
ant to the Skin Clinic of the College of Physicians and Surgeons, New York; Mem¬ 
ber of the New York Dermatological Society, etc., etc. 

1 vol., 8vo. About 450 pages and 66 Woodcuts, Cloth, $4.00. 

Prof. Neumann ranks second only to Hebra, whose assistant he was for many yean 
*nd his work may be considered as a fair exponent of the German practice of Dermatolo¬ 
gy. The book is abundantly illustrated with plates of the histology and pathology of the 
skin. The translator has endeavored, by means of notes from French, English, and Ameri¬ 
can soarces, to make the work valuable to the student as well as to the practitioner. 


“It is a work which I shall heartily recommend to my class of students at the Univerw 
eity of Pennsylvania, and one which I feel sure will do much toward enlightening the pro- 
fession on this subject .”—Louis A. Duhring. 

“ I know it to he a good book, and I am sure that it is well translated; and it is inter¬ 
esting to find it illustrated by references to the views of co-laborers in the same field.”— 
Erasmus Wilson. 

“ So complete as to render it a most useful book of reference.”— T. McCall Anderson. 

“There certainly is no work extant which deals so thoroughly with the Pathological 
Anatomy of the Skin as does this hand-book.”—V. Y. Medical Record. 

“The original notes by Dr. Bulkley are very practical, and are an important adjunct to 
the text. ... I anticipate for it a wide circulation ."Silas Durkee , Boston. 

“I have already twice expressed my favorable opinion of the book in print, and am 
glad that it is given to the public at last .”—James C. White , Boston. 

“More than two years ago we noticed Dr. Neumann’s admirable work in its original 
ebape; and we are therefore absolved from the necessity of saying more than to repeal 
our strong recommendation of it to English readers.”— Practitioner. 




D. Appleton <£* CoSs Medical Publications. 


23 


PAGET. 

Clinical Lectures and Essays. 

By Sir JAMES PAGET, Bart., 

F. It-S., T). C. L., Oxon., LL. D., Cantab.; Sergeant-Surgeon Extraordinary to her Majesty tho 
Hospital^ LU ^ e0fl H* tt 10 Prince of Wales; Consulting Surgeon to St. Bartholomew 1 © 


Edited by HOWARD MARSH, 

Assistant Surgeon to St. Bartholomew’s Hospital, and to the Hospital for Sick Children. 

1 vol., 8vo. Cloth. Price, $5.00. 

CONTENTS. 

The Various Risks of Operations—The Calamities of Surgery—Stam¬ 
mering with other Organs than those of Speech—Cases that Bone-Setters 
cure—Strangulated Hernia—Chronic Pyaemia—Nervous Mimicry—Treat¬ 
ment of Carbuncle—Sexual Hypochondriasis—Gouty Phlebitis—Residual. 
Abscess—Dissection-Poisons—Quiet Necrosis—Senile Scrofula—Scarlet Fe¬ 
ver after Operations—Notes for the Study of some Constitutional Diseases 
—Notes—Index. 

PEASLEE. 

Ovarian Tumors; Their Pathology , Diagnosis , and 

Treatment , with Reference especially to Ovariotomy . 

By E. R. PEASLEE, M.D., 

Professor of Diseases of Women in Dartmouth College; one of the Consulting Pliysicans to the 
New York State Woman’s Hospital; formerly Professor of Obstetrics and Diseases of 
Women in the New York Medical College; Corresponding Member of the Obstetrical 
Society of Berlin, etc. 

1 vol., 8vo. Illustrated with many Woodcuts, and a Steel Engraving of Dr. E. 

McDowell, the “ Father of Ovariotomy.” Price, Cloth, $5.00. 

This valuable work, embracing the results of many years of successful experience in the de¬ 
partment of which it treats, will prove most acceptable to the entire profession; while the high 
standing of the author and his knowledge of the subject combine to make the book the best in 
the language. It is divided into two parts : the first treating of Ovarian Tumors, their anatomy, 
pathology, diagnosis, and treatment, except by extirpation ; the second of Ovariotomy, its history 
and statistics, and of the operation. Fully illustrated, and abounding with information, the result 
of a prolonged study of the subject, the work should be in the hands of every physician in the- 
country. 

The following are some of the opinions of the press, at home and abroad, of this great work T 
which has been justly styled, by an eminent critic, “ the most complete medical monograph on a 
practical subject ever produced in this country .” 

“His opinions upon what others have advised are clearly set forth, and are as interesting and 
important as are the propositions he has himself to advance; while,there are a freshness, a vigor, 
an authority about his writing, which great practical knowledge alone can confer. - ’— The Lancet. 

“Both Wells’s and Peaslee’s works will be received with the respect due to the great repu¬ 
tation and skill of their authors. Both exist not only as masters of their art, but as clear and 
graceful writers. In either work the student and practitioner will find the fruits of rich expe¬ 
rience, of earnest thought, and of steady, well-balanced judgment. As England is proud of 
Wells, so may America well be proud of Peaslee, and the great world of science may be proud 
of both.”— British Medical Journal. 

“ This is an excellent work, and does great credit to the industry, ability, science, and learning 
of Dr. Peaslee. Few works issue from the medical press so complete, so exhaustively learned, 
bo imbued with a practical tone, without losing other substantial good qualities.”— Edinburgh 
Medical Journal. 

“ In closing our review of this work, we cannot avoid again expressing our appreciation of 
the thorough study, the careful and honest statements, and candid spirit, which charactexize it. 
For the use of the student we should give the preference to Dr. Peaslee's work , not only from 
its completeness , but from its more methodical arrangement."—American Journal of Medical 
Sciences. 




24 


J). Appleton & Co.'s Medical Publications 


PEREIRA. 

Dr. Pereira’s Elements of Materia 

Medica and Therapeutics . Abridged and adapted for 
the Use of Medical and Pharmaceutical Practitioners 
and Students, and comprising all the Medicines of the 
British Pharmacopoeia, with such others as are frequently 
ordered in Prescriptions, or required by the Physician. 

Edited by ROBERT BENTLEY and THEOPHILUS REDWOOD. 

25Tew Edition. Brought down to 1872. 1 vol., Royal 8vo. Cloth, $7.00 ; Sheep, 

$ 8 . 00 . 

Reports. Bellevue and Charity Hospital Reports for 
1870 , containing Valuable Contributions from 

2saao E. Taylor, M. D., Austin Flint, M. D., Lewis A. Sayre, M. D., William A. Ham¬ 
mond, M. D., T. Gaillard Thomas, M. D., Frank H. Hamilton, M. D., and others. 

1 vol., 8vo. Cloth, $4.00. 

“These institutions are the most important, as regards accommodations for patients and 
variety of cases treated, of any on this continent, and are surpassed by but few in the world. 
'The gentlemen connected with them are acknowledged to be among the first in their profession, 
.and the volume is an important addition to the professional literature ot this count y.”— Psycho - 
logical Journal. 


RICHARDSON. 


Diseases of Modern Life. 


By Dr. B. W. RICHARDSON, F. R. S. 

1 vol., 12mo. $2.00. 

1’art the First.— PHENOMENA OF DISEASE, INCIDENTAL AND GENERAL. 
Chap. I.—Natural Life to Natural Death. Euthanasia. 

“ II.—Phenomena of Disease, Classification and Distribution. 

“ III.—Disease Antecedent to Birth. 

“ IV.—External Origins and Causes of Disease. 

“ Y.—Phenomena of Disease, from Causes External and Uncontrollable. 

■“ YI.—Phenomena of Disease, from Causes External and Communicable. 

*• YII.—Phenomena of Disease, incidental to Old Age and Natural Decay. 

Part the Second.— PHENOMENA OF DISEASE, INDUCED AND SPECIAL. 
Definition and Classification of Induced Diseases. 

Disease from Worry and Mental Strain (Broken Heart). 

Disease from Worry and Mental Strain, continued (Paralysis). 

Disease from Physical Strain. 

Disease from Combined Physical and Mental Strain. 

Disease from the Influence of the Passions. 

Disease from Alcohol. Physiological Proem. 

Phenomena of Disease from Alcohol. The Functional Type. 

■Organic Disease from Alcohol. 

Disease from Tobacco. Physiological Phenomena. 

Disease from Tobacco, continued (of the Heart and Lungs). 

Disease from Tobacco, continued (of the Brain and Nervous System). 

Disease from the Use of Narcotics (from Opium, Chloral, and Absinthe). 
Disease from Misuse of Foods. 

Disease incident to some Occupations. 

Disease from Late Hours and Deficient Sleep. 

Disease from Imperfect Supply of Air. 

Disease from Imitation and Moral Contagion. 

Part the Third.— SUMMARY OF PRACTICAL APPLICATIONS. 


£5hap. I.— 

“ II.— 

“ III.— 

“ IV.— 

“ V.- 

" VI.- 

“ VII.— 

yiii.— 

IX.- 
“ X.— 

XI.— 
XII.— 
XIII.— 
il XIV.— 

XV.— 
» XVI.— 

» XVII.— 

» XVIII.- 


! 


1 

I 

I 


J 







D. Appleton & Co.'s Medical Publications. 


25 


SAYRE. 

Lectures on Orthopedic Surgery, and 

Diseases of the Joints. Delivered at Dellevue Hospital 
Medical College during the Winter Session of 1874 - 1875 - 

By LEWIS A. SAYRE, M. I)., 

Professor of Orthopedic Surgery, Fractures and Dislocations, and Clinical Surgery, in Bellevue 
Hospital Medical College; Surgeon to Bellevue Hospital; Consulting Surgeon to Charity 
Hospital; Consulting Surgeon to St. Elizabeth’s Hospital; Consulting Surgeon to North¬ 
western Dispensary; Member of the American Medical Association; Permanent Member'’ 
of the New York State Medical Society; Fellow of the New York Academy of Medicinef 
Member of the New York County Medical Society, of the New York Pathological Society, 
of the Society of Neurology, of the Medico-Legal Society; Honorary Member of the New 
Brunswick Medical Society; Honorary Member of the Medical Society of Norway; Knight 
of the Order of Wasa, by His Majesty the King of Sweden, etc., etc. 

Illustrated by Numerous Wood-Engravings. 1 vol., 8vo, Cloth, $5.00; Sheep, 

$ 6 . 00 . 

These lectures are published at the request of medical gentlemen of the highest standing, in 
ditferent sections of our country, as well as many abroad, who are anxious to have Dr. Sayre’s- 
peculiar views and extended experience in this specialty given to the profession in a plain and 
practical manner. The book contains the substance of his course of lectures delivered at Belle¬ 
vue Hospital Medical College, as well as many important cases from his note-book, and from the 
hospital records. Ho has also added a number of cases before presented by him to the profes¬ 
sion in medical journals, or at the different medical societies, which are considered worthy of 
permanent record. 

The work is enriched by beautiful and excellent illustrations, engraved from original draw¬ 
ings and photographs prepared expressly therefor. The author having enjoyed exceptional op¬ 
portunities for the study and treatment of these diseases, the results of his labors cannot fail tc? 
be of inestimable value to every student and practitioner, and of service to suffering humanity. 

STEINER 

Compendium of Children’s Diseases. 

A Hand-book for Practitioners and Students. 

By Dr. JOHANN STEINER, 

Professor of the Diseases of Children In the University of Prague, and Physician to the Francis- 

Joseph Hospital for Sick Children. 

Translated from the Second German Edition by Lawson Tait, P. It. C. S. f 

Surgeon to the Birmingham Hospital for Women; Consulting Surgeon to the West Bromwlclt 
Hospital; Lecturer on Physiology at the Midland Institute. 

1 vol., 8vo. Cloth, $3.50. 

TRANSLATOR’S PREFACE. 

Dr. Steiner’s book has met with such marked success in Germany that a second edition has 
already appeared, a circumstance which has delayed the appearance of its English form, in order 
that I might be able to give his additions and corrections. 

In Germany the use of the metric system has not yet entirely superseded the local measures f 
but it is rapidly doing so, as in England. I have, therefore, rendered all thermometric observa¬ 
tions in the Centigrade scale, and all measurements in centi- and millimetres. 

I have added as an Appendix the “ Rules for Management of Infants” which have been issued 
by the staff of the Birmingham Sick Children’s Hospital, because I think that they have set an 
example by freely distributing these rules among the poor for which they cannot be sufficiently 
commended, and which it would be wise for other sick children’s hospitals to follow. 

I have also added a few notes, chiefly, of course, relating to the surgical ailments of children. 

Bibmingham, October, 1874. LAWSON TAIT. 





/ 


5>G D. Appleton <& Co.'s Medical Publications. 

STROUD. 

The Physical Cause of the Death of 

Christ, arid its Belations to the Principles and Practice 
of Christianity. 

By WILLIAM STROUD, M. D. 

With, a Letter on the Subject, by Sir James Y. Simpson, Bart., M. D. 

1 vol., 12mo. 422 pp. Cloth, $2.00. 

This important and remarkable book is. in its own place, a masterpiece, and will be considered 
as a standard work for many years to come. 

“The principal point insisted on is. that the death of Christ was caused by rupture or lacera¬ 
tion of the heart. Sir James Y. Simpson, who had read the author’s treatise and various com¬ 
ments on it, expressed himself very positively in favor of the views maintained by Dr. Stroud.** 
—Psychological Journal. 

SIMPSON. 

The Posthumous Works of Sir James 

Young Simpson, Bart., M. JD. In Three Volumes. 

Volume I. —Selected Obstetrical and Gynaecological Works of Sir .James Y. Simpson , 
Bart.. M. IX. D. C. L.. late Professor of Midwifery in the University of Edinburgh. Contain¬ 
ing the substance of his Lectures on Midwifery. Edited by J. Watt Black. A. M.. M. D., 
Member of the Royal College of Physicians. London; Physician-Accoucheur to Charing 
Cross Hospital. London; and Lecturer on Midwifery and Diseases of Women and Children 
in the Hospital School of Medicine. 

1 vol., 8vo. 852 pp. Cloth, $3.00. 

This volume contains all the more important contributions of Sir James Y. Simpson to the 
study of obstetrics and diseases of Women, with the exception of his clinical lectures on the latter 
subject, which will shortly appear in a separate volume. This first volume contains many of the 
papers reprinted from his Obstetric Memoirs and Contributions, and also his Lecture Notes, now 
published for the first time, containing the substance of the practical part of his course of mid¬ 
wifery. It is a volume of great interest to the profession, and a fitting memorial of its renowned 
and talented author. 

“To many of our readers, doubtless, the chief of the papers it contains are familiar. To 
others, although probably they may be aware that Sir James Simpson has written on the sub¬ 
jects. the papers themselves will be new and fresh. To the first class we would recommend this 
edition of Sir James Simpson’s works, as a valuable volume of reference; to the latter, as a collec¬ 
tion of the works of a great master and improver of his art, the study of which cannot fail to make 
them bettor prepared to meet and overcome its difficulties.”— Medical Times and Gazette. 

Volume II .—Anaesthesia , H< spitalism, etc. Edited by Sir Walter Simpson, Bart. 

1 vol., 8vo. 560 pp. Cloth, $3.00. 

‘VWe sav of this, as of the first volume, that it should find a place on the table of every prac¬ 
titioner : for. though it is patchwork, each piece may be picked out and studied with pleasure and 
profit .”—The Lancet (London). 

Volume III. —The Diseases of Women. Edited by Alex. Simpson, M. D., Professor 
of Midwifery in the University of Edinburgh. 

1 vol., 8vo. Cloth, $3.00. 

One of the best works on the subject extant. Of inestimable value to every physician. 

SWETT. 

A Treatise on the Diseases of the Chest. 

Being a Course of Lectures delivered at the New York 
Hospital. 

By JOHN A. SWETT, M. D., 

Professor of the Institutes and Practice of Medicine in the New York University; Physician to 
the New York Hospital; Member of the New York Pathological Society. 

1 vol., 8vo. 587 pp. $3.50. 

Embodied in this volume of lectures is the experience of ten years in hospital and private 
practice. 






D. Appleton cb CoSs Medical Publications. 


27 


SAYRE. 

A Practical Manual on the Treatment 

of Club-Foot. 

By LEWIS A. SAYRE, M. I)., 

Professor of Orthopedic Surgery in Bellevue Hospital Medical College; Surgeon to Bellevue and 

Charity Hospitals, etc. 

1 vol, 12mo. New and Enlarged Edition, Cloth, $1.00, 

“The object of this work is to convey, in as concise a manner as possible, all the practical in¬ 
formation and instruction necessary to enable the general practitioner to apply that plan of treat¬ 
ment which has been so successful in my own hands.’’ — Preface. 

‘‘The book will very well satisfy the wants of the majority of general practitioners, for whose 
use, as stated, it is intended.” —Is ecu York Medical Journal. 

SMITH. 

On Foods. 

By EDWARD SMITH, M. D., LL. B., F. R. S., 

Fellow of the Royal College of Physicians of Loudon, etc., etc. 

1 vol., 12mo. Cloth. Frice, 81.75. 

“ Since the issue of the author’s work on " Practical Dietary.” lie has felt the want of another, 
which would embrace all the generally-known and less-known foods, and contain the latest scien¬ 
tific knowledge respecting them. The present volume is intended to meet this want, and will be 
found useful tor reference, to both scientific and general readers. The author extends the ordi¬ 
nary view of foods, and includes water and air, since they are important both in their food and 
sanitary aspects. 

SCHROEDER. 

A Manual of Midwifery. Including the Pa¬ 
thology of Pregnancy and the Puerperal State. 

By Dr. KARL SCHROEDER, 

Professor of Midwifery and Director of the Lying-in Institution in the University of Erlangen. 

TKANSI.ATED FROM T1IE 'III I III) GERMAN EDITION 

By CHARLES H. CARTER, B. A., M. D„ B. S. London, 

Member of the Koval College of Physicians, London, and Physician Accoucheur to St. George’s, 

llanover Square, Dispensary. 

With Twenty-six Engravings on Wood. 1 vol., 8vo. Cloth. 

“The translator feels that no apology is needed in offering to the profession a translation of 
Schroeder’s Manual of Mid .vifery. The work is well known in Germany and extensively used as 
a text-book; it has'alrcady reached a third edition within the short space of two years, ami it is 
hoped that the present translation will meet the want, long felt in this country, of a manual o£ 
midwifery embracing the latest scientific researches on the subject. 

TILT. 

A Hand-Book of Uterine Therapeu- 

tics and of Diseases of Women. 

By EDWARD JOHN TILT, M. D., 

Member of the Royal College of Physicians: Consulting Physician to the Farringdon General 
Dispensary; Fellow of the Royal Medical and Chiritrgical Society, and of several British and 
foreign societies. 

1 vol., 8vo. 345 pp. Cloth, 83.50. 

Second American edition, thoroughly revised and amended. 

“In giving the result of his labers to the profession the author has done a great work. Our 
readers will find its pages very interesting, and. at the end of their task, will feel grateful to the 
author for many very valuable suggestions as to the treatment of uterine diseases.”— The Lancet. 
“Dr. Tilt's • Hand-Book of Uterine Therapeutics * supplies a want which has often been felt. 

. . It may, therefore, be read not only with pleasure and instruction, hut will also be found 
very useful as a book of reference .”—The Medical Mirror. 

“ Second to none on the therapeutics of uterine disease.”— Journal of Obstetrics. 




D. Appleton A Co.'s Medical Publications. 


28 


VAN BUREN AND KEYES, 

A Practical Treatise on the Surgical 

Diseases of the Genito- Urinary Organs , including Syphi¬ 
lis. Designed as a Manual for Students and Practition¬ 
ers. With Engravings and Cases. 

By W. H. VAN BUREN, A. M., M. D., 

Professor of Principles of Surgery. -with Diseases of the Genito-TTrinary System and Clinical 
Surgery, in Bellevue Hospital'Medical College; Consulting Surgeon to the New York Hos¬ 
pital, the Charily Hospital, etc.; and 

E. L. KEYES, A. M. } M. D., 

Professor of Dermatology in Bellevue Hospital Medical College; Surgeon to the Charity Hos¬ 
pital. Venereal Diseases; Consulting Dermatologist to the Bureau of Out-Door Belief Belle¬ 
vue Hospital, etc. 

1 vol., 8vo. Cloth, $5.00; Sheep, $6.00. 

This work is really a compendium of, and a book of reference to, all modem 
works treating in any way of the surgical diseases of the genito-urinaiy organs. At 
the same time, no other single book contains so large an array of original facts con¬ 
cerning the class of diseases with which it deals. These facts are largely drawn 
from the extensive and varied experience of the authors. 

Many important branches of genito-urinary diseases, as the cutaneous maladies 
of the penis and scrotum, receive a thorough and exhaustive treatment that the pro¬ 
fessional reader will search for elsewhere in vain. 

The work is elegantly and profusely illustrated, and enriched by fifty-five 
original cases, setting forth obscure and difficult points in diagnosis and treatment. 

“The first part Is devoted to the Surgical Diseases of the Genito-Urinary Organs; and part 
second treats of Chancroid and Syphilis. The authors 4 appear to have succeeded admirably in 
£\ ving to the world an exhaustive and reliable treatise on this important class of diseases.’ ”— 
Northwestern Medical and Surgical Journal. 

“It is a most complete digest of what has long been known, and of what has been more re¬ 
cently discovered, in the field of syphilitic and genito-urinary disorders. It is perhaps not an 
exaggeration to say that no single work upon the same subject has yet appeared, in this or any 
foreign language, which is superior to it.”— Chicago Medical Examiner. 

44 The commanding reputation of Dr. Yan Buren in this specialty and of the great school and 
•hospital from which he has drawn his clinical materials, together with the general interest which 
attaches to the subject-matter itself, will, we trust, lead very many of those for whom it is our 
office to cater, to possess themselves at once of the volume and form their own opinions of its 
merit.”— Atlanta Medical and Surgical Journal. 


Lectures upon Diseases of the Rectum. 

Delivered at the Bellevue Hospital Medical College. 

Session of 1869-’?0. 

By W. H. YAN BUREN, M. D., 

1 vol., 12mo. 164 pages. Cloth, $1.50. 

“ It seems hardly necessary to more than mention the name of the author of this admirable 
Sittle volume in order to insure the character of his book. No one in this country has enjoyed 
greater advantages, and had a more extensive field of observation in this specialty, than Dr. 
Van Buren, and no one has paid the same amount of attention to the subject. . . . Here is the 
experience of years summed up and given to the professional w orld in a plain and practical man¬ 
ner.”— Psychological Journal. 



29 


D* Appleton efi Co.'s Medical Publications, 


VOGEL. 

A Practical Treatise on the Diseases 

of Children . Second American from the Fourth 
German Fdition . Illustzrated by Six Lithographic 
Plates . 

By ALFRED VOGEL, M. D., 

Professor of Clinical Medicine in the University of Dorpat, RomUl 
TRANSLATED AND EDITED BY 

H. RAPHAEL, M. D., 

i*te House Surgeon to Bellevue Hospital; Physician to the Eastern Dispensary for the Diseases 

of Children, etc., etc. 

1 vol., 8vo. 611 pp. Cloth, $4.50. 

The work is well up to the present state of pathological knowledge; 
complete without unnecessary prolixity; its symptomatology accurate, 
evidently the result of careful observation of a competent and experi¬ 
enced clinical practitioner. The diagnosis and differential relations of 
diseases to each other are accurately described, and the therapeutics 
judicious and discriminating. All polypharmacy is discarded, and only 
the remedies which appeared useful to the author commended. 

It contains much that must gain for it the merited praise of all im¬ 
partial judges, and prove it to bo an invaluable text-book for the stu¬ 
dent and practitioner, and a safe and useful guide in the difficult but all- 
important department of Paodiatrica. 

“ Rapidly passing to a fourth edition in Germany, and translated into three 
other languages, America now has the credit of presenting the first English ver¬ 
sion of a book which must take a prominent, if not the leading, position among 
works devoted to this class of disease.”— N. Y. Medical Journal. 

“ The profession of this country are under many obligations to Dr. Raphael 
for bringing, as he has dona, this truly valuable work to their notice.”— Medical 
Record. 

“The translator has been more than ordinarily successful, and his labors 
have resulted in what, in every sense, is a valuable contribution to medicaa 
science.”— Psychological Journal. 

“We do not know of a compact text-book on the diseases of children more 
complete, more comprehensive, more replete with practical remarks and scientific 
facts, more in keeping with the development of modern medicine, and more 
worthy of the attention of the profession, than that which has been the subject 
of our remarks.”— Journal of Obstetrics. 







30 


D. Appleton & Co.'s Medical Publications. 


WALTON. 

The Mineral Springs of the United 

States and Canada, with Analyses and Notes on the 
Prominent Spas of Europe , and a List of Seaside 
Pesorts. An enlarged and revised edition. 

By GEORGE E. WALTON, M. D., 

Lecturer on Materia Hedica in the Miami Medical College, Cincinnati. 

8econd Edition, revised and enlarged. 1 vol., 12mo. 390 pp., with Maps. $2.00. 

The author has given the analyses of all the springs in this country and 
those of the principal European spas, reduced to a uniform standard of 
one wine-pint, so that they may readily be compared. He has arranged 
the springs of America and Europe in seven distinct classes, and de¬ 
scribed the diseases to which mineral waters are adapted, with refer¬ 
ences to the class of waters applicable to the treatment, and the pecul¬ 
iar characteristics of each spring as near as known are given—also, the 
location, mode of access, and post-office address of every spring are men¬ 
tioned, In addition, he has described the various kinds of baths and 
the appropriate use of them in the treatment of disease. 


EXTRACTS FROM OPINIONS OF THE PRESS. 

“ . . . Precise and comprehensive, presenting not only reliable analyses of 
the waters, but their therapeutic value, so that physicians can hereafter advise 
their use as intelligently and beneficially as they can other valuable alterative 
agents.”— Sanitarian. 

“ . . . Will tend to enlighten both the profession and the people on this 
question.”— N. Y. Medical Journal. 

“ . . . Contains in brief space a vast amount of important and interesting 
matter, well arranged and well presented. Nearly every physician needs just 
such a volume ”— Richmond and Louisville Medical Journal. 

“ . . . Fills this necessity in a scientific and pleasing manner, and can be read 
with advantage by the physician as well as layman.”— American Jour, of Obstetrics. 


Unttkksitt or Y inarm a, June 9, 18T8. 

Gentlemen : I have received by mail a copy of Dr. Walton’s work on the 
Mineral Springs of the United States and Canada. Be pleased to accept my 
thanks for a work which I have been eagerly looking for ever since I had the 
pleasure of meeting the author in the summer of 1871. He satisfied me that 
he was well qualified to write a reliable work on this subject, and I doubt not 
he has met my expectations. Such a work was greatly needed, and, if offered 
for sale at the principal mineral springs of the country, will, I believe, com¬ 
mand a ready sale. Very respectfully yours, 


J. L. Cabell, M. D. 



D. Appleton & Co.’s Medical Publications . 


31 


WELLS. 

Diseases of the Ovaries ; Their Diagnosis 

and Treatment. 

By T. SPENCER WELLS, 

Fellow and Member of Council of the Royal College of Surgeons of England; Honorary Fellow 
of the King and Queen’s College of Physicians in Ireland; Surgeon in Ordinary to the 
Queen’s Household; Surgeon to the Samaritan Hospital for Women; Member of the Im¬ 
perial Society of Surgery of Paris, of the Medical Society of Paris, and of the Medical Soci¬ 
ety of 8weden; Honorary Member of the Royal Society of Medical and Natural Science 
of Brussels, and of the Medical Societies of Pesth and Helsingfors; Honorary Fellow of 
"the Obstetrical Societies of Berlin and Leipzig, 

1 vol., 8vo. 478 pp. Illustrated. Cloth, Price, $4.50. 

In 1865 the author issued a volume containing reports of one hundred and 
fourteen cases of Ovariotomy, which was little more than a simple record of 
facts. The book was soon out of print, and, though repeatedly asked for a 
new edition, the author was unable to do more than prepare papers for the 
Royal Medical and Chirurgical Society, as series after series of a hundred cases 
accumulated. On the completion of five hundred cases he embodied the results 
in the present volume, an entirely new work, for the student and practitioner, 
and trusts it may prove acceptable to them and useful to suffering women. 

“ Arrangements have been made for the publication of this volume in Lon¬ 
don' on the day of its publication in New York.” French and German transla¬ 
tions are already in press. 


WAGNER. 

A Hand-book of Chemical Tech- 

nology. 

By RUDOLPH WAGNER, Ph. D., 

Professor of Chemical Technology at the University of Wurtzburg. 

Translated and edited, from the eighth German edition, with extensive 

additions, 

By WILLIAM CROOKES, F. R. S. 

With 336 Illustrations. 1 vol,, 8vo, 761 pages. Cloth, $5.00. 

Under the head of Metallurgy Chemistry, the latest methods of preparing Iron. Cobalt, 
Nickel, Copper. Copper Salta, Lead and Tin. and their Salts. Bismuth. Zinc, Zinc Salta. Cad¬ 
mium. Antimony, Arsenic, Mercury, Platinum, Silver, Gold, Manganates. Aluminum, and 
Magnesium, are described. The various applications of the Voltaic Current to Electro-Metal¬ 
lurgy follow under this division. The preparation of Potash and Soda Salts, the manufacture 
of Sulphuric Acid, and the recovery of Sulphur from Soda Waste, of course occupy prominent 
places in the consideration of chemical manufactures. It is difficult to over-estimate the mer¬ 
cantile value of Mend’s process, as well as the many new and important applications of Bisul¬ 
phide of Carbon. The manufacture of Soap will he found to include much detail The Tech¬ 
no logv of Glass, Stone-ware, Limes, and Mortars, will present much of interest to the Builder 
and Engineer. The Technology of Vegetable Fihres has been considered to include the prep¬ 
aration of Flax. Hemp. Cotton, as well as Paper-making: while the applications of V egetable 
Products will be found to include Sugar-boiling. Wine and Beer Brewing, the Distillation of 
Spirits, the Baking of Bread, the Preparation of Vinegar, the Preservation of Wood. etc. 

Dr Wagner gives much information in reference to the production of Potash front Sugar 
residues. The use of Barvta Salts is also fullv described, as well as the preparation of Sugar 
from Beet-roots. Tanning, the Preservation of Meat, Milk, etc„ the Preparation of Phospho¬ 
rus and Animal Charcoal, are considered as belonging to the Technology of Animal Products. 
The Preparation of Materials for Dyeing has necessarily required much space : while the final 
Motions of the book have been devoted to the Technology of Heating and illumination 



THE NEW YORE MEDICAL JOURNAL. 

JAMES B. HTJJVTER, M. D., Editor . 

Published Monthly. Volumes begin in January and July, 


“Among the numerous records of Medicine and tile collateral sciences published in America, 
the above Journal occupies a high position, and deservedly so.”— The Lancet {London). 

“One cf the best medical journals, by-the-by, published on the American Continent.”— Lon¬ 
don Medical '1 imes and Gazette. 

“ A very high-class journal.”— London Medical Mirror. 

“The editor and the contributors rank among our most distinguished medical men, and each 
number contains matter that does honor to American medical literature.”— Boston Journal of 
Chemistry. 

“ Full of valuable original papers, abounding in scientific ability.”— Chicago Medical Times 

“ We know no other periodical that we would rather present as a specimen of American skil 
and intelligence than the New York Medical Journal.” — Franklin Repository. 

“The New York Medical Journal, edited by Dr. James B. Hunter, is one of the sterling 
periodicals of this country. The present editor has greatly improved the work, and evinces a 
marked aptitude for the responsible duties so well discharged. The contents of this journal are 
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Terms* $4.00 per Annum ; or 40 Cents per Number. 

-—«——»■- 

THE POPULAR SCIENCE MONTHLY. 

Conducted by Prof. E. L. YOUMANS. 

Each Number contains 128 pages, with numerous Descriptive and 

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covering the whole range of Natural Science, we have the latest thoughts and words of Her¬ 
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JD. APPLET OFT & CO., 

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